Atlas - viewport.c
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[FILE BEGIN]
1/*
2 * This example creates an SDL window and renderer, and then draws some
3 * textures to it every frame, adjusting the viewport.
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;
16static int texture_width = 0;
17static int texture_height = 0;
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_Surface *surface = NULL;
26    char *png_path = NULL;
27
28    SDL_SetAppMetadata("Example Renderer Viewport", "1.0", "com.example.renderer-viewport");
29
30    if (!SDL_Init(SDL_INIT_VIDEO)) {
31        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
32        return SDL_APP_FAILURE;
33    }
34
35    if (!SDL_CreateWindowAndRenderer("examples/renderer/viewport", WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
36        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
37        return SDL_APP_FAILURE;
38    }
39    SDL_SetRenderLogicalPresentation(renderer, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_LOGICAL_PRESENTATION_LETTERBOX);
40
41    /* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
42       engines refer to these as "sprites." We'll do a static texture (upload once, draw many
43       times) with data from a bitmap file. */
44
45    /* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
46       Load a .png into a surface, move it to a texture from there. */
47    SDL_asprintf(&png_path, "%ssample.png", SDL_GetBasePath());  /* allocate a string of the full file path */
48    surface = SDL_LoadPNG(png_path);
49    if (!surface) {
50        SDL_Log("Couldn't load bitmap: %s", SDL_GetError());
51        return SDL_APP_FAILURE;
52    }
53
54    SDL_free(png_path);  /* done with this, the file is loaded. */
55
56    texture_width = surface->w;
57    texture_height = surface->h;
58
59    texture = SDL_CreateTextureFromSurface(renderer, surface);
60    if (!texture) {
61        SDL_Log("Couldn't create static texture: %s", SDL_GetError());
62        return SDL_APP_FAILURE;
63    }
64
65    SDL_DestroySurface(surface);  /* done with this, the texture has a copy of the pixels now. */
66
67    return SDL_APP_CONTINUE;  /* carry on with the program! */
68}
69
70/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
71SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
72{
73    if (event->type == SDL_EVENT_QUIT) {
74        return SDL_APP_SUCCESS;  /* end the program, reporting success to the OS. */
75    }
76    return SDL_APP_CONTINUE;  /* carry on with the program! */
77}
78
79/* This function runs once per frame, and is the heart of the program. */
80SDL_AppResult SDL_AppIterate(void *appstate)
81{
82    SDL_FRect dst_rect = { 0, 0, (float) texture_width, (float) texture_height };
83    SDL_Rect viewport;
84
85    /* Setting a viewport has the effect of limiting the area that rendering
86       can happen, and making coordinate (0, 0) live somewhere else in the
87       window. It does _not_ scale rendering to fit the viewport. */
88
89    /* as you can see from this, rendering draws over whatever was drawn before it. */
90    SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE);  /* black, full alpha */
91    SDL_RenderClear(renderer);  /* start with a blank canvas. */
92
93    /* Draw once with the whole window as the viewport. */
94    viewport.x = 0;
95    viewport.y = 0;
96    viewport.w = WINDOW_WIDTH / 2;
97    viewport.h = WINDOW_HEIGHT / 2;
98    SDL_SetRenderViewport(renderer, NULL);  /* NULL means "use the whole window" */
99    SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
100
101    /* top right quarter of the window. */
102    viewport.x = WINDOW_WIDTH / 2;
103    viewport.y = WINDOW_HEIGHT / 2;
104    viewport.w = WINDOW_WIDTH / 2;
105    viewport.h = WINDOW_HEIGHT / 2;
106    SDL_SetRenderViewport(renderer, &viewport);
107    SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
108
109    /* bottom 20% of the window. Note it clips the width! */
110    viewport.x = 0;
111    viewport.y = WINDOW_HEIGHT - (WINDOW_HEIGHT / 5);
112    viewport.w = WINDOW_WIDTH / 5;
113    viewport.h = WINDOW_HEIGHT / 5;
114    SDL_SetRenderViewport(renderer, &viewport);
115    SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
116
117    /* what happens if you try to draw above the viewport? It should clip! */
118    viewport.x = 100;
119    viewport.y = 200;
120    viewport.w = WINDOW_WIDTH;
121    viewport.h = WINDOW_HEIGHT;
122    SDL_SetRenderViewport(renderer, &viewport);
123    dst_rect.y = -50;
124    SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
125
126    SDL_RenderPresent(renderer);  /* put it all on the screen! */
127
128    return SDL_APP_CONTINUE;  /* carry on with the program! */
129}
130
131/* This function runs once at shutdown. */
132void SDL_AppQuit(void *appstate, SDL_AppResult result)
133{
134    SDL_DestroyTexture(texture);
135    /* SDL will clean up the window/renderer for us. */
136}
137
138
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