nost: touch piano mode (#830)

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

## Description of change
Touch piano mode. Allows piano keys to be played with the touch screen.
Since the touch screen is still needed for menu navigation (including
during songs) a toggle switch is added so that the user can flip between
navigation mode and piano mode.

The touch targets are pixel-perfect. Don't let the game's piano
animations fool you.

## Testing

src/spice2x/CMakeLists.txt

@@ -417,6 +417,7 @@ set(SOURCE_FILES ${SOURCE_FILES}
         games/nost/nost.cpp
         games/nost/io.cpp
         games/nost/poke.cpp
+        games/nost/touch_mode.cpp
         games/gitadora/gitadora.cpp
         games/gitadora/asio.cpp
         games/gitadora/io.cpp
@@ -610,6 +611,7 @@ set(SOURCE_FILES ${SOURCE_FILES}
         overlay/windows/keypad.cpp
         overlay/windows/log.cpp
         overlay/windows/midi.cpp
+        overlay/windows/nostalgia_touch_piano.cpp
         overlay/windows/obs.cpp
         overlay/windows/obs_websocket.cpp
         overlay/windows/patch_manager.cpp

src/spice2x/acio/panb/panb.cpp

@@ -3,6 +3,7 @@
 #include "rawinput/rawinput.h"
 #include "games/nost/io.h"
 #include "games/nost/nost.h"
+#include "games/nost/touch_mode.h"
 #include "util/logging.h"
 #include "avs/game.h"
 
@@ -16,6 +17,7 @@ using namespace GameAPI;
 // static stuff
 static uint8_t STATUS_BUFFER[277];
 static bool STATUS_BUFFER_FREEZE = false;
+static constexpr uint8_t NOST_TOUCH_PIANO_VELOCITY = 11;
 
 /*
  * Implementations
@@ -226,6 +228,8 @@ static bool __cdecl ac_io_panb_update_control_status_buffer() {
                 games::nost::Analogs::Key27, games::nost::Analogs::Key28,
         };
 
+        const auto touch_key_state = games::nost::touch_mode::piano_key_state();
+
         // iterate pairs of keys
         for (size_t key_pair = 0; key_pair < 28 / 2; key_pair++) {
 
@@ -257,6 +261,10 @@ static bool __cdecl ac_io_panb_update_control_status_buffer() {
             if (button0 > 0) {
                 state0 = button0;
             }
+            if ((touch_key_state & (UINT32_C(1) << (key_pair * 2))) &&
+                state0 < NOST_TOUCH_PIANO_VELOCITY) {
+                state0 = NOST_TOUCH_PIANO_VELOCITY;
+            }
 
             const auto button1 = panb_get_button_velocity(
                 buttons.at(button_mapping[key_pair * 2 + 1]),
@@ -267,6 +275,10 @@ static bool __cdecl ac_io_panb_update_control_status_buffer() {
             if (button1 > 0) {
                 state1 = button1;
             }
+            if ((touch_key_state & (UINT32_C(1) << (key_pair * 2 + 1))) &&
+                state1 < NOST_TOUCH_PIANO_VELOCITY) {
+                state1 = NOST_TOUCH_PIANO_VELOCITY;
+            }
 
             // build value
             uint8_t value = 0;

src/spice2x/games/nost/nost.cpp

@@ -1,5 +1,6 @@
 #include "nost.h"
 #include "poke.h"
+#include "touch_mode.h"
 #include "hooks/setupapihook.h"
 #include "touch/native/nativetouchhook.h"
 #include "avs/game.h"
@@ -7,6 +8,7 @@
 namespace games::nost {
 
     bool ENABLE_POKE = false;
+    bool ENABLE_TOUCH_MODE = false;
 
