gitadora: add native dual fullscreen for Arena (#846)

## Link to GitHub Issue or related Pull Request, if one exists

Fixed https://github.com/spice2x/spice2x.github.io/issues/740

## Description of change

- Enable native D3D9 adapter-group dual fullscreen for the GITADORA
Arena model when the two-screen MAIN + SMALL configuration is selected
without windowed mode.
- Present MAIN and SMALL on their respective monitor heads while keeping
the invisible LEFT and RIGHT targets offscreen.
- Scope the new fake-swap-chain query behavior to the hidden GITADORA
two-head targets, preserving existing behavior for other games and
configurations.

The existing borderless-windowed two-screen path could not consistently
keep input and game timing synchronized and also reduced rendering
performance. Native dual fullscreen avoids that windowed composition
path.

## Testing

- Manually tested GITADORA Arena with separate MAIN and SMALL monitors
in fullscreen mode. Windowed mode still works if the user chooses to use
that.
- Confirmed both displays render correctly, touch input works on the
SMALL screen, gameplay input stays synchronized, and gameplay holds a
steady 60 FPS.
- Built `spicetools_spice64` at commit `e4a98e9` with the repository
Docker toolchain.
- Confirmed no new compiler warnings.
- Confirmed the forbidden static DLL import check passes.
- Confirmed the Windows 7 DLL compatibility check reports `All DLLs
OK!`.

---------

Co-authored-by: vgod <428979+vgod@users.noreply.github.com>

src/spice2x/CMakeLists.txt

@@ -536,6 +536,7 @@ set(SOURCE_FILES ${SOURCE_FILES}
         hooks/graphics/nvenc_hook.cpp
         hooks/graphics/backends/d3d9/d3d9_backend.cpp
         hooks/graphics/backends/d3d9/d3d9_device.cpp
+        hooks/graphics/backends/d3d9/d3d9_gfdm.cpp
         hooks/graphics/backends/d3d9/d3d9_live2d.cpp
         hooks/graphics/backends/d3d9/d3d9_fake_swapchain.cpp
         hooks/graphics/backends/d3d9/d3d9_swapchain.cpp

src/spice2x/games/gitadora/gitadora.cpp

@@ -2,12 +2,14 @@
 #include "asio.h"
 #include "handle.h"
 #include "bi2x_hook.h"
+#include <span>
 #include <unordered_map>
 
+#include "cfg/configurator.h"
+#include "cfg/screen_resize.h"
+
 #include <ks.h>
 #include <ksmedia.h>
-
-#include "cfg/configurator.h"
 #include "hooks/audio/audio.h"
 #include "hooks/audio/mme.h"
 #include "hooks/graphics/graphics.h"
@@ -35,6 +37,7 @@ namespace games::gitadora {
     std::optional<std::string> SUBSCREEN_OVERLAY_SIZE;
     std::optional<socd::SocdAlgorithm> PICK_ALGO = socd::SocdAlgorithm::PreferRecent;
     std::optional<uint8_t> ARENA_WINDOW_COUNT = std::nullopt;
+    bool ARENA_TWO_HEAD_EXCLUSIVE = false;
     std::optional<std::string> ASIO_DRIVER = std::nullopt;
     bool ALLOW_REALTEK_AUDIO = false;
 
@@ -271,9 +274,21 @@ namespace games::gitadora {
                         break;
                     case 2:
                         if (!GRAPHICS_WINDOWED) {
-                            log_fatal(
+                            if (D3D9_ADAPTER.has_value()) {
+                                log_fatal(
+                                    "gitadora",
+                                    "arena model: fullscreen two-window mode cannot use -monitor; "
+                                    "use -w for borderless windows instead");
+                            }
+                            ARENA_TWO_HEAD_EXCLUSIVE = true;
+                            log_info(
                                 "gitadora",
-                                "arena model: 2-window mode is not supported in fullscreen, choose 1 or 4");
+                                "arena model: native two-head fullscreen adapter-group mode "
+                                "(MAIN + SMALL; LEFT/RIGHT are virtual)");
+                        } else {
+                            log_info(
+                                "gitadora",
+                                "arena model: two-window mode uses windowed rendering");
                         }
                         log_info("gitadora", "arena model: two-window mode");
                         GRAPHICS_GITADORA_HIDE_SIDE_WINDOWS = true;
@@ -299,10 +314,18 @@ namespace games::gitadora {
     static decltype(QueryDisplayConfig) *QueryDisplayConfig_orig = nullptr;
     static decltype(DisplayConfigGetDeviceInfo) *DisplayConfigGetDeviceInfo_orig = nullptr;
 
-    // cached primary real monitor: its path + source/target mode entries.
-    // modeInfoIdx values on the path are renumbered to 0 / 1 so the cache is self-contained.
+    // Cached real monitor paths and their source/target mode entries. modeInfoIdx values are
+    // renumbered so the cache is self-contained. The normal single-head emulation keeps only
+    // MAIN; the two-head adapter-group mode keeps MAIN and SMALL as real heads.
     static DISPLAYCONFIG_PATH_INFO real_primary_path = {};
     static DISPLAYCONFIG_MODE_INFO real_primary_modes[2] = {}; // [0]=source, [1]=target
+    static DISPLAYCONFIG_PATH_INFO real_small_path = {};
+    static DISPLAYCONFIG_MODE_INFO real_small_modes[2] = {}; // [0]=source, [1]=target
+    static bool real_small_path_available = false;
+
+    static bool is_two_head_exclusive() {
+        return ARENA_TWO_HEAD_EXCLUSIVE && !GRAPHICS_WINDOWED;
+    }
 
     // fake monitors appended after the real ones. the game classifies monitors
     // by outputTechnology + connectorInstance:
@@ -326,12 +349,31 @@ namespace games::gitadora {
     // adapter to a swap chain role via its DisplayConfig connector instance,
     // so the entries here must be listed in the same order the wrapper enumerates
     // them: id=1 -> adapter 1 -> left, id=2 -> adapter 2 -> right, id=3 -> adapter 3 -> small.
-    static constexpr FakeMonitor FAKE_MONITORS[] = {
+    // Normal single-head emulation: every non-MAIN role is fake.
+    static constexpr FakeMonitor FAKE_MONITORS_SINGLE_HEAD[] = {
         { 1, 1080, 1920, -100000, -100000, 0 }, // left  (DP connector instance 0)
         { 2, 1080, 1920, -200000, -200000, 1 }, // right (DP connector instance 1)
         { 3,  800, 1280, -300000, -300000, 2 }, // small (DP connector instance 2, touch)
     };
-    static constexpr UINT32 FAKE_MONITOR_COUNT = static_cast<UINT32>(std::size(FAKE_MONITORS));
+
+    // Two-head fullscreen: adapters 0/1 are the real MAIN/SMALL group heads.
+    // Keep only LEFT/RIGHT fake, with their adapter ids matching the D3D9 wrapper.
+    static constexpr FakeMonitor FAKE_MONITORS_TWO_HEAD[] = {
+        { 2, 1080, 1920, -200000, -200000, 0 }, // left  (DP connector instance 0)
+        { 3, 1080, 1920, -300000, -300000, 1 }, // right (DP connector instance 1)
+    };
+
+    static std::span<const FakeMonitor> get_fake_monitors() {
+        if (is_two_head_exclusive()) {
+            return FAKE_MONITORS_TWO_HEAD;
+        }
+
+        return FAKE_MONITORS_SINGLE_HEAD;
+    }
+
+    static UINT32 real_monitor_count() {
+        return is_two_head_exclusive() ? 2 : 1;
+    }
 
     // call QueryDisplayConfig once, keep only the primary monitor's path and its
     // two referenced modes (source + target). modeInfoIdx values are rewritten to
@@ -369,13 +411,55 @@ namespace games::gitadora {
             log_fatal("gitadora", "cache_primary_monitor_info: no primary monitor found");
         }
 
+        if (primary->targetInfo.modeInfoIdx >= all_modes.size()) {
+            log_fatal("gitadora", "cache_primary_monitor_info: primary target mode is missing");
+        }
+
         real_primary_modes[0] = all_modes[primary->sourceInfo.modeInfoIdx];
         real_primary_modes[1] = all_modes[primary->targetInfo.modeInfoIdx];
         real_primary_path = *primary;
         real_primary_path.sourceInfo.modeInfoIdx = 0;
         real_primary_path.targetInfo.modeInfoIdx = 1;
 
-        log_info("gitadora", "cache_primary_monitor_info: cached primary monitor");
+        real_small_path_available = false;
+        if (is_two_head_exclusive()) {
+            if (all_paths.size() != 2) {
+                log_fatal(
+                    "gitadora",
+                    "two-head fullscreen mode requires exactly two active display paths, found {}",
+                    all_paths.size());
+            }
+
+            const auto secondary = std::find_if(all_paths.begin(), all_paths.end(),
+                [&](const auto &p) {
+                    return &p != &*primary;
+                });
+            if (secondary == all_paths.end() ||
+                    secondary->sourceInfo.modeInfoIdx >= all_modes.size() ||
+                    secondary->targetInfo.modeInfoIdx >= all_modes.size()) {
+                log_fatal("gitadora", "could not identify the physical SMALL monitor");
+            }
+            const LUID primary_adapter = primary->sourceInfo.adapterId;
+            const LUID secondary_adapter = secondary->sourceInfo.adapterId;
+            const bool same_adapter = primary_adapter.HighPart == secondary_adapter.HighPart &&
+                primary_adapter.LowPart == secondary_adapter.LowPart;
+            if (!same_adapter) {
+                log_fatal(
+                    "gitadora",
+                    "MAIN and SMALL must use the same display adapter");
+            }
+
+            real_small_modes[0] = all_modes[secondary->sourceInfo.modeInfoIdx];
+            real_small_modes[1] = all_modes[secondary->targetInfo.modeInfoIdx];
+            real_small_path = *secondary;
+            real_small_path.sourceInfo.modeInfoIdx = 2;
+            real_small_path.targetInfo.modeInfoIdx = 3;
+            real_small_path_available = true;
+
+            log_info("gitadora", "cache_primary_monitor_info: cached real MAIN and SMALL monitors");
+        } else {
+            log_info("gitadora", "cache_primary_monitor_info: cached primary monitor");
+        }
     }
 
     static
@@ -390,33 +474,36 @@ namespace games::gitadora {
         static std::once_flag populate_once;
         std::call_once(populate_once, cache_primary_monitor_info);
 
-        // always report exactly 1 real + N fake monitors
-        *pNumPathArrayElements = 1 + FAKE_MONITOR_COUNT;
-        *pNumModeInfoArrayElements = 2 + FAKE_MONITOR_COUNT * 2;
+        const auto fake_monitors = get_fake_monitors();
+        const auto fake_count = static_cast<UINT32>(fake_monitors.size());
+        const UINT32 real_count = real_monitor_count();
+        *pNumPathArrayElements = real_count + fake_count;
+        *pNumModeInfoArrayElements = (real_count + fake_count) * 2;
 
         log_info(
             "gitadora",
-            "GetDisplayConfigBufferSizes: 1 real path + {} fake monitor(s)",
-            FAKE_MONITOR_COUNT);
+            "GetDisplayConfigBufferSizes: {} real path(s) + {} fake monitor(s)",
+            real_count,
+            fake_count);
 
         return ERROR_SUCCESS;
     }
 
-    // write fake monitor i into the caller's path/mode arrays. layout (single-monitor
-    // assumption): index 0 in both arrays holds the cached primary real monitor, so
-    // fake i occupies path slot (1 + i) and mode slots (2 + i*2) / (2 + i*2 + 1).
+    // Write a fake monitor after the real paths. The cache is packed as [source, target]
+    // mode pairs, so each path consumes two mode entries.
     static void insert_fake_monitor(
         DISPLAYCONFIG_PATH_INFO *paths,
         DISPLAYCONFIG_MODE_INFO *modes,
-        UINT32 i)
+        const FakeMonitor &m,
+        UINT32 path_index,
+        UINT32 source_mode_index)
     {
-        const FakeMonitor &m = FAKE_MONITORS[i];
-        const UINT32 src_idx = 2 + i * 2;
+        const UINT32 src_idx = source_mode_index;
         const UINT32 tgt_idx = src_idx + 1;
         const LUID adapter_id { .LowPart = static_cast<DWORD>(-m.id), .HighPart = -m.id };
         const UINT32 uid = static_cast<UINT32>(-m.id);
 
-        paths[1 + i] = {
+        paths[path_index] = {
             .sourceInfo = {
                 .adapterId = adapter_id,
                 .id = uid,
@@ -474,21 +561,35 @@ namespace games::gitadora {
         DISPLAYCONFIG_MODE_INFO* modeInfoArray,
         DISPLAYCONFIG_TOPOLOGY_ID* currentTopologyId)
     {
-        // copy cached primary real monitor into caller buffers at index 0
+        // Copy cached real monitor paths into the caller buffers.
         pathArray[0] = real_primary_path;
         modeInfoArray[0] = real_primary_modes[0];
         modeInfoArray[1] = real_primary_modes[1];
-        *numPathArrayElements = 1 + FAKE_MONITOR_COUNT;
-        *numModeInfoArrayElements = 2 + FAKE_MONITOR_COUNT * 2;
+        if (is_two_head_exclusive() && real_small_path_available) {
+            pathArray[1] = real_small_path;
+            modeInfoArray[2] = real_small_modes[0];
+            modeInfoArray[3] = real_small_modes[1];
+        }
+
+        const auto fake_monitors = get_fake_monitors();
+        const auto fake_count = static_cast<UINT32>(fake_monitors.size());
+        const UINT32 real_count = real_monitor_count();
+        *numPathArrayElements = real_count + fake_count;
+        *numModeInfoArrayElements = (real_count + fake_count) * 2;
         if (currentTopologyId != nullptr) {
             *currentTopologyId = DISPLAYCONFIG_TOPOLOGY_EXTEND;
         }
 
         log_misc("gitadora", "QueryDisplayConfig returning fake monitor paths and modes");
 
-        // append fake monitors after the real one
-        for (UINT32 i = 0; i < FAKE_MONITOR_COUNT; i++) {
-            insert_fake_monitor(pathArray, modeInfoArray, i);
+        // Append fake monitors after the real path(s).
+        for (UINT32 i = 0; i < fake_count; i++) {
+            insert_fake_monitor(
+                pathArray,
+                modeInfoArray,
+                fake_monitors[i],
+                real_count + i,
+                real_count * 2 + i * 2);
         }
 
         return ERROR_SUCCESS;
@@ -519,7 +620,8 @@ namespace games::gitadora {
                 const auto targetName = reinterpret_cast<DISPLAYCONFIG_TARGET_DEVICE_NAME*>(requestPacket);
                 const LONG fake_id = -id;
                 UINT32 conn_inst = 0xff;
-                for (const auto& f : FAKE_MONITORS) {
+                const auto fake_monitors = get_fake_monitors();
+                for (const auto &f : fake_monitors) {
                     if (f.id == fake_id) {
                         conn_inst = f.connector_instance;
                         break;
@@ -542,18 +644,27 @@ namespace games::gitadora {
             return ret;
         }
 
