Backends: fixed comment to state that ImGuiViewport::PlaformHandle is used to store SDL's WindowID, not SDL_Window*. (#7853)

Amend 2d99052

Author: ocornut

backends/imgui_impl_dx10.cpp

@@ -638,7 +638,7 @@ static void ImGui_ImplDX10_CreateWindow(ImGuiViewport* viewport)
     ImGui_ImplDX10_ViewportData* vd = IM_NEW(ImGui_ImplDX10_ViewportData)();
     viewport->RendererUserData = vd;
 
-    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL's WindowID).
     // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
     HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);

backends/imgui_impl_dx11.cpp

@@ -670,7 +670,7 @@ static void ImGui_ImplDX11_CreateWindow(ImGuiViewport* viewport)
     ImGui_ImplDX11_ViewportData* vd = IM_NEW(ImGui_ImplDX11_ViewportData)();
     viewport->RendererUserData = vd;
 
-    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL's WindowID).
     // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
     HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);

backends/imgui_impl_dx12.cpp

@@ -919,7 +919,7 @@ static void ImGui_ImplDX12_CreateWindow(ImGuiViewport* viewport)
     ImGui_ImplDX12_ViewportData* vd = IM_NEW(ImGui_ImplDX12_ViewportData)(bd->numFramesInFlight);
     viewport->RendererUserData = vd;
 
-    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL's WindowID).
     // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
     HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);

backends/imgui_impl_dx9.cpp

@@ -460,7 +460,7 @@ static void ImGui_ImplDX9_CreateWindow(ImGuiViewport* viewport)
     ImGui_ImplDX9_ViewportData* vd = IM_NEW(ImGui_ImplDX9_ViewportData)();
     viewport->RendererUserData = vd;
 
-    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL's WindowID).
     // Some backends will leave PlatformHandleRaw == 0, in which case we assume PlatformHandle will contain the HWND.
     HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);

backends/imgui_impl_glfw.cpp

@@ -1050,10 +1050,10 @@ void ImGui_ImplGlfw_InstallEmscriptenCallbacks(GLFWwindow* window, const char* c
 // If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
 //--------------------------------------------------------------------------------------------------------
 
-// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+// Helper structure we store in the void* PlatformUserData field of each ImGuiViewport to easily retrieve our backend data.
 struct ImGui_ImplGlfw_ViewportData
 {
-    GLFWwindow* Window;
+    GLFWwindow* Window;             // Stored in ImGuiViewport::PlatformHandle
     bool        WindowOwned;
     int         IgnoreWindowPosEventFrame;
     int         IgnoreWindowSizeEventFrame;

backends/imgui_impl_sdl2.cpp

@@ -141,7 +141,7 @@ static const Uint32 SDL_WINDOW_VULKAN = 0x10000000;
 struct ImGui_ImplSDL2_Data
 {
     SDL_Window*             Window;
-    Uint32                  WindowID;
+    Uint32                  WindowID;       // Stored in ImGuiViewport::PlatformHandle. Use SDL_GetWindowFromID() to get SDL_Window* from Uint32 WindowID.
     SDL_Renderer*           Renderer;
     Uint64                  Time;
     char*                   ClipboardTextData;
@@ -951,16 +951,16 @@ void ImGui_ImplSDL2_NewFrame()
 // If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
 //--------------------------------------------------------------------------------------------------------
 
-// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+// Helper structure we store in the void* PlatformUserData field of each ImGuiViewport to easily retrieve our backend data.
 struct ImGui_ImplSDL2_ViewportData
 {
     SDL_Window*     Window;
-    Uint32          WindowID;
+    Uint32          WindowID;       // Stored in ImGuiViewport::PlatformHandle. Use SDL_GetWindowFromID() to get SDL_Window* from Uint32 WindowID.
     bool            WindowOwned;
     SDL_GLContext   GLContext;
 