     NostGame::NostGame() : Game("Nostalgia") {
     }
@@ -40,6 +42,9 @@ namespace games::nost {
         setupapihook_add(touch_settings);
 
         nativetouch::hook(avs::game::DLL_INSTANCE);
+        if (ENABLE_TOUCH_MODE) {
+            touch_mode::enable();
+        }
     }
 
     void NostGame::post_attach() {
@@ -49,6 +54,9 @@ namespace games::nost {
     }
 
     void NostGame::detach() {
+        if (ENABLE_TOUCH_MODE) {
+            touch_mode::disable();
+        }
         if (ENABLE_POKE) {
             poke::disable();
         }

src/spice2x/games/nost/nost.h

@@ -5,6 +5,7 @@
 namespace games::nost {
 
     extern bool ENABLE_POKE;
+    extern bool ENABLE_TOUCH_MODE;
 
     class NostGame : public games::Game {
     public:

src/spice2x/games/nost/touch_mode.cpp

@@ -0,0 +1,233 @@
+#include "touch_mode.h"
+
+#include <atomic>
+#include <mutex>
+#include <unordered_map>
+
+#include "touch/native/nativetouchhook.h"
+#include "util/logging.h"
+
+namespace games::nost::touch_mode {
+
+    // native contact positions feed piano input directly. native events reach the game
+    // in nav mode and are suppressed in piano mode. mode-button contacts are always
+    // suppressed and change that routing after release.
+    static constexpr LONG PIANO_LEFT_GAP = 11;
+    static constexpr LONG PIANO_RIGHT_GAP = 10;
+    static constexpr uint32_t PIANO_KEY_COUNT = 28;
+
+    struct TouchGeometry {
+        HWND window = nullptr;
+        RECT mode_button {};
+        LONG client_width = 0;
+        LONG client_height = 0;
+
+        bool valid() const {
+            return window != nullptr && client_width > 0 && client_height > 0;
+        }
+    };
+
+    struct NativeContact {
+        POINT position {};
+
+        // position contains game-client coordinates
+        bool client_position_valid = false;
+
+        // down began on the mode switch button; remains true through up
+        bool mode_button = false;
+    };
+
+    static std::atomic_bool accept_events { false };
+    static std::atomic<Mode> current_mode_state { Mode::Nav };
+    static std::mutex state_mutex;
+    static TouchGeometry touch_geometry;
+
+    // native contacts are kept by ID so each contact contributes exactly one position
+    static std::unordered_map<DWORD, NativeContact> active_contacts;
+
+    // a hardware button release requests one change after all contacts are released
+    static bool mode_change_pending = false;
+
+    static void reset_state_locked() {
+        current_mode_state.store(Mode::Nav, std::memory_order_release);
+        touch_geometry = {};
+        active_contacts.clear();
+        mode_change_pending = false;
+    }
+
+    // hardware contacts arrive in screen coordinates
+    static bool native_touch_in_button(const nativetouch::NativeTouchEvent &event) {
+        if (!touch_geometry.valid()) {
+            return false;
+        }
+
+        POINT position { event.x, event.y };
+        if (!ScreenToClient(touch_geometry.window, &position)) {
+            return false;
+        }
+        return PtInRect(&touch_geometry.mode_button, position) != FALSE;
+    }
+
+    static bool update_touch_state(const nativetouch::NativeTouchEvent &event) {
+        std::lock_guard<std::mutex> lock(state_mutex);
+
+        // first, process down / move events
+        if (event.down || event.move) {
+            auto contact = active_contacts.try_emplace(event.id).first;
+
+            // keep track of IDs that began as a down on the mode switch button
+            if (event.down) {
+                contact->second.mode_button = native_touch_in_button(event);
+            }
+
+            // check for valid position
+            POINT position { event.x, event.y };
+            if (touch_geometry.window != nullptr &&
+                ScreenToClient(touch_geometry.window, &position)) {
+                contact->second.position = position;
+                contact->second.client_position_valid = true;
+            }
+        }
+
+        const auto contact = active_contacts.find(event.id);
+        const bool mode_button_contact = contact != active_contacts.end() &&
+            contact->second.mode_button;
+
+        // process up events
+        if (event.up) {
+            active_contacts.erase(event.id);
+
+            // if a contact that began down event on the mode switch button has
+            // been released, a mode switch is now pending
+            if (mode_button_contact) {
+                mode_change_pending = true;
+            }
+
+            // apply the change on the final hardware up. switching earlier would
+            // split another contact's down and up events across different modes
