Backends: Win32: Add support for untranslated key codes

Author: thedmd

backends/imgui_impl_win32.cpp

@@ -78,6 +78,7 @@ struct ImGui_ImplWin32_Data
     ImGuiMouseCursor            LastMouseCursor;
     bool                        HasGamepad;
     bool                        WantUpdateHasGamepad;
+    bool                        WantUpdateScancodes;
 
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
     HMODULE                     XInputDLL;
@@ -102,6 +103,38 @@ static ImGui_ImplWin32_Data* ImGui_ImplWin32_GetBackendData()
 }
 
 // Functions
+static void ImGui_ImplWin32_UpdateScancodes()
+{
+    ImGui_ImplWin32_Data* bd = ImGui_ImplWin32_GetBackendData();
+
+    if (!bd->WantUpdateScancodes)
+        return;
+
+    bd->WantUpdateScancodes = false;
+
+    ImGuiIO& io = ImGui::GetIO();
+
+    for (int i = 0; i < IM_ARRAYSIZE(io.ScancodeMap); ++i)
+        io.ScancodeMap[i] = -1;
+
+    HKL layout = LoadKeyboardLayoutA("00000409", 0); // U.S. English
+    if (layout == NULL)
+        return;
+
+    for (int i = 0; i < IM_ARRAYSIZE(io.ScancodeMap); ++i)
+    {
+        int scancode = io.KeyMap[i] > 0 ? (int)MapVirtualKey(io.KeyMap[i], MAPVK_VK_TO_VSC) : 0;
+        if (scancode > 0)
+        {
+            auto us_vk = MapVirtualKeyExA(scancode, MAPVK_VSC_TO_VK, layout);
+            if (us_vk > 0)
+                io.ScancodeMap[i] = us_vk;
+        }
+    }
+
+    UnloadKeyboardLayout(layout);
+}
+
 bool    ImGui_ImplWin32_Init(void* hwnd)
 {
     ImGuiIO& io = ImGui::GetIO();
@@ -119,6 +152,7 @@ bool    ImGui_ImplWin32_Init(void* hwnd)
     io.BackendPlatformName = "imgui_impl_win32";
     io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;         // We can honor GetMouseCursor() values (optional)
     io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos;          // We can honor io.WantSetMousePos requests (optional, rarely used)
+    io.BackendFlags |= ImGuiBackednFlags_HasUntranslatedKeys;     // We can support mapping keys scancodes into ImGuiKey_XXX (optional, useful in games)
 
     bd->hWnd = (HWND)hwnd;
     bd->WantUpdateHasGamepad = true;
@@ -245,6 +279,8 @@ bool    ImGui_ImplWin32_Init(void* hwnd)
     io.KeyMap[ImGuiKey_F12] = VK_F12;
 #endif // IMGUI_HAS_EXTRA_KEYS
 
+    ImGui_ImplWin32_UpdateScancodes();
+
     // Dynamically load XInput library
 #ifndef IMGUI_IMPL_WIN32_DISABLE_GAMEPAD
     const char* xinput_dll_names[] =
@@ -432,6 +468,8 @@ void    ImGui_ImplWin32_NewFrame()
 
     // Update game controllers (if enabled and available)
     ImGui_ImplWin32_UpdateGamepads();
+
+    ImGui_ImplWin32_UpdateScancodes();
 }
 
 // Allow compilation with old Windows SDK. MinGW doesn't have default _WIN32_WINNT/WINVER versions.
@@ -566,6 +604,10 @@ IMGUI_IMPL_API LRESULT ImGui_ImplWin32_WndProcHandler(HWND hwnd, UINT msg, WPARA
         if ((UINT)wParam == DBT_DEVNODES_CHANGED)
             bd->WantUpdateHasGamepad = true;
         return 0;
+    case WM_INPUTLANGCHANGE:
+        if (io.BackendFlags & ImGuiBackednFlags_HasUntranslatedKeys)
+            bd->WantUpdateScancodes = true;
+        return 0;
     }
     return 0;
 }