Atlas - clear.c
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[FILE BEGIN]
1/*
2 * This example code creates an SDL window and renderer, and then clears the
3 * window to a different color every frame, so you'll effectively get a window
4 * that's smoothly fading between colors.
5 *
6 * This code is public domain. Feel free to use it for any purpose!
7 */
8
9#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
10#include <SDL3/SDL.h>
11#include <SDL3/SDL_main.h>
12
13/* We will use this renderer to draw into this window every frame. */
14static SDL_Window *window = NULL;
15static SDL_Renderer *renderer = NULL;
16
17/* This function runs once at startup. */
18SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
19{
20    SDL_SetAppMetadata("Example Renderer Clear", "1.0", "com.example.renderer-clear");
21
22    if (!SDL_Init(SDL_INIT_VIDEO)) {
23        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
24        return SDL_APP_FAILURE;
25    }
26
27    if (!SDL_CreateWindowAndRenderer("examples/renderer/clear", 640, 480, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
28        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
29        return SDL_APP_FAILURE;
30    }
31    SDL_SetRenderLogicalPresentation(renderer, 640, 480, SDL_LOGICAL_PRESENTATION_LETTERBOX);
32
33    return SDL_APP_CONTINUE;  /* carry on with the program! */
34}
35
36/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
37SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
38{
39    if (event->type == SDL_EVENT_QUIT) {
40        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
41    }
42    return SDL_APP_CONTINUE;  /* carry on with the program! */
43}
44
45/* This function runs once per frame, and is the heart of the program. */
46SDL_AppResult SDL_AppIterate(void *appstate)
47{
48    const double now = ((double)SDL_GetTicks()) / 1000.0;  /* convert from milliseconds to seconds. */
49    /* choose the color for the frame we will draw. The sine wave trick makes it fade between colors smoothly. */
50    const float red = (float) (0.5 + 0.5 * SDL_sin(now));
51    const float green = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 2 / 3));
52    const float blue = (float) (0.5 + 0.5 * SDL_sin(now + SDL_PI_D * 4 / 3));
53    SDL_SetRenderDrawColorFloat(renderer, red, green, blue, SDL_ALPHA_OPAQUE_FLOAT);  /* new color, full alpha. */
54
55    /* clear the window to the draw color. */
56    SDL_RenderClear(renderer);
57
58    /* put the newly-cleared rendering on the screen. */
59    SDL_RenderPresent(renderer);
60
61    return SDL_APP_CONTINUE;  /* carry on with the program! */
62}
63
64/* This function runs once at shutdown. */
65void SDL_AppQuit(void *appstate, SDL_AppResult result)
66{
67    /* SDL will clean up the window/renderer for us. */
68}
69
70
[FILE END]
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