In the new KMS APIs, the legacy drmModeSetCursor ioctl actually waits
for a vblank after changing the cursor image before returning, meaning
that the X server, in attempting to hide the cursor before updating
its image, actually makes that hide *visible* for a full vblank.
It's unknown why the X server does this by default, but turn it off.
If we're with a legacy driver that doesn't support the modern
drmModeSetCursor by waiting for a vblank before returning, we're going
to get a tiny bit of tearing on the cursor plane. But between tearing
with a new cursor image and tearing with a blank cursor image, I'd
rather the former.
The only proper solution to this is an atomic ioctl that page flips
all planes, including the cursor plane, at vblank time and at the same
time.
Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
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