-        // override the cached primary real monitor target info to look like HDMI/0
+        // Override MAIN to HDMI/0 and retag the real second head as the DP/2 SMALL
+        // display expected by the cabinet software in two-head fullscreen mode.
         const auto targetName = reinterpret_cast<DISPLAYCONFIG_TARGET_DEVICE_NAME*>(requestPacket);
-        const auto& target = real_primary_path.targetInfo;
-        if (target.id == targetName->header.id &&
-            target.adapterId.HighPart == targetName->header.adapterId.HighPart &&
-            target.adapterId.LowPart == targetName->header.adapterId.LowPart)
-        {
+        const auto target_matches = [&](const DISPLAYCONFIG_PATH_TARGET_INFO &target) {
+            return target.id == targetName->header.id &&
+                target.adapterId.HighPart == targetName->header.adapterId.HighPart &&
+                target.adapterId.LowPart == targetName->header.adapterId.LowPart;
+        };
+        if (target_matches(real_primary_path.targetInfo)) {
             targetName->outputTechnology = DISPLAYCONFIG_OUTPUT_TECHNOLOGY_HDMI;
             targetName->connectorInstance = 0;
             log_info("gitadora",
                 "overriding primary monitor (id={}) to pretend to be HDMI",
                 targetName->header.id);
+        } else if (is_two_head_exclusive() && real_small_path_available &&
+                target_matches(real_small_path.targetInfo)) {
+            targetName->outputTechnology = DISPLAYCONFIG_OUTPUT_TECHNOLOGY_DISPLAYPORT_EXTERNAL;
+            targetName->connectorInstance = 2;
+            log_info("gitadora",
+                "overriding secondary monitor (id={}) to pretend to be SMALL DP/2",
+                targetName->header.id);
         }
         return ret;
     }
@@ -651,7 +762,8 @@ namespace games::gitadora {
                 hooks::audio::INJECT_FAKE_REALTEK_AUDIO = true;
             }
 
-            // monitor/touch hooks (windowed or full screen)
+            // Single-window mode needs touch injection for its overlay. Two-head fullscreen
+            // mode uses the real SMALL output, so it only needs the display-topology shim.
             if (GRAPHICS_PREVENT_SECONDARY_WINDOWS) {
                 // enable touch hook for subscreen overlay
                 const auto native_touch_ready = !wintouchemu::FORCE &&
@@ -661,25 +773,28 @@ namespace games::gitadora {
                     wintouchemu::INJECT_MOUSE_AS_WM_TOUCH = true;
                     wintouchemu::hook("GITADORA", avs::game::DLL_INSTANCE);
                 }
+            }
 
 #if !SPICE_XP
 
-                if (!GRAPHICS_WINDOWED) {
-                    // monitor hook: always pretend to have 1 primary real monitor + 3 fake monitors
-                    // (LEFT / RIGHT / SMALL) so the game accepts the arena cab topology
-                    GetDisplayConfigBufferSizes_orig =
-                        detour::iat_try("GetDisplayConfigBufferSizes",
-                            GetDisplayConfigBufferSizes_hook, avs::game::DLL_INSTANCE);
-                    QueryDisplayConfig_orig =
-                        detour::iat_try("QueryDisplayConfig",
-                            QueryDisplayConfig_hook, avs::game::DLL_INSTANCE);
-                    DisplayConfigGetDeviceInfo_orig =
-                        detour::iat_try("DisplayConfigGetDeviceInfo",
-                            DisplayConfigGetDeviceInfo_hook, avs::game::DLL_INSTANCE);
+            if (!GRAPHICS_WINDOWED &&
+                    (GRAPHICS_PREVENT_SECONDARY_WINDOWS || ARENA_TWO_HEAD_EXCLUSIVE)) {
+                if (ARENA_TWO_HEAD_EXCLUSIVE) {
+                    log_info(
+                        "gitadora",
+                        "exposing physical MAIN/SMALL and virtual LEFT/RIGHT");
                 }
-#endif
-
+                GetDisplayConfigBufferSizes_orig =
+                    detour::iat_try("GetDisplayConfigBufferSizes",
+                        GetDisplayConfigBufferSizes_hook, avs::game::DLL_INSTANCE);
+                QueryDisplayConfig_orig =
+                    detour::iat_try("QueryDisplayConfig",
+                        QueryDisplayConfig_hook, avs::game::DLL_INSTANCE);
+                DisplayConfigGetDeviceInfo_orig =
+                    detour::iat_try("DisplayConfigGetDeviceInfo",
+                        DisplayConfigGetDeviceInfo_hook, avs::game::DLL_INSTANCE);
             }
+#endif
         }
 
         // window patch

src/spice2x/games/gitadora/gitadora.h

@@ -19,6 +19,7 @@ namespace games::gitadora {
     extern std::optional<std::string> SUBSCREEN_OVERLAY_SIZE;
     extern std::optional<socd::SocdAlgorithm> PICK_ALGO;
     extern std::optional<uint8_t> ARENA_WINDOW_COUNT;
+    extern bool ARENA_TWO_HEAD_EXCLUSIVE;
     extern std::optional<std::string> ASIO_DRIVER;
     extern bool ALLOW_REALTEK_AUDIO;
 

src/spice2x/hooks/graphics/backends/d3d9/d3d9_backend.cpp

@@ -113,7 +113,10 @@ static Direct3DCreate9On12Ex_t Direct3DCreate9On12Ex_orig = nullptr;
 static bool ATTEMPTED_SUB_SWAP_CHAIN_ACQUIRE = false;
 static IDirect3DSwapChain9 *SUB_SWAP_CHAIN = nullptr;
 
-static void graphics_d3d9_ldj_init_sub_screen(IDirect3DDevice9Ex *device, D3DPRESENT_PARAMETERS *present_params);
+static void graphics_d3d9_ldj_init_sub_screen(
+        IDirect3DDevice9Ex *device,
+        D3DPRESENT_PARAMETERS *present_params,
+        UINT gfdm_small_swapchain);
 
 static std::string behavior2s(DWORD behavior_flags) {
     FLAGS_START(behavior_flags);
@@ -409,7 +412,8 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::QueryInterface(
         return E_POINTER;
     }
 
-    if (riid == IID_WrappedIDirect3D9 ||
+    if ((riid == IID_IUnknown && gfdm_two_head_exclusive()) ||
+        riid == IID_WrappedIDirect3D9 ||
         riid == IID_IDirect3D9 ||
         riid == IID_IDirect3D9Ex)
     {
@@ -467,6 +471,18 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::RegisterSoftwareDevice(void *pIniti
 UINT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterCount() {
     UINT result = pReal->GetAdapterCount();
 
+    if (gfdm_two_head_exclusive()) {
+        if (result == 2) {
+            FAKE_SUBSCREEN_ADAPTER = true;
+            return GFDM_LOGICAL_HEAD_COUNT;
+        }
+        log_warning(
+                "graphics::d3d9",
+                "two-head mode requires two native adapters; found {}",
+                result);
+        return result;
+    }
+
     if (!FAKE_SUBSCREEN_ADAPTER) {
         if (games::popn::is_pikapika_model() && result == 1) {
             FAKE_SUBSCREEN_ADAPTER = true;
@@ -493,7 +509,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterIdentifier(
         D3DADAPTER_IDENTIFIER9 *pIdentifier)
 {
 
-    if (FAKE_SUBSCREEN_ADAPTER && Adapter > 0 && pIdentifier) {
+    if (is_fake_subscreen_adapter(Adapter) && pIdentifier) {
         *pIdentifier = {};
         const std::string adapter_name = fmt::format("\\\\.\\DISPLAY_SPICE_FAKE_{}", Adapter);
         strcpy(pIdentifier->DeviceName, adapter_name.c_str()); 
@@ -509,7 +525,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterIdentifier(
 }
 
 UINT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterModeCount(UINT Adapter, D3DFORMAT Format) {
-    if (FAKE_SUBSCREEN_ADAPTER && Adapter > 0) {
+    if (is_fake_subscreen_adapter(Adapter)) {
         log_misc("graphics::d3d9", "GetAdapterModeCount called for fake subscreen adapter {}", Adapter);
         return 1;
     }
@@ -523,13 +539,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::EnumAdapterModes(
         UINT Mode,
         D3DDISPLAYMODE *pMode)
 {
-    if (FAKE_SUBSCREEN_ADAPTER && Adapter > 0) {
+    if (is_fake_subscreen_adapter(Adapter)) {
         log_misc("graphics::d3d9", "EnumAdapterModes called for fake subscreen adapter {}", Adapter);
         if (Mode == 0 && pMode) {
-            pMode->Width = 1280;
-            pMode->Height = 800;
-            pMode->RefreshRate = 60;
-            pMode->Format = D3DFMT_X8R8G8B8;
+            get_fake_subscreen_display_mode(Adapter, pMode);
             return S_OK;
         } else {
             return D3DERR_INVALIDCALL;
@@ -611,6 +624,14 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::EnumAdapterModes(
 }
 
 HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterDisplayMode(UINT Adapter, D3DDISPLAYMODE *pMode) {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        if (pMode == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        get_fake_subscreen_display_mode(Adapter, pMode);
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->GetAdapterDisplayMode(Adapter, pMode));
 }
 
@@ -621,6 +642,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CheckDeviceType(
         D3DFORMAT BackBufferFormat,
         BOOL bWindowed)
 {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(iAdapter)) {
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->CheckDeviceType(iAdapter, DevType, DisplayFormat, BackBufferFormat, bWindowed));
 }
 
@@ -632,7 +657,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CheckDeviceFormat(
         D3DRESOURCETYPE RType,
         D3DFORMAT CheckFormat)
 {
-    if (FAKE_SUBSCREEN_ADAPTER && Adapter > 0) {
+    if (is_fake_subscreen_adapter(Adapter)) {
         log_misc("graphics::d3d9", "CheckDeviceFormat called for fake subscreen adapter {}", Adapter);
         return D3D_OK;
     }
@@ -648,6 +673,13 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CheckDeviceMultiSampleType(
         D3DMULTISAMPLE_TYPE MultiSampleType,
         DWORD *pQualityLevels)
 {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        if (pQualityLevels != nullptr) {
+            *pQualityLevels = 1;
+        }
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->CheckDeviceMultiSampleType(
             Adapter,
             DeviceType,
@@ -664,6 +696,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CheckDepthStencilMatch(
         D3DFORMAT RenderTargetFormat,
         D3DFORMAT DepthStencilFormat)
 {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->CheckDepthStencilMatch(
             Adapter,
             DeviceType,
@@ -678,6 +714,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CheckDeviceFormatConversion(
         D3DFORMAT SourceFormat,
         D3DFORMAT TargetFormat)
 {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->CheckDeviceFormatConversion(Adapter, DeviceType, SourceFormat, TargetFormat));
 }
 
@@ -689,6 +729,20 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetDeviceCaps(UINT Adapter, D3DDEVT
         return D3DERR_INVALIDCALL;
     }
 
+    if (gfdm_two_head_exclusive() && Adapter < GFDM_LOGICAL_HEAD_COUNT) {
+        HRESULT ret = this->pReal->GetDeviceCaps(
+                Adapter >= 2 ? 0 : Adapter,
+                DeviceType,
+                pCaps);
+        if (SUCCEEDED(ret)) {
+            pCaps->NumberOfAdaptersInGroup =
+                    Adapter == 0 ? GFDM_LOGICAL_HEAD_COUNT : 0;
+            pCaps->MasterAdapterOrdinal = 0;
+            pCaps->AdapterOrdinalInGroup = Adapter;
+        }
+        return ret;
+    }
+
     // SDVX uses `NumberOfAdaptersInGroup` to allocate a vector and the Microsoft documentation states:
     // "The value will be 0 for a subordinate adapter of a multihead card. Each card can have at most one
     // master, but may have many subordinates." Therefore, this must point to the master adapter.
@@ -741,6 +795,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetDeviceCaps(UINT Adapter, D3DDEVT
 }
 
 HMONITOR STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterMonitor(UINT Adapter) {
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        return pReal->GetAdapterMonitor(0);
+    }
+
     return pReal->GetAdapterMonitor(Adapter);
 }
 
@@ -861,7 +919,8 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDevice(
             "either use -graphics-force-refresh option or change the desktop resolution beforehand.");
     }
 
-    if (!GRAPHICS_WINDOWED && num_adapters >= 2 && GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
+    if (!GRAPHICS_WINDOWED && num_adapters >= 2
+            && GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
         log_info("graphics::d3d9", "force sub refresh rate: {} => {} Hz (-graphics-force-refresh-sub option)",
                 pPresentationParameters[1].FullScreen_RefreshRateInHz,
                 GRAPHICS_FORCE_REFRESH_SUB.value());
@@ -902,7 +961,9 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDevice(
     } else if (!D3D9_DEVICE_HOOK_DISABLE) {
         graphics_hook_window(hFocusWindow, pPresentationParameters);
 
-        *ppReturnedDeviceInterface = new WrappedIDirect3DDevice9(hFocusWindow, *ppReturnedDeviceInterface);
+        *ppReturnedDeviceInterface = new WrappedIDirect3DDevice9(
+                hFocusWindow,
+                *ppReturnedDeviceInterface);
     }
 
     // return result
@@ -916,6 +977,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDevice(
 UINT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterModeCountEx(UINT Adapter, const D3DDISPLAYMODEFILTER *pFilter) {
     assert(is_d3d9ex);
 
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        return 1;
+    }
+
     return static_cast<IDirect3D9Ex *>(pReal)->GetAdapterModeCountEx(Adapter, pFilter);
 }
 
@@ -926,6 +991,14 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::EnumAdapterModesEx(
         D3DDISPLAYMODEEX *pMode)
 {
     assert(is_d3d9ex);
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        if (Mode != 0 || pMode == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        get_fake_subscreen_display_mode_ex(Adapter, pMode);
+        return D3D_OK;
+    }
+
     CHECK_RESULT(static_cast<IDirect3D9Ex *>(pReal)->EnumAdapterModesEx(Adapter, pFilter, Mode, pMode));
 }
 
