examples/renderer/18-debug-text/debug-text.c

/*
 * This example creates an SDL window and renderer, and then draws some text
 * using SDL_RenderDebugText() every frame.
 *
 * 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;

#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_SetAppMetadata("Example Renderer Debug Texture", "1.0", "com.example.renderer-debug-text");

    if (!SDL_Init(SDL_INIT_VIDEO)) {
        SDL_Log("Couldn't initialize SDL: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }

    if (!SDL_CreateWindowAndRenderer("examples/renderer/debug-text", WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_RESIZABLE, &window, &renderer)) {
        SDL_Log("Couldn't create window/renderer: %s", SDL_GetError());
        return SDL_APP_FAILURE;
    }
    SDL_SetRenderLogicalPresentation(renderer, WINDOW_WIDTH, WINDOW_HEIGHT, SDL_LOGICAL_PRESENTATION_LETTERBOX);

    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)
{
    const int charsize = SDL_DEBUG_TEXT_FONT_CHARACTER_SIZE;

    /* 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. */

    SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE);  /* white, full alpha */
    SDL_RenderDebugText(renderer, 272, 100, "Hello world!");
    SDL_RenderDebugText(renderer, 224, 150, "This is some debug text.");

    SDL_SetRenderDrawColor(renderer, 51, 102, 255, SDL_ALPHA_OPAQUE);  /* light blue, full alpha */
    SDL_RenderDebugText(renderer, 184, 200, "You can do it in different colors.");
    SDL_SetRenderDrawColor(renderer, 255, 255, 255, SDL_ALPHA_OPAQUE);  /* white, full alpha */

    SDL_SetRenderScale(renderer, 4.0f, 4.0f);
    SDL_RenderDebugText(renderer, 14, 65, "It can be scaled.");
    SDL_SetRenderScale(renderer, 1.0f, 1.0f);
    SDL_RenderDebugText(renderer, 64, 350, "This only does ASCII chars. So this laughing emoji won't draw: 🤣");

    SDL_RenderDebugTextFormat(renderer, (float) ((WINDOW_WIDTH - (charsize * 46)) / 2), 400, "(This program has been running for %" SDL_PRIu64 " seconds.)", SDL_GetTicks() / 1000);

    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 will clean up the window/renderer for us. */
}