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d="scan'208,217";a="151895430" To: BALATON Zoltan CC: "qemu-devel@nongnu.org" , "marcandre.lureau@redhat.com" , "armbru@redhat.com" , "eblake@redhat.com" Subject: =?gb2312?B?tPC4tDogW0V4dGVybmFsIE1haWxdUmU6IFtQQVRDSCBxZW11XSB1aS9zZGwy?= =?gb2312?B?OiBhZGQgZ3JhYi1vbi10YWJsZXQgb3B0aW9uIGZvciBhYnNvbHV0ZSBpbnB1?= =?gb2312?Q?t_devices?= Thread-Topic: [External Mail]Re: [PATCH qemu] ui/sdl2: add grab-on-tablet option for absolute input devices Thread-Index: AQHc9QrzLXP+H0KPgk2jkMDCAfr3kLYw1kzJ Date: Sat, 6 Jun 2026 03:01:13 +0000 Message-ID: <8d662e1969be4a9a89c0b38991986ebe@xiaomi.com> References: <178065435170.20548.15372728064868431795-0@git.sr.ht>, In-Reply-To: Accept-Language: zh-CN, en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.237.8.165] Content-Type: multipart/alternative; boundary="_000_8d662e1969be4a9a89c0b38991986ebexiaomicom_" MIME-Version: 1.0 Received-SPF: pass client-ip=118.143.206.90; envelope-from=rongyichang@xiaomi.com; helo=outboundhk.mxmail.xiaomi.com X-Spam_score_int: 38 X-Spam_score: 3.8 X-Spam_bar: +++ X-Spam_report: (3.8 / 5.0 requ) BAYES_00=-1.9, CHARSET_FARAWAY_HEADER=3.2, HTML_MESSAGE=0.001, MIME_CHARSET_FARAWAY=2.45, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-Mailman-Approved-At: Sat, 06 Jun 2026 09:47:42 -0400 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-to: =?gb2312?B?yNnS5bL9?= From: =?gb2312?B?yNnS5bL9?= via qemu development Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org --_000_8d662e1969be4a9a89c0b38991986ebexiaomicom_ Content-Type: text/plain; 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charset="gb2312" Content-Transfer-Encoding: quoted-printable

Hi,

Thanks for the review.

If we use a generic name like "click-to-grab" (not tablet-sp= ecific),
should we also consider the reverse direction =A1=AA i.e., allowing re= lative
(mouse) devices to use the tablet-style edge-ungrab/regrab behavior
via something like "click-to-grab=3Doff"?

Currently relative devices always use click-to-grab, and absolute
devices always use edge-based auto-grab. If we make this a generic
toggle, the semantics would be:

  -display sdl,click-to-grab=3Don   =A1=FA both device = types use click-to-grab
  -display sdl,click-to-grab=3Doff  =A1=FA both device types= use edge-ungrab

However, edge-ungrab doesn't really work for relative (mouse) devices,=
because once the mouse escapes the window, SDL stops delivering motion=
events and the guest cursor becomes uncontrollable.

So in practice, this option can only meaningfully change behavior for<= /div>
absolute devices. That's why I chose a tablet-specific name =A1=AA to = make
it clear that it only affects absolute coordinate devices.

That said, I'm open to "click-to-grab=3Don|off" if you prefe= r a more
generic name. The implementation would remain the same (only affecting=
absolute devices), just with a more gen= eral name.

What do you think?

Best regards,
Yichang

=B7=A2=BC=FE=C8=CB: BALAT= ON Zoltan <balaton@eik.bme.hu>
=B7=A2=CB=CD=CA=B1=BC=E4: 2026=C4=EA6=D4=C26=C8=D5 0:47:00
=CA=D5=BC=FE=C8=CB: =C8=D9=D2=E5=B2=FD
=B3=AD=CB=CD: qemu-devel@nongnu.org; marcandre.lureau@redhat.com; ar= mbru@redhat.com; eblake@redhat.com
=D6=F7=CC=E2: [External Mail]Re: [PATCH qemu] ui/sdl2: add grab-on-t= ablet option for absolute input devices
 
[=CD=E2=B2=BF=D3=CA=BC=FE] =B4=CB=D3=CA=BC=FE=C0= =B4=D4=B4=D3=DA=D0=A1=C3=D7=B9=AB=CB=BE=CD=E2=B2=BF=A3=AC=C7=EB=BD=F7=C9=F7= =B4=A6=C0=ED=A1=A3=C8=F4=B6=D4=D3=CA=BC=FE=B0=B2=C8=AB=D0=D4=B4=E6=D2=C9=A3= =AC=C7=EB=BD=AB=D3=CA=BC=FE=D7=AA=B7=A2=B8=F8misec@xiaomi.com=BD=F8=D0=D0= =B7=B4=C0=A1

On Fri, 5 Jun 2026, ~rongyichang wrote:
> From: rongyichang <rongyichang@xiaomi.com>
>
> When using absolute coordinate input devices (e.g. virtio-tablet-devic= e),
> the SDL display backend implements a "soft grab" where the m= ouse is
> automatically grabbed when it enters the window interior and ungrabbed=
> when it hits the window edge. This edge-ungrab behavior causes problem= s
> 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=3Don option that makes absolute<= br> > coordinate devices use the same grab behavior as relative (mouse)
> devices: user must click to grab, Ctrl+Alt+G to release, and n= o
> 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
#/******=B1=BE=D3=CA=BC=FE=BC=B0=C6=E4=B8=BD=BC=FE=BA=AC=D3= =D0=D0=A1=C3=D7=B9=AB=CB=BE=B5=C4=B1=A3=C3=DC=D0=C5=CF=A2=A3=AC=BD=F6=CF=DE= =D3=DA=B7=A2=CB=CD=B8=F8=C9=CF=C3=E6=B5=D8=D6=B7=D6=D0=C1=D0=B3=F6=B5=C4=B8= =F6=C8=CB=BB=F2=C8=BA=D7=E9=A1=A3=BD=FB=D6=B9=C8=CE=BA=CE=C6=E4=CB=FB=C8=CB= =D2=D4=C8=CE=BA=CE=D0=CE=CA=BD=CA=B9=D3=C3=A3=A8=B0=FC=C0=A8=B5=AB=B2=BB=CF= =DE=D3=DA=C8=AB=B2=BF=BB=F2=B2=BF=B7=D6=B5=D8=D0=B9=C2=B6=A1=A2=B8=B4=D6=C6= =A1=A2=BB=F2=C9=A2=B7=A2=A3=A9=B1=BE=D3=CA=BC=FE=D6=D0=B5=C4=D0=C5=CF=A2=A1= =A3=C8=E7=B9=FB=C4=FA=B4=ED=CA=D5=C1=CB=B1=BE=D3=CA=BC=FE=A3=AC=C7=EB=C4=FA= =C1=A2=BC=B4=B5=E7=BB=B0=BB=F2=D3=CA=BC=FE=CD=A8=D6=AA=B7=A2=BC=FE=C8=CB=B2= =A2=C9=BE=B3=FD=B1=BE=D3=CA=BC=FE=A3=A1 This e-mail and its attachments con= tain confidential information from XIAOMI, which is intended only for the p= erson or entity whose address is listed above. Any use of the information contained= herein in any way (including, but not limited to, total or partial disclos= ure, reproduction, or dissemination) by persons other than the intended rec= ipient(s) is prohibited. If you receive this e-mail in error, please notify the sender by phone or email i= mmediately and delete it!******/# --_000_8d662e1969be4a9a89c0b38991986ebexiaomicom_--