+            if (mode_change_pending && active_contacts.empty()) {
+                mode_change_pending = false;
+                const auto next_mode = current_mode() == Mode::Nav ? Mode::Piano : Mode::Nav;
+                current_mode_state.store(next_mode, std::memory_order_release);
+            }
+        }
+        return mode_button_contact;
+    }
+
+    // install the Nostalgia-specific native touch interception
+    void enable() {
+        if (accept_events.exchange(true, std::memory_order_acq_rel)) {
+            return;
+        }
+
+        {
+            std::lock_guard<std::mutex> lock(state_mutex);
+            reset_state_locked();
+        }
+
+        nativetouch::set_input_filter(filter_native_touch);
+        log_info("nost::touch", "enabled");
+    }
+
+    void disable() {
+        if (!accept_events.exchange(false, std::memory_order_acq_rel)) {
+            return;
+        }
+
+        nativetouch::set_input_filter(nullptr);
+
+        std::lock_guard<std::mutex> lock(state_mutex);
+        reset_state_locked();
+    }
+
+    bool enabled() {
+        return accept_events.load(std::memory_order_acquire);
+    }
+
+    Mode current_mode() {
+        return current_mode_state.load(std::memory_order_acquire);
+    }
+
+    // publish the rendered overlay button rectangle in game-client pixels
+    void publish_button_bounds(HWND window, const RECT &client_bounds) {
+        TouchGeometry next {};
+        RECT client_rect {};
+        if (window != nullptr && GetClientRect(window, &client_rect) &&
+            client_rect.right > 0 && client_rect.bottom > 0) {
+            next.window = window;
+            next.mode_button = client_bounds;
+            next.client_width = client_rect.right;
+            next.client_height = client_rect.bottom;
+        }
+
+        std::lock_guard<std::mutex> lock(state_mutex);
+        touch_geometry = next;
+    }
+
+    // return the active 28-key piano bitfield for the PANB input update
+    uint32_t piano_key_state() {
+        if (!enabled() || current_mode() != Mode::Piano) {
+            return 0;
+        }
+
+        std::lock_guard<std::mutex> lock(state_mutex);
+        if (current_mode() != Mode::Piano || !touch_geometry.valid()) {
+            return 0;
+        }
+
+        uint32_t state = 0;
+        for (const auto &contact : active_contacts) {
+            // invalid position or mode-button contact; ignore these contacts
+            if (!contact.second.client_position_valid || contact.second.mode_button) {
+                continue;
+            }
+
+            const auto &position = contact.second.position;
+
+            // outside the client area or on the mode button; ignore these contacts
+            if (position.x < 0 || position.x >= touch_geometry.client_width ||
+                position.y < 0 || position.y >= touch_geometry.client_height ||
+                PtInRect(&touch_geometry.mode_button, position)) {
+                continue;
+            }
+
+            // divide the inset width evenly; touches in either side gap clamp to
+            // the nearest outer key so the physical screen edges remain playable
+            const auto piano_width =
+                touch_geometry.client_width - PIANO_LEFT_GAP - PIANO_RIGHT_GAP;
+            uint32_t key = 0;
+            if (position.x >= touch_geometry.client_width - PIANO_RIGHT_GAP) {
+                key = PIANO_KEY_COUNT - 1;
+            } else if (position.x >= PIANO_LEFT_GAP && piano_width > 0) {
+                key = static_cast<uint32_t>(
+                    (position.x - PIANO_LEFT_GAP) * PIANO_KEY_COUNT / piano_width);
+            }
+            state |= UINT32_C(1) << key;
+        }
+
+        return state;
+    }
+
+    // update native contacts and report whether this event should be hidden from the game
+    bool filter_native_touch(const nativetouch::NativeTouchEvent &event) {
+        // synthetic events are outside this hardware-only feature
+        if (!enabled() || event.synthetic) {
+            // false leaves the event visible to the game
+            return false;
+        }
+
+        // snapshot routing before an up event can commit a pending mode switch
+        const bool piano_mode_before_update = current_mode() == Mode::Piano;
+
+        // update the contact lifetime and commit any pending switch when safe
+        const bool mode_button_contact = update_touch_state(event);
+
+        // hide every event in a contact that began on the mode switch button
+        if (mode_button_contact) {
+            return true;
+        }
+
+        // piano mode consumes hardware events; nav mode forwards them to the game
+        return piano_mode_before_update;
+    }
+}

