Addendum to #2635. Add support for multi-viewports in SDL+DX!! example. making all Win32-centric back-ends handle PlatformHandleRaw. Using the field to use/store the HWND for internal purpose in SDL/GLFW back-ends. (#1542)

examples/example_sdl_directx11/main.cpp

@@ -51,13 +51,25 @@ int main(int, char**)
     IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
-    //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
+    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;       // Enable Keyboard Controls
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+    io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;           // Enable Docking
+    io.ConfigFlags |= ImGuiConfigFlags_ViewportsEnable;         // Enable Multi-Viewport / Platform Windows
+    //io.ConfigViewportsNoAutoMerge = true;
+    //io.ConfigViewportsNoTaskBarIcon = true;
 
     // Setup Dear ImGui style
     ImGui::StyleColorsDark();
     //ImGui::StyleColorsClassic();
 
+    // When viewports are enabled we tweak WindowRounding/WindowBg so platform windows can look identical to regular ones.
+    ImGuiStyle& style = ImGui::GetStyle();
+    if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+    {
+        style.WindowRounding = 0.0f;
+        style.Colors[ImGuiCol_WindowBg].w = 1.0f;
+    }
+
     // Setup Platform/Renderer bindings
     ImGui_ImplSDL2_InitForD3D(window);
     ImGui_ImplDX11_Init(g_pd3dDevice, g_pd3dDeviceContext);
@@ -149,6 +161,13 @@ int main(int, char**)
         g_pd3dDeviceContext->ClearRenderTargetView(g_mainRenderTargetView, (float*)&clear_color);
         ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
 
+        // Update and Render additional Platform Windows
+        if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+        {
+            ImGui::UpdatePlatformWindows();
+            ImGui::RenderPlatformWindowsDefault();
+        }
+
         g_pSwapChain->Present(1, 0); // Present with vsync
         //g_pSwapChain->Present(0, 0); // Present without vsync
     }

examples/imgui_impl_dx10.cpp

@@ -553,7 +553,9 @@ static void ImGui_ImplDX10_CreateWindow(ImGuiViewport* viewport)
     ImGuiViewportDataDx10* data = IM_NEW(ImGuiViewportDataDx10)();
     viewport->RendererUserData = data;
 
-    HWND hwnd = (HWND)viewport->PlatformHandle;
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some back-ends will leave PlatformHandleRaw NULL, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);
 
     // Create swap chain

examples/imgui_impl_dx11.cpp

@@ -564,13 +564,9 @@ static void ImGui_ImplDX11_CreateWindow(ImGuiViewport* viewport)
     ImGuiViewportDataDx11* data = IM_NEW(ImGuiViewportDataDx11)();
     viewport->RendererUserData = data;
 
-    // When using SDL, PlatformHandleRaw will be the HWND (because PlatformHandle would be the SDL_Window)
-    // If not using SDL, PlatformHandleRaw will be null and PlatformHandle will contain the HWND
-    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
-    if (hwnd == 0)
-    {
-        hwnd = (HWND)viewport->PlatformHandle;
-    }
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some back-end will leave PlatformHandleRaw NULL, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);
 
     // Create swap chain

examples/imgui_impl_dx12.cpp

@@ -4,7 +4,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'D3D12_GPU_DESCRIPTOR_HANDLE' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
 //  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bits indices.
-// Issues:
+// Missing features, issues:
+//  [ ] Renderer: Missing multi-viewport support.
 //  [ ] 64-bit only for now! (Because sizeof(ImTextureId) == sizeof(void*)). See github.com/ocornut/imgui/pull/301
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
@@ -680,7 +681,9 @@ static void ImGui_ImplDX12_CreateWindow(ImGuiViewport* viewport)
 
     /*
     // FIXME-PLATFORM
-    HWND hwnd = (HWND)viewport->PlatformHandle;
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some back-ends will leave PlatformHandleRaw NULL, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
     IM_ASSERT(hwnd != 0);
 
     // Create swap chain

examples/imgui_impl_dx12.h

@@ -4,7 +4,8 @@
 // Implemented features:
 //  [X] Renderer: User texture binding. Use 'D3D12_GPU_DESCRIPTOR_HANDLE' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
 //  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bits indices.
-// Issues:
+// Missing features, issues:
+//  [ ] Renderer: Missing multi-viewport support.
 //  [ ] 64-bit only for now! (Because sizeof(ImTextureId) == sizeof(void*)). See github.com/ocornut/imgui/pull/301
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.

examples/imgui_impl_dx9.cpp

@@ -319,8 +319,10 @@ static void ImGui_ImplDX9_CreateWindow(ImGuiViewport* viewport)
     ImGuiViewportDataDx9* data = IM_NEW(ImGuiViewportDataDx9)();
     viewport->RendererUserData = data;
 
