Backends: Enhance SDL_Surface example to match the renderer example

examples/example_sdl2_surface/main.cpp

@@ -9,15 +9,24 @@
 
 int main(int, char**)
 {
-    if (SDL_Init(SDL_INIT_VIDEO) != 0)
+    // Setup SDL
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER | SDL_INIT_GAMECONTROLLER) != 0)
     {
         printf("Error: %s\n", SDL_GetError());
         return -1;
     }
 
+    // From 2.0.18: Enable native IME.
+#ifdef SDL_HINT_IME_SHOW_UI
+    SDL_SetHint(SDL_HINT_IME_SHOW_UI, "1");
+#endif
+
+    // Create window
+    float main_scale = ImGui_ImplSDL2_GetContentScaleForDisplay(0);
+    SDL_WindowFlags window_flags = (SDL_WindowFlags)(SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI | SDL_WINDOW_SHOWN);
     SDL_Window* window = SDL_CreateWindow("Dear ImGui SDL2+Surface Example",
         SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
-        1280, 720, SDL_WINDOW_SHOWN);
+        (int)(1280 * main_scale), (int)(720 * main_scale), window_flags);
     if (!window)
     {
         printf("Error creating window: %s\n", SDL_GetError());
@@ -31,53 +40,134 @@ int main(int, char**)
         return -1;
     }
 
-    SDL_Surface* framebuffer = SDL_CreateRGBSurfaceWithFormat(0, 1280, 720, 32, SDL_PIXELFORMAT_RGBA32);
+    int win_w = window_surface->w;
+    int win_h = window_surface->h;
+    SDL_Surface* framebuffer = SDL_CreateRGBSurfaceWithFormat(0, win_w, win_h, 32, SDL_PIXELFORMAT_RGBA32);
     if (!framebuffer)
     {
         printf("Error creating framebuffer: %s\n", SDL_GetError());
         return -1;
     }
 
+    // Setup Dear ImGui context
     IMGUI_CHECKVERSION();
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
-    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  
+    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
-    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;  
+    io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
 
+    // Setup Dear ImGui style
     ImGui::StyleColorsDark();
-    ImGui_ImplSDL2_InitForSDLRenderer(window, nullptr);
+
+    // Setup scaling
+    ImGuiStyle& style = ImGui::GetStyle();
+    style.ScaleAllSizes(main_scale);        // Bake a fixed style scale.
+    style.FontScaleDpi = main_scale;
+
+    // Setup Platform/Renderer backends
+    ImGui_ImplSDL2_InitForOther(window);
     ImGui_ImplSDL2_SetGamepadMode(ImGui_ImplSDL2_GamepadMode_AutoFirst, nullptr, 0);
     ImGui_ImplSDLSurface2_Init(framebuffer);
 
+    // Our state
     bool show_demo_window = true;
+    bool show_another_window = false;
     ImVec4 clear_color = ImVec4(0.45f, 0.55f, 0.60f, 1.00f);
 
+    // Main loop
     bool done = false;
     while (!done)
     {
+        // Poll and handle events (inputs, window resize, etc.)
         SDL_Event event;
         while (SDL_PollEvent(&event))
         {
             ImGui_ImplSDL2_ProcessEvent(&event);
             if (event.type == SDL_QUIT)
                 done = true;
-            if (event.type == SDL_WINDOWEVENT && event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
+
+            if (event.type == SDL_WINDOWEVENT)
+            {
+                if (event.window.event == SDL_WINDOWEVENT_CLOSE && event.window.windowID == SDL_GetWindowID(window))
                     done = true;
+
+                if (event.window.event == SDL_WINDOWEVENT_SIZE_CHANGED || event.window.event == SDL_WINDOWEVENT_RESIZED)
+                {
+                    // Recreate framebuffer at new size
+                    window_surface = SDL_GetWindowSurface(window);
+                    int new_w = window_surface->w;
+                    int new_h = window_surface->h;
+                    if (new_w != win_w || new_h != win_h)
+                    {
+                        SDL_FreeSurface(framebuffer);
+                        framebuffer = SDL_CreateRGBSurfaceWithFormat(0, new_w, new_h, 32, SDL_PIXELFORMAT_RGBA32);
+                        if (!framebuffer) { printf("Error creating framebuffer after resize: %s\n", SDL_GetError()); return -1; }
+                        win_w = new_w; win_h = new_h;
+                        // Re-init the backend with the new framebuffer
+                        ImGui_ImplSDLSurface2_Shutdown();
+                        ImGui_ImplSDLSurface2_Init(framebuffer);
+                    }
+                }
+            }
         }
 
+        // Skip rendering when minimized to avoid busy-looping
+        if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
+        {
+            SDL_Delay(10);
+            continue;
+        }
+
+        // Start the Dear ImGui frame
         ImGui_ImplSDLSurface2_NewFrame();
         ImGui_ImplSDL2_NewFrame();
         ImGui::NewFrame();
 
+        // 1. Show the big demo window
         if (show_demo_window)
             ImGui::ShowDemoWindow(&show_demo_window);
 
+        // 2. Show a simple window that we create ourselves. Mirror the SDL_Renderer example.
+        {
+            static float f = 0.0f;
+            static int counter = 0;
+
+            ImGui::Begin("Hello, world!");                          // Create a window called "Hello, world!" and append into it.
+
+            ImGui::Text("This is some useful text.");               // Display some text
+            ImGui::Checkbox("Demo Window", &show_demo_window);      // Edit bools storing our window open/close state
+            ImGui::Checkbox("Another Window", &show_another_window);
+
+            ImGui::SliderFloat("float", &f, 0.0f, 1.0f);            // Edit 1 float using a slider from 0.0f to 1.0f
+            ImGui::ColorEdit3("clear color", (float*)&clear_color); // Edit 3 floats representing a color
+
+            if (ImGui::Button("Button"))                            // Buttons return true when clicked
+                counter++;
+            ImGui::SameLine();
+            ImGui::Text("counter = %d", counter);
+
+            ImGui::Text("Application average %.3f ms/frame (%.1f FPS)", 1000.0f / io.Framerate, io.Framerate);
+            ImGui::End();
+        }
+
+        // 3. Show another simple window.
+        if (show_another_window)
+        {
+            ImGui::Begin("Another Window", &show_another_window);   // Pass a pointer to our bool variable (the window will have a closing button that will clear the bool when clicked)
+            ImGui::Text("Hello from another window!");
+            if (ImGui::Button("Close Me"))
+                show_another_window = false;
+            ImGui::End();
+        }
+
+        // Rendering
         ImGui::Render();
 
-        SDL_FillRect(framebuffer, nullptr, SDL_MapRGB(framebuffer->format,
+        SDL_FillRect(framebuffer, nullptr, SDL_MapRGBA(framebuffer->format,
             (Uint8)(clear_color.x * 255),
             (Uint8)(clear_color.y * 255),
-            (Uint8)(clear_color.z * 255)));
+            (Uint8)(clear_color.z * 255),
+            (Uint8)(clear_color.w * 255)));
 
         ImGui_ImplSDLSurface2_RenderDrawData(ImGui::GetDrawData());