Backends: GLFW, Emscripten: fixes for canvas resizing, amends. (#6751)

Amend 22a7d24

backends/imgui_impl_glfw.cpp

@@ -20,7 +20,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
-//  2023-12-18: Emscripten: Change the size of the GLFW window according to the size of the canvas
+//  2023-12-19: Emscripten: Added ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback() to register canvas selector and auto-resize GLFW window.
 //  2023-10-05: Inputs: Added support for extra ImGuiKey values: F13 to F24 function keys.
 //  2023-07-18: Inputs: Revert ignoring mouse data on GLFW_CURSOR_DISABLED as it can be used differently. User may set ImGuiConfigFLags_NoMouse if desired. (#5625, #6609)
 //  2023-06-12: Accept glfwGetTime() not returning a monotonically increasing value. This seems to happens on some Windows setup when peripherals disconnect, and is likely to also happen on browser + Emscripten. (#6491)
@@ -814,40 +814,33 @@ void ImGui_ImplGlfw_NewFrame()
 #ifdef __EMSCRIPTEN__
 static EM_BOOL ImGui_ImplGlfw_OnCanvasSizeChange(int event_type, const EmscriptenUiEvent* event, void* user_data)
 {
-    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data *) user_data;
-
+    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)user_data;
     double canvas_width, canvas_height;
     emscripten_get_element_css_size(bd->CanvasSelector, &canvas_width, &canvas_height);
-
     glfwSetWindowSize(bd->Window, (int)canvas_width, (int)canvas_height);
-
     return true;
 }
 
-static EM_BOOL ImGui_ImplGlfw_OnFullscreenChange(int event_type, const EmscriptenFullscreenChangeEvent* event, void* user_data)
+static EM_BOOL ImGui_ImplEmscripten_FullscreenChangeCallback(int event_type, const EmscriptenFullscreenChangeEvent* event, void* user_data)
 {
-    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data *) user_data;
-
+    ImGui_ImplGlfw_Data* bd = (ImGui_ImplGlfw_Data*)user_data;
     double canvas_width, canvas_height;
     emscripten_get_element_css_size(bd->CanvasSelector, &canvas_width, &canvas_height);
-
     glfwSetWindowSize(bd->Window, (int)canvas_width, (int)canvas_height);
-
     return true;
 }
 
-/**
- * @param canvas_selector A CSS selector, the event listener is applied to the first element that matches the query.
- */
-void ImGui_ImplGlfw_SetEmscriptenCanvasSelector(const char *canvas_selector)
+// 'canvas_selector' is a CSS selector. The event listener is applied to the first element that matches the query.
+// STRING MUST PERSIST FOR THE APPLICATION DURATION. PLEASE USE A STRING LITERAL OR ENSURE POINTER WILL STAY VALID.
+void ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback(const char* canvas_selector)
 {
     IM_ASSERT(canvas_selector != nullptr);
     ImGui_ImplGlfw_Data* bd = ImGui_ImplGlfw_GetBackendData();
     IM_ASSERT(bd != nullptr && "Did you call ImGui_ImplGlfw_InitForXXX()?");
-    bd->CanvasSelector = canvas_selector;
 
+    bd->CanvasSelector = canvas_selector;
     emscripten_set_resize_callback(EMSCRIPTEN_EVENT_TARGET_WINDOW, bd, false, ImGui_ImplGlfw_OnCanvasSizeChange);
-    emscripten_set_fullscreenchange_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, bd, false, ImGui_ImplGlfw_OnFullscreenChange);
+    emscripten_set_fullscreenchange_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, bd, false, ImGui_ImplEmscripten_FullscreenChangeCallback);
 
     // Change the size of the GLFW window according to the size of the canvas
     ImGui_ImplGlfw_OnCanvasSizeChange(EMSCRIPTEN_EVENT_RESIZE, {}, bd);

backends/imgui_impl_glfw.h

@@ -32,7 +32,7 @@ IMGUI_IMPL_API void     ImGui_ImplGlfw_NewFrame();
 
 // Emscripten related initialization phase methods
 #ifdef __EMSCRIPTEN__
-IMGUI_IMPL_API void     ImGui_ImplGlfw_SetEmscriptenCanvasSelector(const char* canvas_selector);
+IMGUI_IMPL_API void     ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback(const char* canvas_selector);
 #endif
 
 // GLFW callbacks install

docs/CHANGELOG.txt

@@ -84,8 +84,12 @@ Other changes:
   like most printf implementations. (#7016, #3466, #6846) [@codefrog2002]
 - Misc: Renamed some defines in imstb_textedit.h to avoid conflicts when using unity/jumbo builds
   on a codebase where another copy of the library is used.
+- Backends: GLFW, Emscripten: Added ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback() to
+  register canvas selector and auto-resize GLFW window. (#6751) [@Traveller23, @ypujante]
 - Backends: Vulkan: Fixed mismatching allocator passed to vkCreateCommandPool() vs
   vkDestroyCommandPool(). (#7075) [@FoonTheRaccoon]
+- Examples: GLFW+Emscripten: Fixed examples not consistently resizing according to host canvas.
+  (#6751) [@Traveller23, @ypujante]
 
 
 -----------------------------------------------------------------------

examples/example_emscripten_wgpu/main.cpp

@@ -26,8 +26,6 @@ static WGPUSwapChain     wgpu_swap_chain = nullptr;
 static int               wgpu_swap_chain_width = 0;
 static int               wgpu_swap_chain_height = 0;
 
-const char* canvas_selector = "#canvas";
-
 // Forward declarations
 static void MainLoopStep(void* window);
 static bool InitWGPU();
@@ -78,7 +76,7 @@ int main(int, char**)
 
     // Setup Platform/Renderer backends
     ImGui_ImplGlfw_InitForOther(window, true);
-    ImGui_ImplGlfw_SetEmscriptenCanvasSelector(canvas_selector);
+    ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback("#canvas");
     ImGui_ImplWGPU_Init(wgpu_device, 3, wgpu_preferred_fmt, WGPUTextureFormat_Undefined);
 
     // Load Fonts

examples/example_glfw_opengl3/main.cpp

@@ -26,13 +26,9 @@
 
 // This example can also compile and run with Emscripten! See 'Makefile.emscripten' for details.
 #ifdef __EMSCRIPTEN__
-#include <emscripten.h>
-#include <emscripten/html5.h>
 #include "../libs/emscripten/emscripten_mainloop_stub.h"
 #endif
 
-const char* canvas_selector = "#canvas";
-
 static void glfw_error_callback(int error, const char* description)
 {
     fprintf(stderr, "GLFW Error %d: %s\n", error, description);
@@ -89,7 +85,7 @@ int main(int, char**)
     // Setup Platform/Renderer backends
     ImGui_ImplGlfw_InitForOpenGL(window, true);
 #ifdef __EMSCRIPTEN__
-    ImGui_ImplGlfw_SetEmscriptenCanvasSelector(canvas_selector);
+    ImGui_ImplGlfw_InstallEmscriptenCanvasResizeCallback("#canvas");
 #endif
     ImGui_ImplOpenGL3_Init(glsl_version);