Atlas - streaming-textures.c
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[FILE BEGIN]
1/*
2 * This example creates an SDL window and renderer, and then draws a streaming
3 * texture 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 SDL_Texture *texture = NULL;
16
17#define TEXTURE_SIZE 150
18
19#define WINDOW_WIDTH 640
20#define WINDOW_HEIGHT 480
21
22/* This function runs once at startup. */
23SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
24{
25    SDL_SetAppMetadata("Example Renderer Streaming Textures", "1.0", "com.example.renderer-streaming-textures");
26
27    if (!SDL_Init(SDL_INIT_VIDEO)) {
28        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
29        return SDL_APP_FAILURE;
30    }
31
32    if (!SDL_CreateWindowAndRenderer("examples/renderer/streaming-textures", WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
33        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
34        return SDL_APP_FAILURE;
35    }
36    SDL_SetRenderLogicalPresentation(renderer, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_LOGICAL_PRESENTATION_LETTERBOX);
37
38    texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_RGBA8888, SDL_TEXTUREACCESS_STREAMING, TEXTURE_SIZE, TEXTURE_SIZE);
39    if (!texture) {
40        SDL_Log("Couldn't create streaming texture: %s", SDL_GetError());
41        return SDL_APP_FAILURE;
42    }
43
44    return SDL_APP_CONTINUE;  /* carry on with the program! */
45}
46
47/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
48SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
49{
50    if (event->type == SDL_EVENT_QUIT) {
51        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
52    }
53    return SDL_APP_CONTINUE;  /* carry on with the program! */
54}
55
56/* This function runs once per frame, and is the heart of the program. */
57SDL_AppResult SDL_AppIterate(void *appstate)
58{
59    SDL_FRect dst_rect;
60    const Uint64 now = SDL_GetTicks();
61    SDL_Surface *surface = NULL;
62
63    /* we'll have some color move around over a few seconds. */
64    const float direction = ((now % 2000) >= 1000) ? 1.0f : -1.0f;
65    const float scale = ((float) (((int) (now % 1000)) - 500) / 500.0f) * direction;
66
67    /* To update a streaming texture, you need to lock it first. This gets you access to the pixels.
68       Note that this is considered a _write-only_ operation: the buffer you get from locking
69       might not acutally have the existing contents of the texture, and you have to write to every
70       locked pixel! */
71
72    /* You can use SDL_LockTexture() to get an array of raw pixels, but we're going to use
73       SDL_LockTextureToSurface() here, because it wraps that array in a temporary SDL_Surface,
74       letting us use the surface drawing functions instead of lighting up individual pixels. */
75    if (SDL_LockTextureToSurface(texture, NULL, &surface)) {
76        SDL_Rect r;
77        SDL_FillSurfaceRect(surface, NULL, SDL_MapRGB(SDL_GetPixelFormatDetails(surface->format), NULL, 0, 0, 0));  /* make the whole surface black */
78        r.w = TEXTURE_SIZE;
79        r.h = TEXTURE_SIZE / 10;
80        r.x = 0;
81        r.y = (int) (((float) (TEXTURE_SIZE - r.h)) * ((scale + 1.0f) / 2.0f));
82        SDL_FillSurfaceRect(surface, &r, SDL_MapRGB(SDL_GetPixelFormatDetails(surface->format), NULL, 0, 255, 0));  /* make a strip of the surface green */
83        SDL_UnlockTexture(texture);  /* upload the changes (and frees the temporary surface)! */
84    }
85
86    /* as you can see from this, rendering draws over whatever was drawn before it. */
87    SDL_SetRenderDrawColor(renderer, 66, 66, 66, SDL_ALPHA_OPAQUE);  /* grey, full alpha */
88    SDL_RenderClear(renderer);  /* start with a blank canvas. */
89
90    /* Just draw the static texture a few times. You can think of it like a
91       stamp, there isn't a limit to the number of times you can draw with it. */
92
93    /* Center this one. It'll draw the latest version of the texture we drew while it was locked. */
94    dst_rect.x = ((float) (WINDOW_WIDTH - TEXTURE_SIZE)) / 2.0f;
95    dst_rect.y = ((float) (WINDOW_HEIGHT - TEXTURE_SIZE)) / 2.0f;
96    dst_rect.w = dst_rect.h = (float) TEXTURE_SIZE;
97    SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
98
99    SDL_RenderPresent(renderer);  /* put it all on the screen! */
100
101    return SDL_APP_CONTINUE;  /* carry on with the program! */
102}
103
104/* This function runs once at shutdown. */
105void SDL_AppQuit(void *appstate, SDL_AppResult result)
106{
107    SDL_DestroyTexture(texture);
108    /* SDL will clean up the window/renderer for us. */
109}
110
111
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