src/spice2x/games/nost/touch_mode.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <cstdint>
+#include <windows.h>
+
+#include "touch/native/nativetouchhook.h"
+
+namespace games::nost::touch_mode {
+
+    // nav mode forwards contacts to the game; piano mode converts them into piano keys
+    enum class Mode {
+        Nav,
+        Piano,
+    };
+
+    void enable();
+    void disable();
+    bool enabled();
+
+    Mode current_mode();
+
+    void publish_button_bounds(HWND window, const RECT &client_bounds);
+
+    uint32_t piano_key_state();
+
+    bool filter_native_touch(const nativetouch::NativeTouchEvent &event);
+}

src/spice2x/launcher/launcher.cpp

@@ -1786,7 +1786,16 @@ int main_implementation(int argc, char *argv[]) {
             games::iidx::poke::enable();
         }
         if (options[launcher::Options::NostalgiaPoke].is_active()) {
-            games::nost::ENABLE_POKE = TRUE;
+            games::nost::ENABLE_POKE = true;
+        }
+        if (options[launcher::Options::NostalgiaTouchMode].is_active()) {
+            if (overlay::ENABLED) {
+                games::nost::ENABLE_TOUCH_MODE = true;
+            } else {
+                log_warning(
+                    "launcher",
+                    "Nostalgia Touch Mode requires the global overlay; ignoring -nosttouch");
+            }
         }
     }
 

src/spice2x/launcher/options.cpp

@@ -3149,6 +3149,21 @@ static const std::vector<OptionDefinition> OPTION_DEFINITIONS = {
         .type = OptionType::Bool,
         .game_name = "Nostalgia",
         .category = "Game Options",
+        .quick_setting_category = "Game",
+    },
+    {
+        // NostalgiaTouchMode
+        .title = "Nostalgia Touch Piano",
+        .name = "nosttouch",
+        .desc =
+            "Allows you to play the piano by touching the screen instead of a controller. "
+            "Use the mode switch button to toggle between interacting with the menu and playing the piano.\n\n"
+            "Velocity sensitivity is not supported. Touch targets will be pixel-perfect aligned with the "
+            "judgement line, key beams, and notes.",
+        .type = OptionType::Bool,
+        .game_name = "Nostalgia",
+        .category = "Game Options",
+        .quick_setting_category = "Game",
     },
     {
         // ForceBackBufferCount

src/spice2x/launcher/options.h

@@ -297,6 +297,7 @@ namespace launcher {
             DDRP4IOBufferMode,
             InputRequiresFocus,
             NostalgiaPoke,
+            NostalgiaTouchMode,
             ForceBackBufferCount,
             SDVXWindowedSubscreenSize,
             SDVXWindowedSubscreenPosition,

src/spice2x/overlay/overlay.cpp

@@ -5,6 +5,7 @@
 #include "games/io.h"
 #include "games/gitadora/gitadora.h"
 #include "games/iidx/iidx.h"
+#include "games/nost/nost.h"
 #include "games/popn/popn.h"
 #include "games/rb/touch_debug.h"
 #include "hooks/graphics/graphics.h"
@@ -51,6 +52,7 @@
 #include "windows/sdvx_sub.h"
 #include "windows/keypad.h"
 #include "windows/log.h"
+#include "windows/nostalgia_touch_piano.h"
 #include "windows/obs.h"
 #include "windows/patch_manager.h"
 #include "windows/exitprompt.cpp"
@@ -404,6 +406,12 @@ void overlay::SpiceOverlay::init() {
         window_fps->set_active(true);
     }
 
+    if (!cfg::CONFIGURATOR_STANDALONE &&
+        avs::game::is_model("PAN") && games::nost::ENABLE_TOUCH_MODE) {
+        window_nostalgia_touch_piano =
+            std::make_unique<overlay::windows::NostalgiaTouchPiano>(this);
+    }
+
     // owned separately from `windows` so it is not part of the overlay window layer
     window_main_menu = std::make_unique<overlay::windows::ExitPrompt>(this);
 
@@ -556,13 +564,18 @@ void overlay::SpiceOverlay::new_frame() {
     const bool draw_fps_persistent = this->renderer != OverlayRenderer::SOFTWARE
         && this->window_fps->get_active();
 
+    const bool draw_nostalgia_touch_piano = this->renderer != OverlayRenderer::SOFTWARE
+        && this->window_nostalgia_touch_piano
+        && this->window_nostalgia_touch_piano->get_active();
+
     // draw RB touch diagnostics
     const bool draw_rb_touch_debug = this->renderer != OverlayRenderer::SOFTWARE
         && games::rb::touch_debug_overlay_enabled();
 
