Cairo+SDL2.cpp

#include <SDL2/SDL.h>
#include <cairo/cairo.h>
#include <math.h>

void draw(cairo_t *cr) {
    cairo_text_extents_t extents;
    const char *utf8 = "cairo";

    // Hello world cairo
    double x, y;
    cairo_select_font_face(cr, "Sans",
        CAIRO_FONT_SLANT_NORMAL,
        CAIRO_FONT_WEIGHT_NORMAL);

    cairo_set_font_size(cr, 100.0);
    cairo_text_extents(cr, utf8, &extents);

    x = 0;
    y = 0;

    cairo_move_to(cr, x, y);
    cairo_show_text(cr, utf8);

    /* draw helping lines */
    cairo_set_source_rgba(cr, 1, 0.2, 0.2, 0.6);
    cairo_set_line_width(cr, 6.0);
    cairo_arc(cr, x, y, 10.0, 0, 2*M_PI);
    cairo_fill(cr);
    cairo_move_to(cr, x, y);
    cairo_rel_line_to(cr, 0, -extents.height);
    cairo_rel_line_to(cr, extents.width, 0);
    cairo_rel_line_to(cr, extents.x_bearing, -extents.y_bearing);
    cairo_stroke(cr);
}

int main(int argc, char const *argv[]) {
    SDL_Window *window;
    SDL_Renderer *renderer;
    SDL_Event event;

    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        SDL_LogError(
            SDL_LOG_CATEGORY_APPLICATION,
            "Couldn't initialize SDL: %s",
            SDL_GetError());
        return 3;
    }

    if (SDL_CreateWindowAndRenderer(
            320,
            240,
            SDL_WINDOW_RESIZABLE,
            &window,
            &renderer)) {
        SDL_LogError(
            SDL_LOG_CATEGORY_APPLICATION,
            "Couldn't create window and renderer: %s",
            SDL_GetError());
        return 3;
    }

    SDL_Texture *texture = SDL_CreateTexture(
        renderer,
        SDL_PIXELFORMAT_ARGB32,
        SDL_TEXTUREACCESS_STREAMING,
        320, 240);
    if (!texture) {
        SDL_LogError(
            SDL_LOG_CATEGORY_APPLICATION,
            "Couldn't create texture: %s",
            SDL_GetError());
        return 3;
    }

    void *pixels;
    int pitch;

    cairo_surface_t *surface = cairo_image_surface_create_for_data(
        (unsigned char *)pixels,
        CAIRO_FORMAT_ARGB32,
        320, 240, pitch);
    cairo_t *cr = cairo_create(surface);

    SDL_LockTexture(texture, nullptr, &pixels, &pitch);

    draw(cr);

    while (1) {
        SDL_PollEvent(&event);
        if (event.type == SDL_QUIT) {
            break;
        }

        SDL_RenderClear(renderer);

        SDL_RenderCopy(renderer, texture, nullptr, nullptr);

        SDL_RenderPresent(renderer);
    }

    SDL_UnlockTexture(texture);

    cairo_destroy(cr);
    cairo_surface_destroy(surface);
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);

    SDL_Quit();

    return 0;
}