Re: [AD] acquire_bitmap weirdness

[Chris <chris.kcat@xxxxxxxxxx>]

On Sunday 01 January 2006 17:58, Elias Pschernig wrote:
> About X11, I don't think acquire_bitmap makes lots of difference there.
> I certainly never use it.

Using normal double buffering you won't see a difference. But for things like 
page flipping or dirty rectangles (eg. with the GUI), or something.

Personally, I don't think the X driver should take a virtual screen size at 
all. It's a hack, and is just implemented using an extra-large memory bitmap 
and offsetting the operations (which incurs an overhead cost for writing to 
"off-screen" areas, to offset and clip the drawing ops before sending to X). 
There's no acceleration either, so normal double buffering would be about 
just as fast (if not faster). When you use OpenGL in X, you can use video 
bitmaps and acceleration but it requires you to use 0,0 for the virtual 
screen size and doesn't use acquire/release, as I understand it.

I think the only reason X uses it is because both the Windows and X ports came 
right from DOS, which did use it, so the X implementation just wanted to 
emulate it to retain as much compatibility with existing programs as 
possible. Honorable, but given the Windows port's lack of this ability and 
OpenGL's method of dealing with it all, I don't think it's needed anymore.

> And in X11, there's also the issue of the
> auto-line-updater running in the background all the time - but that's
> for another time.

I think that's only for when X "requests" a redraw of the window, since it 
doesn't preserve the contents itself. I don't believe it runs "all the time", 
unless I'm misunderstanding something (if it does, I think it should be 
looked at).