Atlas - load-bitmaps.c
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[FILE BEGIN]
1/*
2 * This example code loads a bitmap with asynchronous i/o and renders it.
3 *
4 * This code is public domain. Feel free to use it for any purpose!
5 */
6
7#define SDL_MAIN_USE_CALLBACKS 1  /* use the callbacks instead of main() */
8#include <SDL3/SDL.h>
9#include <SDL3/SDL_main.h>
10
11/* We will use this renderer to draw into this window every frame. */
12static SDL_Window *window = NULL;
13static SDL_Renderer *renderer = NULL;
14static SDL_AsyncIOQueue *queue = NULL;
15
16#define TOTAL_TEXTURES 4
17static const char * const pngs[TOTAL_TEXTURES] = { "sample.png", "gamepad_front.png", "speaker.png", "icon2x.png" };
18static SDL_Texture *textures[TOTAL_TEXTURES];
19static const SDL_FRect texture_rects[TOTAL_TEXTURES] = {
20    { 116, 156, 408, 167 },
21    { 20, 200, 96, 60 },
22    { 525, 180, 96, 96 },
23    { 288, 375, 64, 64 }
24};
25
26/* This function runs once at startup. */
27SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
28{
29    int i;
30
31    if (!SDL_Init(SDL_INIT_VIDEO)) {
32        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't initialize SDL!", SDL_GetError(), NULL);
33        return SDL_APP_FAILURE;
34    }
35
36    if (!SDL_CreateWindowAndRenderer("examples/asyncio/load-bitmaps", 640, 480, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
37        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create window/renderer!", SDL_GetError(), NULL);
38        return SDL_APP_FAILURE;
39    }
40    SDL_SetRenderLogicalPresentation(renderer, 640, 480, SDL_LOGICAL_PRESENTATION_LETTERBOX);
41
42    queue = SDL_CreateAsyncIOQueue();
43    if (!queue) {
44        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create async i/o queue!", SDL_GetError(), NULL);
45        return SDL_APP_FAILURE;
46    }
47
48    /* Load some .png files asynchronously from wherever the app is being run from, put them in the same queue. */
49    for (i = 0; i < SDL_arraysize(pngs); i++) {
50        char *path = NULL;
51        SDL_asprintf(&path, "%s%s", SDL_GetBasePath(), pngs[i]);  /* allocate a string of the full file path */
52        /* you _should) check for failure, but we'll just go on without files here. */
53        SDL_LoadFileAsync(path, queue, (void *) pngs[i]);  /* attach the filename as app-specific data, so we can see it later. */
54        SDL_free(path);
55    }
56
57    return SDL_APP_CONTINUE;  /* carry on with the program! */
58}
59
60/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
61SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
62{
63    if (event->type == SDL_EVENT_QUIT) {
64        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
65    }
66
67    return SDL_APP_CONTINUE;  /* carry on with the program! */
68}
69
70/* This function runs once per frame, and is the heart of the program. */
71SDL_AppResult SDL_AppIterate(void *appstate)
72{
73    SDL_AsyncIOOutcome outcome;
74    int i;
75
76    if (SDL_GetAsyncIOResult(queue, &outcome)) {  /* a .png file load has finished? */
77        if (outcome.result == SDL_ASYNCIO_COMPLETE) {
78            /* this might be _any_ of the pngs; they might finish loading in any order. */
79            for (i = 0; i < SDL_arraysize(pngs); i++) {
80                /* this doesn't need a strcmp because we gave the pointer from this array to SDL_LoadFileAsync */
81                if (outcome.userdata == pngs[i]) {
82                    break;
83                }
84            }
85
86            if (i < SDL_arraysize(pngs)) {  /* (just in case.) */
87                SDL_Surface *surface = SDL_LoadPNG_IO(SDL_IOFromConstMem(outcome.buffer, (size_t) outcome.bytes_transferred), true);
88                if (surface) {  /* the renderer is not multithreaded, so create the texture here once the data loads. */
89                    textures[i] = SDL_CreateTextureFromSurface(renderer, surface);
90                    if (!textures[i]) {
91                        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR, "Couldn't create texture!", SDL_GetError(), NULL);
92                        return SDL_APP_FAILURE;
93                    }
94                    SDL_DestroySurface(surface);
95                }
96            }
97        }
98        SDL_free(outcome.buffer);
99    }
100
101    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
102    SDL_RenderClear(renderer);
103
104    for (i = 0; i < SDL_arraysize(textures); i++) {
105        SDL_RenderTexture(renderer, textures[i], NULL, &texture_rects[i]);
106    }
107
108    SDL_RenderPresent(renderer);
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    int i;
117
118    SDL_DestroyAsyncIOQueue(queue);
119
120    for (i = 0; i < SDL_arraysize(textures); i++) {
121        SDL_DestroyTexture(textures[i]);
122    }
123
124    /* SDL will clean up the window/renderer for us. */
125}
126
127
[FILE END]
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