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95 lines
3.7 KiB
C
95 lines
3.7 KiB
C
/*
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* This example creates an SDL window and renderer, and then draws some lines
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* to it every frame.
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*
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* This code is public domain. Feel free to use it for any purpose!
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*/
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#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
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#include <SDL3/SDL.h>
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#include <SDL3/SDL_main.h>
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/* We will use this renderer to draw into this window every frame. */
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static SDL_Window *window = NULL;
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static SDL_Renderer *renderer = NULL;
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/* This function runs once at startup. */
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SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
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{
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SDL_SetAppMetadata("Example Renderer Lines", "1.0", "com.example.renderer-lines");
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if (!SDL_Init(SDL_INIT_VIDEO)) {
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SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
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return SDL_APP_FAILURE;
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}
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if (!SDL_CreateWindowAndRenderer("examples/renderer/lines", 640, 480, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
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SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
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return SDL_APP_FAILURE;
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}
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SDL_SetRenderLogicalPresentation(renderer, 640, 480, SDL_LOGICAL_PRESENTATION_LETTERBOX);
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
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SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
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{
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if (event->type == SDL_EVENT_QUIT) {
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return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
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}
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs once per frame, and is the heart of the program. */
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SDL_AppResult SDL_AppIterate(void *appstate)
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{
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int i;
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/* Lines (line segments, really) are drawn in terms of points: a set of
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X and Y coordinates, one set for each end of the line.
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(0, 0) is the top left of the window, and larger numbers go down
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and to the right. This isn't how geometry works, but this is pretty
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standard in 2D graphics. */
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static const SDL_FPoint line_points[] = {
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{ 100, 354 }, { 220, 230 }, { 140, 230 }, { 320, 100 }, { 500, 230 },
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{ 420, 230 }, { 540, 354 }, { 400, 354 }, { 100, 354 }
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};
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/* as you can see from this, rendering draws over whatever was drawn before it. */
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SDL_SetRenderDrawColor(renderer, 100, 100, 100, SDL_ALPHA_OPAQUE); /* grey, full alpha */
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SDL_RenderClear(renderer); /* start with a blank canvas. */
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/* You can draw lines, one at a time, like these brown ones... */
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SDL_SetRenderDrawColor(renderer, 127, 49, 32, SDL_ALPHA_OPAQUE);
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SDL_RenderLine(renderer, 240, 450, 400, 450);
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SDL_RenderLine(renderer, 240, 356, 400, 356);
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SDL_RenderLine(renderer, 240, 356, 240, 450);
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SDL_RenderLine(renderer, 400, 356, 400, 450);
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/* You can also draw a series of connected lines in a single batch... */
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SDL_SetRenderDrawColor(renderer, 0, 255, 0, SDL_ALPHA_OPAQUE);
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SDL_RenderLines(renderer, line_points, SDL_arraysize(line_points));
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/* here's a bunch of lines drawn out from a center point in a circle. */
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/* we randomize the color of each line, so it functions as animation. */
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for (i = 0; i < 360; i++) {
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const float size = 30.0f;
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const float x = 320.0f;
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const float y = 95.0f - (size / 2.0f);
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SDL_SetRenderDrawColor(renderer, SDL_rand(256), SDL_rand(256), SDL_rand(256), SDL_ALPHA_OPAQUE);
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SDL_RenderLine(renderer, x, y, x + SDL_sinf((float) i) * size, y + SDL_cosf((float) i) * size);
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}
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SDL_RenderPresent(renderer); /* put it all on the screen! */
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return SDL_APP_CONTINUE; /* carry on with the program! */
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}
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/* This function runs once at shutdown. */
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void SDL_AppQuit(void *appstate, SDL_AppResult result)
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{
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/* SDL will clean up the window/renderer for us. */
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}
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