iidx: show error message for emulated I/O mismatch in LDJ/TDJ sub overlay (#555)

## Link to GitHub Issue, if one exists
#345 

## Description of change
When DLL is configured to use TDJ I/O but spice is in LDJ mode, show an
error in LED ticker suggesting the user to turn on `-iidxtdj`.

When DLL is configured to use LDJ I/O but spice is in TDJ mode, show an
error in TDJ overaly suggesting the user to fix the DLL.

Fix a small bug that caused a white window to be created when `-w` is
enabled even when `-iidxtdj` is not, but DLL is using TDJ I/O.

src/spice2x/overlay/windows/generic_sub.cpp

@@ -85,10 +85,12 @@ namespace overlay::windows {
     }
 
     void GenericSubScreen::touch_transform(const ImVec2 xy_in, LONG *x_out, LONG *y_out) {}
+    void GenericSubScreen::check_for_errors() {}
 
     void GenericSubScreen::build_content() {
         this->flags |= ImGuiWindowFlags_NoBackground;
         
+        check_for_errors();
         if (this->disabled_message.has_value()) {
             this->draws_window = true;
             this->flags &= ~ImGuiWindowFlags_NoBackground;

src/spice2x/overlay/windows/generic_sub.h

@@ -31,6 +31,7 @@ namespace overlay::windows {
 
     protected:
         virtual void touch_transform(const ImVec2 xy_in, LONG *x_out, LONG *y_out);
+        virtual void check_for_errors();
         ImVec2 overlay_content_top_left;
         ImVec2 overlay_content_size;
         std::optional<std::string> disabled_message = std::nullopt;

src/spice2x/overlay/windows/iidx_seg.cpp

@@ -14,6 +14,7 @@ namespace overlay::windows {
 
     static const size_t TICKER_SIZE = 9;
     static const ImVec4 DARK_GRAY(0.1f, 0.1f, 0.1f, 1.f);
+    static const ImVec4 YELLOW(1.f, 1.f, 0.f, 1.f);
     static const ImVec4 RED(1.f, 0.f, 0.f, 1.f);
     static const float PADDING_Y = 8.f;
     static const float PADDING_X = 4.f;
@@ -91,6 +92,23 @@ namespace overlay::windows {
     }
 
     void IIDXSegmentDisplay::build_content() {
+
+        // explicitly check if TDJ I/O is enabled to account for the fact that I/O emulation may be
+        // disabled
+        if (games::iidx::CURRENT_IO_EMULATION_STATE == games::iidx::iidx_aio_emulation_state::bi2x_hook) {
+            ImGui::TextUnformatted("");
+            ImGui::TextColored(
+                YELLOW,
+                "%s",
+                "Invalid I/O mode; DLL is configured for TDJ I/O!\n"
+                "Enable -iidxtdj if you want TDJ subscreen overlay.");
+            ImGui::TextUnformatted("");
+            if (ImGui::Button("Close")) {
+                this->set_active(false);
+            }
+            return;
+        }
+
         char input_ticker[TICKER_SIZE];
 
         // get ticker content from game

src/spice2x/overlay/windows/iidx_sub.cpp

@@ -12,11 +12,9 @@ namespace overlay::windows {
         this->title = "IIDX TDJ Subscreen";
 
         if (GRAPHICS_IIDX_WSUB) {
-            this->disabled_message =
-                "Close this overlay and use the second window (ALT+TAB).\n"
-                "If you don't see the window, double check your DLL type and apply TDJ I/O patches as needed.";
+            this->disabled_message = "Close this overlay and use the second window. (try ALT+TAB)";
         } else if (games::iidx::IIDX_TDJ_MONITOR_WARNING) {
-            this->disabled_message = "TDJ mode subscreen overlay is not compatible with -monitor option";
+            this->disabled_message = "TDJ mode subscreen overlay is not compatible with -monitor option.";
         }
 
         float size = 0.5f;
@@ -44,6 +42,18 @@ namespace overlay::windows {
             ImGui::GetIO().DisplaySize.y - this->init_size.y - (ImGui::GetFrameHeight() / 2));
     }
 
+    void IIDXSubScreen::check_for_errors() {
+        if (games::iidx::CURRENT_IO_EMULATION_STATE ==
+            games::iidx::iidx_aio_emulation_state::bi2a_com2) {
+
+            // explicitly check if LDJ I/O is enabled (as opposed to checking if NOT TDJ I/O)
+            // to account for the fact that I/O emulation may be disabled
+            this->disabled_message =
+                "LDJ I/O detected; TDJ mode subscreen overlay requires TDJ I/O.\n"
+                "Ensure you apply applicable TDJ I/O patches, or run with TDJ DLL.";
+        }
+    }
+
     void IIDXSubScreen::touch_transform(const ImVec2 xy_in, LONG *x_out, LONG *y_out) {
         if (!this->get_active()) {
             return;

src/spice2x/overlay/windows/iidx_sub.h

@@ -12,6 +12,7 @@ namespace overlay::windows {
 
     protected:
         void touch_transform(const ImVec2 xy_in, LONG *x_out, LONG *y_out) override;
+        void check_for_errors() override;
     };
 }