Viewport, Platform: Added void* to render/swap buffer functions. Comments. (#1542, #1042)

examples/directx10_example/main.cpp

@@ -208,9 +208,9 @@ int main(int, char**)
         ImGui::Render();
         ImGui_ImplDX10_RenderDrawData(ImGui::GetDrawData());
 
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         g_pSwapChain->Present(1, 0); // Present with vsync
         //g_pSwapChain->Present(0, 0); // Present without vsync

examples/directx11_example/main.cpp

@@ -226,9 +226,9 @@ int main(int, char**)
         ImGui::Render();
         ImGui_ImplDX11_RenderDrawData(ImGui::GetDrawData());
 
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         g_pSwapChain->Present(1, 0); // Present with vsync
         //g_pSwapChain->Present(0, 0); // Present without vsync

examples/directx12_example/main.cpp

@@ -401,9 +401,9 @@ int main(int, char**)
 
         g_pd3dCommandQueue->ExecuteCommandLists(1, (ID3D12CommandList* const*)&g_pd3dCommandList);
 
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         g_pSwapChain->Present(1, 0); // Present with vsync
         //g_pSwapChain->Present(0, 0); // Present without vsync

examples/imgui_impl_dx10.cpp

@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] User texture binding. Use 'ID3D10ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
@@ -581,7 +582,7 @@ static void ImGui_ImplDX10_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
     }
 }
 
-static void ImGui_ImplDX10_RenderViewport(ImGuiViewport* viewport)
+static void ImGui_ImplDX10_RenderViewport(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx10* data = (ImGuiViewportDataDx10*)viewport->RendererUserData;
     ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
@@ -591,7 +592,7 @@ static void ImGui_ImplDX10_RenderViewport(ImGuiViewport* viewport)
     ImGui_ImplDX10_RenderDrawData(viewport->DrawData);
 }
 
-static void ImGui_ImplDX10_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplDX10_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx10* data = (ImGuiViewportDataDx10*)viewport->RendererUserData;
     data->SwapChain->Present(0, 0); // Present without vsync

examples/imgui_impl_dx10.h

@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] User texture binding. Use 'ID3D10ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().

examples/imgui_impl_dx11.cpp

@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
@@ -589,7 +590,7 @@ static void ImGui_ImplDX11_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
     }
 }
 
-static void ImGui_ImplDX11_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplDX11_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx11* data = (ImGuiViewportDataDx11*)viewport->RendererUserData;
     ImVec4 clear_color = ImVec4(0.0f, 0.0f, 0.0f, 1.0f);
@@ -599,7 +600,7 @@ static void ImGui_ImplDX11_RenderWindow(ImGuiViewport* viewport)
     ImGui_ImplDX11_RenderDrawData(viewport->DrawData);
 }
 
-static void ImGui_ImplDX11_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplDX11_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx11* data = (ImGuiViewportDataDx11*)viewport->RendererUserData;
     data->SwapChain->Present(0, 0); // Present without vsync

examples/imgui_impl_dx11.h

@@ -3,6 +3,7 @@
 
 // Implemented features:
 //  [X] User texture binding. Use 'ID3D11ShaderResourceView*' as ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().

examples/imgui_impl_dx12.cpp

@@ -726,7 +726,7 @@ static void ImGui_ImplDX12_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
     */
 }
 
-static void ImGui_ImplDX12_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplDX12_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx12* data = (ImGuiViewportDataDx12*)viewport->RendererUserData;
     IM_ASSERT(0);
@@ -740,7 +740,7 @@ static void ImGui_ImplDX12_RenderWindow(ImGuiViewport* viewport)
     ImGui_ImplDX12_RenderDrawData(viewport->DrawData);
 }
 
-static void ImGui_ImplDX12_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplDX12_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataDx12* data = (ImGuiViewportDataDx12*)viewport->RendererUserData;
     IM_ASSERT(0);

examples/imgui_impl_glfw.cpp

@@ -4,6 +4,7 @@
 
 // Implemented features:
 //  [X] Gamepad navigation mapping. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
+//  [X] Multi-viewport windows (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
@@ -448,14 +449,14 @@ static void ImGui_ImplGlfw_SetWindowTitle(ImGuiViewport* viewport, const char* t
     glfwSetWindowTitle(data->Window, title);
 }
 
