Re: X cursor

Keith Packard wrote:
> Around 21 o'clock on Nov 13, David Morse wrote:
> 
> 
>>I've always wondered, what *is* the mouse cursor?  Do video cards have a 
>>2 bit overlay plane just for the mouse cursor, or are they doing 
>>save-unders, or what?
> 
> 
> Most have a 2-bit overlay, newer ones have a 32-bit ARGB overlay.  Using
> the overlay is really nice as it allows you to update the mouse position
> from the mouse input processing handler directly (a SIGIO handler in most
> Linux X servers).
> 
> So, the server ends up supporting software cursor for cards that don't 
> have ARGB overlays (as modern cursors are all multi color), and also for 
> cursors which don't fit in the overlay.
> 
> I guess we need to figure out precisely how the various systems glue would 
> glue together with a GL accelerated X server so that we can add hooks in 
> the right places to get from the mouse to the cursor.

I think the issues are identical to the regular X server in this case - the 
overlay gets used when it can, otherwise you need to do some copying.

For what it's worth, the current software implementation of 32bit cursors 
breaks with direct rendering as the X server doesn't know to copy the cursor 
in that case, and the DRI drivers were designed to assume a hardware cursor.

Keith