[PATCH] mi: removed the invisible cursor sprite; use NullCursor instead.

[Tiago Vignatti]

On Tue, May 18, 2010 at 08:34:39AM +0200, ext Keith Packard wrote:
> On Tue, 18 May 2010 08:44:27 +0300, Oliver McFadden <oliver.mcfadden at nokia.com> wrote:
> 
> > I suppose for HW cursor it doesn't really matter since we wouldn't take
> > damage on that, right? We just draw everything normally, then tell the
> > HW to draw a sprite at X,Y? (Again, haven't looked at HW cursor code so
> > perhaps I'm totally off the mark.)
> 
> Right, there won't be damage, the question is whether I can remove the
> empty invisible cursor safely now, or whether drivers are all going to
> explode when presented with a NULL cursor.

The patch is inserting a conditional to not let the server goes further from
miPointerRealizeCursor when pCursor is null, i.e., when cursor is hidden. The
stack bellow (without the patch applied) shows that there's a plenty of code
to run when hardware cursor is being used after this function:


#0  miDCRealizeCursor (pScreen=0x997b6d8, pCursor=0x99a4940) at
midispcur.c:178
#1  0x081fb557 in miSpriteRealizeCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99a4940) at misprite.c:775
#2  0x081d4856 in xf86CursorRealizeCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCurs=0x99a4940) at xf86Cursor.c:278
#3  0x080c85d3 in VGAarbiterSpriteRealizeCursor (pDev=0x99b9e80, 
    pScreen=0x997b6d8, pCur=0x99a4940) at xf86VGAarbiter.c:981
#4  0x080ab75e in miPointerRealizeCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99a4940) at mipointer.c:168
#5  0x080c6a18 in VGAarbiterRealizeCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99a4940) at xf86VGAarbiter.c:436
#6  0x081a78bb in AnimCurRealizeCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99a4940) at animcur.c:283
#7  0x080fc827 in CursorDisplayCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99c1be0) at cursor.c:154
#8  0x081a774d in AnimCurDisplayCursor (pDev=0x99b9e80, pScreen=0x997b6d8, 
    pCursor=0x99c1be0) at animcur.c:247
#9  0x08077856 in InitializeSprite (pDev=0x99b9e80, pWin=0x99a77e8)
    at events.c:3017
#10 0x0806d61f in EnableDevice (dev=0x99b9e80, sendevent=1 '\001')
    at devices.c:292
#11 0x0806e114 in InitCoreDevices () at devices.c:606
#12 0x08064bcd in main (argc=3, argv=0xbf9d90f4, envp=0xbf9d9104) at
main.c:254


The code that runs after miPointerRealizeCursor looks worth, because it
initializes a bunch of sprite and pointer structures. So I'd say it's not
safety to insert the conditional there for hardware cursors. Another approach
should be used or certify that such code ran after miPointerRealizeCursor is
worthless.

On the other hand, I tested in my machine the patch and it works okay for hw
cursor case! Xserver regen also works okay. To have a complete testing
coverage we should test for multiple cursors though (two cases here: sw
cursors only and mixed of sw cursors + the hw one).

            Tiago