Function sdl2_sys::SDL_SetSurfaceAlphaMod

source ยท 
pub unsafe extern "C" fn SDL_SetSurfaceAlphaMod(
    surface: *mut SDL_Surface,
    alpha: Uint8,
) -> c_int
Expand description

Set an additional alpha value used in blit operations.

When this surface is blitted, during the blit operation the source alpha value is modulated by this alpha value according to the following formula:

srcA = srcA * (alpha / 255)

\param surface the SDL_Surface structure to update \param alpha the alpha value multiplied into blit operations \returns 0 on success or a negative error code on failure; call SDL_GetError() for more information.

\since This function is available since SDL 2.0.0.

\sa SDL_GetSurfaceAlphaMod \sa SDL_SetSurfaceColorMod