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1/*
2 * This example creates an SDL window and renderer, and then draws some points
3 * to it every frame.
4 *
5 * This code is public domain. Feel free to use it for any purpose!
6 */
7
8#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
9#include <SDL3/SDL.h>
10#include <SDL3/SDL_main.h>
11
12/* We will use this renderer to draw into this window every frame. */
13static SDL_Window *window = NULL;
14static SDL_Renderer *renderer = NULL;
15static Uint64 last_time = 0;
16
17#define WINDOW_WIDTH 640
18#define WINDOW_HEIGHT 480
19
20#define NUM_POINTS 500
21#define MIN_PIXELS_PER_SECOND 30 /* move at least this many pixels per second. */
22#define MAX_PIXELS_PER_SECOND 60 /* move this many pixels per second at most. */
23
24/* (track everything as parallel arrays instead of a array of structs,
25 so we can pass the coordinates to the renderer in a single function call.) */
26
27/* Points are plotted as a set of X and Y coordinates.
28 (0, 0) is the top left of the window, and larger numbers go down
29 and to the right. This isn't how geometry works, but this is pretty
30 standard in 2D graphics. */
31static SDL_FPoint points[NUM_POINTS];
32static float point_speeds[NUM_POINTS];
33
34/* This function runs once at startup. */
35SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
36{
37 int i;
38
39 SDL_SetAppMetadata("Example Renderer Points", "1.0", "com.example.renderer-points");
40
41 if (!SDL_Init(SDL_INIT_VIDEO)) {
42 SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
43 return SDL_APP_FAILURE;
44 }
45
46 if (!SDL_CreateWindowAndRenderer("examples/renderer/points", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
47 SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
48 return SDL_APP_FAILURE;
49 }
50
51 /* set up the data for a bunch of points. */
52 for (i = 0; i < SDL_arraysize(points); i++) {
53 points[i].x = SDL_randf() * ((float) WINDOW_WIDTH);
54 points[i].y = SDL_randf() * ((float) WINDOW_HEIGHT);
55 point_speeds[i] = MIN_PIXELS_PER_SECOND + (SDL_randf() * (MAX_PIXELS_PER_SECOND - MIN_PIXELS_PER_SECOND));
56 }
57
58 last_time = SDL_GetTicks();
59
60 return SDL_APP_CONTINUE; /* carry on with the program! */
61}
62
63/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
64SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
65{
66 if (event->type == SDL_EVENT_QUIT) {
67 return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
68 }
69 return SDL_APP_CONTINUE; /* carry on with the program! */
70}
71
72/* This function runs once per frame, and is the heart of the program. */
73SDL_AppResult SDL_AppIterate(void *appstate)
74{
75 const Uint64 now = SDL_GetTicks();
76 const float elapsed = ((float) (now - last_time)) / 1000.0f; /* seconds since last iteration */
77 int i;
78
79 /* let's move all our points a little for a new frame. */
80 for (i = 0; i < SDL_arraysize(points); i++) {
81 const float distance = elapsed * point_speeds[i];
82 points[i].x += distance;
83 points[i].y += distance;
84 if ((points[i].x >= WINDOW_WIDTH) || (points[i].y >= WINDOW_HEIGHT)) {
85 /* off the screen; restart it elsewhere! */
86 if (SDL_rand(2)) {
87 points[i].x = SDL_randf() * ((float) WINDOW_WIDTH);
88 points[i].y = 0.0f;
89 } else {
90 points[i].x = 0.0f;
91 points[i].y = SDL_randf() * ((float) WINDOW_HEIGHT);
92 }
93 point_speeds[i] = MIN_PIXELS_PER_SECOND + (SDL_randf() * (MAX_PIXELS_PER_SECOND - MIN_PIXELS_PER_SECOND));
94 }
95 }
96
97 last_time = now;
98
99 /* as you can see from this, rendering draws over whatever was drawn before it. */
100 SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE); /* black, full alpha */
101 SDL_RenderClear(renderer); /* start with a blank canvas. */
102 SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE); /* white, full alpha */
103 SDL_RenderPoints(renderer, points, SDL_arraysize(points)); /* draw all the points! */
104
105 /* You can also draw single points with SDL_RenderPoint(), but it's
106 cheaper (sometimes significantly so) to do them all at once. */
107
108 SDL_RenderPresent(renderer); /* put it all on the screen! */
109
110 return SDL_APP_CONTINUE; /* carry on with the program! */
111}
112
113/* This function runs once at shutdown. */
114void SDL_AppQuit(void *appstate, SDL_AppResult result)
115{
116 /* SDL will clean up the window/renderer for us. */
117}
118