     // check if there is nothing to draw
     this->has_pending_frame = false;
-    if (!this->active && !draw_notifications && !draw_fps_persistent && !draw_rb_touch_debug) {
+    if (!this->active && !draw_notifications && !draw_fps_persistent &&
+        !draw_nostalgia_touch_piano && !draw_rb_touch_debug) {
         return;
     }
 
@@ -596,7 +609,13 @@ void overlay::SpiceOverlay::new_frame() {
         for (auto &window : this->windows) {
             window->build();
         }
+    }
 
+    if (draw_nostalgia_touch_piano) {
+        this->window_nostalgia_touch_piano->build();
+    }
+
+    if (this->active) {
         // draw the main menu on top of the overlay windows
         this->window_main_menu->build();
 
@@ -819,6 +838,10 @@ void overlay::SpiceOverlay::update() {
     // FPS window
     this->window_fps->update();
 
+    if (this->window_nostalgia_touch_piano) {
+        this->window_nostalgia_touch_piano->update();
+    }
+
     // main menu (owned separately from the overlay window layer)
     this->window_main_menu->update();
 

src/spice2x/overlay/overlay.h

@@ -83,6 +83,7 @@ namespace overlay {
         // not part of `windows`: drawn/updated on the persistent layer (like
         // notifications), independent of the overlay's active state and input gates.
         std::unique_ptr<Window> window_fps;
+        std::unique_ptr<Window> window_nostalgia_touch_piano;
 
         // not part of `windows`: the main menu / launcher. owned and drawn
         // separately from the overlay window layer; it drives the overlay's
@@ -138,6 +139,9 @@ namespace overlay {
         inline IDirect3DDevice9 *get_device() {
             return this->device;
         }
+        inline HWND get_window() {
+            return this->hWnd;
+        }
 
         bool can_transform_touch_input() {
             return (this->subscreen_mouse_handler != nullptr);

