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/*
* This example creates an SDL window and renderer, and then draws some
* textures to it every frame, adjusting the viewport.
*
* This code is public domain. Feel free to use it for any purpose!
*/
#define SDL_MAIN_USE_CALLBACKS 1 /* use the callbacks instead of main() */
#include <SDL3/SDL.h>
#include <SDL3/SDL_main.h>
/* We will use this renderer to draw into this window every frame. */
static SDL_Window *window = NULL;
static SDL_Renderer *renderer = NULL;
static SDL_Texture *texture = NULL;
static int texture_width = 0;
static int texture_height = 0;
#define WINDOW_WIDTH 640
#define WINDOW_HEIGHT 480
/* This function runs once at startup. */
SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
{
SDL_Surface *surface = NULL;
char *bmp_path = NULL;
SDL_SetAppMetadata("Example Renderer Viewport", "1.0", "com.example.renderer-viewport");
if (!SDL_Init(SDL_INIT_VIDEO)) {
SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
if (!SDL_CreateWindowAndRenderer("examples/renderer/viewport", WINDOW_WIDTH, WINDOW_HEIGHT, 0, &window, &renderer)) {
SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
/* Textures are pixel data that we upload to the video hardware for fast drawing. Lots of 2D
engines refer to these as "sprites." We'll do a static texture (upload once, draw many
times) with data from a bitmap file. */
/* SDL_Surface is pixel data the CPU can access. SDL_Texture is pixel data the GPU can access.
Load a .bmp into a surface, move it to a texture from there. */
SDL_asprintf(&bmp_path, "%ssample.bmp", SDL_GetBasePath()); /* allocate a string of the full file path */
surface = SDL_LoadBMP(bmp_path);
if (!surface) {
SDL_Log("Couldn't load bitmap: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
SDL_free(bmp_path); /* done with this, the file is loaded. */
texture_width = surface->w;
texture_height = surface->h;
texture = SDL_CreateTextureFromSurface(renderer, surface);
if (!texture) {
SDL_Log("Couldn't create static texture: %s", SDL_GetError());
return SDL_APP_FAILURE;
}
SDL_DestroySurface(surface); /* done with this, the texture has a copy of the pixels now. */
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs when a new event (mouse input, keypresses, etc) occurs. */
SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
{
if (event->type == SDL_EVENT_QUIT) {
return SDL_APP_SUCCESS; /* end the program, reporting success to the OS. */
}
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs once per frame, and is the heart of the program. */
SDL_AppResult SDL_AppIterate(void *appstate)
{
SDL_FRect dst_rect = { 0, 0, (float) texture_width, (float) texture_height };
SDL_Rect viewport;
/* Setting a viewport has the effect of limiting the area that rendering
can happen, and making coordinate (0, 0) live somewhere else in the
window. It does _not_ scale rendering to fit the viewport. */
/* as you can see from this, rendering draws over whatever was drawn before it. */
SDL_SetRenderDrawColor(renderer, 0, 0, 0, SDL_ALPHA_OPAQUE); /* black, full alpha */
SDL_RenderClear(renderer); /* start with a blank canvas. */
/* Draw once with the whole window as the viewport. */
viewport.x = 0;
viewport.y = 0;
viewport.w = WINDOW_WIDTH / 2;
viewport.h = WINDOW_HEIGHT / 2;
SDL_SetRenderViewport(renderer, NULL); /* NULL means "use the whole window" */
SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
/* top right quarter of the window. */
viewport.x = WINDOW_WIDTH / 2;
viewport.y = WINDOW_HEIGHT / 2;
viewport.w = WINDOW_WIDTH / 2;
viewport.h = WINDOW_HEIGHT / 2;
SDL_SetRenderViewport(renderer, &viewport);
SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
/* bottom 20% of the window. Note it clips the width! */
viewport.x = 0;
viewport.y = WINDOW_HEIGHT - (WINDOW_HEIGHT / 5);
viewport.w = WINDOW_WIDTH / 5;
viewport.h = WINDOW_HEIGHT / 5;
SDL_SetRenderViewport(renderer, &viewport);
SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
/* what happens if you try to draw above the viewport? It should clip! */
viewport.x = 100;
viewport.y = 200;
viewport.w = WINDOW_WIDTH;
viewport.h = WINDOW_HEIGHT;
SDL_SetRenderViewport(renderer, &viewport);
dst_rect.y = -50;
SDL_RenderTexture(renderer, texture, NULL, &dst_rect);
SDL_RenderPresent(renderer); /* put it all on the screen! */
return SDL_APP_CONTINUE; /* carry on with the program! */
}
/* This function runs once at shutdown. */
void SDL_AppQuit(void *appstate, SDL_AppResult result)
{
SDL_DestroyTexture(texture);
/* SDL will clean up the window/renderer for us. */
}
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