-    ImGui_ImplSDL2_ViewportData() { Window = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
-    ~ImGui_ImplSDL2_ViewportData() { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
+    ImGui_ImplSDL2_ViewportData()   { Window = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
+    ~ImGui_ImplSDL2_ViewportData()  { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
 };
 
 static void ImGui_ImplSDL2_CreateWindow(ImGuiViewport* viewport)

backends/imgui_impl_sdl3.cpp

@@ -902,17 +902,17 @@ void ImGui_ImplSDL3_NewFrame()
 // If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
 //--------------------------------------------------------------------------------------------------------
 
-// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+// Helper structure we store in the void* PlatformUserData field of each ImGuiViewport to easily retrieve our backend data.
 struct ImGui_ImplSDL3_ViewportData
 {
     SDL_Window*     Window;
     SDL_Window*     ParentWindow;
-    Uint32          WindowID;
+    Uint32          WindowID;       // Stored in ImGuiViewport::PlatformHandle. Use SDL_GetWindowFromID() to get SDL_Window* from Uint32 WindowID.
     bool            WindowOwned;
     SDL_GLContext   GLContext;
 
-    ImGui_ImplSDL3_ViewportData() { Window = ParentWindow = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
-    ~ImGui_ImplSDL3_ViewportData() { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
+    ImGui_ImplSDL3_ViewportData()   { Window = ParentWindow = nullptr; WindowID = 0; WindowOwned = false; GLContext = nullptr; }
+    ~ImGui_ImplSDL3_ViewportData()  { IM_ASSERT(Window == nullptr && GLContext == nullptr); }
 };
 
 static SDL_Window* ImGui_ImplSDL3_GetSDLWindowFromViewportID(ImGuiID viewport_id)

backends/imgui_impl_win32.cpp

@@ -1046,10 +1046,10 @@ void ImGui_ImplWin32_EnableAlphaCompositing(void* hwnd)
 // If you are new to dear imgui or creating a new binding for dear imgui, it is recommended that you completely ignore this section first..
 //--------------------------------------------------------------------------------------------------------
 
-// Helper structure we store in the void* RendererUserData field of each ImGuiViewport to easily retrieve our backend data.
+// Helper structure we store in the void* PlatformUserData field of each ImGuiViewport to easily retrieve our backend data.
 struct ImGui_ImplWin32_ViewportData
 {
-    HWND    Hwnd;
+    HWND    Hwnd;               // Stored in ImGuiViewport::PlatformHandle + PlatformHandleRaw
     HWND    HwndParent;
     bool    HwndOwned;
     DWORD   DwStyle;

imgui.h

@@ -3679,8 +3679,8 @@ struct ImGuiViewport
     // The library never uses those fields, they are merely storage to facilitate backend implementation.
     void*               RendererUserData;       // void* to hold custom data structure for the renderer (e.g. swap chain, framebuffers etc.). generally set by your Renderer_CreateWindow function.
     void*               PlatformUserData;       // void* to hold custom data structure for the OS / platform (e.g. windowing info, render context). generally set by your Platform_CreateWindow function.
-    void*               PlatformHandle;         // void* to hold higher-level, platform window handle (e.g. HWND, GLFWWindow*, SDL_Window*), for FindViewportByPlatformHandle().
-    void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (under Win32 this is expected to be a HWND, unused for other platforms), when using an abstraction layer like GLFW or SDL (where PlatformHandle would be a SDL_Window*)
+    void*               PlatformHandle;         // void* to hold higher-level, platform window handle (e.g. HWND for Win32 backend, Uint32 WindowID for SDL, GLFWWindow* for GLFW), for FindViewportByPlatformHandle().
+    void*               PlatformHandleRaw;      // void* to hold lower-level, platform-native window handle (always HWND on Win32 platform, unused for other platforms).
     bool                PlatformWindowCreated;  // Platform window has been created (Platform_CreateWindow() has been called). This is false during the first frame where a viewport is being created.
     bool                PlatformRequestMove;    // Platform window requested move (e.g. window was moved by the OS / host window manager, authoritative position will be OS window position)
     bool                PlatformRequestResize;  // Platform window requested resize (e.g. window was resized by the OS / host window manager, authoritative size will be OS window size)