-    HWND hWnd = (HWND)viewport->PlatformHandle;
-    IM_ASSERT(hWnd != 0);
+    // PlatformHandleRaw should always be a HWND, whereas PlatformHandle might be a higher-level handle (e.g. GLFWWindow*, SDL_Window*).
+    // Some back-ends will leave PlatformHandleRaw NULL, in which case we assume PlatformHandle will contain the HWND.
+    HWND hwnd = viewport->PlatformHandleRaw ? (HWND)viewport->PlatformHandleRaw : (HWND)viewport->PlatformHandle;
+    IM_ASSERT(hwnd != 0);
 
     ZeroMemory(&data->d3dpp, sizeof(D3DPRESENT_PARAMETERS));
     data->d3dpp.Windowed = TRUE;
@@ -328,7 +330,7 @@ static void ImGui_ImplDX9_CreateWindow(ImGuiViewport* viewport)
     data->d3dpp.BackBufferWidth = (UINT)viewport->Size.x;
     data->d3dpp.BackBufferHeight = (UINT)viewport->Size.y;
     data->d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;
-    data->d3dpp.hDeviceWindow = hWnd;
+    data->d3dpp.hDeviceWindow = hwnd;
     data->d3dpp.EnableAutoDepthStencil = FALSE;
     data->d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
     data->d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;   // Present without vsync

examples/imgui_impl_glfw.cpp

@@ -202,6 +202,9 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
     main_viewport->PlatformHandle = (void*)g_Window;
+#ifdef _WIN32
+    main_viewport->PlatformHandleRaw = glfwGetWin32Window(g_Window);
+#endif
     if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
         ImGui_ImplGlfw_InitPlatformInterface();
 
@@ -444,6 +447,9 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     data->Window = glfwCreateWindow((int)viewport->Size.x, (int)viewport->Size.y, "No Title Yet", NULL, share_window);
     data->WindowOwned = true;
     viewport->PlatformHandle = (void*)data->Window;
+#ifdef _WIN32
+    viewport->PlatformHandleRaw = glfwGetWin32Window(data->Window);
+#endif
     glfwSetWindowPos(data->Window, (int)viewport->Pos.x, (int)viewport->Pos.y);
 
     // Install callbacks for secondary viewports
@@ -468,7 +474,7 @@ static void ImGui_ImplGlfw_DestroyWindow(ImGuiViewport* viewport)
         if (data->WindowOwned)
         {
 #if GLFW_HAS_GLFW_HOVERED && defined(_WIN32)
-            HWND hwnd = glfwGetWin32Window(data->Window);
+            HWND hwnd = (HWND)viewport->PlatformHandleRaw;
             ::RemovePropA(hwnd, "IMGUI_VIEWPORT");
 #endif
             glfwDestroyWindow(data->Window);
@@ -504,7 +510,7 @@ static void ImGui_ImplGlfw_ShowWindow(ImGuiViewport* viewport)
 
 #if defined(_WIN32)
     // GLFW hack: Hide icon from task bar
-    HWND hwnd = glfwGetWin32Window(data->Window);
+    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
     if (viewport->Flags & ImGuiViewportFlags_NoTaskBarIcon)
     {
         LONG ex_style = ::GetWindowLong(hwnd, GWL_EXSTYLE);
@@ -633,8 +639,7 @@ static void ImGui_ImplGlfw_SwapBuffers(ImGuiViewport* viewport, void*)
 static void ImGui_ImplWin32_SetImeInputPos(ImGuiViewport* viewport, ImVec2 pos)
 {
     COMPOSITIONFORM cf = { CFS_FORCE_POSITION, { (LONG)(pos.x - viewport->Pos.x), (LONG)(pos.y - viewport->Pos.y) }, { 0, 0, 0, 0 } };
-    if (ImGuiViewportDataGlfw* data = (ImGuiViewportDataGlfw*)viewport->PlatformUserData)
-        if (HWND hwnd = glfwGetWin32Window(data->Window))
+    if (HWND hwnd = (HWND)viewport->PlatformHandleRaw)
         if (HIMC himc = ::ImmGetContext(hwnd))
         {
             ::ImmSetCompositionWindow(himc, &cf);

examples/imgui_impl_sdl.cpp

@@ -200,6 +200,12 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window, void* sdl_gl_context)
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
     main_viewport->PlatformHandle = (void*)window;
+#if defined(_WIN32)
+    SDL_SysWMinfo info;
+    SDL_VERSION(&info.version);
+    if (SDL_GetWindowWMInfo(window, &info))
+        main_viewport->PlatformHandleRaw = info.info.win.window;
+#endif
 
