Get the size of a window's underlying drawable in pixels.
void SDL_GL_GetDrawableSize(SDL_Window * window, int *w, int *h);
|window||the window from which the drawable size should be queried|
|w||a pointer to variable for storing the width in pixels, may be NULL|
|h||a pointer to variable for storing the height in pixels, may be NULL|
This returns info useful for calling glViewport().
This may differ from SDL_GetWindowSize() if we're rendering to a high-DPI drawable, i.e. the window was created with
SDL_WINDOW_ALLOW_HIGHDPI on a platform with high-DPI support (Apple calls this "Retina"), and not disabled by the
This function is available since SDL 2.0.1.