-static void ImGui_ImplGlfw_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplGlfw_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataGlfw* data = (ImGuiViewportDataGlfw*)viewport->PlatformUserData;
     if (g_ClientApi == GlfwClientApi_OpenGL)
         glfwMakeContextCurrent(data->Window);
 }
 
-static void ImGui_ImplGlfw_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplGlfw_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataGlfw* data = (ImGuiViewportDataGlfw*)viewport->PlatformUserData;
     if (g_ClientApi == GlfwClientApi_OpenGL)

examples/imgui_impl_glfw.h

@@ -4,6 +4,7 @@
 
 // Implemented features:
 //  [X] Gamepad navigation mapping. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
+//  [X] Multi-viewport windows (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().

examples/imgui_impl_opengl2.cpp

@@ -1,6 +1,9 @@
 // ImGui Renderer for: OpenGL2 (legacy OpenGL, fixed pipeline)
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 
+// Implemented features:
+//  [X] User texture binding. Use 'GLUint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+
 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in imgui_impl_opengl3.cpp**
 // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.

examples/imgui_impl_opengl2.h

@@ -1,6 +1,9 @@
 // ImGui Renderer for: OpenGL2 (legacy OpenGL, fixed pipeline)
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 
+// Implemented features:
+//  [X] User texture binding. Use 'GLUint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+
 // **DO NOT USE THIS CODE IF YOUR CODE/ENGINE IS USING MODERN OPENGL (SHADERS, VBO, VAO, etc.)**
 // **Prefer using the code in imgui_impl_opengl3.cpp**
 // This code is mostly provided as a reference to learn how ImGui integration works, because it is shorter to read.

examples/imgui_impl_opengl3.cpp

@@ -2,6 +2,10 @@
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 // (Note: We are using GL3W as a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc..)
 
+// Implemented features:
+//  [X] User texture binding. Use 'GLUint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
+
 // CHANGELOG 
 // (minor and older changes stripped away, please see git history for details)
 //  2018-XX-XX: Platform: Added support for multiple windows via the ImGuiPlatformIO interface.
@@ -328,7 +332,7 @@ void    ImGui_ImplOpenGL3_DestroyDeviceObjects()
 // Platform Interface (Optional, for multi-viewport support)
 //--------------------------------------------------------------------------------------------------------
 
-static void ImGui_ImplOpenGL3_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplOpenGL3_RenderWindow(ImGuiViewport* viewport, void*)
 {
     if (!(viewport->Flags & ImGuiViewportFlags_NoRendererClear))
     {

examples/imgui_impl_opengl3.h

@@ -2,6 +2,10 @@
 // This needs to be used along with a Platform Binding (e.g. GLFW, SDL, Win32, custom..)
 // (Note: We are using GL3W as a helper library to access OpenGL functions since there is no standard header to access modern OpenGL functions easily. Alternatives are GLEW, Glad, etc..)
 
+// Implemented features:
+//  [X] User texture binding. Use 'GLUint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled).
+
 IMGUI_API bool  ImGui_ImplOpenGL3_Init(const char* glsl_version = NULL);
 IMGUI_API void  ImGui_ImplOpenGL3_Shutdown();
 IMGUI_API void  ImGui_ImplOpenGL3_NewFrame();

examples/imgui_impl_sdl2.cpp

@@ -3,7 +3,7 @@
 // (Info: SDL2 is a cross-platform general purpose library for handling windows, inputs, graphics context creation, etc.)
 
 // Implemented features:
-//  [X] User texture binding. Cast 'GLuint' OpenGL texture identifier as void*/ImTextureID. Read the FAQ about ImTextureID in imgui.cpp.
+//  [X] Multi-viewport windows (when ImGuiConfigFlags_EnableViewports is enabled).
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
@@ -400,14 +400,14 @@ static void ImGui_ImplSDL2_SetWindowTitle(ImGuiViewport* viewport, const char* t
     SDL_SetWindowTitle(data->Window, title);
 }
 
-static void ImGui_ImplSDL2_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplSDL2_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataSDL2* data = (ImGuiViewportDataSDL2*)viewport->PlatformUserData;
     if (data->GLContext)
         SDL_GL_MakeCurrent(data->Window, data->GLContext);
 }
 
-static void ImGui_ImplSDL2_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplSDL2_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataSDL2* data = (ImGuiViewportDataSDL2*)viewport->PlatformUserData;
     if (data->GLContext)

examples/imgui_impl_sdl2.h

@@ -2,6 +2,9 @@
 // This needs to be used along with a Renderer (e.g. DirectX11, OpenGL3, Vulkan..)
 // (Info: SDL2 is a cross-platform general purpose library for handling windows, inputs, graphics context creation, etc.)
 