     // We need SDL_CaptureMouse(), SDL_GetGlobalMouseState() from SDL 2.0.4+ to support multiple viewports.
     // We left the call to ImGui_ImplSDL2_InitPlatformInterface() outside of #ifdef to avoid unused-function warnings.
@@ -455,16 +461,13 @@ static void ImGui_ImplSDL2_CreateWindow(ImGuiViewport* viewport)
     }
     if (use_opengl && backup_context)
         SDL_GL_MakeCurrent(data->Window, backup_context);
-    viewport->PlatformHandle = (void*)data->Window;
 
+    viewport->PlatformHandle = (void*)data->Window;
 #if defined(_WIN32)
-    // save the window handle for render that needs it (directX)
     SDL_SysWMinfo info;
     SDL_VERSION(&info.version);
     if (SDL_GetWindowWMInfo(data->Window, &info))
-    {
         viewport->PlatformHandleRaw = info.info.win.window;
-    }
 #endif
 }
 
@@ -487,11 +490,7 @@ static void ImGui_ImplSDL2_ShowWindow(ImGuiViewport* viewport)
 {
     ImGuiViewportDataSDL2* data = (ImGuiViewportDataSDL2*)viewport->PlatformUserData;
 #if defined(_WIN32)
-    SDL_SysWMinfo info;
-    SDL_VERSION(&info.version);
-    if (SDL_GetWindowWMInfo(data->Window, &info))
-    {
-        HWND hwnd = info.info.win.window;
+    HWND hwnd = (HWND)viewport->PlatformHandleRaw;
 
     // SDL hack: Hide icon from task bar
     // Note: SDL 2.0.6+ has a SDL_WINDOW_SKIP_TASKBAR flag which is supported under Windows but the way it create the window breaks our seamless transition.
@@ -509,7 +508,6 @@ static void ImGui_ImplSDL2_ShowWindow(ImGuiViewport* viewport)
         ::ShowWindow(hwnd, SW_SHOWNA);
         return;
     }
-    }
 #endif
 
     SDL_ShowWindow(data->Window);

examples/imgui_impl_vulkan.cpp

@@ -3,8 +3,8 @@
 
 // Implemented features:
 //  [X] Renderer: Support for large meshes (64k+ vertices) with 16-bits indices.
+//  [x] Platform: Multi-viewport / platform windows. With issues (flickering when creating a new viewport).
 // Missing features:
-//  [ ] Platform: Multi-viewport / platform windows.
 //  [ ] Renderer: User texture binding. Changes of ImTextureID aren't supported by this binding! See https://github.com/ocornut/imgui/pull/914
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.

examples/imgui_impl_win32.cpp

@@ -73,7 +73,7 @@ bool    ImGui_ImplWin32_Init(void* hwnd)
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     g_hWnd = (HWND)hwnd;
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
-    main_viewport->PlatformHandle = (void*)g_hWnd;
+    main_viewport->PlatformHandle = main_viewport->PlatformHandleRaw = (void*)g_hWnd;
     if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
         ImGui_ImplWin32_InitPlatformInterface();
 
@@ -547,7 +547,7 @@ static void ImGui_ImplWin32_CreateWindow(ImGuiViewport* viewport)
         parent_window, NULL, ::GetModuleHandle(NULL), NULL);                    // Parent window, Menu, Instance, Param
     data->HwndOwned = true;
     viewport->PlatformRequestResize = false;
-    viewport->PlatformHandle = data->Hwnd;
+    viewport->PlatformHandle = viewport->PlatformHandleRaw = data->Hwnd;
 }
 
 static void ImGui_ImplWin32_DestroyWindow(ImGuiViewport* viewport)

imgui.h

@@ -2398,8 +2398,8 @@ struct ImGuiViewport
 
     void*               RendererUserData;       // void* to hold custom data structure for the renderer (e.g. swap chain, frame-buffers etc.)
     void*               PlatformUserData;       // void* to hold custom data structure for the OS / platform (e.g. windowing info, render context)
-    void*               PlatformHandle;         // void* for FindViewportByPlatformHandle(). (e.g. suggested to use natural platform handle such as HWND, GlfwWindow*, SDL_Window*)
-    void*               PlatformHandleRaw;      // void* to hold the platfor-native windows handle (e.g. the HWND) when using an abstraction layer like SDL (where PlatformHandle would be a SDL_Window*)
+    void*               PlatformHandle;         // void* for FindViewportByPlatformHandle(). (e.g. suggested to use natural platform handle such as HWND, GLFWWindow*, SDL_Window*)
+    void*               PlatformHandleRaw;      // void* to hold low-level, platform-native window handle (e.g. the HWND) when using an abstraction layer like GLFW or SDL (where PlatformHandle would be a SDL_Window*)
     bool                PlatformRequestClose;   // Platform window requested closure (e.g. window was moved by the OS / host window manager, e.g. pressing ALT-F4)
     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)