@@ -935,6 +1008,17 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterDisplayModeEx(
         D3DDISPLAYROTATION *pRotation)
 {
     assert(is_d3d9ex);
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        if (pMode == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        get_fake_subscreen_display_mode_ex(Adapter, pMode);
+        if (pRotation != nullptr) {
+            *pRotation = D3DDISPLAYROTATION_IDENTITY;
+        }
+        return D3D_OK;
+    }
+
     CHECK_RESULT(static_cast<IDirect3D9Ex *>(pReal)->GetAdapterDisplayModeEx(Adapter, pMode, pRotation));
 }
 
@@ -963,6 +1047,14 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
 
         return D3DERR_INVALIDCALL;
     }
+    if (gfdm_two_head_exclusive() && GRAPHICS_FS_CUSTOM_RESOLUTION_SUB.has_value()) {
+        log_warning(
+                "graphics::d3d9",
+                "-forceressub is unavailable; SMALL must remain {}x{}",
+                GFDM_SMALL_WIDTH,
+                GFDM_SMALL_HEIGHT);
+        return D3DERR_INVALIDCALL;
+    }
 
     DWORD orig_behavior_flags = BehaviorFlags;
     size_t num_adapters = 1;
@@ -989,6 +1081,9 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
         if (SUCCEEDED(this->pReal->GetDeviceCaps(Adapter, DeviceType, &device_caps))) {
             num_adapters = device_caps.NumberOfAdaptersInGroup;
         }
+        if (gfdm_two_head_exclusive()) {
+            num_adapters = GFDM_LOGICAL_HEAD_COUNT;
+        }
     }
 
     for (size_t i = 0; i < num_adapters; i++) {
@@ -1105,7 +1200,8 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
         }
     }
 
-    if (!GRAPHICS_WINDOWED && num_adapters >= 2 && GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
+    if (!GRAPHICS_WINDOWED && !gfdm_two_head_exclusive()
+            && num_adapters >= 2 && GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
         log_info("graphics::d3d9", "force sub refresh rate: {} => {} Hz (-graphics-force-refresh-sub option)",
                 pPresentationParameters[1].FullScreen_RefreshRateInHz,
                 GRAPHICS_FORCE_REFRESH_SUB.value());
@@ -1131,16 +1227,93 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
         pPresentationParameters->BackBufferCount = GRAPHICS_FORCE_VSYNC_BUFFER.value();
     }
 
+    GfdmTwoHeadDeviceState gfdm_parameters(
+            pPresentationParameters,
+            pFullscreenDisplayMode);
+    if (gfdm_two_head_exclusive()) {
+        if (!(BehaviorFlags & D3DCREATE_ADAPTERGROUP_DEVICE)) {
+            log_warning(
+                    "graphics::d3d9",
+                    "CreateDeviceEx did not request an adapter-group device");
+            return D3DERR_NOTAVAILABLE;
+        }
+        HRESULT select = graphics_d3d9_gfdm_select_two_head_group_parameters(
+                pPresentationParameters,
+                pFullscreenDisplayMode,
+                gfdm_parameters.native_presentation_parameters.data(),
+                gfdm_parameters.native_fullscreen_display_modes.data(),
+                &gfdm_parameters.logical_small_swapchain,
+                "CreateDeviceEx");
+        if (FAILED(select)) {
+            return select;
+        }
+        if (GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
+            gfdm_parameters.native_presentation_parameters[1]
+                    .FullScreen_RefreshRateInHz =
+                    GRAPHICS_FORCE_REFRESH_SUB.value();
+            if (pFullscreenDisplayMode != nullptr) {
+                gfdm_parameters.native_fullscreen_display_modes[1].RefreshRate =
+                        GRAPHICS_FORCE_REFRESH_SUB.value();
+            }
+        }
+        HRESULT remap = graphics_d3d9_gfdm_remap_two_head_group_parameters(
+                gfdm_parameters.native_presentation_parameters.data(),
+                pFullscreenDisplayMode != nullptr
+                        ? gfdm_parameters.native_fullscreen_display_modes.data()
+                        : nullptr,
+                "CreateDeviceEx");
+        if (FAILED(remap)) {
+            return remap;
+        }
+        if (pFullscreenDisplayMode != nullptr) {
+            graphics_d3d9_gfdm_align_two_head_refresh_to_desktop(
+                    static_cast<IDirect3D9Ex *>(this->pReal),
+                    Adapter,
+                    gfdm_parameters.native_presentation_parameters.data(),
+                    gfdm_parameters.native_fullscreen_display_modes.data(),
+                    "CreateDeviceEx");
+        }
+        if (!graphics_gitadora_prepare_two_head_device_window(
+                    gfdm_parameters.native_presentation_parameters[1].hDeviceWindow,
+                    this->pReal->GetAdapterMonitor(Adapter + 1),
+                    gfdm_parameters.native_presentation_parameters[1].BackBufferWidth,
+                    gfdm_parameters.native_presentation_parameters[1].BackBufferHeight))
+        {
+            return D3DERR_INVALIDCALL;
+        }
+        HRESULT validation = validate_gfdm_two_head_exclusive(
+                this->pReal,
+                Adapter,
+                DeviceType,
+                BehaviorFlags,
+                gfdm_parameters.native_presentation_parameters.data());
+        if (FAILED(validation)) {
+            return validation;
+        }
+        gfdm_parameters.use_native_parameters();
+    }
+
     // call original
     HRESULT result = static_cast<IDirect3D9Ex *>(this->pReal)->CreateDeviceEx(
             Adapter,
             DeviceType,
             hFocusWindow,
             BehaviorFlags,
-            pPresentationParameters,
-            pFullscreenDisplayMode,
+            gfdm_parameters.presentation_parameters,
+            gfdm_parameters.fullscreen_display_modes,
             ppReturnedDeviceInterface);
 
+    if (SUCCEEDED(result) && gfdm_two_head_exclusive()) {
+        pPresentationParameters[0] = gfdm_parameters.presentation_parameters[0];
+        pPresentationParameters[gfdm_parameters.logical_small_swapchain] =
+                gfdm_parameters.presentation_parameters[1];
+        if (pFullscreenDisplayMode != nullptr) {
+            pFullscreenDisplayMode[0] = gfdm_parameters.fullscreen_display_modes[0];
+            pFullscreenDisplayMode[gfdm_parameters.logical_small_swapchain] =
+                    gfdm_parameters.fullscreen_display_modes[1];
+        }
+    }
+
     // check for error
     if (result != D3D_OK) {
 
@@ -1151,17 +1324,28 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
     } else if (!D3D9_DEVICE_HOOK_DISABLE) {
         graphics_hook_window(hFocusWindow, pPresentationParameters);
 
-        *ppReturnedDeviceInterface = new WrappedIDirect3DDevice9(hFocusWindow, *ppReturnedDeviceInterface);
+        *ppReturnedDeviceInterface = new WrappedIDirect3DDevice9(
+                hFocusWindow,
+                *ppReturnedDeviceInterface,
+                gfdm_parameters.logical_small_swapchain,
+                gfdm_two_head_exclusive() ? static_cast<IDirect3D9 *>(this) : nullptr,
+                gfdm_two_head_exclusive() ? pPresentationParameters : nullptr);
 
         // initialize sub screen if the game requested a multi-head context
         if (avs::game::is_model({"LDJ", "KFC", "M39", "M32"}) &&
             (orig_behavior_flags & D3DCREATE_ADAPTERGROUP_DEVICE)) {
 
-            UINT i = 1;
-            if (games::gitadora::is_arena_model()) {
-                i = 2;
-            }
-            graphics_d3d9_ldj_init_sub_screen(*ppReturnedDeviceInterface, &pPresentationParameters[i]);
+            UINT i = games::gitadora::is_arena_model()
+                    ? gfdm_parameters.logical_small_swapchain
+                    : 1;
+            D3DPRESENT_PARAMETERS *subscreen_parameters =
+                    gfdm_two_head_exclusive()
+                    ? &gfdm_parameters.presentation_parameters[1]
+                    : &pPresentationParameters[i];
+            graphics_d3d9_ldj_init_sub_screen(
+                    *ppReturnedDeviceInterface,
+                    subscreen_parameters,
+                    i);
         }
     }
 
@@ -1170,6 +1354,14 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::CreateDeviceEx(
 
 HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterLUID(UINT Adapter, LUID *pLUID) {
     assert(is_d3d9ex);
+    if (gfdm_two_head_exclusive() && is_fake_subscreen_adapter(Adapter)) {
+        if (pLUID == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        pLUID->LowPart = static_cast<DWORD>(-static_cast<LONG>(Adapter));
+        pLUID->HighPart = -static_cast<LONG>(Adapter);
+        return D3D_OK;
+    }
     CHECK_RESULT(static_cast<IDirect3D9Ex *>(pReal)->GetAdapterLUID(Adapter, pLUID));
 }
 
@@ -1178,7 +1370,11 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3D9::GetAdapterLUID(UINT Adapter, LUID *
 // The sub screen swap chain should be created if:
 // - Running windowed with `NumberOfAdaptersInGroup >= 2` (game expects implicit swap chain to exist)
 // - Running fullscreen with `NumberOfAdaptersInGroup < 2` (overridden `GetDeviceCaps` structure)
-static void graphics_d3d9_ldj_init_sub_screen(IDirect3DDevice9Ex *device, D3DPRESENT_PARAMETERS *present_params) {
+static void graphics_d3d9_ldj_init_sub_screen(
+        IDirect3DDevice9Ex *device,
+        D3DPRESENT_PARAMETERS *present_params,
+        UINT gfdm_small_swapchain)
+{
     D3DCAPS9 caps {};
     HRESULT hr = device->GetDeviceCaps(&caps);
     if (FAILED(hr)) {
@@ -1212,10 +1408,9 @@ static void graphics_d3d9_ldj_init_sub_screen(IDirect3DDevice9Ex *device, D3DPRE
         }
     } else {
 
-        int swapchain = 1;
-        if (games::gitadora::is_arena_model()) {
-            swapchain = 2;
-        }
+        const int swapchain = games::gitadora::is_arena_model()
+                ? static_cast<int>(gfdm_small_swapchain)
+                : 1;
 
         hr = device->GetSwapChain(swapchain, &SUB_SWAP_CHAIN);
         if (FAILED(hr)) {

src/spice2x/hooks/graphics/backends/d3d9/d3d9_backend.h

@@ -2,6 +2,8 @@
 
 #include <d3d9.h>
 
+#include "d3d9_gfdm.h"
+
 // {EEE9CCF6-53D6-4326-9AE5-60921B3DB394}
 static const GUID IID_WrappedIDirect3D9 = {
     0xeee9ccf6, 0x53d6, 0x4326, { 0x9a, 0xe5, 0x60, 0x92, 0x1b, 0x3d, 0xb3, 0x94 }

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.cpp

@@ -41,7 +41,6 @@
 constexpr bool CUSTOM_RESET = false;
 
 constexpr D3DFORMAT D3DFMT_DF24 = static_cast<D3DFORMAT>(MAKEFOURCC('D', 'F', '2', '4'));
-
 auto format_as(D3DPOOL f) {
     return fmt::underlying(f);
 }
@@ -85,7 +84,8 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::QueryInterface(
         return E_POINTER;
     }
 
-    if (riid == IID_WrappedIDirect3DDevice9 ||
+    if ((riid == IID_IUnknown && is_gfdm_two_head_exclusive()) ||
+        riid == IID_WrappedIDirect3DDevice9 ||
         riid == IID_IDirect3DDevice9 ||
         riid == IID_IDirect3DDevice9Ex)
     {
@@ -202,6 +202,15 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetDirect3D(
         IDirect3D9 **ppD3D9)
 {
     WRAP_VERBOSE;
+    if (is_gfdm_two_head_exclusive() && gfdm_parent_d3d != nullptr) {
+        if (ppD3D9 == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        gfdm_parent_d3d->AddRef();
+        *ppD3D9 = gfdm_parent_d3d;
+        return D3D_OK;
+    }
+
     CHECK_RESULT(pReal->GetDirect3D(ppD3D9));
 }
 
@@ -209,7 +218,13 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetDeviceCaps(
         D3DCAPS9 *pCaps)
 {
     WRAP_VERBOSE;
-    CHECK_RESULT(pReal->GetDeviceCaps(pCaps));
+    HRESULT result = pReal->GetDeviceCaps(pCaps);
+    if (SUCCEEDED(result) && is_gfdm_two_head_exclusive() && pCaps != nullptr) {
+        pCaps->NumberOfAdaptersInGroup = GFDM_LOGICAL_HEAD_COUNT;
+        pCaps->MasterAdapterOrdinal = 0;
+        pCaps->AdapterOrdinalInGroup = 0;
+    }
+    CHECK_RESULT(result);
 }
 
 HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetDisplayMode(
@@ -217,6 +232,17 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetDisplayMode(
         D3DDISPLAYMODE *pMode)
 {
     WRAP_VERBOSE;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return ensure_gfdm_hidden_side_swapchain(iSwapChain)->GetDisplayMode(pMode);
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(pReal->GetDisplayMode(GFDM_NATIVE_SMALL_SWAPCHAIN, pMode));
+    }
+
     CHECK_RESULT(pReal->GetDisplayMode(iSwapChain, pMode));
 }
 
@@ -258,6 +284,51 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::CreateAdditionalSwapChain(
 {
     WRAP_VERBOSE;
 
+    if (pPresentationParameters == nullptr || ppSwapChain == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (is_gfdm_two_head_exclusive()) {
+        if (pPresentationParameters->BackBufferWidth == 800) {
+            return GetSwapChain(gfdm_logical_small_swapchain, ppSwapChain);
+        }
+        if (pPresentationParameters->BackBufferWidth != 1080) {
+            log_warning(
+                    "graphics::d3d9",
+                    "two-head exclusive: rejecting unexpected additional swap chain {}x{}",
+                    pPresentationParameters->BackBufferWidth,
+                    pPresentationParameters->BackBufferHeight);
+            return D3DERR_INVALIDCALL;
+        }
+
+        size_t index = 3;
+        for (UINT logical_swapchain = 1;
+                logical_swapchain < GFDM_LOGICAL_HEAD_COUNT;
+                logical_swapchain++)
+        {
+            if (!is_gfdm_logical_side_swapchain(logical_swapchain)) {
+                continue;
+            }
+            const size_t candidate =
+                    gfdm_hidden_side_swapchain_slot(logical_swapchain);
+            if (fake_sub_swapchain[candidate] == nullptr) {
+                index = candidate;
+                break;
+            }
+        }
+        if (index == 3) {
+            return D3DERR_OUTOFVIDEOMEMORY;
+        }
+        fake_sub_swapchain[index] = new FakeIDirect3DSwapChain9(
+                this,
+                pPresentationParameters,
+                is_d3d9ex,
+                true);
+        fake_sub_swapchain[index]->AddRef();
+        *ppSwapChain = static_cast<IDirect3DSwapChain9 *>(fake_sub_swapchain[index]);
+        return D3D_OK;
+    }
+
     int index = 0;
     bool create_swap_chain = false;
     bool create_fake_swap_chain = false;
@@ -271,6 +342,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::CreateAdditionalSwapChain(
             // SMALL (subscreen)
             create_swap_chain = true;
             index = 0;
+
         } else if (pPresentationParameters->BackBufferWidth == 1080) {
             // LEFT/RIGHT
             create_swap_chain = true;
@@ -335,6 +407,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetSwapChain(
 {
     WRAP_VERBOSE_FMT("GetSwapChain({})", iSwapChain);
 
