On Tue, 21 May 2002, Aurelien Fenals wrote:
> Hi,
> I'm making some tests on DGA 2 library in order to use it in the
> future. But i've got some problems in understanding how it works.
> First of all, i've understand that the function XDGASetViewport()
> allow us to change the viewport in order to act as a flip function. So
> to change the viewport i need an image size that is at least twice
> larger than the screen size. For example if the video mode is 640x480, i
> need an image of 1280x480 or of 640x960.
> But in the list of the modes given by XDGAQueryModes() i can't have
> such an image size. This means that i can't use XDGASetViewport in order
> to do double buffering, doesn't it ?
The imageHeight field in the XDGAMode needs to be at least twice
the viewportHeight in order to flip.
> Here a part of my XF86Config:
>
> subsection "display"
> depth 24
> modes "1024x768" "800x600" "640x480"
> endsubsection
>
> In the list of modes, i can choose a mode where the image size is
> 1024x480 for a screen size of 640x480, but it's not enough !! I've got
> an ATI Xpert 2000 pro with 32mo. So normaly, i can use video memory in
> order to do double buffering.
> Is DGA only able to use the video memory allocated by the Xserver so
> here 1024x768 ??
What XDGAModes get offered is entirely up to the driver.
>
> I've got a another question, it's about the DGA blitting functions.
> According to the flags given by DGA, i'm able to use the HW-blitting but
> i've read in the src code of SDL that we can't blit on the memory area
> where the screen is !! So if i can't use the XDGASetViewport i can't
> use the XDGACopyArea() too !!
There are no such limitations in DGA.
>
> If somebody have examples of using DGA 2 or a good documentation (not
> the README.DGA), i'm very interested !! Could you please send it to me
> ??
>
There's no other documentation, but I've got some sample apps
on my web page:
http://www.xfree86.org/~mvojkovi/
These work fine on NVIDIA cards.
Mark.
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