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I'm trying to render a texture(picture), but SDL_RenderCopy keeps the window's background black.

Here's the relevant code:

SDL_Rect rect; rect.x = 0, rect.y = 0;
while(!quit)
{
    SDL_RenderCopy(g_renderer, g_texture, NULL, &rect);
    SDL_RenderPresent(g_renderer);
    // Window stays dark although i've rendered via RenderCopy
    SDL_Delay(500);

    while(SDL_PollEvent(&event) != 0)
    {
        if(event.type == SDL_QUIT)
            quit = true;

        else if (event.type == SDL_KEYDOWN)
            move_picture(event.key.keysym.sym, rect);
    }
}

If I change the SDL_RenderCopy function call to:

SDL_RenderCopy(g_renderer, g_texture, NULL, NULL);

The picture is visible in the center of the window, but its not the result I'm looking for, as I would want the image to render to the position I set to my rectangle.

After a couple of searches I've found that this is a known behavior. I've tried changing the way I'm loading a texture from CreateTextureFromSurface to IMG_LoadSurface, but the rendering still doesn't work.

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1 Answer 1

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You need to set the size of your destination rectangle. Currently you're rendering a 0x0 portion of the texture. So change your code to also include the size of the preferred result. See https://wiki.libsdl.org/SDL_RenderCopy for more info.

Assuming your image you're trying to render is 32 wide and 32 tall, you would need to set the size of the rect like this: rect.w = 32; rect.h = 32;. Then as you're using NULL as the source rectangle, SDL will stretch the texture to the size you want.

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  • \$\begingroup\$ Well, it works, thank you! is there a way to find the .w and .h of a picture without guessing? \$\endgroup\$
    – RedWhistle
    Nov 22, 2015 at 17:13
  • 1
    \$\begingroup\$ Yes, use SDL_QueryTexture. (Also as the most friendly reminder, don't forget to upvote and accept my answer if you found it useful.) \$\endgroup\$
    – user35344
    Nov 22, 2015 at 19:11

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