+    if (ppSwapChain == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
     if (iSwapChain == 0) {
         if (!main_swapchain) {
             HRESULT ret = pReal->GetSwapChain(iSwapChain, ppSwapChain);
@@ -344,7 +420,12 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetSwapChain(
                 return ret;
             }
 
-            main_swapchain = new WrappedIDirect3DSwapChain9(this, *ppSwapChain);
+            main_swapchain = new WrappedIDirect3DSwapChain9(
+                    this,
+                    *ppSwapChain,
+                    is_gfdm_two_head_exclusive()
+                            ? WrappedIDirect3DSwapChain9::NativeGroupHead::Main
+                            : WrappedIDirect3DSwapChain9::NativeGroupHead::Unknown);
         }
 
         main_swapchain->AddRef();
@@ -354,6 +435,39 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetSwapChain(
         return D3D_OK;
     }
 
+    if (is_gfdm_two_head_exclusive()) {
+        if (is_gfdm_logical_small_swapchain(iSwapChain)) {
+            if (!sub_swapchain[0]) {
+                IDirect3DSwapChain9 *real_swapchain = nullptr;
+                HRESULT ret = pReal->GetSwapChain(
+                        GFDM_NATIVE_SMALL_SWAPCHAIN,
+                        &real_swapchain);
+                if (FAILED(ret)) {
+                    return ret;
+                }
+                sub_swapchain[0] = new WrappedIDirect3DSwapChain9(
+                        this,
+                        real_swapchain,
+                        WrappedIDirect3DSwapChain9::NativeGroupHead::Small);
+                sub_swapchain[0]->should_run_hooks = false;
+            }
+
+            sub_swapchain[0]->AddRef();
+            *ppSwapChain = static_cast<IDirect3DSwapChain9 *>(sub_swapchain[0]);
+            graphics_screens_register(iSwapChain);
+            return D3D_OK;
+        }
+        if (is_gfdm_logical_side_swapchain(iSwapChain)) {
+            FakeIDirect3DSwapChain9 *swapchain =
+                    ensure_gfdm_hidden_side_swapchain(iSwapChain);
+            swapchain->AddRef();
+            *ppSwapChain = static_cast<IDirect3DSwapChain9 *>(swapchain);
+            graphics_screens_register(iSwapChain);
+            return D3D_OK;
+        }
+        return D3DERR_INVALIDCALL;
+    }
+
     bool swap = false;
     if (iSwapChain == 1 && avs::game::is_model({"LDJ", "KFC", "M39"})) {
         swap = true;
@@ -390,6 +504,10 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetSwapChain(
 UINT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetNumberOfSwapChains() {
     WRAP_VERBOSE;
 
+    if (is_gfdm_two_head_exclusive()) {
+        return GFDM_LOGICAL_HEAD_COUNT;
+    }
+
     UINT n = pReal->GetNumberOfSwapChains();
 
     if (sub_swapchain[0] && avs::game::is_model({"LDJ", "KFC", "M39"})) {
@@ -453,6 +571,24 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetBackBuffer(
         IDirect3DSurface9 **ppBackBuffer)
 {
     WRAP_VERBOSE;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return ensure_gfdm_hidden_side_swapchain(iSwapChain)->GetBackBuffer(
+                iBackBuffer,
+                Type,
+                ppBackBuffer);
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(pReal->GetBackBuffer(
+                GFDM_NATIVE_SMALL_SWAPCHAIN,
+                iBackBuffer,
+                Type,
+                ppBackBuffer));
+    }
+
     CHECK_RESULT(pReal->GetBackBuffer(iSwapChain, iBackBuffer, Type, ppBackBuffer));
 }
 
@@ -461,6 +597,20 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetRasterStatus(
         D3DRASTER_STATUS *pRasterStatus)
 {
     WRAP_DEBUG;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return ensure_gfdm_hidden_side_swapchain(iSwapChain)->GetRasterStatus(
+                pRasterStatus);
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(pReal->GetRasterStatus(
+                GFDM_NATIVE_SMALL_SWAPCHAIN,
+                pRasterStatus));
+    }
+
     CHECK_RESULT(pReal->GetRasterStatus(iSwapChain, pRasterStatus));
 }
 
@@ -477,6 +627,18 @@ void STDMETHODCALLTYPE WrappedIDirect3DDevice9::SetGammaRamp(
         const D3DGAMMARAMP *pRamp)
 {
     WRAP_DEBUG;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return;
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        pReal->SetGammaRamp(GFDM_NATIVE_SMALL_SWAPCHAIN, Flags, pRamp);
+        return;
+    }
+
     pReal->SetGammaRamp(iSwapChain, Flags, pRamp);
 }
 
@@ -485,6 +647,21 @@ void STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetGammaRamp(
         D3DGAMMARAMP *pRamp)
 {
     WRAP_DEBUG;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        if (pRamp != nullptr) {
+            *pRamp = {};
+        }
+        return;
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        pReal->GetGammaRamp(GFDM_NATIVE_SMALL_SWAPCHAIN, pRamp);
+        return;
+    }
+
     pReal->GetGammaRamp(iSwapChain, pRamp);
 }
 
@@ -685,6 +862,19 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetFrontBufferData(
         IDirect3DSurface9 *pDestSurface)
 {
     WRAP_DEBUG;
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return D3DERR_INVALIDCALL;
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(pReal->GetFrontBufferData(
+                GFDM_NATIVE_SMALL_SWAPCHAIN,
+                pDestSurface));
+    }
+
     CHECK_RESULT(pReal->GetFrontBufferData(iSwapChain, pDestSurface));
 }
 
@@ -1779,6 +1969,18 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::WaitForVBlank(
     WRAP_DEBUG;
 
     assert(is_d3d9ex);
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return D3D_OK;
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(static_cast<IDirect3DDevice9Ex *>(pReal)->WaitForVBlank(
+                GFDM_NATIVE_SMALL_SWAPCHAIN));
+    }
+
     CHECK_RESULT(static_cast<IDirect3DDevice9Ex *>(pReal)->WaitForVBlank(iSwapChain));
 }
 
@@ -1882,6 +2084,14 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::ResetEx(
 
     log_misc("graphics::d3d9", "WrappedIDirect3DDevice9::ResetEx");
 
+    if (is_gfdm_two_head_exclusive()) {
+        gfdm_disarm_present_mode_recovery();
+        if (pPresentationParameters == nullptr) {
+            return D3DERR_INVALIDCALL;
+        }
+        release_gfdm_hidden_side_swapchains();
+    }
+
     if (GRAPHICS_WINDOWED) {
         if (pPresentationParameters) {
             pPresentationParameters->Windowed = true;
@@ -1898,13 +2108,115 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::ResetEx(
         }
     }
 
+    GfdmTwoHeadDeviceState gfdm_parameters(
+            pPresentationParameters,
+            pFullscreenDisplayMode,
+            gfdm_logical_small_swapchain);
+    if (is_gfdm_two_head_exclusive()) {
+        HRESULT result = graphics_d3d9_gfdm_select_two_head_group_parameters(
+                pPresentationParameters,
+                pFullscreenDisplayMode,
+                gfdm_parameters.native_presentation_parameters.data(),
+                pFullscreenDisplayMode != nullptr
+                        ? gfdm_parameters.native_fullscreen_display_modes.data()
+                        : nullptr,
+                &gfdm_parameters.logical_small_swapchain,
+                "ResetEx");
+        if (FAILED(result)) {
+            return result;
+        }
+        set_gfdm_logical_group_parameters(pPresentationParameters);
+        gfdm_parameters.use_native_parameters();
+        if (gfdm_parameters.native_presentation_parameters[0].Windowed
+                || gfdm_parameters.native_presentation_parameters[1].Windowed)
+        {
+            return D3DERR_INVALIDCALL;
+        }
+        if (GRAPHICS_FORCE_REFRESH_SUB.has_value()) {
+            gfdm_parameters.native_presentation_parameters[1]
+                    .FullScreen_RefreshRateInHz =
+                    GRAPHICS_FORCE_REFRESH_SUB.value();
+            if (gfdm_parameters.fullscreen_display_modes != nullptr) {
+                gfdm_parameters.fullscreen_display_modes[1].RefreshRate =
+                        GRAPHICS_FORCE_REFRESH_SUB.value();
+            }
+        }
+        result = graphics_d3d9_gfdm_remap_two_head_group_parameters(
+                gfdm_parameters.native_presentation_parameters.data(),
+                gfdm_parameters.fullscreen_display_modes,
+                "ResetEx");
+        if (FAILED(result)) {
+            return result;
+        }
+        if (!graphics_gitadora_prepare_two_head_device_window(
+                    gfdm_parameters.native_presentation_parameters[1].hDeviceWindow,
+                    nullptr,
+                    gfdm_parameters.native_presentation_parameters[1].BackBufferWidth,
+                    gfdm_parameters.native_presentation_parameters[1].BackBufferHeight))
+        {
+            return D3DERR_INVALIDCALL;
+        }
+        if (gfdm_parameters.fullscreen_display_modes != nullptr) {
+            IDirect3D9 *raw_d3d = nullptr;
+            IDirect3D9Ex *raw_d3d_ex = nullptr;
+            D3DDEVICE_CREATION_PARAMETERS creation {};
+            HRESULT raw_result = pReal->GetDirect3D(&raw_d3d);
+            if (SUCCEEDED(raw_result) && raw_d3d != nullptr) {
+                raw_result = raw_d3d->QueryInterface(IID_PPV_ARGS(&raw_d3d_ex));
+            }
+            if (SUCCEEDED(raw_result)) {
+                raw_result = pReal->GetCreationParameters(&creation);
+            }
+            if (SUCCEEDED(raw_result) && raw_d3d_ex != nullptr) {
+                graphics_d3d9_gfdm_align_two_head_refresh_to_desktop(
+                        raw_d3d_ex,
+                        creation.AdapterOrdinal,
+                        gfdm_parameters.native_presentation_parameters.data(),
+                        gfdm_parameters.fullscreen_display_modes,
+                        "ResetEx");
+            }
+            if (raw_d3d_ex != nullptr) {
+                raw_d3d_ex->Release();
+            }
+            if (raw_d3d != nullptr) {
+                raw_d3d->Release();
+            }
+            gfdm_parameters.recovery_parameters =
+                    gfdm_parameters.native_presentation_parameters;
+            gfdm_parameters.recovery_modes =
+                    gfdm_parameters.native_fullscreen_display_modes;
+            gfdm_parameters.recovery_candidate = true;
+        }
+    }
+
     // reset overlay
     if (overlay::OVERLAY && overlay::OVERLAY->uses_device(pReal)) {
         overlay::OVERLAY->reset_invalidate();
     }
 
     HRESULT res = static_cast<IDirect3DDevice9Ex *>(pReal)->ResetEx(
-            pPresentationParameters, pFullscreenDisplayMode);
+            gfdm_parameters.presentation_parameters,
+            gfdm_parameters.fullscreen_display_modes);
+
+    if (is_gfdm_two_head_exclusive()
+            && SUCCEEDED(res)
+            && gfdm_parameters.recovery_candidate)
+    {
+        gfdm_arm_present_mode_recovery(
+                gfdm_parameters.recovery_parameters.data(),
+                gfdm_parameters.recovery_modes.data());
+    }
+    if (is_gfdm_two_head_exclusive() && SUCCEEDED(res)) {
+        gfdm_logical_small_swapchain = gfdm_parameters.logical_small_swapchain;
+        pPresentationParameters[0] = gfdm_parameters.presentation_parameters[0];
+        pPresentationParameters[gfdm_parameters.logical_small_swapchain] =
+                gfdm_parameters.presentation_parameters[1];
+        if (pFullscreenDisplayMode != nullptr) {
+            pFullscreenDisplayMode[0] = gfdm_parameters.fullscreen_display_modes[0];
+            pFullscreenDisplayMode[gfdm_parameters.logical_small_swapchain] =
+                    gfdm_parameters.fullscreen_display_modes[1];
+        }
+    }
 
     // recreate overlay
     if (overlay::OVERLAY && overlay::OVERLAY->uses_device(pReal) && SUCCEEDED(res)) {
@@ -1922,6 +2234,22 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DDevice9::GetDisplayModeEx(
     WRAP_DEBUG;
 
     assert(is_d3d9ex);
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_side_swapchain(iSwapChain))
+    {
+        return ensure_gfdm_hidden_side_swapchain(iSwapChain)->GetDisplayModeEx(
+                pMode,
+                pRotation);
+    }
+    if (is_gfdm_two_head_exclusive()
+            && is_gfdm_logical_small_swapchain(iSwapChain))
+    {
+        CHECK_RESULT(static_cast<IDirect3DDevice9Ex *>(pReal)->GetDisplayModeEx(
+                GFDM_NATIVE_SMALL_SWAPCHAIN,
+                pMode,
+                pRotation));
+    }
+
     CHECK_RESULT(static_cast<IDirect3DDevice9Ex *>(pReal)->GetDisplayModeEx(
             iSwapChain, pMode, pRotation));
 }

src/spice2x/hooks/graphics/backends/d3d9/d3d9_device.h

@@ -1,6 +1,8 @@
 #pragma once
 
+#include <array>
 #include <atomic>
+#include <mutex>
 
 #include <initguid.h>
 #include <d3d9.h>
@@ -40,23 +42,54 @@ static const GUID IID_WrappedIDirect3DDevice9 = {
 void SurfaceHook(IDirect3DDevice9 *pReal);
 
 struct WrappedIDirect3DDevice9 : IDirect3DDevice9Ex {
-    explicit WrappedIDirect3DDevice9(HWND hFocusWindow, IDirect3DDevice9 *orig)
-        : hFocusWindow(hFocusWindow), pReal(orig), is_d3d9ex(false) {
+    explicit WrappedIDirect3DDevice9(
+            HWND hFocusWindow,
+            IDirect3DDevice9 *orig,
+            UINT gfdm_logical_small_swapchain = 2,
+            IDirect3D9 *gfdm_parent_d3d = nullptr,
+            const D3DPRESENT_PARAMETERS *gfdm_logical_group_parameters = nullptr)
+        : hFocusWindow(hFocusWindow),
+          pReal(orig),
+          is_d3d9ex(false),
+          gfdm_logical_small_swapchain(gfdm_logical_small_swapchain),
+          gfdm_parent_d3d(gfdm_parent_d3d) {
+        if (this->gfdm_parent_d3d != nullptr) {
+            this->gfdm_parent_d3d->AddRef();
+        }
         IDirect3DDevice9Ex *device = nullptr;
 
