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xcb: update libXi version requirement in the README file

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... from 1.7.4 to 1.7.5 (released Sep, 2015).

Some more locking issues were fixed after 1.7.4. Testing
for a prolonged period of time has showed that 1.7.5 does
not cause a system lock-up.

[ChangeLog][Platform Specific Changes][X11 / XCB] Minimal libXi
version requirement has been updated from 1.7.4 to 1.7.5. This
is because XIAllowTouchEvents is known to deadlock with libXi 1.7.4
and earlier. When touch events are never received, this is not
an issue. Plain mouse / keyboard systems are not affected.

Task-number: QTBUG-62224
Change-Id: Ie70264b9af0390df33c417f660350d4bce48c6d3
Reviewed-by: Laszlo Agocs <laszlo.agocs@qt.io>
This commit is contained in:
Gatis Paeglis 2017-12-11 09:55:53 +01:00
parent ba44cdae38
commit 9dc7904556
2 changed files with 4 additions and 4 deletions
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3
src/plugins/platforms/xcb/README
View File

@ -25,9 +25,8 @@ This should allow for binaries that are portable across most modern Linux distri
PACKAGE VERSION REQUIREMENTS
When using touch input via XInput 2.2 or higher, there is a potential issue on systems that ship with
a libXi older than 1.7.4. This is because XIAllowTouchEvents can deadlock with libXi 1.7.3 and earlier.
a libXi older than 1.7.5. This is because XIAllowTouchEvents can deadlock with libXi 1.7.4 and earlier.
When touch events are never received, this is not an issue, so plain mouse/keyboard systems are not affected.
See http://lists.x.org/archives/xorg-devel/2014-July/043059.html for details on the libXi patch.
Qt versions before 5.8 attempted to recognize this scenario based on the pkg-config package version and skip
the call. This has been removed starting from 5.8 since relying on pkg-config package versions is unsafe given
that Qt must also support systems with limited or incomplete pkg-config setups.

5
src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
View File

@ -700,8 +700,9 @@ void QXcbConnection::xi2ProcessTouch(void *xiDevEvent, QXcbWindow *platformWindo
// Touches must be accepted when we are grabbing touch events. Otherwise the entire sequence
// will get replayed when the grab ends.
if (m_xiGrab) {
// XIAllowTouchEvents deadlocks with libXi < 1.7.4 (this has nothing to do with the XI2 versions like 2.2)
// http://lists.x.org/archives/xorg-devel/2014-July/043059.html
// Note that XIAllowTouchEvents is known to deadlock with older libXi versions,
// for details see qtbase/src/plugins/platforms/xcb/README. This has nothing to
// do with the XInput protocol version, but is a bug in libXi implementation instead.
XIAllowTouchEvents(static_cast<Display *>(m_xlib_display), xiDeviceEvent->deviceid,
xiDeviceEvent->detail, xiDeviceEvent->event, XIAcceptTouch);
}