Backends: Metal: Add a workaround for resizing windows on monitors wi…

…th DPI scale not matching OS configuration.

Backends: SDL+GLFW: Fix viewport support with metal backend.
Examples: SDL+Metal, GLFW+Metal: Add viewports support.

Fixes ocornut#5392.

backends/imgui_impl_glfw.cpp

@@ -70,7 +70,10 @@
 #endif
 
 // GLFW
+#define GLFW_EXPOSE_NATIVE_COCOA
 #include <GLFW/glfw3.h>
+#include <GLFW/glfw3native.h>
+
 #ifdef _WIN32
 #undef APIENTRY
 #define GLFW_EXPOSE_NATIVE_WIN32
@@ -538,6 +541,8 @@ static bool ImGui_ImplGlfw_Init(GLFWwindow* window, bool install_callbacks, Glfw
     main_viewport->PlatformHandle = (void*)bd->Window;
 #ifdef _WIN32
     main_viewport->PlatformHandleRaw = glfwGetWin32Window(bd->Window);
+#elif defined(__APPLE__)
+    main_viewport->PlatformHandleRaw = (void*)glfwGetCocoaWindow(bd->Window);
 #endif
     if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
         ImGui_ImplGlfw_InitPlatformInterface();
@@ -877,6 +882,8 @@ static void ImGui_ImplGlfw_CreateWindow(ImGuiViewport* viewport)
     viewport->PlatformHandle = (void*)vd->Window;
 #ifdef _WIN32
     viewport->PlatformHandleRaw = glfwGetWin32Window(vd->Window);
+#elif defined(__APPLE__)
+    viewport->PlatformHandleRaw = (void*)glfwGetCocoaWindow(vd->Window);
 #endif
     glfwSetWindowPos(vd->Window, (int)viewport->Pos.x, (int)viewport->Pos.y);
 

backends/imgui_impl_metal.mm

@@ -442,6 +442,16 @@ inline static CGSize MakeScaledSize(CGSize size, CGFloat scale)
 static void ImGui_ImplMetal_SetWindowSize(ImGuiViewport* viewport, ImVec2 size)
 {
     ImGuiViewportDataMetal* data = (ImGuiViewportDataMetal*)viewport->RendererUserData;
+#if TARGET_OS_OSX
+    // FIXME-VIEWPORT: On MacOS we expect to scale windows by using backingScaleFactor, however SDL backend sets actual
+    //  monitor scaling factor to monitor.DpiScale, which in turn gets set to viewport->DpiScale by core library. When
+    //  a common (non-Apple-made) monitor is attached to MacOS host, SDL will report actual monitor scale factor, which
+    //  may not match backingScaleFactor. In such cases resizing a viewport window would produce inaccurate metal
+    //  drawable size not covering entire Cocoa window precisely.
+    void* handle = viewport->PlatformHandleRaw ? viewport->PlatformHandleRaw : viewport->PlatformHandle;
+    NSWindow* window = (__bridge NSWindow*)handle;
+    viewport->DpiScale = static_cast<float>(window.backingScaleFactor);
+#endif
     data->MetalLayer.drawableSize = MakeScaledSize(CGSizeMake(size.x, size.y), viewport->DpiScale);
 }
 

backends/imgui_impl_sdl.cpp

@@ -408,12 +408,18 @@ static bool ImGui_ImplSDL2_Init(SDL_Window* window, SDL_Renderer* renderer, void
     // Our mouse update function expect PlatformHandle to be filled for the main viewport
     ImGuiViewport* main_viewport = ImGui::GetMainViewport();
     main_viewport->PlatformHandle = (void*)window;
-#ifdef _WIN32
     SDL_SysWMinfo info;
     SDL_VERSION(&info.version);
     if (SDL_GetWindowWMInfo(window, &info))
+    {
+#ifdef _WIN32
         main_viewport->PlatformHandleRaw = (void*)info.info.win.window;
+#elif defined(__APPLE__)
+        main_viewport->PlatformHandleRaw = (void*)info.info.cocoa.window;
+#else
+        (void);
 #endif
+    }
 
     // Set SDL hint to receive mouse click events on window focus, otherwise SDL doesn't emit the event.
     // Without this, when clicking to gain focus, our widgets wouldn't activate even though they showed as hovered.
@@ -639,6 +645,8 @@ static void ImGui_ImplSDL2_UpdateMonitors()
         monitor.WorkSize = ImVec2((float)r.w, (float)r.h);
 #endif
 #if SDL_HAS_PER_MONITOR_DPI
+        // FIXME-VIEWPORT: On MacOS SDL reports actual monitor DPI scale, ignoring OS configuration. We may want to set
+        //  DpiScale to cocoa_window.backingScaleFactor here.
         float dpi = 0.0f;
         if (!SDL_GetDisplayDPI(n, &dpi, NULL, NULL))
             monitor.DpiScale = dpi / 96.0f;
@@ -748,12 +756,18 @@ static void ImGui_ImplSDL2_CreateWindow(ImGuiViewport* viewport)
         SDL_GL_MakeCurrent(vd->Window, backup_context);
 
     viewport->PlatformHandle = (void*)vd->Window;
-#if defined(_WIN32)
     SDL_SysWMinfo info;
     SDL_VERSION(&info.version);
     if (SDL_GetWindowWMInfo(vd->Window, &info))
+    {
+#if defined(_WIN32)
         viewport->PlatformHandleRaw = info.info.win.window;
+#elif defined(__APPLE__)
+        viewport->PlatformHandleRaw = (void*)info.info.cocoa.window;
+#else
+        (void);
 #endif
+    }
 }
 
 static void ImGui_ImplSDL2_DestroyWindow(ImGuiViewport* viewport)

examples/example_glfw_metal/main.mm

@@ -29,11 +29,21 @@ int main(int, char**)
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //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
 
     // Setup 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;
+    }
+
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
@@ -64,7 +74,7 @@ int main(int, char**)
     id <MTLCommandQueue> commandQueue = [device newCommandQueue];
 
     // Setup Platform/Renderer backends
-    ImGui_ImplGlfw_InitForOpenGL(window, true);
+    ImGui_ImplGlfw_InitForOther(window, true);
     ImGui_ImplMetal_Init(device);
 
     NSWindow *nswin = glfwGetCocoaWindow(window);
@@ -152,6 +162,13 @@ int main(int, char**)
             ImGui::Render();
             ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);
 
+            // Update and Render additional Platform Windows
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::UpdatePlatformWindows();
+                ImGui::RenderPlatformWindowsDefault();
+            }
+
             [renderEncoder popDebugGroup];
             [renderEncoder endEncoding];
 

examples/example_sdl_metal/main.mm

@@ -20,11 +20,21 @@ int main(int, char**)
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //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
 
     // Setup 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;
+    }
+
     // Load Fonts
     // - If no fonts are loaded, dear imgui will use the default font. You can also load multiple fonts and use ImGui::PushFont()/PopFont() to select them.
     // - AddFontFromFileTTF() will return the ImFont* so you can store it if you need to select the font among multiple.
@@ -160,6 +170,13 @@ int main(int, char**)
             ImGui::Render();
             ImGui_ImplMetal_RenderDrawData(ImGui::GetDrawData(), commandBuffer, renderEncoder);
 
+            // Update and Render additional Platform Windows
+            if (io.ConfigFlags & ImGuiConfigFlags_ViewportsEnable)
+            {
+                ImGui::UpdatePlatformWindows();
+                ImGui::RenderPlatformWindowsDefault();
+            }
+
             [renderEncoder popDebugGroup];
             [renderEncoder endEncoding];