         // attempt to upgrade handle
         if (SUCCEEDED(this->QueryInterface(IID_PPV_ARGS(&device))) && device != nullptr) {
             device->Release();
         }
+        set_gfdm_logical_group_parameters(gfdm_logical_group_parameters);
     }
 
-    explicit WrappedIDirect3DDevice9(HWND hFocusWindow, IDirect3DDevice9Ex *orig)
-        : hFocusWindow(hFocusWindow), pReal(orig), is_d3d9ex(true) {}
+    explicit WrappedIDirect3DDevice9(
+            HWND hFocusWindow,
+            IDirect3DDevice9Ex *orig,
+            UINT gfdm_logical_small_swapchain = 2,
+            IDirect3D9 *gfdm_parent_d3d = nullptr,
+            const D3DPRESENT_PARAMETERS *gfdm_logical_group_parameters = nullptr)
+        : hFocusWindow(hFocusWindow),
+          pReal(orig),
+          is_d3d9ex(true),
+          gfdm_logical_small_swapchain(gfdm_logical_small_swapchain),
+          gfdm_parent_d3d(gfdm_parent_d3d) {
+        if (this->gfdm_parent_d3d != nullptr) {
+            this->gfdm_parent_d3d->AddRef();
+        }
+        set_gfdm_logical_group_parameters(gfdm_logical_group_parameters);
+    }
 
     WrappedIDirect3DDevice9(const WrappedIDirect3DDevice9 &) = delete;
     WrappedIDirect3DDevice9 &operator=(const WrappedIDirect3DDevice9 &) = delete;
 
-    virtual ~WrappedIDirect3DDevice9() = default;
+    virtual ~WrappedIDirect3DDevice9() {
+        if (gfdm_parent_d3d != nullptr) {
+            gfdm_parent_d3d->Release();
+        }
+    }
 
 #pragma region IUnknown
     virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, void **ppvObj) override;
@@ -201,6 +234,27 @@ struct WrappedIDirect3DDevice9 : IDirect3DDevice9Ex {
     virtual HRESULT STDMETHODCALLTYPE GetDisplayModeEx(UINT iSwapChain, D3DDISPLAYMODEEX *pMode, D3DDISPLAYROTATION *pRotation) override;
 #pragma endregion
 
+    bool is_gfdm_two_head_exclusive() const;
+    bool is_gfdm_logical_small_swapchain(UINT swapchain) const;
+    bool is_gfdm_logical_side_swapchain(UINT swapchain) const;
+    size_t gfdm_hidden_side_swapchain_slot(UINT swapchain) const;
+    void set_gfdm_logical_group_parameters(
+            const D3DPRESENT_PARAMETERS *presentation_parameters);
+    FakeIDirect3DSwapChain9 *ensure_gfdm_hidden_side_swapchain(UINT iSwapChain);
+    void release_gfdm_hidden_side_swapchains();
+
+    enum class GfdmPresentModeRecoveryResult {
+        NotAttempted,
+        ReadyToRetry,
+        Failed,
+    };
+    void gfdm_disarm_present_mode_recovery();
+    void gfdm_arm_present_mode_recovery(
+            const D3DPRESENT_PARAMETERS *native_presentation_parameters,
+            const D3DDISPLAYMODEEX *native_fullscreen_display_modes);
+    GfdmPresentModeRecoveryResult gfdm_recover_present_mode_change(
+            HRESULT *failure_result);
+
     HWND const hFocusWindow;
     IDirect3DDevice9 *pReal;
     bool is_d3d9ex = false;
@@ -211,5 +265,17 @@ struct WrappedIDirect3DDevice9 : IDirect3DDevice9Ex {
     WrappedIDirect3DSwapChain9 *sub_swapchain[3] = { nullptr, nullptr, nullptr };
     FakeIDirect3DSwapChain9 *fake_sub_swapchain[3] = { nullptr, nullptr, nullptr };
 
+    UINT gfdm_logical_small_swapchain = 2;
+    std::array<D3DPRESENT_PARAMETERS, 4> gfdm_logical_group_parameters {};
+    bool gfdm_logical_group_parameters_valid = false;
+    IDirect3D9 *gfdm_parent_d3d = nullptr;
+
+    std::mutex gfdm_recovery_mutex;
+    std::array<D3DPRESENT_PARAMETERS, 2> gfdm_recovery_parameters {};
+    std::array<D3DDISPLAYMODEEX, 2> gfdm_recovery_modes {};
+    bool gfdm_recovery_armed = false;
+    std::atomic_bool gfdm_recovery_consumed {false};
+    const DWORD gfdm_device_creation_thread_id = GetCurrentThreadId();
+
     IDirect3DVertexShader9 *vertex_shader = nullptr;
 };

src/spice2x/hooks/graphics/backends/d3d9/d3d9_fake_swapchain.cpp

@@ -59,7 +59,12 @@ HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::Present(const RECT *pSourceRe
         log_misc("graphics::d3d9", "FakeIDirect3DSwapChain9::Present");
     });
 
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    present_count.fetch_add(1, std::memory_order_relaxed);
+    return D3D_OK;
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetFrontBufferData(IDirect3DSurface9 *pDestSurface) {
     WRAP_VERBOSE;
@@ -86,11 +91,32 @@ HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetBackBuffer(UINT iBackBuffe
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetRasterStatus(D3DRASTER_STATUS *pRasterStatus) {
     WRAP_VERBOSE;
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pRasterStatus == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    *pRasterStatus = {};
+    return D3D_OK;
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetDisplayMode(D3DDISPLAYMODE *pMode) {
     WRAP_VERBOSE;
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pMode == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    pMode->Width = present_params.BackBufferWidth;
+    pMode->Height = present_params.BackBufferHeight;
+    pMode->RefreshRate = present_params.FullScreen_RefreshRateInHz;
+    pMode->Format = present_params.BackBufferFormat;
+    return D3D_OK;
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetDevice(IDirect3DDevice9 **ppDevice) {
     WRAP_VERBOSE;
@@ -108,17 +134,46 @@ HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetPresentParameters(
         D3DPRESENT_PARAMETERS *pPresentationParameters)
 {
     WRAP_VERBOSE;
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pPresentationParameters == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    *pPresentationParameters = present_params;
+    return D3D_OK;
 }
 
 // IDirect3DSwapChain9Ex
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetLastPresentCount(UINT *pLastPresentCount) {
     assert(is_d3d9ex);
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pLastPresentCount == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    *pLastPresentCount = present_count.load(std::memory_order_relaxed);
+    return D3D_OK;
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetPresentStats(D3DPRESENTSTATS *pPresentationStatistics) {
     assert(is_d3d9ex);
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pPresentationStatistics == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    *pPresentationStatistics = {};
+    pPresentationStatistics->PresentCount =
+        present_count.load(std::memory_order_relaxed);
+    return D3D_OK;
 }
 HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetDisplayModeEx(D3DDISPLAYMODEEX *pMode,
         D3DDISPLAYROTATION *pRotation)
@@ -126,5 +181,22 @@ HRESULT STDMETHODCALLTYPE FakeIDirect3DSwapChain9::GetDisplayModeEx(D3DDISPLAYMO
     WRAP_VERBOSE;
 
     assert(is_d3d9ex);
-    return D3DERR_INVALIDCALL;
+    if (!is_hidden) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (pMode == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    pMode->Size = sizeof(*pMode);
+    pMode->Width = present_params.BackBufferWidth;
+    pMode->Height = present_params.BackBufferHeight;
+    pMode->RefreshRate = present_params.FullScreen_RefreshRateInHz;
+    pMode->Format = present_params.BackBufferFormat;
+    pMode->ScanLineOrdering = D3DSCANLINEORDERING_PROGRESSIVE;
+    if (pRotation != nullptr) {
+        *pRotation = D3DDISPLAYROTATION_IDENTITY;
+    }
+    return D3D_OK;
 }

src/spice2x/hooks/graphics/backends/d3d9/d3d9_fake_swapchain.h

@@ -6,14 +6,19 @@
 #endif
 
 #include <atomic>
+#include <vector>
 
 #include <d3d9.h>
 
 #include "util/logging.h"
 
 struct FakeIDirect3DSwapChain9 : IDirect3DSwapChain9Ex {
-    FakeIDirect3DSwapChain9(IDirect3DDevice9 *pDev, D3DPRESENT_PARAMETERS *present_params, bool is_d3d9ex) :
-        pDev(pDev), is_d3d9ex(is_d3d9ex)
+    FakeIDirect3DSwapChain9(
+            IDirect3DDevice9 *pDev,
+            D3DPRESENT_PARAMETERS *present_params,
+            bool is_d3d9ex,
+            bool is_hidden = false) :
+        pDev(pDev), is_d3d9ex(is_d3d9ex), is_hidden(is_hidden)
     {
         // copy presentation parameters
         memcpy(&this->present_params, present_params, sizeof(this->present_params));
@@ -78,8 +83,10 @@ struct FakeIDirect3DSwapChain9 : IDirect3DSwapChain9Ex {
 
     IDirect3DDevice9 *const pDev;
     bool is_d3d9ex;
+    bool is_hidden;
 
     std::atomic<ULONG> ref_cnt = 1;
+    std::atomic<UINT> present_count = 0;
 
     D3DPRESENT_PARAMETERS present_params {};
     std::vector<IDirect3DSurface9 *> render_targets;