+// Implemented features:
+//  [X] Multi-viewport windows (when ImGuiConfigFlags_EnableViewports is enabled).
+
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 4 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXXX_NewFrame(), ImGui::Render() and ImGui_ImplXXXX_Shutdown().
 // If you are new to ImGui, see examples/README.txt and documentation at the top of imgui.cpp.

examples/imgui_impl_vulkan.cpp

@@ -3,6 +3,7 @@
 
 // Missing features:
 //  [ ] User texture binding. Changes of ImTextureID aren't supported by this binding! See https://github.com/ocornut/imgui/pull/914
+//  [ ] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled). WORK-IN-PROGRESS.
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 5 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXX_CreateFontsTexture(), ImGui_ImplXXXX_NewFrame(), ImGui_ImplXXXX_Render() and ImGui_ImplXXXX_Shutdown().
@@ -1113,7 +1114,7 @@ static void ImGui_ImplVulkan_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
     ImGui_ImplVulkanH_CreateWindowDataSwapChainAndFramebuffer(g_PhysicalDevice, g_Device, &data->WindowData, g_Allocator, (int)size.x, (int)size.y);
 }
 
-static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport)
+static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataVulkan* data = (ImGuiViewportDataVulkan*)viewport->RendererUserData;
     ImGui_ImplVulkan_WindowData* wd = &data->WindowData;
@@ -1184,7 +1185,7 @@ static void ImGui_ImplVulkan_RenderWindow(ImGuiViewport* viewport)
     }
 }
 
-static void ImGui_ImplVulkan_SwapBuffers(ImGuiViewport* viewport)
+static void ImGui_ImplVulkan_SwapBuffers(ImGuiViewport* viewport, void*)
 {
     ImGuiViewportDataVulkan* data = (ImGuiViewportDataVulkan*)viewport->RendererUserData;
     ImGui_ImplVulkan_WindowData* wd = &data->WindowData;

examples/imgui_impl_vulkan.h

@@ -3,6 +3,7 @@
 
 // Missing features:
 //  [ ] User texture binding. Changes of ImTextureID aren't supported by this binding! See https://github.com/ocornut/imgui/pull/914
+//  [ ] Multi-viewport rendering (when ImGuiConfigFlags_EnableViewports is enabled). WORK-IN-PROGRESS.
 
 // You can copy and use unmodified imgui_impl_* files in your project. See main.cpp for an example of using this.
 // If you use this binding you'll need to call 5 functions: ImGui_ImplXXXX_Init(), ImGui_ImplXXX_CreateFontsTexture(), ImGui_ImplXXXX_NewFrame(), ImGui_ImplXXXX_Render() and ImGui_ImplXXXX_Shutdown().

examples/opengl3_example/main.cpp

@@ -124,9 +124,9 @@ int main(int, char**)
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
     	
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         glfwMakeContextCurrent(window);
         glfwSwapBuffers(window);

examples/sdl_opengl3_example/main.cpp

@@ -132,9 +132,9 @@ int main(int, char**)
         glClear(GL_COLOR_BUFFER_BIT);
         ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
 
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         SDL_GL_MakeCurrent(window, gl_context);
         SDL_GL_SwapWindow(window);

examples/sdl_vulkan_example/main.cpp

@@ -469,9 +469,9 @@ int main(int, char**)
         memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
 		FrameRender(wd);
         
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         FramePresent(wd);
     }

examples/vulkan_example/main.cpp

@@ -479,9 +479,9 @@ int main(int, char**)
         memcpy(&wd->ClearValue.color.float32[0], &clear_color, 4 * sizeof(float));
 		FrameRender(wd);
 
