CODEWITHSUNDEEP
c++fullscreencenteringsdl-2aspect-ratio
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Reputation: 562

How to center fullscreen window

I have a 16:9 display where I'd like to show fullscreen SDL window which is in 4:3 mode.SDL_SetWindowFullscreen(window, SDL_WINDOW_FULLSCREEN) sets the window to the left side of the screen and leaves a big black bar to the right.

I'd like to center the window and have black bars on the left and the right side.

It seems that SDL_SetWindowPosition(window, x, y) has no effect on window when it is in fullscreen mode. Can I center the fullscreen window in SDL2?

Upvotes: 1

Views: 1568

Answers (1)

fnaith
fnaith

Reputation: 127

There are two situation: (1) display with renderer and texture base on window size. (2) display with screen and surface base on pixel.

For (1) here is a simple solution base on setting view port for renderer.(no testing but a guideline)

void SDL_SetRendererViewportRatio_4_3(SDL_Window *window,
                                      SDL_Renderer *renderer
                                      SDL_Rect *viewport) {
    Uint8 r, g, b, a;
    SDL_GetRenderDrawColor(renderer, &r, &g, &b, &a);
    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
    SDL_RenderClear(renderer);
    SDL_RenderPresent(renderer);
    SDL_SetRenderDrawColor(renderer, r, g, b, a);
    int w, h;
    SDL_GetWindowSize(window, &w, &h);
    if (w * 3 > h * 4) {
        viewport->w = h * 4 / 3;
        viewport->h = h;
    } else {
        viewport->w = w;
        viewport->h = w * 3 / 4;
    }
    viewport->x = (w - viewport->w) / 2;
    viewport->y = (h - viewport->h) / 2;
    SDL_RenderSetViewport(renderer, viewport);
}

Note that you should call this function whenever window changed size.

For (2) I guess you should calculate the coordinate of surface and draw big black bars by yourself. It is more difficult that I cannot prove simple solution.

Upvotes: 2

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