src/spice2x/hooks/graphics/backends/d3d9/d3d9_gfdm.cpp

@@ -0,0 +1,715 @@
+#include "d3d9_gfdm.h"
+
+#include <algorithm>
+#include <cassert>
+#include <mutex>
+
+#include "games/gitadora/gitadora.h"
+#include "hooks/graphics/graphics.h"
+#include "util/logging.h"
+
+#include "d3d9_device.h"
+
+bool gfdm_two_head_exclusive() {
+    return games::gitadora::is_arena_model()
+            && games::gitadora::ARENA_TWO_HEAD_EXCLUSIVE
+            && !GRAPHICS_WINDOWED;
+}
+
+HRESULT graphics_d3d9_gfdm_select_two_head_group_parameters(
+        const D3DPRESENT_PARAMETERS *logical_presentation_parameters,
+        const D3DDISPLAYMODEEX *logical_fullscreen_display_modes,
+        D3DPRESENT_PARAMETERS *native_presentation_parameters,
+        D3DDISPLAYMODEEX *native_fullscreen_display_modes,
+        UINT *logical_small_swapchain,
+        const char *operation)
+{
+    if (!gfdm_two_head_exclusive()
+            || logical_presentation_parameters == nullptr
+            || native_presentation_parameters == nullptr
+            || logical_small_swapchain == nullptr)
+    {
+        return D3DERR_INVALIDCALL;
+    }
+
+    UINT small_slot = GFDM_LOGICAL_HEAD_COUNT;
+    for (UINT i = 1; i < GFDM_LOGICAL_HEAD_COUNT; i++) {
+        const auto &params = logical_presentation_parameters[i];
+        if (params.BackBufferWidth != GFDM_SMALL_WIDTH
+                || params.BackBufferHeight != GFDM_SMALL_HEIGHT)
+        {
+            continue;
+        }
+        if (small_slot != GFDM_LOGICAL_HEAD_COUNT) {
+            log_warning(
+                    "graphics::d3d9",
+                    "two-head exclusive: {} found multiple SMALL slots: {} and {}",
+                    operation,
+                    small_slot,
+                    i);
+            return D3DERR_INVALIDCALL;
+        }
+        small_slot = i;
+    }
+
+    if (small_slot == GFDM_LOGICAL_HEAD_COUNT) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive: {} could not find an 800x1280 logical SMALL descriptor",
+                operation);
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (logical_fullscreen_display_modes != nullptr
+            && (logical_fullscreen_display_modes[small_slot].Width != GFDM_SMALL_WIDTH
+                    || logical_fullscreen_display_modes[small_slot].Height != GFDM_SMALL_HEIGHT))
+    {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive: {} SMALL slot {} mode is {}x{}, expected {}x{}",
+                operation,
+                small_slot,
+                logical_fullscreen_display_modes[small_slot].Width,
+                logical_fullscreen_display_modes[small_slot].Height,
+                GFDM_SMALL_WIDTH,
+                GFDM_SMALL_HEIGHT);
+        return D3DERR_INVALIDCALL;
+    }
+
+    native_presentation_parameters[0] = logical_presentation_parameters[0];
+    native_presentation_parameters[1] = logical_presentation_parameters[small_slot];
+    if (logical_fullscreen_display_modes != nullptr
+            && native_fullscreen_display_modes != nullptr)
+    {
+        native_fullscreen_display_modes[0] = logical_fullscreen_display_modes[0];
+        native_fullscreen_display_modes[1] = logical_fullscreen_display_modes[small_slot];
+    }
+
+    log_info(
+            "graphics::d3d9",
+            "two-head exclusive: {} selected logical SMALL slot {} -> native group head 1{}",
+            operation,
+            small_slot,
+            logical_presentation_parameters[small_slot].hDeviceWindow == GFDM_SUBSCREEN_WINDOW
+                    ? " (named SMALL host)"
+                    : "");
+    *logical_small_swapchain = small_slot;
+    return D3D_OK;
+}
+
+bool is_fake_subscreen_adapter(UINT adapter) {
+    // MAIN and SMALL remain native D3D heads; LEFT/RIGHT are virtual.
+    if (gfdm_two_head_exclusive()) {
+        return adapter >= 2 && adapter < GFDM_LOGICAL_HEAD_COUNT;
+    }
+
+    return FAKE_SUBSCREEN_ADAPTER && adapter > 0;
+}
+
+void get_fake_subscreen_display_mode(
+        UINT adapter,
+        D3DDISPLAYMODE *mode)
+{
+    (void) adapter;
+    if (gfdm_two_head_exclusive()) {
+        mode->Width = GFDM_SIDE_WIDTH;
+        mode->Height = GFDM_SIDE_HEIGHT;
+    } else {
+        mode->Width = 1280;
+        mode->Height = 800;
+    }
+    mode->RefreshRate = 60;
+    mode->Format = D3DFMT_X8R8G8B8;
+}
+
+void get_fake_subscreen_display_mode_ex(
+        UINT adapter,
+        D3DDISPLAYMODEEX *mode)
+{
+    D3DDISPLAYMODE legacy_mode {};
+    get_fake_subscreen_display_mode(adapter, &legacy_mode);
+
+    mode->Size = sizeof(*mode);
+    mode->Width = legacy_mode.Width;
+    mode->Height = legacy_mode.Height;
+    mode->RefreshRate = legacy_mode.RefreshRate;
+    mode->Format = legacy_mode.Format;
+    mode->ScanLineOrdering = D3DSCANLINEORDERING_PROGRESSIVE;
+}
+
+HRESULT graphics_d3d9_gfdm_remap_two_head_group_parameters(
+        D3DPRESENT_PARAMETERS *presentation_parameters,
+        D3DDISPLAYMODEEX *fullscreen_display_modes,
+        const char *operation)
+{
+    if (!gfdm_two_head_exclusive()) {
+        return D3D_OK;
+    }
+    if (presentation_parameters == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+
+    auto &secondary = presentation_parameters[1];
+    if (secondary.BackBufferWidth != GFDM_SMALL_WIDTH
+            || secondary.BackBufferHeight != GFDM_SMALL_HEIGHT)
+    {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive: {} expected physical SMALL {}x{} at group slot 1, got {}x{}",
+                operation,
+                GFDM_SMALL_WIDTH,
+                GFDM_SMALL_HEIGHT,
+                secondary.BackBufferWidth,
+                secondary.BackBufferHeight);
+        return D3DERR_INVALIDCALL;
+    }
+
+    if (GFDM_SUBSCREEN_WINDOW == nullptr || !IsWindow(GFDM_SUBSCREEN_WINDOW)) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive: {} cannot use the named SMALL window as physical group head 1",
+                operation);
+        return D3DERR_INVALIDCALL;
+    }
+    secondary.hDeviceWindow = GFDM_SUBSCREEN_WINDOW;
+
+    if (fullscreen_display_modes != nullptr
+            && (fullscreen_display_modes[1].Width != GFDM_SMALL_WIDTH
+                    || fullscreen_display_modes[1].Height != GFDM_SMALL_HEIGHT))
+    {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive: {} SMALL head mode is {}x{}, expected 800x1280",
+                operation,
+                fullscreen_display_modes[1].Width,
+                fullscreen_display_modes[1].Height);
+        return D3DERR_INVALIDCALL;
+    }
+
+    return D3D_OK;
+}
+
+void graphics_d3d9_gfdm_align_two_head_refresh_to_desktop(
+        IDirect3D9Ex *d3d,
+        UINT master_adapter,
+        D3DPRESENT_PARAMETERS *presentation_parameters,
+        D3DDISPLAYMODEEX *fullscreen_display_modes,
+        const char *operation)
+{
+    if (d3d == nullptr
+            || presentation_parameters == nullptr
+            || fullscreen_display_modes == nullptr)
+    {
+        return;
+    }
+
+    for (UINT head = 0; head < 2; head++) {
+        const bool explicitly_forced =
+                (head == 0 && GRAPHICS_FORCE_REFRESH > 0)
+                || (head == 1 && GRAPHICS_FORCE_REFRESH_SUB.has_value());
+        if (explicitly_forced) {
+            continue;
+        }
+
+        D3DDISPLAYMODEEX desktop_mode {};
+        desktop_mode.Size = sizeof(desktop_mode);
+        D3DDISPLAYROTATION rotation = D3DDISPLAYROTATION_IDENTITY;
+        const HRESULT result = d3d->GetAdapterDisplayModeEx(
+                master_adapter + head,
+                &desktop_mode,
+                &rotation);
+        if (FAILED(result)) {
+            log_warning(
+                    "graphics::d3d9",
+                    "two-head exclusive: {} could not query native head {} desktop refresh, hr={}",
+                    operation,
+                    head,
+                    FMT_HRESULT(result));
+            continue;
+        }
+
+        const auto &parameters = presentation_parameters[head];
+        if (desktop_mode.Width != parameters.BackBufferWidth
+                || desktop_mode.Height != parameters.BackBufferHeight
+                || desktop_mode.Format != parameters.BackBufferFormat
+                || desktop_mode.RefreshRate == 0)
+        {
+            log_warning(
+                    "graphics::d3d9",
+                    "two-head exclusive: {} head {} mode differs from the desktop",
+                    operation,
+                    head);
+            continue;
+        }
+
+        if (parameters.FullScreen_RefreshRateInHz != desktop_mode.RefreshRate
+                || fullscreen_display_modes[head].RefreshRate != desktop_mode.RefreshRate)
+        {
+            log_info(
+                    "graphics::d3d9",
+                    "two-head exclusive: {} head {} refresh {} / {} -> {} (rotation {})",
+                    operation,
+                    head,
+                    parameters.FullScreen_RefreshRateInHz,
+                    fullscreen_display_modes[head].RefreshRate,
+                    desktop_mode.RefreshRate,
+                    static_cast<UINT>(rotation));
+            presentation_parameters[head].FullScreen_RefreshRateInHz =
+                    desktop_mode.RefreshRate;
+            fullscreen_display_modes[head].RefreshRate =
+                    desktop_mode.RefreshRate;
+        }
+    }
+}
+
+HRESULT validate_gfdm_two_head_exclusive(
+        IDirect3D9 *d3d,
+        UINT adapter,
+        D3DDEVTYPE device_type,
+        DWORD behavior_flags,
+        const D3DPRESENT_PARAMETERS *presentation_parameters)
+{
+    if (!(behavior_flags & D3DCREATE_ADAPTERGROUP_DEVICE)) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head mode requires D3DCREATE_ADAPTERGROUP_DEVICE");
+        return D3DERR_NOTAVAILABLE;
+    }
+    if (adapter != 0) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive mode currently requires master adapter 0, game requested {}",
+                adapter);
+        return D3DERR_NOTAVAILABLE;
+    }
+    if (presentation_parameters == nullptr) {
+        return D3DERR_INVALIDCALL;
+    }
+    const UINT native_adapter_count = d3d->GetAdapterCount();
+    if (native_adapter_count != 2) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head mode requires two native D3D9 adapters; found {}",
+                native_adapter_count);
+        return D3DERR_NOTAVAILABLE;
+    }
+
+    D3DCAPS9 caps {};
+    const HRESULT caps_result = d3d->GetDeviceCaps(adapter, device_type, &caps);
+    if (FAILED(caps_result)) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive mode could not query native adapter caps, hr={}",
+                FMT_HRESULT(caps_result));
+        return caps_result;
+    }
+    if (caps.MasterAdapterOrdinal != adapter
+            || caps.AdapterOrdinalInGroup != 0
+            || caps.NumberOfAdaptersInGroup != 2)
+    {
+        log_warning(
+                "graphics::d3d9",
+                "invalid adapter group: master={}, index={}, size={}",
+                caps.MasterAdapterOrdinal,
+                caps.AdapterOrdinalInGroup,
+                caps.NumberOfAdaptersInGroup);
+        return D3DERR_NOTAVAILABLE;
+    }
+
+    const auto &main = presentation_parameters[0];
+    const auto &small_params = presentation_parameters[1];
+    if (main.Windowed || small_params.Windowed) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head exclusive mode requires both group heads to be fullscreen");
+        return D3DERR_INVALIDCALL;
+    }
+    if (small_params.BackBufferWidth != GFDM_SMALL_WIDTH
+            || small_params.BackBufferHeight != GFDM_SMALL_HEIGHT)
+    {
+        log_warning(
+                "graphics::d3d9",
+                "SMALL head must be {}x{}; got {}x{}",
+                GFDM_SMALL_WIDTH,
+                GFDM_SMALL_HEIGHT,
+                small_params.BackBufferWidth,
+                small_params.BackBufferHeight);
+        return D3DERR_INVALIDCALL;
+    }
+    if (main.EnableAutoDepthStencil != small_params.EnableAutoDepthStencil) {
+        log_warning(
+                "graphics::d3d9",
+                "two-head mode requires matching automatic depth-stencil settings");
+        return D3DERR_INVALIDCALL;
+    }
+    if (main.EnableAutoDepthStencil
+            && (main.AutoDepthStencilFormat != small_params.AutoDepthStencilFormat
+                    || main.BackBufferWidth != small_params.BackBufferWidth
+                    || main.BackBufferHeight != small_params.BackBufferHeight
+                    || main.BackBufferFormat != small_params.BackBufferFormat))
+    {
+        log_warning(
+                "graphics::d3d9",
+                "two-head mode cannot use unequal sizes with automatic depth-stencil");
+        return D3DERR_INVALIDCALL;
+    }
+
+    return D3D_OK;
+}
+
+static bool gfdm_find_alternate_small_mode(
+        IDirect3D9Ex *d3d,
+        UINT adapter,
+        const D3DDISPLAYMODEEX &desired,
+        D3DDISPLAYMODEEX *alternate)
+{
+    if (d3d == nullptr || alternate == nullptr) {
+        return false;
+    }
+
+    D3DDISPLAYMODEFILTER filter {};
+    filter.Size = sizeof(filter);
+    filter.Format = desired.Format;
+    filter.ScanLineOrdering = D3DSCANLINEORDERING_UNKNOWN;
+    const UINT count = d3d->GetAdapterModeCountEx(adapter, &filter);
+    const bool portrait = desired.Width < desired.Height;
+
+    for (UINT index = 0; index < count; index++) {
+        D3DDISPLAYMODEEX mode {};
+        mode.Size = sizeof(mode);
+        if (FAILED(d3d->EnumAdapterModesEx(adapter, &filter, index, &mode))
+                || mode.Width != desired.Width
+                || mode.Height != desired.Height
+                || mode.Format != desired.Format
+                || (mode.RefreshRate == desired.RefreshRate
+                        && mode.ScanLineOrdering == desired.ScanLineOrdering))
+        {
+            continue;
+        }
+        *alternate = mode;
+        return true;
+    }
+
+    for (int preserve_orientation = 1; preserve_orientation >= 0; preserve_orientation--) {
+        for (int preserve_refresh = 1; preserve_refresh >= 0; preserve_refresh--) {
+            for (UINT index = 0; index < count; index++) {
+                D3DDISPLAYMODEEX mode {};
+                mode.Size = sizeof(mode);
+                if (FAILED(d3d->EnumAdapterModesEx(adapter, &filter, index, &mode))
+                        || (mode.Width == desired.Width && mode.Height == desired.Height)
+                        || mode.Format != desired.Format)
+                {
+                    continue;
+                }
+                if (preserve_orientation && (mode.Width < mode.Height) != portrait) {
+                    continue;
+                }
+                if (preserve_refresh && mode.RefreshRate != desired.RefreshRate) {
+                    continue;
+                }
+                *alternate = mode;
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+static bool gfdm_wait_for_small_mode(
+        HWND window,
+        const D3DDISPLAYMODEEX &expected)
+{
+    const HMONITOR monitor =
+            window != nullptr ? MonitorFromWindow(window, MONITOR_DEFAULTTONULL) : nullptr;
+    MONITORINFOEXA monitor_info {};
+    monitor_info.cbSize = sizeof(monitor_info);
+    if (monitor == nullptr || !GetMonitorInfoA(monitor, &monitor_info)) {
+        return false;
+    }
+
+    for (UINT poll = 0; poll < 50; poll++) {
+        DEVMODEA current {};
+        current.dmSize = sizeof(current);
+        if (EnumDisplaySettingsExA(
+                    monitor_info.szDevice,
+                    ENUM_CURRENT_SETTINGS,
+                    &current,
+                    0)
+                && current.dmPelsWidth == expected.Width
+                && current.dmPelsHeight == expected.Height
+                && (expected.RefreshRate == 0
+                        || current.dmDisplayFrequency == expected.RefreshRate))
+        {
+            return true;
+        }
+        Sleep(10);
+    }
+    return false;
+}
+
+HRESULT graphics_d3d9_gfdm_recover_two_head_present_mode(
+        IDirect3D9Ex *d3d,
+        IDirect3DDevice9Ex *device,
+        UINT master_adapter,
+        const D3DPRESENT_PARAMETERS *desired_parameters,
+        const D3DDISPLAYMODEEX *desired_modes)
+{
+    if (d3d == nullptr
+            || device == nullptr
+            || desired_parameters == nullptr
+            || desired_modes == nullptr)
+    {
+        return D3DERR_INVALIDCALL;
+    }
+
+    D3DDISPLAYMODEEX alternate_small {};
+    if (!gfdm_find_alternate_small_mode(
+                d3d,
+                master_adapter + 1,
+                desired_modes[1],
+                &alternate_small))
+    {
+        log_warning("graphics::d3d9", "no alternate SMALL mode is available for recovery");
+        return D3DERR_NOTAVAILABLE;
+    }
+
+    D3DPRESENT_PARAMETERS temporary_parameters[2] {
+            desired_parameters[0],
+            desired_parameters[1]};
+    D3DDISPLAYMODEEX temporary_modes[2] {
+            desired_modes[0],
+            desired_modes[1]};
+    temporary_parameters[1].BackBufferWidth = alternate_small.Width;
+    temporary_parameters[1].BackBufferHeight = alternate_small.Height;
+    temporary_parameters[1].BackBufferFormat = alternate_small.Format;
+    temporary_parameters[1].FullScreen_RefreshRateInHz = alternate_small.RefreshRate;
+    temporary_modes[1] = alternate_small;
+
+    HRESULT temporary_result = device->ResetEx(temporary_parameters, temporary_modes);
+    const bool temporary_settled =
+            temporary_result == D3D_OK
+            && gfdm_wait_for_small_mode(desired_parameters[1].hDeviceWindow, alternate_small);
+
+    D3DPRESENT_PARAMETERS restore_parameters[2] {
+            desired_parameters[0],
+            desired_parameters[1]};
+    D3DDISPLAYMODEEX restore_modes[2] {
+            desired_modes[0],
+            desired_modes[1]};
+    HRESULT restore_result = device->ResetEx(restore_parameters, restore_modes);
+    const bool restore_settled =
+            restore_result == D3D_OK
+            && gfdm_wait_for_small_mode(desired_parameters[1].hDeviceWindow, desired_modes[1]);
+
+    if (temporary_result != D3D_OK) {
+        return temporary_result;
+    }
+    if (restore_result != D3D_OK) {
+        return restore_result;
+    }
+    if (!temporary_settled || !restore_settled) {
+        return D3DERR_NOTAVAILABLE;
+    }
+    return device->CheckDeviceState(desired_parameters[0].hDeviceWindow) == D3D_OK
+            ? D3D_OK
+            : D3DERR_NOTAVAILABLE;
+}
+
+bool WrappedIDirect3DDevice9::is_gfdm_two_head_exclusive() const {
+    return ::gfdm_two_head_exclusive();
+}
+
+bool WrappedIDirect3DDevice9::is_gfdm_logical_small_swapchain(
+        UINT swapchain) const
+{
+    return swapchain == gfdm_logical_small_swapchain;
+}
+
+bool WrappedIDirect3DDevice9::is_gfdm_logical_side_swapchain(
+        UINT swapchain) const
+{
+    return swapchain > 0
+            && swapchain < GFDM_LOGICAL_HEAD_COUNT
+            && swapchain != gfdm_logical_small_swapchain;
+}
+
+size_t WrappedIDirect3DDevice9::gfdm_hidden_side_swapchain_slot(
+        UINT swapchain) const
+{
+    assert(is_gfdm_logical_side_swapchain(swapchain));
+    return swapchain < gfdm_logical_small_swapchain
+            ? swapchain
+            : swapchain - 1;
+}
+
+void WrappedIDirect3DDevice9::set_gfdm_logical_group_parameters(
+        const D3DPRESENT_PARAMETERS *presentation_parameters)
+{
+    if (presentation_parameters == nullptr) {
+        gfdm_logical_group_parameters_valid = false;
+        return;
+    }
+    std::copy_n(
+            presentation_parameters,
+            gfdm_logical_group_parameters.size(),
+            gfdm_logical_group_parameters.begin());
+    gfdm_logical_group_parameters_valid = true;
+}
+
+FakeIDirect3DSwapChain9 *
+WrappedIDirect3DDevice9::ensure_gfdm_hidden_side_swapchain(UINT iSwapChain) {
+    assert(is_gfdm_logical_side_swapchain(iSwapChain));
+
+    const size_t index = gfdm_hidden_side_swapchain_slot(iSwapChain);
+    if (fake_sub_swapchain[index] == nullptr) {
+        D3DPRESENT_PARAMETERS params {};
+        if (gfdm_logical_group_parameters_valid) {
+            params = gfdm_logical_group_parameters[iSwapChain];
+        } else {
+            params.BackBufferWidth = 1080;
+            params.BackBufferHeight = 1920;
+            params.BackBufferFormat = D3DFMT_X8R8G8B8;
+            params.BackBufferCount = 1;
+            params.MultiSampleType = D3DMULTISAMPLE_NONE;
+            params.SwapEffect = D3DSWAPEFFECT_DISCARD;
+            params.Windowed = FALSE;
+            params.FullScreen_RefreshRateInHz = 60;
+            params.EnableAutoDepthStencil = FALSE;
+            params.PresentationInterval = D3DPRESENT_INTERVAL_ONE;
+        }
+        fake_sub_swapchain[index] = new FakeIDirect3DSwapChain9(
+                this,
+                &params,
+                is_d3d9ex,
+                true);
+    }
+    return fake_sub_swapchain[index];
+}
+
+void WrappedIDirect3DDevice9::release_gfdm_hidden_side_swapchains() {
+    for (UINT i = 1; i < GFDM_LOGICAL_HEAD_COUNT; i++) {
+        if (!is_gfdm_logical_side_swapchain(i)) {
+            continue;
+        }
+        const size_t index = gfdm_hidden_side_swapchain_slot(i);
+        if (fake_sub_swapchain[index] != nullptr) {
+            fake_sub_swapchain[index]->Release();
+            fake_sub_swapchain[index] = nullptr;
+        }
+    }
+}
+
+void WrappedIDirect3DDevice9::gfdm_disarm_present_mode_recovery() {
+    std::lock_guard<std::mutex> lock(gfdm_recovery_mutex);
+    gfdm_recovery_armed = false;
+    gfdm_recovery_consumed.store(true, std::memory_order_release);
+}
+
+void WrappedIDirect3DDevice9::gfdm_arm_present_mode_recovery(
+        const D3DPRESENT_PARAMETERS *native_presentation_parameters,
+        const D3DDISPLAYMODEEX *native_fullscreen_display_modes)
+{
+    if (native_presentation_parameters == nullptr
+            || native_fullscreen_display_modes == nullptr)
+    {
+        return;
+    }
+
+    std::lock_guard<std::mutex> lock(gfdm_recovery_mutex);
+    gfdm_recovery_parameters[0] = native_presentation_parameters[0];
+    gfdm_recovery_parameters[1] = native_presentation_parameters[1];
+    gfdm_recovery_modes[0] = native_fullscreen_display_modes[0];
+    gfdm_recovery_modes[1] = native_fullscreen_display_modes[1];
+    if (gfdm_recovery_modes[0].Size == 0) {
+        gfdm_recovery_modes[0].Size = sizeof(D3DDISPLAYMODEEX);
+    }
+    if (gfdm_recovery_modes[1].Size == 0) {
+        gfdm_recovery_modes[1].Size = sizeof(D3DDISPLAYMODEEX);
+    }
+    gfdm_recovery_armed =
+            !gfdm_recovery_parameters[0].Windowed
+            && !gfdm_recovery_parameters[1].Windowed
+            && IsWindow(gfdm_recovery_parameters[1].hDeviceWindow);
+    gfdm_recovery_consumed.store(
+            !gfdm_recovery_armed,
+            std::memory_order_release);
+}
+
+WrappedIDirect3DDevice9::GfdmPresentModeRecoveryResult
+WrappedIDirect3DDevice9::gfdm_recover_present_mode_change(
+        HRESULT *failure_result)
+{
+    if (failure_result != nullptr) {
+        *failure_result = D3D_OK;
+    }
+    if (!is_gfdm_two_head_exclusive() || !is_d3d9ex
+            || gfdm_recovery_consumed.exchange(
+                    true,
+                    std::memory_order_acq_rel))
+    {
+        return GfdmPresentModeRecoveryResult::NotAttempted;
+    }
+    if (GetCurrentThreadId() != gfdm_device_creation_thread_id) {
+        if (failure_result != nullptr) {
+            *failure_result = D3DERR_INVALIDCALL;
+        }
+        return GfdmPresentModeRecoveryResult::Failed;
+    }
+
+    std::array<D3DPRESENT_PARAMETERS, 2> parameters {};
+    std::array<D3DDISPLAYMODEEX, 2> modes {};
+    {
+        std::lock_guard<std::mutex> lock(gfdm_recovery_mutex);
+        if (!gfdm_recovery_armed) {
+            return GfdmPresentModeRecoveryResult::NotAttempted;
+        }
+        parameters = gfdm_recovery_parameters;
+        modes = gfdm_recovery_modes;
+    }
+
+    IDirect3D9 *raw_d3d = nullptr;
+    HRESULT result = pReal->GetDirect3D(&raw_d3d);
+    IDirect3D9Ex *raw_d3d_ex = nullptr;
+    if (SUCCEEDED(result)) {
+        result = raw_d3d != nullptr
+                ? raw_d3d->QueryInterface(IID_PPV_ARGS(&raw_d3d_ex))
+                : E_FAIL;
+    }
+    D3DDEVICE_CREATION_PARAMETERS creation {};
+    if (SUCCEEDED(result)) {
+        result = pReal->GetCreationParameters(&creation);
+    }
+    if (FAILED(result) || raw_d3d_ex == nullptr) {
+        if (raw_d3d_ex != nullptr) {
+            raw_d3d_ex->Release();
+        }
+        if (raw_d3d != nullptr) {
+            raw_d3d->Release();
+        }
+        if (failure_result != nullptr) {
+            *failure_result = result;
+        }
+        return GfdmPresentModeRecoveryResult::Failed;
+    }
+
+    result = graphics_d3d9_gfdm_recover_two_head_present_mode(
+            raw_d3d_ex,
+            static_cast<IDirect3DDevice9Ex *>(pReal),
+            creation.AdapterOrdinal,
+            parameters.data(),
+            modes.data());
+    raw_d3d_ex->Release();
+    raw_d3d->Release();
+
+    if (result == D3DERR_NOTAVAILABLE) {
+        return GfdmPresentModeRecoveryResult::NotAttempted;
+    }
+    if (FAILED(result)) {
+        if (failure_result != nullptr) {
+            *failure_result = result;
+        }
+        return GfdmPresentModeRecoveryResult::Failed;
+    }
+    return GfdmPresentModeRecoveryResult::ReadyToRetry;
+}
+

