Backends: SDL2, SDL3, GLFW: Backport small part of c90ea13 from docking.

backends/imgui_impl_glfw.cpp

@@ -868,20 +868,26 @@ float ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor)
 #endif
 }
 
+static void ImGui_ImplGlfw_GetWindowSizeAndFramebufferScale(GLFWwindow* window, ImVec2* out_size, ImVec2* out_framebuffer_scale)
+{
+    int w, h;
+    int display_w, display_h;
+    glfwGetWindowSize(window, &w, &h);
+    glfwGetFramebufferSize(window, &display_w, &display_h);
+    if (out_size != nullptr)
+        *out_size = ImVec2((float)w, (float)h);
+    if (out_framebuffer_scale != nullptr)
+        *out_framebuffer_scale = (w > 0 && h > 0) ? ImVec2((float)display_w / (float)w, (float)display_h / (float)h) : ImVec2(1.0f, 1.0f);
+}
+
 void ImGui_ImplGlfw_NewFrame()
 {
     ImGuiIO& io = ImGui::GetIO();
     ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplGlfw_InitForXXX()?");
 
-    // Setup display size (every frame to accommodate for window resizing)
-    int w, h;
-    int display_w, display_h;
-    glfwGetWindowSize(bd->Window, &w, &h);
-    glfwGetFramebufferSize(bd->Window, &display_w, &display_h);
-    io.DisplaySize = ImVec2((float)w, (float)h);
-    if (w > 0 && h > 0)
-        io.DisplayFramebufferScale = ImVec2((float)display_w / (float)w, (float)display_h / (float)h);
+    // Setup main viewport size (every frame to accommodate for window resizing)
+    ImGui_ImplGlfw_GetWindowSizeAndFramebufferScale(bd->Window, &io.DisplaySize, &io.DisplayFramebufferScale);
 
     // Setup time step
     // (Accept glfwGetTime() not returning a monotonically increasing value. Seems to happens on disconnecting peripherals and probably on VMs and Emscripten, see #6491, #6189, #6114, #3644)

backends/imgui_impl_sdl2.cpp

@@ -720,6 +720,7 @@ float ImGui_ImplSDL2_GetContentScaleForDisplay(int display_index)
         return dpi / 96.0f;
 #endif
 #endif
+    IM_UNUSED(display_index);
     return 1.0f;
 }
 
@@ -825,29 +826,35 @@ static void ImGui_ImplSDL2_UpdateGamepads()
     ImGui_ImplSDL2_UpdateGamepadAnalog(bd, io, ImGuiKey_GamepadRStickDown,  SDL_CONTROLLER_AXIS_RIGHTY, +thumb_dead_zone, +32767);
 }
 
