On Fri, 5 Jun 2026, ~rongyichang wrote:
From: rongyichang <[email protected]>
When using absolute coordinate input devices (e.g. virtio-tablet-device),
the SDL display backend implements a "soft grab" where the mouse is
automatically grabbed when it enters the window interior and ungrabbed
when it hits the window edge. This edge-ungrab behavior causes problems
in embedded emulation scenarios:
1. Mouse escapes the SDL window at edges
2. SDL does not deliver BUTTONUP events for the escaped mouse
3. The guest gets stuck in a pressed/touch-down state
4. First click back into the window is silently dropped
This issue is confirmed as a known SDL limitation (SDL issue #5301).
Add a new -display sdl,grab-on-tablet=on option that makes absolute
coordinate devices use the same grab behavior as relative (mouse)
devices: user must click to grab, Ctrl+Alt+G to release, and no
automatic grab on window enter or edge-based ungrab/regrab.
Maybe it's better to name the option click-to-grab or grab-on-click or
something similar as that's what it changes and not specific to tablets.
Regards.
BALATON Zoltan
