Flickering in fullscreen

SDL Development
1

hi, i am currently doing some fullscreen animation and have noticed some
flickering only in the region of a blit from one surface to another. It
doesn’t occur, or is at least not noticeable in a window. has anyone come
across this before? or know of possible reasons/fixes?

–Keith

2

Are you using SDL_HWSURFACE without using SDL_DOUBLEBUF? Unless you
sync (somehow) with the verticle retrace, you will get tearing… Also,
even if you do v-sync, if you blit a non-final image (a multiple layer
image for instance that is not pre-composited) you will get a flicker…

the best solution is to either:

1) pre composite all layers to an off-screen buffer, and use some dirty

rect system to blit the composited image to the screen… (you still
need to account for the v-sync somehow)

or

2) use SDL_DOUBLEBUF, and SDL_Flip() when you are done drawing each

frame… (this will probably work the best)…

-LorenOn Thu, 2002-10-03 at 10:01, Keith Swyer wrote:

hi, i am currently doing some fullscreen animation and have noticed some
flickering only in the region of a blit from one surface to another. It
doesn’t occur, or is at least not noticeable in a window. has anyone come
across this before? or know of possible reasons/fixes?

–Keith

3

no, i was just using the SDL_HWSURFACE. I gonig to try thr SDL_DOUBLEBUF,
however i am not 100% sure how to use it correctly. Do i just call flip
after i blit each screen? or does it do the blit ? or do i call it before
the blit? or to i have to keep track of two different surfaces, drawing the
new image to the surface not seen, then blit it calling sdl_flip?

Are you using SDL_HWSURFACE without using SDL_DOUBLEBUF? Unless you
sync (somehow) with the verticle retrace, you will get tearing… Also,
even if you do v-sync, if you blit a non-final image (a multiple layer
image for instance that is not pre-composited) you will get a flicker…

the best solution is to either:

  1. pre composite all layers to an off-screen buffer, and use some dirty
    rect system to blit the composited image to the screen… (you still
    need to account for the v-sync somehow)

or

  1. use SDL_DOUBLEBUF, and SDL_Flip() when you are done drawing each
    frame… (this will probably work the best)…

-Loren

hi, i am currently doing some fullscreen animation and have noticed some
flickering only in the region of a blit from one surface to another. It
doesn’t occur, or is at least not noticeable in a window. has anyone
come> On Thu, 2002-10-03 at 10:01, Keith Swyer wrote:

across this before? or know of possible reasons/fixes?

–Keith

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

4

before each frame update (or flip) you do all the requied blitting with no
updateRect()s at all, then you call SDL_Flip(). you only have to deal with
one surface:

SDL_Surface *screen;
screen = SDL_SetVideoMode( width, height, bpp, SDL_HWSURFACE|SDL_DOUBLEBUF|
OTHER_FLAGS );

while( some_condition ) {

do all the blitting you want onto the screen surface

you might want to wait a short period to keep a constant frame rate

SDL_Flip( screen );

}

Hope this helps,
Mahmoud Al Gammal>no, i was just using the SDL_HWSURFACE. I gonig to try thr SDL_DOUBLEBUF,

however i am not 100% sure how to use it correctly. Do i just call flip
after i blit each screen? or does it do the blit ? or do i call it before
the blit? or to i have to keep track of two different surfaces, drawing the
new image to the surface not seen, then blit it calling sdl_flip?

Are you using SDL_HWSURFACE without using SDL_DOUBLEBUF? Unless you
sync (somehow) with the verticle retrace, you will get tearing… Also,
even if you do v-sync, if you blit a non-final image (a multiple layer
image for instance that is not pre-composited) you will get a flicker…

the best solution is to either:

  1. pre composite all layers to an off-screen buffer, and use some dirty
    rect system to blit the composited image to the screen… (you still
    need to account for the v-sync somehow)

or

  1. use SDL_DOUBLEBUF, and SDL_Flip() when you are done drawing each
    frame… (this will probably work the best)…

-Loren

On Thu, 2002-10-03 at 10:01, Keith Swyer wrote:

hi, i am currently doing some fullscreen animation and have noticed some
flickering only in the region of a blit from one surface to another. It
doesn’t occur, or is at least not noticeable in a window. has anyone
come

across this before? or know of possible reasons/fixes?

–Keith

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl