Why the sdl window is always top most in windows?

SDL Development
1

in smpeg0.4.4+SDL1.2,
in some machine(windows2000),the play window is always on top most,when I
minize the
window, the show rect still is on topmost, It can’t been covered with any
other windows.
Why?
I use
video_flags = SDL_SWSURFACE;
video_flags |= SDL_RESIZABLE;
video_flags |= SDL_ASYNCBLIT;
screen = SDL_SetVideoMode(w,h,video_bpp,video_flags);

btw,I found that if the machine video ram<16M,the SDL window only show one
movie,
the other movie is black.

2

fu wrote:

in smpeg0.4.4+SDL1.2,
in some machine(windows2000),the play window is always on top most,when I
minize the
window, the show rect still is on topmost, It can’t been covered with any
other windows.
Why?
I use
video_flags = SDL_SWSURFACE;
video_flags |= SDL_RESIZABLE;
video_flags |= SDL_ASYNCBLIT;
screen = SDL_SetVideoMode(w,h,video_bpp,video_flags);

btw,I found that if the machine video ram<16M,the SDL window only show one
movie, the other movie is black.

SDL is using your video card’s “video overlay” planes. this is a special
part of video card memory that lives in a different colorspace than the
normal rgb desktop. this video overlay is always on top of anything else on
the screen (sort of like how video cards usually draw the mouse in a
separate overlay, so nothing can cover it)

3

This is not necessary true.

DirectX supports colorkeying overlay with most cards (at least NVIDIA
and Matrox ones), this method is used also by XVideo extension as
default.

So SDL hw overlays DON’T stay on top of every window in the X enviroment
(with Xvideo extension) but they does in win32 enviroment since the SDL
overlay support use the “simple” overlay method and not the colorkey
one.

I suppose they use the simple one since directx colorkeying has a lot of
problems with 16bit depth desktops where you risk to get you colorkey
color dithered by windows. Anyway these problems can be avoided, I hope
to see a more complete win32 overlay implementation in the next versions
of SDL (I don’t dare to do it myself since I hate directx programming,
never seen a wrost API, expecially for 2d and sound stuff, also C=64
GEOS was more friendly… )

Bye,
GabryOn Tue, 2002-07-23 at 17:27, Pete Shinners wrote:

SDL is using your video card’s “video overlay” planes. this is a special
part of video card memory that lives in a different colorspace than the
normal rgb desktop. this video overlay is always on top of anything else on
the screen (sort of like how video cards usually draw the mouse in a
separate overlay, so nothing can cover it)

4

thanks for your answers!

How can I complete the overlay implementation ? Where I can find the reference?> ----- Original Message -----

From: gabrielegreco@tin.it (Gabriele Greco)
Newsgroups: loki.open-source.sdl
To:
Sent: Tuesday, July 23, 2002 11:57 PM
Subject: Re: [SDL] Re: why the sdl window is always top most in windows?

On Tue, 2002-07-23 at 17:27, Pete Shinners wrote:

SDL is using your video card’s “video overlay” planes. this is a special
part of video card memory that lives in a different colorspace than the
normal rgb desktop. this video overlay is always on top of anything else on
the screen (sort of like how video cards usually draw the mouse in a
separate overlay, so nothing can cover it)

This is not necessary true.

DirectX supports colorkeying overlay with most cards (at least NVIDIA
and Matrox ones), this method is used also by XVideo extension as
default.

So SDL hw overlays DON’T stay on top of every window in the X enviroment
(with Xvideo extension) but they does in win32 enviroment since the SDL
overlay support use the “simple” overlay method and not the colorkey
one.

I suppose they use the simple one since directx colorkeying has a lot of
problems with 16bit depth desktops where you risk to get you colorkey
color dithered by windows. Anyway these problems can be avoided, I hope
to see a more complete win32 overlay implementation in the next versions
of SDL (I don’t dare to do it myself since I hate directx programming,
never seen a wrost API, expecially for 2d and sound stuff, also C=64
GEOS was more friendly… )

Bye,
Gabry

5

thanks for your answers!

How can I complete the overlay implementation ? Where I can find the reference?

Maybe you can find the information on Microsoft’s website?

See ya,
-Sam Lantinga, Software Engineer, Blizzard Entertainment