src/spice2x/hooks/graphics/backends/d3d9/d3d9_gfdm.h

@@ -0,0 +1,78 @@
+#pragma once
+
+#include <array>
+
+#include <d3d9.h>
+
+inline constexpr UINT GFDM_SIDE_WIDTH = 1080;
+inline constexpr UINT GFDM_SIDE_HEIGHT = 1920;
+inline constexpr UINT GFDM_SMALL_WIDTH = 800;
+inline constexpr UINT GFDM_SMALL_HEIGHT = 1280;
+inline constexpr UINT GFDM_LOGICAL_HEAD_COUNT = 4;
+inline constexpr UINT GFDM_NATIVE_SMALL_SWAPCHAIN = 1;
+
+struct GfdmTwoHeadDeviceState {
+    explicit GfdmTwoHeadDeviceState(
+            D3DPRESENT_PARAMETERS *presentation_parameters,
+            D3DDISPLAYMODEEX *fullscreen_display_modes,
+            UINT logical_small_swapchain = 2)
+        : presentation_parameters(presentation_parameters),
+          fullscreen_display_modes(fullscreen_display_modes),
+          logical_small_swapchain(logical_small_swapchain) {}
+
+    void use_native_parameters() {
+        presentation_parameters = native_presentation_parameters.data();
+        fullscreen_display_modes = source_fullscreen_display_modes != nullptr
+                ? native_fullscreen_display_modes.data()
+                : nullptr;
+    }
+
+    std::array<D3DPRESENT_PARAMETERS, 2> native_presentation_parameters {};
+    std::array<D3DDISPLAYMODEEX, 2> native_fullscreen_display_modes {};
+    std::array<D3DPRESENT_PARAMETERS, 2> recovery_parameters {};
+    std::array<D3DDISPLAYMODEEX, 2> recovery_modes {};
+    D3DPRESENT_PARAMETERS *presentation_parameters;
+    D3DDISPLAYMODEEX *fullscreen_display_modes;
+    D3DDISPLAYMODEEX *const source_fullscreen_display_modes = fullscreen_display_modes;
+    UINT logical_small_swapchain;
+    bool recovery_candidate = false;
+};
+
+bool gfdm_two_head_exclusive();
+bool is_fake_subscreen_adapter(UINT adapter);
+void get_fake_subscreen_display_mode(UINT adapter, D3DDISPLAYMODE *mode);
+void get_fake_subscreen_display_mode_ex(UINT adapter, D3DDISPLAYMODEEX *mode);
+
+HRESULT graphics_d3d9_gfdm_select_two_head_group_parameters(
+        const D3DPRESENT_PARAMETERS *logical_presentation_parameters,
+        const D3DDISPLAYMODEEX *logical_fullscreen_display_modes,
+        D3DPRESENT_PARAMETERS *native_presentation_parameters,
+        D3DDISPLAYMODEEX *native_fullscreen_display_modes,
+        UINT *logical_small_swapchain,
+        const char *operation);
+
+HRESULT graphics_d3d9_gfdm_remap_two_head_group_parameters(
+        D3DPRESENT_PARAMETERS *presentation_parameters,
+        D3DDISPLAYMODEEX *fullscreen_display_modes,
+        const char *operation);
+
+void graphics_d3d9_gfdm_align_two_head_refresh_to_desktop(
+        IDirect3D9Ex *d3d,
+        UINT master_adapter,
+        D3DPRESENT_PARAMETERS *presentation_parameters,
+        D3DDISPLAYMODEEX *fullscreen_display_modes,
+        const char *operation);
+
+HRESULT validate_gfdm_two_head_exclusive(
+        IDirect3D9 *d3d,
+        UINT adapter,
+        D3DDEVTYPE device_type,
+        DWORD behavior_flags,
+        const D3DPRESENT_PARAMETERS *presentation_parameters);
+
+HRESULT graphics_d3d9_gfdm_recover_two_head_present_mode(
+        IDirect3D9Ex *d3d,
+        IDirect3DDevice9Ex *device,
+        UINT master_adapter,
+        const D3DPRESENT_PARAMETERS *desired_parameters,
+        const D3DDISPLAYMODEEX *desired_modes);

src/spice2x/hooks/graphics/backends/d3d9/d3d9_swapchain.cpp

@@ -26,7 +26,7 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DSwapChain9::QueryInterface(REFIID riid
         return E_POINTER;
     }
 
-    if (//riid == __uuidof(IUnknown) || Ignore IUnknown, it's often queried to test object equality between different interfaces
+    if ((riid == IID_IUnknown && pDev->is_gfdm_two_head_exclusive()) ||
         riid == IID_IDirect3DSwapChain9 ||
         riid == IID_IDirect3DSwapChain9Ex)
     {
@@ -89,7 +89,42 @@ HRESULT STDMETHODCALLTYPE WrappedIDirect3DSwapChain9::Present(const RECT *pSourc
         graphics_d3d9_on_present(pDev->hFocusWindow, pDev->pReal, pDev);
     }
 
-    CHECK_RESULT(pReal->Present(pSourceRect, pDestRect, hDestWindowOverride, pDirtyRegion, dwFlags));
+    HRESULT result = pReal->Present(
+            pSourceRect,
+            pDestRect,
+            hDestWindowOverride,
+            pDirtyRegion,
+            dwFlags);
+
+    // Some drivers report S_PRESENT_MODE_CHANGED after Windows moves the portrait SMALL
+    // head into the requested exclusive mode, leaving both group heads black. Toggle SMALL
+    // through another supported mode and restore it once, then retry the interrupted MAIN
+    // present. Recovery is restricted to the creation thread and consumes its armed state,
+    // so subsequent presents cannot repeat the mode switch.
+    if (pDev->is_gfdm_two_head_exclusive()
+            && native_group_head == NativeGroupHead::Main
+            && result == S_PRESENT_MODE_CHANGED)
+    {
+        HRESULT recovery_failure = D3D_OK;
+        const auto recovery = pDev->gfdm_recover_present_mode_change(
+                &recovery_failure);
+        if (recovery
+                == WrappedIDirect3DDevice9::GfdmPresentModeRecoveryResult::ReadyToRetry)
+        {
+            result = pReal->Present(
+                    pSourceRect,
+                    pDestRect,
+                    hDestWindowOverride,
+                    pDirtyRegion,
+                    dwFlags);
+        } else if (recovery
+                        == WrappedIDirect3DDevice9::GfdmPresentModeRecoveryResult::Failed
+                && FAILED(recovery_failure))
+        {
+            result = recovery_failure;
+        }
+    }
+    CHECK_RESULT(result);
 }
 HRESULT STDMETHODCALLTYPE WrappedIDirect3DSwapChain9::GetFrontBufferData(IDirect3DSurface9 *pDestSurface) {
     CHECK_RESULT(pReal->GetFrontBufferData(pDestSurface));

src/spice2x/hooks/graphics/backends/d3d9/d3d9_swapchain.h

@@ -5,8 +5,13 @@
 interface WrappedIDirect3DDevice9;
 
 struct WrappedIDirect3DSwapChain9 : IDirect3DSwapChain9Ex {
-    WrappedIDirect3DSwapChain9(WrappedIDirect3DDevice9 *dev, IDirect3DSwapChain9 *orig) :
-        pDev(dev), pReal(orig), is_d3d9ex(false)
+    enum class NativeGroupHead { Unknown, Main, Small };
+
+    WrappedIDirect3DSwapChain9(
+            WrappedIDirect3DDevice9 *dev,
+            IDirect3DSwapChain9 *orig,
+            NativeGroupHead native_group_head = NativeGroupHead::Unknown) :
+        pDev(dev), pReal(orig), is_d3d9ex(false), native_group_head(native_group_head)
     {
         IDirect3DSwapChain9Ex *swapchain = nullptr;
 
