examples: added renderer/05-rectangles

examples/CMakeLists.txt

@@ -124,6 +124,7 @@ add_sdl_example_executable(renderer-clear SOURCES renderer/01-clear/renderer-cle
 add_sdl_example_executable(renderer-primitives SOURCES renderer/02-primitives/renderer-primitives.c)
 add_sdl_example_executable(renderer-lines SOURCES renderer/03-lines/renderer-lines.c)
 add_sdl_example_executable(renderer-points SOURCES renderer/04-points/renderer-points.c)
+add_sdl_example_executable(renderer-rectangles SOURCES renderer/05-rectangles/renderer-rectangles.c)
 add_sdl_example_executable(audio-simple-playback SOURCES audio/01-simple-playback/simple-playback.c)
 add_sdl_example_executable(audio-simple-playback-callback SOURCES audio/02-simple-playback-callback/simple-playback-callback.c)
 add_sdl_example_executable(audio-load-wav SOURCES audio/03-load-wav/load-wav.c DATAFILES ${CMAKE_CURRENT_SOURCE_DIR}/../test/sample.wav)

examples/renderer/05-rectangles/README.txt

@@ -0,0 +1,3 @@
+This example creates an SDL window and renderer, and then draws a few
+rectangles that change size each frame.
+

examples/renderer/05-rectangles/renderer-rectangles.c

@@ -0,0 +1,110 @@
+/*
+ * This example creates an SDL window and renderer, and then draws some
+ * rectangles to it every frame.
+ *
+ * This code is public domain. Feel free to use it for any purpose!
+ */
+
+#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+/* We will use this renderer to draw into this window every frame. */
+static SDL_Window *window = NULL;
+static SDL_Renderer *renderer = NULL;
+
+#define WINDOW_WIDTH 640
+#define WINDOW_HEIGHT 480
+
+/* This function runs once at startup. */
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    if (!SDL_Init(SDL_INIT_VIDEO)) {
+        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't initialize SDL!", SDL_GetError(), NULL);
+        return SDL_APP_FAILURE;
+    }
+
+    if (!SDL_CreateWindowAndRenderer("examples/renderer/rectangles", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
+        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
+        return SDL_APP_FAILURE;
+    }
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+    if (event->type == SDL_EVENT_QUIT) {
+        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
+    }
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once per frame, and is the heart of the program. */
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+    SDL_FRect rects[16];
+    const Uint64 now = SDL_GetTicks();
+    int i;
+
+    /* we'll have the rectangles grow and shrink over a few seconds. */
+    const float direction = ((now % 2000) >= 1000) ? 1.0f : -1.0f;
+    const float scale = ((float) (((int) (now % 1000)) - 500) / 500.0f) * direction;
+
+    /* as you can see from this, rendering draws over whatever was drawn before it. */
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);  /* black, full alpha */
+    SDL_RenderClear(renderer);  /* start with a blank canvas. */
+
+    /* Rectangles are comprised of set of X and Y coordinates, plus width and
+       height. (0, 0) is the top left of the window, and larger numbers go
+       down and to the right. This isn't how geometry works, but this is
+       pretty standard in 2D graphics. */
+
+    /* Let's draw a single rectangle (square, really). */
+    rects[0].x = rects[0].y = 100;
+    rects[0].w = rects[0].h = 100 + (100 * scale);
+    SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);  /* red, full alpha */
+    SDL_RenderRect(renderer, &rects[0]);
+
+    /* Now let's draw several rectangles with one function call. */
+    for (i = 0; i < 3; i++) {
+        const float size = (i+1) * 50.0f;
+        rects[i].w = rects[i].h = size + (size * scale);
+        rects[i].x = (WINDOW_WIDTH - rects[i].w) / 2;  /* center it. */
+        rects[i].y = (WINDOW_HEIGHT - rects[i].h) / 2;  /* center it. */
+    }
+    SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255);  /* green, full alpha */
+    SDL_RenderRects(renderer, rects, 3);  /* draw three rectangles at once */
+
+    /* those were rectangle _outlines_, really. You can also draw _filled_ rectangles! */
+    rects[0].x = 400;
+    rects[0].y = 50;
+    rects[0].w = 100 + (100 * scale);
+    rects[0].h = 50 + (50 * scale);
+    SDL_SetRenderDrawColor(renderer, 0, 0, 255, 255);  /* blue, full alpha */
+    SDL_RenderFillRect(renderer, &rects[0]);
+
+    /* ...and also fill a bunch of rectangles at once... */
+    for (i = 0; i < SDL_arraysize(rects); i++) {
+        const float w = (float) (WINDOW_WIDTH / SDL_arraysize(rects));
+        const float h = i * 8.0f;
+        rects[i].x = i * w;
+        rects[i].y = WINDOW_HEIGHT - h;
+        rects[i].w = w;
+        rects[i].h = h;
+    }
+    SDL_SetRenderDrawColor(renderer, 255, 255, 255, 255);  /* white, full alpha */
+    SDL_RenderFillRects(renderer, rects, SDL_arraysize(rects));
+
+    SDL_RenderPresent(renderer);  /* put it all on the screen! */
+
+    return SDL_APP_CONTINUE;  /* carry on with the program! */
+}
+
+/* This function runs once at shutdown. */
+void SDL_AppQuit(void *appstate)
+{
+    /* SDL will clean up the window/renderer for us. */
+}
+