-        // Update and Render additional Platform Windows
+        // Update and Render additional Platform Windows (when ImGuiConfigFlags_EnableViewports is enabled)
         ImGui::UpdatePlatformWindows();
-        ImGui::RenderPlatformWindows();
+        ImGui::RenderPlatformWindows(NULL, NULL);
 
         FramePresent(wd);
     }

imgui.cpp

@@ -3559,7 +3559,7 @@ void ImGui::UpdatePlatformWindows()
 
 // This is a default/basic function for performing the rendering/swap of multiple platform windows.
 // Custom renderers may prefer to not call this function at all, and instead iterate the platform data and handle rendering/sync themselves.
-// The Render/Swap functions stored in ImGuiPlatformInterface are merely here to allow for this helper to exist, but you can do it yourself:
+// The Render/Swap functions stored in ImGuiPlatformIO are merely here to allow for this helper to exist, but you can do it yourself:
 //
 //    ImGuiPlatformData* data = ImGui::GetPlatformData();
 //    for (int i = 1; i < data->Viewports.Size; i++)
@@ -3568,7 +3568,7 @@ void ImGui::UpdatePlatformWindows()
 //        MySwapBufferFunction(data->Viewports[i], my_args);
 //
 // Note how we intentionally skip the main viewport (index 0) which is generally rendered as part of our main application.
-void ImGui::RenderPlatformWindows()
+void ImGui::RenderPlatformWindows(void* platform_render_arg, void* renderer_render_arg)
 {
     if (!(ImGui::GetIO().ConfigFlags & ImGuiConfigFlags_EnableViewports))
         return;
@@ -3578,18 +3578,14 @@ void ImGui::RenderPlatformWindows()
     for (int i = 1; i < data->Viewports.Size; i++)
     {
         ImGuiViewport* viewport = data->Viewports[i];
-        if (platform_io.Platform_RenderWindow) 
-            platform_io.Platform_RenderWindow(viewport);
-        if (platform_io.Renderer_RenderWindow) 
-            platform_io.Renderer_RenderWindow(viewport);
+        if (platform_io.Platform_RenderWindow) platform_io.Platform_RenderWindow(viewport, platform_render_arg);
+        if (platform_io.Renderer_RenderWindow) platform_io.Renderer_RenderWindow(viewport, renderer_render_arg);
     }
     for (int i = 1; i < data->Viewports.Size; i++)
     {
         ImGuiViewport* viewport = data->Viewports[i];
-        if (platform_io.Platform_SwapBuffers)
-            platform_io.Platform_SwapBuffers(viewport);
-        if (platform_io.Renderer_SwapBuffers)
-            platform_io.Renderer_SwapBuffers(viewport);
+        if (platform_io.Platform_SwapBuffers) platform_io.Platform_SwapBuffers(viewport, platform_render_arg);
+        if (platform_io.Renderer_SwapBuffers) platform_io.Renderer_SwapBuffers(viewport, renderer_render_arg);
     }
 }
 

imgui.h

@@ -545,12 +545,12 @@ namespace ImGui
     IMGUI_API void          SetClipboardText(const char* text);
 
     // (Optional) Platform interface for multi-viewport support
-    IMGUI_API ImGuiPlatformIO&   GetPlatformIO();           // Platform/Renderer functions.
-    IMGUI_API ImGuiPlatformData* GetPlatformData();         // List of viewports.
-    IMGUI_API ImGuiViewport*     GetMainViewport();         // GetPlatformData()->MainViewport
-    IMGUI_API void               UpdatePlatformWindows();   // Call in main loop. Create/Destroy/Resize platform windows so there's one for each viewport
-    IMGUI_API void               RenderPlatformWindows();   // Call in main loop. Call RenderWindow/SwapBuffers from the ImGuiPlatformIO structure. May be reimplemented by user.
-    IMGUI_API void               DestroyPlatformWindows();  // Call in back-end shutdown.
+    IMGUI_API ImGuiPlatformIO&   GetPlatformIO();                   // Platform/Renderer function, for back-end to setup.
+    IMGUI_API ImGuiPlatformData* GetPlatformData();                 // List of viewports. Viewport 0 is always the main viewport, followed by the secondary viewports.
+    IMGUI_API ImGuiViewport*     GetMainViewport();                 // GetPlatformData()->MainViewport
+    IMGUI_API void               UpdatePlatformWindows();           // Call in main loop. Create/Destroy/Resize platform windows so there's one for each viewport
+    IMGUI_API void               RenderPlatformWindows(void* platform_render_arg, void* renderer_render_arg); // Call in main loop. Call RenderWindow/SwapBuffers from the ImGuiPlatformIO structure. May be reimplemented by user.
+    IMGUI_API void               DestroyPlatformWindows();          // (Optional) Call in back-end shutdown if you need to close Platform Windows before imgui shutdown.
     IMGUI_API ImGuiViewport*     FindViewportByPlatformHandle(void* platform_handle);
 
