ttf.c

/*
Render two lines of text.

Based on SDL_ttf, which is has a separate source tree
https://www.libsdl.org/projects/SDL_ttf/, but is packaged
together with SDL on Debian

Requires re-rasterting and creating textures all the time,
no cache nor atlas mechanism, so not efficient out of the box:
http://stackoverflow.com/questions/29064904/rendering-fonts-and-text-with-sdl2-efficiently

Likely only does simple rastering. Consider freetype-gl for more advanced
and efficient text operations.
*/

#include "common.h"

#define MAX_STRING_LEN 4

/*
- x, y: upper left corner of string
- rect output Width and height contain rendered dimensions.
*/
void render_text(
    SDL_Renderer *renderer,
    int x,
    int y,
    const char *text,
    TTF_Font *font,
    SDL_Rect *rect,
    SDL_Color *color
) {
    SDL_Surface *surface;
    SDL_Texture *texture;

    surface = TTF_RenderText_Solid(font, text, *color);
    texture = SDL_CreateTextureFromSurface(renderer, surface);
    rect->x = x;
    rect->y = y;
    rect->w = surface->w;
    rect->h = surface->h;
    /* This is wasteful for textures that stay the same.
     * But makes things less stateful and easier to use.
     * Not going to code an atlas solution here... are we? */
    SDL_FreeSurface(surface);
    SDL_RenderCopy(renderer, texture, NULL, rect);
    SDL_DestroyTexture(texture);
}

int main(int argc, char **argv) {
    SDL_Color color;
    SDL_Event event;
    SDL_Rect rect;
    SDL_Renderer *renderer;
    SDL_Window *window;
    char *font_path, text[MAX_STRING_LEN];

    /* CLI arguments. */
    if (argc == 1) {
        font_path = "FreeSans.ttf";
    } else if (argc == 2) {
        font_path = argv[1];
    } else {
        fprintf(stderr, "error: too many arguments\n");
        exit(EXIT_FAILURE);
    }

    /* initialize variables. */
    color.r = COMMON_COLOR_MAX;
    color.g = COMMON_COLOR_MAX;
    color.b = COMMON_COLOR_MAX;
    color.a = COMMON_COLOR_MAX;

    /* Init window. */
    SDL_Init(SDL_INIT_TIMER | SDL_INIT_VIDEO);
    SDL_CreateWindowAndRenderer(
        COMMON_WINDOW_WIDTH,
        COMMON_WINDOW_WIDTH,
        0,
        &window,
        &renderer
    );

    /* Init TTF. */
    TTF_Init();
    TTF_Font *font = TTF_OpenFont(font_path, 24);
    if (font == NULL) {
        fprintf(stderr, "error: font not found\n");
        exit(EXIT_FAILURE);
    }

    /* Main loop. */
    common_fps_init();
    while (1) {
        if (SDL_PollEvent(&event) && event.type == SDL_QUIT) {
            break;
        }

        /* Use TTF. */
        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
        SDL_RenderClear(renderer);
        render_text(renderer, 0, 0,               "hello", font, &rect, &color);
        render_text(renderer, 0, rect.y + rect.h, "world", font, &rect, &color);
        snprintf(text, MAX_STRING_LEN, "%u", (unsigned int)(time(NULL) % 1000));
        render_text(renderer, 0, rect.y + rect.h, text, font, &rect, &color);
        SDL_RenderPresent(renderer);

        common_fps_update_and_print();
    }

    /* Cleanup. */
    TTF_Quit();
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    SDL_Quit();
    return EXIT_SUCCESS;
}