-void ImGui_ImplSDL2_NewFrame()
+static void ImGui_ImplSDL2_GetWindowSizeAndFramebufferScale(SDL_Window* window, SDL_Renderer* renderer, ImVec2* out_size, ImVec2* out_framebuffer_scale)
 {
-    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
-    IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDL2_Init()?");
-    ImGuiIO& io = ImGui::GetIO();
-
-    // Setup display size (every frame to accommodate for window resizing)
     int w, h;
     int display_w, display_h;
-    SDL_GetWindowSize(bd->Window, &w, &h);
-    if (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_MINIMIZED)
+    SDL_GetWindowSize(window, &w, &h);
+    if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
         w = h = 0;
-    if (bd->Renderer != nullptr)
-        SDL_GetRendererOutputSize(bd->Renderer, &display_w, &display_h);
+    if (renderer != nullptr)
+        SDL_GetRendererOutputSize(renderer, &display_w, &display_h);
 #if SDL_HAS_VULKAN
-    else if (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_VULKAN)
-        SDL_Vulkan_GetDrawableSize(bd->Window, &display_w, &display_h);
+    else if (SDL_GetWindowFlags(window) & SDL_WINDOW_VULKAN)
+        SDL_Vulkan_GetDrawableSize(window, &display_w, &display_h);
 #endif
     else
-        SDL_GL_GetDrawableSize(bd->Window, &display_w, &display_h);
-    io.DisplaySize = ImVec2((float)w, (float)h);
-    if (w > 0 && h > 0)
-        io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
+        SDL_GL_GetDrawableSize(window, &display_w, &display_h);
+    if (out_size != nullptr)
+        *out_size = ImVec2((float)w, (float)h);
+    if (out_framebuffer_scale != nullptr)
+        *out_framebuffer_scale = (w > 0 && h > 0) ? ImVec2((float)display_w / w, (float)display_h / h) : ImVec2(1.0f, 1.0f);
+}
+
+void ImGui_ImplSDL2_NewFrame()
+{
+    ImGui_ImplSDL2_Data* bd = ImGui_ImplSDL2_GetBackendData();
+    IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDL2_Init()?");
+    ImGuiIO& io = ImGui::GetIO();
+
+    // Setup main viewport size (every frame to accommodate for window resizing)
+    ImGui_ImplSDL2_GetWindowSizeAndFramebufferScale(bd->Window, bd->Renderer, &io.DisplaySize, &io.DisplayFramebufferScale);
 
     // Setup time step (we don't use SDL_GetTicks() because it is using millisecond resolution)
     // (Accept SDL_GetPerformanceCounter() not returning a monotonically increasing value. Happens in VMs and Emscripten, see #6189, #6114, #3644)

backends/imgui_impl_sdl3.cpp

@@ -771,22 +771,28 @@ static void ImGui_ImplSDL3_UpdateGamepads()
     ImGui_ImplSDL3_UpdateGamepadAnalog(bd, io, ImGuiKey_GamepadRStickDown,  SDL_GAMEPAD_AXIS_RIGHTY, +thumb_dead_zone, +32767);
 }
 
+static void ImGui_ImplSDL3_GetWindowSizeAndFramebufferScale(SDL_Window* window, ImVec2* out_size, ImVec2* out_framebuffer_scale)
+{
+    int w, h;
+    int display_w, display_h;
+    SDL_GetWindowSize(window, &w, &h);
+    if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
+        w = h = 0;
+    SDL_GetWindowSizeInPixels(window, &display_w, &display_h);
+    if (out_size != nullptr)
+        *out_size = ImVec2((float)w, (float)h);
+    if (out_framebuffer_scale != nullptr)
+        *out_framebuffer_scale = (w > 0 && h > 0) ? ImVec2((float)display_w / w, (float)display_h / h) : ImVec2(1.0f, 1.0f);
+}
+
 void ImGui_ImplSDL3_NewFrame()
 {
     ImGui_ImplSDL3_Data* bd = ImGui_ImplSDL3_GetBackendData();
     IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDL3_Init()?");
     ImGuiIO& io = ImGui::GetIO();
 
-    // Setup display size (every frame to accommodate for window resizing)
-    int w, h;
-    int display_w, display_h;
-    SDL_GetWindowSize(bd->Window, &w, &h);
-    if (SDL_GetWindowFlags(bd->Window) & SDL_WINDOW_MINIMIZED)
-        w = h = 0;
-    SDL_GetWindowSizeInPixels(bd->Window, &display_w, &display_h);
-    io.DisplaySize = ImVec2((float)w, (float)h);
-    if (w > 0 && h > 0)
-        io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);
+    // Setup main viewport size (every frame to accommodate for window resizing)
+    ImGui_ImplSDL3_GetWindowSizeAndFramebufferScale(bd->Window, &io.DisplaySize, &io.DisplayFramebufferScale);
 
     // Setup time step (we could also use SDL_GetTicksNS() available since SDL3)
     // (Accept SDL_GetPerformanceCounter() not returning a monotonically increasing value. Happens in VMs and Emscripten, see #6189, #6114, #3644)