@@ -16,8 +21,11 @@ struct WrappedIDirect3DSwapChain9 : IDirect3DSwapChain9Ex {
         }
     }
 
-    WrappedIDirect3DSwapChain9(WrappedIDirect3DDevice9 *dev, IDirect3DSwapChain9Ex *orig) :
-        pDev(dev), pReal(orig), is_d3d9ex(true)
+    WrappedIDirect3DSwapChain9(
+            WrappedIDirect3DDevice9 *dev,
+            IDirect3DSwapChain9Ex *orig,
+            NativeGroupHead native_group_head = NativeGroupHead::Unknown) :
+        pDev(dev), pReal(orig), is_d3d9ex(true), native_group_head(native_group_head)
     {
     }
 
@@ -53,6 +61,7 @@ struct WrappedIDirect3DSwapChain9 : IDirect3DSwapChain9Ex {
 
     IDirect3DSwapChain9 *pReal;
     bool is_d3d9ex = false;
+    NativeGroupHead native_group_head = NativeGroupHead::Unknown;
 
     bool should_run_hooks = true;
 };

src/spice2x/hooks/graphics/graphics.cpp

@@ -44,6 +44,8 @@ HWND SDVX_SUBSCREEN_WINDOW = nullptr;
 HWND GFDM_SUBSCREEN_WINDOW = nullptr;
 static HWND GFDM_LEFT_WINDOW = nullptr;
 static HWND GFDM_RIGHT_WINDOW = nullptr;
+static HMONITOR GFDM_TWO_HEAD_SMALL_MONITOR = nullptr;
+static HWND GFDM_TWO_HEAD_SMALL_WINDOW = nullptr;
 HWND POPN_SUBSCREEN_WINDOW = nullptr;
 bool FAKE_SUBSCREEN_ADAPTER = false;
 
@@ -183,6 +185,13 @@ static bool is_gfdm_known_window(HWND hWnd) {
     return gitadora_window_name_for_hwnd(hWnd) != nullptr;
 }
 
+static bool is_gfdm_two_head_small_window(HWND hWnd) {
+    return games::gitadora::is_arena_model() &&
+        games::gitadora::ARENA_TWO_HEAD_EXCLUSIVE &&
+        hWnd != nullptr &&
+        hWnd == GFDM_TWO_HEAD_SMALL_WINDOW;
+}
+
 static bool gitadora_should_block_game_window_placement(HWND hWnd) {
     if (!GRAPHICS_WINDOWED || !games::gitadora::is_arena_model()) {
         return false;
@@ -204,6 +213,95 @@ static void gitadora_remember_window(HWND hWnd, const std::string &window_name)
     }
 }
 
+bool graphics_gitadora_prepare_two_head_device_window(
+        HWND hWnd, HMONITOR target_monitor, UINT desired_width, UINT desired_height) {
+    if (hWnd == nullptr || !IsWindow(hWnd)) {
+        log_warning(
+            "graphics",
+            "two-head exclusive: native secondary device window is invalid: {}",
+            fmt::ptr(hWnd));
+        return false;
+    }
+    if (ShowWindow_orig == nullptr || SetWindowLongA_orig == nullptr ||
+            SetWindowPos_orig == nullptr) {
+        log_warning(
+            "graphics",
+            "two-head exclusive: window hooks are not initialized for {}",
+            fmt::ptr(hWnd));
+        return false;
+    }
+
+    RECT rect_before {};
+    GetWindowRect(hWnd, &rect_before);
+    const DWORD style_before = static_cast<DWORD>(GetWindowLongA(hWnd, GWL_STYLE));
+    const BOOL visible_before = IsWindowVisible(hWnd);
+
+    if (target_monitor != nullptr) {
+        GFDM_TWO_HEAD_SMALL_MONITOR = target_monitor;
+    }
+    const HMONITOR monitor = target_monitor != nullptr
+        ? target_monitor
+        : (GFDM_TWO_HEAD_SMALL_MONITOR != nullptr
+            ? GFDM_TWO_HEAD_SMALL_MONITOR
+            : MonitorFromWindow(hWnd, MONITOR_DEFAULTTONULL));
+    MONITORINFO monitor_info {};
+    monitor_info.cbSize = sizeof(monitor_info);
+    if (monitor == nullptr || !GetMonitorInfoA(monitor, &monitor_info)) {
+        log_warning(
+            "graphics",
+            "two-head exclusive: could not find the SMALL monitor for {}",
+            fmt::ptr(hWnd));
+        return false;
+    }
+
+    // Arena requests D3DCREATE_NOWINDOWCHANGES, so place its SMALL window on
+    // the second head before D3D9 takes ownership of it.
+    const DWORD fullscreen_style = (style_before & ~WS_OVERLAPPEDWINDOW) | WS_POPUP;
+    const bool style_changed = fullscreen_style != style_before;
+    if (style_changed) {
+        SetWindowLongA_orig(hWnd, GWL_STYLE, static_cast<LONG>(fullscreen_style));
+    }
+    const RECT &monitor_rect = monitor_info.rcMonitor;
+    const int host_width = desired_width != 0
+        ? static_cast<int>(desired_width)
+        : monitor_rect.right - monitor_rect.left;
+    const int host_height = desired_height != 0
+        ? static_cast<int>(desired_height)
+        : monitor_rect.bottom - monitor_rect.top;
+    const bool rect_changed = rect_before.left != monitor_rect.left ||
+        rect_before.top != monitor_rect.top ||
+        rect_before.right != monitor_rect.left + host_width ||
+        rect_before.bottom != monitor_rect.top + host_height;
+    if ((style_changed || rect_changed) && !SetWindowPos_orig(
+        hWnd,
+        HWND_TOP,
+        monitor_rect.left,
+        monitor_rect.top,
+        host_width,
+        host_height,
+        SWP_NOACTIVATE | SWP_NOOWNERZORDER | SWP_FRAMECHANGED)) {
+        log_warning(
+            "graphics",
+            "two-head exclusive: failed to place SMALL window, error={}",
+            GetLastError());
+        return false;
+    }
+
+    if (!visible_before) {
+        ShowWindow_orig(hWnd, SW_SHOWNOACTIVATE);
+    }
+    if (MonitorFromWindow(hWnd, MONITOR_DEFAULTTONULL) != monitor) {
+        log_warning(
+            "graphics",
+            "two-head exclusive: SMALL window {} is on the wrong monitor",
+            fmt::ptr(hWnd));
+        return false;
+    }
+
+    GFDM_TWO_HEAD_SMALL_WINDOW = hWnd;
+    return true;
+}
+
 static bool gitadora_should_allow_small_resize() {
     return GRAPHICS_WINDOWED &&
         games::gitadora::is_arena_model() &&
@@ -618,9 +716,16 @@ static HWND WINAPI CreateWindowExA_hook(DWORD dwExStyle, LPCSTR lpClassName, LPC
     }
 
     // only hook touch window if multiple windows are allowed
-    if (is_gfdm_sub_window && GRAPHICS_WINDOWED && !GRAPHICS_PREVENT_SECONDARY_WINDOWS) {
+    if (gfdm_window_name == "LEFT" || gfdm_window_name == "RIGHT") {
         gitadora_remember_window(result, gfdm_window_name);
-        graphics_hook_subscreen_window(GFDM_SUBSCREEN_WINDOW);
+    }
+    if (is_gfdm_sub_window &&
+            ((GRAPHICS_WINDOWED && !GRAPHICS_PREVENT_SECONDARY_WINDOWS) ||
+             games::gitadora::ARENA_TWO_HEAD_EXCLUSIVE)) {
+        gitadora_remember_window(result, gfdm_window_name);
+        if (GRAPHICS_WINDOWED && !GRAPHICS_PREVENT_SECONDARY_WINDOWS) {
+            graphics_hook_subscreen_window(GFDM_SUBSCREEN_WINDOW);
+        }
     }
     if (is_gfdm_window && GRAPHICS_WINDOWED && !GRAPHICS_PREVENT_SECONDARY_WINDOWS) {
         gitadora_force_window_style(result);
@@ -767,6 +872,10 @@ static BOOL WINAPI MoveWindow_hook(HWND hWnd, int X, int Y, int nWidth, int nHei
         nHeight,
         bRepaint);
 
+    if (is_gfdm_two_head_small_window(hWnd)) {
+        return TRUE;
+    }
+
     // sound voltex windowed mode adjustments
     if (GRAPHICS_WINDOWED && GRAPHICS_SDVX_FORCE_720 && avs::game::is_model("KFC")) {
         RECT rect {};
@@ -874,6 +983,11 @@ static HCURSOR WINAPI SetCursor_hook(HCURSOR hCursor) {
 
 static LONG WINAPI SetWindowLongA_hook(HWND hWnd, int nIndex, LONG dwNewLong) {
 
+    if (is_gfdm_two_head_small_window(hWnd) &&
+            (nIndex == GWL_STYLE || nIndex == GWL_EXSTYLE)) {
+        return GetWindowLongA(hWnd, nIndex);
+    }
+
     // DDR window style fix
     if (nIndex == GWL_STYLE && avs::game::is_model("MDX")) {
         dwNewLong |= WS_OVERLAPPEDWINDOW;
@@ -894,6 +1008,11 @@ static LONG WINAPI SetWindowLongA_hook(HWND hWnd, int nIndex, LONG dwNewLong) {
 
 static LONG WINAPI SetWindowLongW_hook(HWND hWnd, int nIndex, LONG dwNewLong) {
 
+    if (is_gfdm_two_head_small_window(hWnd) &&
+            (nIndex == GWL_STYLE || nIndex == GWL_EXSTYLE)) {
+        return GetWindowLongW(hWnd, nIndex);
+    }
+
     // DDR overlapped window fix
     if (nIndex == GWL_STYLE && avs::game::is_model("MDX")) {
         dwNewLong |= WS_OVERLAPPEDWINDOW;
@@ -915,6 +1034,12 @@ static LONG WINAPI SetWindowLongW_hook(HWND hWnd, int nIndex, LONG dwNewLong) {
 static BOOL WINAPI SetWindowPos_hook(HWND hWnd, HWND hWndInsertAfter,
         int X, int Y, int cx, int cy, UINT uFlags) {
 
+    if (is_gfdm_two_head_small_window(hWnd) &&
+            ((uFlags & SWP_HIDEWINDOW) ||
+             (uFlags & (SWP_NOMOVE | SWP_NOSIZE)) != (SWP_NOMOVE | SWP_NOSIZE))) {
+        return TRUE;
+    }
+
     // windowed mode adjustments
     if (GRAPHICS_WINDOWED && (avs::game::is_model("LMA") || avs::game::is_model("MDX"))) {
         return TRUE;
@@ -939,6 +1064,13 @@ static BOOL WINAPI SetWindowPos_hook(HWND hWnd, HWND hWndInsertAfter,
 }
 
 static BOOL WINAPI ShowWindow_hook(HWND hWnd, int nCmdShow) {
+    if (is_gfdm_two_head_small_window(hWnd) &&
+            (nCmdShow == SW_HIDE || nCmdShow == SW_MINIMIZE ||
+             nCmdShow == SW_SHOWMINIMIZED || nCmdShow == SW_SHOWMINNOACTIVE ||
+             nCmdShow == SW_FORCEMINIMIZE)) {
+        return TRUE;
+    }
+
     if (games::gitadora::is_arena_model() &&
         GRAPHICS_PREVENT_SECONDARY_WINDOWS &&
         hWnd != GRAPHICS_HOOKED_WINDOW) {

src/spice2x/hooks/graphics/graphics.h

@@ -119,6 +119,15 @@ extern bool D3D9_DEVICE_HOOK_DISABLE;
 
 void graphics_init();
 void graphics_hook_window(HWND hWnd, D3DPRESENT_PARAMETERS *pPresentationParameters);
+// The native GITADORA two-head D3D9 group uses the game's named SMALL
+// device window for the native physical SMALL head. The game requests
+// D3DCREATE_NOWINDOWCHANGES, so this host must be made borderless and sized
+// to the requested native SMALL mode before the native fullscreen device is
+// created. During the adapter-group startup warmup, the monitor can briefly
+// report a different mode; preserve its origin but not that temporary size.
+bool graphics_gitadora_prepare_two_head_device_window(
+    HWND hWnd, HMONITOR target_monitor = nullptr, UINT desired_width = 0,
+    UINT desired_height = 0);
 void graphics_add_wnd_proc(WNDPROC wndProc);
 void graphics_remove_wnd_proc(WNDPROC wndProc);
 void graphics_hook_subscreen_window(HWND hWnd);

src/spice2x/launcher/options.cpp

@@ -1299,7 +1299,9 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .name = "gdalayout",
         .desc = "For Arena Model: select how many windows to create.\n\n"
             "1 window: main only; use the subscreen overlay for SMALL.\n\n"
-            "2 windows: main + SMALL. Note: currently only works for windowed mode, broken for fullscreen.\n\n"
+            "2 windows: main + SMALL. Without -w, this uses native D3D9 adapter-group fullscreen "
+            "with physical MAIN/SMALL and virtual LEFT/RIGHT. It requires two active displays on "
+            "one adapter group. With -w, it uses borderless windows instead.\n\n"
             "4 windows: main + LEFT + RIGHT + SMALL. Fullscreen requires exactly 4 monitors in the "
             "right resolution; see wiki for details.",
         .type = OptionType::Enum,