src/spice2x/overlay/windows/nostalgia_touch_piano.cpp

@@ -0,0 +1,149 @@
+#include "nostalgia_touch_piano.h"
+
+#include <cmath>
+
+#include "external/imgui/imgui_internal.h"
+#include "games/nost/touch_mode.h"
+
+namespace overlay::windows {
+
+    static constexpr float BUTTON_WIDTH = 144.f;
+    static constexpr float BUTTON_HEIGHT = 40.f;
+    static constexpr float WINDOW_PADDING = 4.f;
+    static constexpr float EDGE_MARGIN = 4.f;
+    static constexpr float PIANO_HEIGHT_RATIO = 0.08f;
+    static constexpr float PIANO_LEFT_GAP = 11.f;
+    static constexpr float PIANO_RIGHT_GAP = 10.f;
+    static constexpr uint32_t PIANO_KEY_COUNT = 28;
+
+    static constexpr ImU32 PIANO_KEY_COLOR = IM_COL32(255, 255, 255, 50);
+    static constexpr ImU32 PIANO_KEY_ACTIVE_COLOR = IM_COL32(255, 48, 48, 160);
+    static constexpr ImU32 PIANO_KEY_BORDER_COLOR = IM_COL32(0, 0, 0, 100);
+
+    struct ButtonPalette {
+        ImVec4 normal;
+        ImVec4 hovered;
+        ImVec4 active;
+    };
+
+    static const ButtonPalette NAV_MODE_PALETTE {
+        ImVec4(0.10f, 0.45f, 0.28f, 0.72f),
+        ImVec4(0.14f, 0.58f, 0.36f, 0.82f),
+        ImVec4(0.08f, 0.34f, 0.21f, 0.90f),
+    };
+    static const ButtonPalette PIANO_MODE_PALETTE {
+        ImVec4(0.15f, 0.32f, 0.62f, 0.72f),
+        ImVec4(0.20f, 0.42f, 0.78f, 0.82f),
+        ImVec4(0.10f, 0.24f, 0.50f, 0.90f),
+    };
+
+    static void draw_piano_keys(
+        const ImVec2 &display_size,
+        LONG client_width,
+        uint32_t key_state) {
+
+        if (display_size.x <= 0.f || display_size.y <= 0.f || client_width <= 0) {
+            return;
+        }
+
+        // this is only a visual guide; native touch routing owns the actual input
+        const float left_gap = PIANO_LEFT_GAP * display_size.x / client_width;
+        const float right_gap = PIANO_RIGHT_GAP * display_size.x / client_width;
+        const float piano_width = display_size.x - left_gap - right_gap;
+        if (piano_width <= 0.f) {
+            return;
+        }
+
+        const float key_width = piano_width / PIANO_KEY_COUNT;
+        const float key_top = display_size.y * (1.f - PIANO_HEIGHT_RATIO);
+        auto *draw_list = ImGui::GetBackgroundDrawList();
+
+        for (uint32_t key = 0; key < PIANO_KEY_COUNT; key++) {
+            const ImVec2 key_min(left_gap + key * key_width, key_top);
+            const ImVec2 key_max(left_gap + (key + 1) * key_width, display_size.y);
+            const bool active = (key_state & (UINT32_C(1) << key)) != 0;
+            draw_list->AddRectFilled(
+                key_min,
+                key_max,
+                active ? PIANO_KEY_ACTIVE_COLOR : PIANO_KEY_COLOR);
+            draw_list->AddRect(key_min, key_max, PIANO_KEY_BORDER_COLOR);
+        }
+    }
+
+    NostalgiaTouchPiano::NostalgiaTouchPiano(SpiceOverlay *overlay) : Window(overlay) {
+        this->title = "Nostalgia Touch Piano";
+        this->flags = ImGuiWindowFlags_NoTitleBar
+            | ImGuiWindowFlags_NoResize
+            | ImGuiWindowFlags_NoCollapse
+            | ImGuiWindowFlags_NoMove
+            | ImGuiWindowFlags_NoDocking
+            | ImGuiWindowFlags_NoBackground
+            | ImGuiWindowFlags_NoSavedSettings
+            | ImGuiWindowFlags_NoNav
+            | ImGuiWindowFlags_NoBringToFrontOnFocus;
+        this->window_padding = overlay::apply_scaling_to_vector(WINDOW_PADDING, WINDOW_PADDING);
+        this->set_active(true);
+    }
+
+    void NostalgiaTouchPiano::calculate_initial_window() {
+        this->init_size = overlay::apply_scaling_to_vector(
+            BUTTON_WIDTH + WINDOW_PADDING * 2,
+            BUTTON_HEIGHT + WINDOW_PADDING * 2);
+        this->init_pos = overlay::apply_scaling_to_vector(EDGE_MARGIN, EDGE_MARGIN);
+    }
+
+    void NostalgiaTouchPiano::build_content() {
+        // keep the control anchored while the game window changes size or mode
+        ImGui::SetWindowPos(
+            overlay::apply_scaling_to_vector(EDGE_MARGIN, EDGE_MARGIN),
+            ImGuiCond_Always);
+
+        // stay above regular overlay windows, but never cover a blocking modal
+        ImGuiWindow *mode_window = ImGui::GetCurrentWindow();
+        if (ImGuiWindow *modal = ImGui::GetTopMostPopupModal()) {
+            ImGui::BringWindowToDisplayBehind(mode_window, modal);
+        } else {
+            ImGui::BringWindowToDisplayFront(mode_window);
+        }
+
+        const bool nav_mode =
+            games::nost::touch_mode::current_mode() == games::nost::touch_mode::Mode::Nav;
+        const char *label = nav_mode ? "Nav Mode" : "Piano Mode";
+
+        // make the active routing mode recognizable without reading the label
+        const auto &palette = nav_mode ? NAV_MODE_PALETTE : PIANO_MODE_PALETTE;
+        ImGui::PushStyleColor(ImGuiCol_Button, palette.normal);
+        ImGui::PushStyleColor(ImGuiCol_ButtonHovered, palette.hovered);
+        ImGui::PushStyleColor(ImGuiCol_ButtonActive, palette.active);
+        ImGui::Button(label, overlay::apply_scaling_to_vector(BUTTON_WIDTH, BUTTON_HEIGHT));
+        ImGui::PopStyleColor(3);
+
+        const auto &io = ImGui::GetIO();
+        RECT client_rect {};
+        if (io.DisplaySize.x > 0.f && io.DisplaySize.y > 0.f &&
+            GetClientRect(this->overlay->get_window(), &client_rect)) {
+
+            // convert the rendered imgui rectangle into the client coordinates
+            // used by hardware touch publication and piano-key mapping
+            const auto item_min = ImGui::GetItemRectMin();
+            const auto item_max = ImGui::GetItemRectMax();
+            const auto client_width = client_rect.right - client_rect.left;
+            const auto client_height = client_rect.bottom - client_rect.top;
+            if (!nav_mode) {
+                draw_piano_keys(
+                    io.DisplaySize,
+                    client_width,
+                    games::nost::touch_mode::piano_key_state());
+            }
+
+            RECT button_bounds {
+                static_cast<LONG>(std::lround(item_min.x * client_width / io.DisplaySize.x)),
+                static_cast<LONG>(std::lround(item_min.y * client_height / io.DisplaySize.y)),
+                static_cast<LONG>(std::lround(item_max.x * client_width / io.DisplaySize.x)),
+                static_cast<LONG>(std::lround(item_max.y * client_height / io.DisplaySize.y)),
+            };
+            games::nost::touch_mode::publish_button_bounds(
+                this->overlay->get_window(), button_bounds);
+        }
+    }
+}