     // Memory Utilities
@@ -1868,6 +1868,8 @@ struct ImFont
 // This is designed so we can mix and match two imgui_impl_xxxx files, one for the Platform (~ Windowing), one for Renderer.
 // Custom engine back-ends will often provide both Platform and Renderer interfaces and thus may not need to use all functions.
 // Platform functions are typically called before their Renderer counterpart, apart from Destroy which are called the other way.
+// RenderPlatformWindows() basically iterate secondary viewports and call Platform+Renderer's RenderWindow then Platform+Renderer's SwapBuffers,
+// You may skip using RenderPlatformWindows() and call your functions yourself if you need specific behavior for your multi-window rendering.
 struct ImGuiPlatformIO
 {
     // Platform (e.g. Win32, GLFW, SDL2)
@@ -1880,8 +1882,8 @@ struct ImGuiPlatformIO
     ImVec2  (*Platform_GetWindowSize)(ImGuiViewport* vp);
     void    (*Platform_SetWindowTitle)(ImGuiViewport* vp, const char* title);
     void    (*Platform_SetWindowAlpha)(ImGuiViewport* vp, float alpha);     // (Optional) Setup window transparency
-    void    (*Platform_RenderWindow)(ImGuiViewport* vp);                    // (Optional) Setup for render (platform side)
-    void    (*Platform_SwapBuffers)(ImGuiViewport* vp);                     // (Optional) Call Present/SwapBuffers (platform side)
+    void    (*Platform_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // (Optional) Setup for render (platform side)
+    void    (*Platform_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // (Optional) Call Present/SwapBuffers (platform side)
     float   (*Platform_GetWindowDpiScale)(ImGuiViewport* vp);               // (Optional) DPI handling: Return DPI scale for this viewport. 1.0f = 96 DPI. (FIXME-DPI)
     void    (*Platform_OnChangedViewport)(ImGuiViewport* vp);               // (Optional) DPI handling: Called during Begin() every time the viewport we are outputting into changes, so back-end has a chance to swap fonts to adjust style.
     int     (*Platform_CreateVkSurface)(ImGuiViewport* vp, ImU64 vk_inst, const void* vk_allocators, ImU64* out_vk_surface); // (Optional) For Renderer to call into Platform code
@@ -1890,8 +1892,8 @@ struct ImGuiPlatformIO
     void    (*Renderer_CreateWindow)(ImGuiViewport* vp);                    // Create swap chains, frame buffers etc.
     void    (*Renderer_DestroyWindow)(ImGuiViewport* vp);
     void    (*Renderer_SetWindowSize)(ImGuiViewport* vp, ImVec2 size);      // Resize swap chain, frame buffers etc.
-    void    (*Renderer_RenderWindow)(ImGuiViewport* vp);                    // (Optional) Clear targets, Render viewport->DrawData
-    void    (*Renderer_SwapBuffers)(ImGuiViewport* vp);                     // (Optional) Call Present/SwapBuffers (renderer side)
+    void    (*Renderer_RenderWindow)(ImGuiViewport* vp, void* render_arg);  // (Optional) Clear targets, Render viewport->DrawData
+    void    (*Renderer_SwapBuffers)(ImGuiViewport* vp, void* render_arg);   // (Optional) Call Present/SwapBuffers (renderer side)
 };
 
 // List of viewports to render as platform window (updated by ImGui::UpdatePlatformWindows)