Backends: SDL2: fixed querying framebuffer scale/density when using Metal. (#5592)

Author: ocornut

backends/imgui_impl_sdl2.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2026-08-06: Fixed querying framebuffer scale when using Metal. (#5592)
 //  2026-07-15: Inputs: restore SDL_StartTextInput()/SDL_StopTextInput() in IME handler for on-screen keyboard support on Android/mobile. (#7636, #9474)
 //  2026-04-16: Made ImGui_ImplSDL2_GetContentScaleForWindow(), ImGui_ImplSDL2_GetContentScaleForDisplay() helpers return a minimum of 1.0f, as some Linux setup seems to report <1.0f value and this breaks scaling border size. (#9369)
 //  2026-02-13: Inputs: systems other than X11 are back to starting mouse capture on mouse down (reverts 2025-02-26 change). Only X11 requires waiting for a drag by default (not ideal, but a better default for X11 users). Added ImGui_ImplSDL2_SetMouseCaptureMode() for X11 debugger users. (#3650, #6410, #9235)
@@ -135,10 +136,18 @@
 #endif
 #define SDL_HAS_PER_MONITOR_DPI             SDL_VERSION_ATLEAST(2,0,4)
 #define SDL_HAS_VULKAN                      SDL_VERSION_ATLEAST(2,0,6)
+#if defined(__APPLE__)
+#define SDL_HAS_METAL                       SDL_VERSION_ATLEAST(2,0,14)
+#else
+#define SDL_HAS_METAL                       0
+#endif
 #define SDL_HAS_OPEN_URL                    SDL_VERSION_ATLEAST(2,0,14)
 #if SDL_HAS_VULKAN
 #include <SDL_vulkan.h>
 #endif
+#if SDL_HAS_METAL
+#include <SDL_metal.h>
+#endif
 
 // SDL Data
 struct ImGui_ImplSDL2_Data
@@ -899,6 +908,10 @@ static void ImGui_ImplSDL2_GetWindowSizeAndFramebufferScale(SDL_Window* window,
 #if SDL_HAS_VULKAN
     else if (SDL_GetWindowFlags(window) & SDL_WINDOW_VULKAN)
         SDL_Vulkan_GetDrawableSize(window, &display_w, &display_h);
+#endif
+#if SDL_HAS_METAL
+    else if (SDL_GetWindowFlags(window) & SDL_WINDOW_METAL)
+        SDL_Metal_GetDrawableSize(window, &display_w, &display_h);
 #endif
     else
         SDL_GL_GetDrawableSize(window, &display_w, &display_h);

docs/CHANGELOG.txt

@@ -62,6 +62,7 @@ Other Changes:
     - Circle and Curves tessellation error are scaled accordingly.
 - Backends:
   - QNX: added QNX Screen backend. (#9492) [@mgorchak-blackberry]
+  - SDL2: fixed querying framebuffer scale/density when using Metal. (#5592) [@lailoken]
 - Examples:
   - QNX+OpenGL3, QNX+Vulkan: added QNX Screen examples. (#9492) [@mgorchak-blackberry]
 

examples/example_sdl2_metal/main.mm

@@ -56,13 +56,15 @@ int main(int, char**)
         return 1;
     }
 
-    // Inform SDL that we will be using metal for rendering. Without this hint initialization of metal renderer may fail.
+    // Inform SDL that we will be using metal for rendering. Without this hint initialization of Metal renderer may fail.
     SDL_SetHint(SDL_HINT_RENDER_DRIVER, "metal");
 
-    // Enable native IME.
+    // From 2.0.18: Enable native IME.
+#ifdef SDL_HINT_IME_SHOW_UI
     SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
+#endif
 
-    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL+Metal example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 800, SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
+    SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+Metal example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 1280, 800, SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI);
     if (window == nullptr)
     {
         printf("Error creating window: %s\n", SDL_GetError());