src/spice2x/overlay/windows/nostalgia_touch_piano.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "overlay/window.h"
+
+namespace overlay::windows {
+
+    // persistent mode control rendered independently of the main overlay visibility
+    class NostalgiaTouchPiano : public Window {
+    public:
+        explicit NostalgiaTouchPiano(SpiceOverlay *overlay);
+
+        void calculate_initial_window() override;
+        void build_content() override;
+    };
+}

src/spice2x/touch/native/nativetouchhook.cpp

@@ -2,6 +2,9 @@
 // mingw otherwise doesn't load touch stuff
 #define _WIN32_WINNT 0x0601
 
+#include <atomic>
+
+#include "nativetouchhook.h"
 #include "avs/game.h"
 #include "rawinput/touch.h"
 #include "inject.h"
@@ -32,6 +35,7 @@ namespace nativetouch {
 
     static decltype(GetSystemMetrics) *GetSystemMetrics_orig = nullptr;
     static decltype(GetTouchInputInfo) *GetTouchInputInfo_orig = nullptr;
+    static std::atomic<TouchInputFilter> touch_input_filter { nullptr };
     static bool native_touch_hooked = false;
     static bool native_display_initialized = false;
     static DWORD native_display_orientation = DMDO_DEFAULT;
@@ -184,6 +188,22 @@ namespace nativetouch {
                     point->dwFlags = 0;
                 }
             }
+
+            const auto filter = touch_input_filter.load(std::memory_order_acquire);
+            if (point->dwFlags != 0 && filter != nullptr) {
+                const NativeTouchEvent event {
+                    .id = point->dwID,
+                    .x = point->x / 100,
+                    .y = point->y / 100,
+                    .down = (point->dwFlags & TOUCHEVENTF_DOWN) != 0,
+                    .move = (point->dwFlags & TOUCHEVENTF_MOVE) != 0,
+                    .up = (point->dwFlags & TOUCHEVENTF_UP) != 0,
+                    .synthetic = synthetic,
+                };
+                if (filter(event)) {
+                    point->dwFlags = 0;
+                }
+            }
         }
         
         return result;
@@ -193,6 +213,10 @@ namespace nativetouch {
         return native_touch_hooked;
     }
 
+    void set_input_filter(TouchInputFilter filter) {
+        touch_input_filter.store(filter, std::memory_order_release);
+    }
+
     void refresh_contact_lifetime() {
         if (settings::REFRESH_CONTACT_LIFETIME_FROM_GAME_LOOP) {
             inject::refresh_contact_lifetime();

src/spice2x/touch/native/nativetouchhook.h

@@ -1,8 +1,23 @@
+#pragma once
+
 #include <windows.h>
 
 namespace nativetouch {
+    struct NativeTouchEvent {
+        DWORD id;
+        LONG x;
+        LONG y;
+        bool down;
+        bool move;
+        bool up;
+        bool synthetic;
+    };
+
+    using TouchInputFilter = bool (*)(const NativeTouchEvent &event);
+
     void hook(HMODULE module);
     void refresh_contact_lifetime();
+    void set_input_filter(TouchInputFilter filter);
 
     // true once hook() has installed the native touch stack for the current game;
     // such games consume touch through the GetTouchInputInfo hook rather than spicetouch