I'm currently walking through the Lazy Foo tutorials for SDL2 (I'm doing this on a Linux machine) and I'm encountering some kind of bug where the inclusion of
SDL_PollEvent
SDL_UpdateWindowSurface
SDL_PollEvent
SDL_PollEvent
SDL_PollEvent
SDL_PollEvent
SDL_PollEvent
while( !quit )
{
//Handle events on queue
while( SDL_PollEvent( &e ) != 0 )
{
//User requests quit
if( e.type == SDL_QUIT )
{
quit = true;
}
}
//Apply the image
SDL_BlitSurface( gXOut, NULL, gScreenSurface, NULL );
//Update the surface
SDL_UpdateWindowSurface( gWindow );
}
while( !quit )
{
//Apply the image
SDL_BlitSurface( gXOut, NULL, gScreenSurface, NULL );
//Update the surface
SDL_UpdateWindowSurface( gWindow );
}
SDL_PollEvent
while( !quit )
{
SDL_PollEvent(&e);
//Apply the image
SDL_BlitSurface( gXOut, NULL, gScreenSurface, NULL );
//Update the surface
SDL_UpdateWindowSurface( gWindow );
}
SDL_GetWindowSurface documentation says This surface will be invalidated if the window is resized
. Upon initial window creation several events are generated, like SDL_WINDOWEVENT_SHOWN
and SDL_WINDOWEVENT_EXPOSED
. While window isn't marked as user-resizable, I suppose window manager still have an ability to perform resize; you may want to check which events are placed in your event queue (as I cannot reproduce your problem - may be e.g. window manager specific).
To put it in other worlds, window surface isn't guaranteed to persist after some events, so theoretically flushing event queue can invalidate surface. You need to get window surface after flushing event queue just before drawing, on each frame:
while( !quit )
{
// event loop here
// get surface to draw on
gScreenSurface = SDL_GetWindowSurface(gWindow);
//Apply the image
SDL_BlitSurface( gXOut, NULL, gScreenSurface, NULL );
//Update the surface
SDL_UpdateWindowSurface( gWindow );
}