Backends: GLFW, SDL2: ImplXXX_GetContentScaleXXX() helpers return 1.0f on emscripten / apple / android (#8742, #8733)

We can divide platforms into two cases based on how they report screen geometry:
- Case 1: Platforms which report screen size in "physical pixels": Windows (for "Dpi aware" apps), Linux (with Wayland)
- Case 2: Platforms which report screen size in "density-independent pixels": macOS, iOS, Android, emscripten

As a consequence, there are two important things we need to know:
- FramebufferScale: The scaling factor FrameBufferSize / ScreenSize
  - In case 1, the framebuffer size is equal to the screen size and DisplayFramebufferScale=1.
  - In case 2, the framebuffer size is equal to the screen size multiplied by a factor, for example DisplayFramebufferScale=2.
- ContentScale The scaling factor for the content that we will display
  - In case 1, the content scale will often need to be > 1 (e.g., 2), because we will need to display bigger elements so that they show with a correct physical size on the screen.
  - In case 2, the content scale is equal to 1
This commit fixes ContentScale for platforms in case 2.

Author: pthom

backends/imgui_impl_glfw.cpp

@@ -29,6 +29,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-07-08: Made ImGui_ImplGlfw_GetContentScaleForWindow(), ImGui_ImplGlfw_GetContentScaleForMonitor() helpers return 1.0f on Emscripten and Android platforms, matching macOS logic. (#8742, #8733)
 //  2025-06-18: Added support for multiple Dear ImGui contexts. (#8676, #8239, #8069)
 //  2025-06-11: Added ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window) and ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor) helper to facilitate making DPI-aware apps.
 //  2025-03-10: Map GLFW_KEY_WORLD_1 and GLFW_KEY_WORLD_2 into ImGuiKey_Oem102.
@@ -876,7 +877,7 @@ static void ImGui_ImplGlfw_UpdateGamepads()
 // - Some accessibility applications are declaring virtual monitors with a DPI of 0.0f, see #7902. We preserve this value for caller to handle.
 float ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window)
 {
-#if GLFW_HAS_PER_MONITOR_DPI && !defined(__APPLE__)
+#if GLFW_HAS_PER_MONITOR_DPI && !(defined(__APPLE__) || defined(__EMSCRIPTEN__) || defined(__ANDROID__))
     float x_scale, y_scale;
     glfwGetWindowContentScale(window, &x_scale, &y_scale);
     return x_scale;
@@ -888,7 +889,7 @@ float ImGui_ImplGlfw_GetContentScaleForWindow(GLFWwindow* window)
 
 float ImGui_ImplGlfw_GetContentScaleForMonitor(GLFWmonitor* monitor)
 {
-#if GLFW_HAS_PER_MONITOR_DPI && !defined(__APPLE__)
+#if GLFW_HAS_PER_MONITOR_DPI && !(defined(__APPLE__) || defined(__EMSCRIPTEN__) || defined(__ANDROID__))
     float x_scale, y_scale;
     glfwGetMonitorContentScale(monitor, &x_scale, &y_scale);
     return x_scale;

backends/imgui_impl_sdl2.cpp

@@ -21,6 +21,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2025-07-08: Made ImGui_ImplSDL2_GetContentScaleForWindow(), ImGui_ImplSDL2_GetContentScaleForDisplay() helpers return 1.0f on Emscripten and Android platforms, matching macOS logic. (#8742, #8733)
 //  2025-06-11: Added ImGui_ImplSDL2_GetContentScaleForWindow(SDL_Window* window) and ImGui_ImplSDL2_GetContentScaleForDisplay(int display_index) helper to facilitate making DPI-aware apps.
 //  2025-04-09: Don't attempt to call SDL_CaptureMouse() on drivers where we don't call SDL_GetGlobalMouseState(). (#8561)
 //  2025-03-21: Fill gamepad inputs and set ImGuiBackendFlags_HasGamepad regardless of ImGuiConfigFlags_NavEnableGamepad being set.
@@ -719,7 +720,7 @@ float ImGui_ImplSDL2_GetContentScaleForWindow(SDL_Window* window)
 float ImGui_ImplSDL2_GetContentScaleForDisplay(int display_index)
 {
 #if SDL_HAS_PER_MONITOR_DPI
-#ifndef __APPLE__
+#if !defined(__APPLE__) && !defined(__EMSCRIPTEN__) && !defined(__ANDROID__)
     float dpi = 0.0f;
     if (SDL_GetDisplayDPI(display_index, &dpi, nullptr, nullptr) == 0)
         return dpi / 96.0f;

docs/CHANGELOG.txt

@@ -61,6 +61,9 @@ Other changes:
 - Demo: Added "Text -> Font Size" demo section. (#8738) [@Demonese]
 - CI: Fixed dllimport/dllexport tests. (#8757) [@AidanSun05]
 - CI: Updated to use latest Windows image + VS2022.
+- Backends: GLFW, SDL2 made ImGui_ImplGLFW_GetContentScaleXXX() and 
+  ImGui_ImplSDL2_GetContentScaleXXXX() helpers return 1.0f on Emscripten 
+  and Android platforms, matching macOS logic. (#8742, #8733) [@pthom]
 - Backends: SDL3: avoid calling SDL_StartTextInput() again if already active.
   (fixes e.g.: an issue on iOS where the keyboard animation will popup every 
   time the user types a key + probably other things) (#8727) [@morrazzzz]

imgui.h

@@ -29,7 +29,7 @@
 // Library Version
 // (Integer encoded as XYYZZ for use in #if preprocessor conditionals, e.g. '#if IMGUI_VERSION_NUM >= 12345')
 #define IMGUI_VERSION       "1.92.1 WIP"
-#define IMGUI_VERSION_NUM   19201
+#define IMGUI_VERSION_NUM   19202
 #define IMGUI_HAS_TABLE             // Added BeginTable() - from IMGUI_VERSION_NUM >= 18000
 #define IMGUI_HAS_TEXTURES          // Added ImGuiBackendFlags_RendererHasTextures - from IMGUI_VERSION_NUM >= 19198