Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Ralf Jung]

Hi,

With the gcc5 transition in testing, due to this bug in Qt, I now have
the choice between not updating my system at all, or having my entire DE
crash every time I (un)plug my external screen. Both of these options
are fairly suboptimal ;-)

I saw that Qt5.5 is in experimental. It seems to be mostly installable
(I couldn't test, due to some multiarch-packages preventing me from even
staging an upgrade to the new gcc). I backported the patch from Qt
upstream that fixes this issue; you can find the patch against the Qt
debian package attached. Compilation is still on-going, but the patch
seems to apply cleanly, and it works upstream. If you could apply this
patch, that would be great - with the next Qt upload to experimental, I
could finally use Qt5 applications without them crashing all the time :D

Kind regards,
Ralf
commit 139103ae1850c8f82a497d8823a028f45f565678
Author: Ralf Jung 
Date:   Mon Sep 7 18:14:54 2015 +0200

Backport: When a screen comes back online, the windows need to be told about it

diff --git a/debian/changelog b/debian/changelog
index 61a235c..19ac4d4 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,10 @@
+qtbase-opensource-src (5.5.0+dfsg-6) UNRELEASED; urgency=medium
+
+  * When a screen comes back online, the windows need to be told
+about it (screen_crash.diff) (Closes: #787680)
+
+ -- Debian Qt/KDE Maintainers   Mon, 07 Sep 2015 18:13:16 +0200
+
 qtbase-opensource-src (5.5.0+dfsg-5) experimental; urgency=medium
 
   * Update debian/copyright for 5.5.0.
diff --git a/debian/patches/screen_crash.patch b/debian/patches/screen_crash.patch
new file mode 100644
index 000..59b526c
--- /dev/null
+++ b/debian/patches/screen_crash.patch
@@ -0,0 +1,30 @@
+Description: When a screen comes back online, the windows need to be told
+ about it
+Author: Ralf Jung 
+Forwarded: b0b08cc0e4e38504d6b833702f7477aee4e2a192
+Last-Update: 2015-09-07
+
+---
+ src/plugins/platforms/xcb/qxcbconnection.cpp | 8 
+ 1 file changed, 8 insertions(+)
+
+--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
 b/src/plugins/platforms/xcb/qxcbconnection.cpp
+@@ -252,6 +252,14 @@ void QXcbConnection::updateScreens(const xcb_randr_notify_event_t *event)
+ otherScreen->addVirtualSibling(screen);
+ m_screens << screen;
+ QXcbIntegration::instance()->screenAdded(screen, screen->isPrimary());
++
++// Windows which had null screens have already had expose events by now.
++// They need to be told the screen is back, it's OK to render.
++foreach (QWindow *window, QGuiApplication::topLevelWindows()) {
++QXcbWindow *xcbWin = static_cast(window->handle());
++if (xcbWin)
++xcbWin->maybeSetScreen(screen);
++}
+ }
+ // else ignore disabled screens
+ } else if (screen) {
+-- 
+2.4.6
+
diff --git a/debian/patches/series b/debian/patches/series
index 148b172..3d777a4 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -1,5 +1,6 @@
 # Backported stuff
 Fix-compile-error-on-big-endian.patch
+screen_crash.patch
 
 # Debian specific.
 gnukfreebsd.diff

Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Ralf Jung]

Hi,

>> That patch has now been accepted and merged upstream:
>> 
>> Considering how many KDE packages landed in their Qt 5 version recently,
>> it'd be great if a recent enough snapshot (or 5.5.0 with the patch
>> backported) could fix this issue.
> 
> Sadly the patch is not easy to backport as the code has changed too much 
> between 5.4.2 and 5.0.0 

Yeah, a backport wouldn't be worth it - this builds on top of quite a
few other changes that made the screen stuff much more reliable. The
actual patch only fixes a small missing piece, but it's been the last
piece for me ;-)

> so it won't happen before the gcc5 transition which is 
> due to start in a week.
> 
> I will probably not work too much (if anything at all) in 5.5.0 until we get 
> the gcc5 transition stuff solved, so it will be most probably material for 
> 5.5.1.

I see, okay. Good luck with that transition!

Kind regards,
Ralf


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Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Lisandro Damián Nicanor Pérez Meyer]

On Thursday 23 July 2015 12:58:30 Ralf Jung wrote:
[snip] 
> That patch has now been accepted and merged upstream:
> 
> Considering how many KDE packages landed in their Qt 5 version recently,
> it'd be great if a recent enough snapshot (or 5.5.0 with the patch
> backported) could fix this issue.

Sadly the patch is not easy to backport as the code has changed too much 
between 5.4.2 and 5.0.0 so it won't happen before the gcc5 transition which is 
due to start in a week.

I will probably not work too much (if anything at all) in 5.5.0 until we get 
the gcc5 transition stuff solved, so it will be most probably material for 
5.5.1.

Kinds regards, Lisandro.

-- 

Lisandro Damián Nicanor Pérez Meyer
http://perezmeyer.com.ar/
http://perezmeyer.blogspot.com/


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Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Ralf Jung]

Hi,


> On Sunday 05 July 2015 13:13:10 Ralf Jung wrote:
> > For the record, there's two more related upstream issues:
> > 
> > 
> > 
> > With Qt 5.5, there was lots of work on this issue. It did not get fixed,
> > though - at least on my system. I came up with a patch against Qt 5.5
> > that fixes the problem here, it's linked from the 2nd bugreport above
> > and currently under review at the Qt project.
> > 
> > There's hope at the horizon :D (at least once Qt 5.5 lands in Debian ;-).
> 
> Once the patch gets accepted by upstream :)

That patch has now been accepted and merged upstream:

Considering how many KDE packages landed in their Qt 5 version recently,
it'd be great if a recent enough snapshot (or 5.5.0 with the patch
backported) could fix this issue.

Kind regards,
Ralf


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Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Lisandro Damián Nicanor Pérez Meyer]

On Sunday 05 July 2015 13:13:10 Ralf Jung wrote:
> For the record, there's two more related upstream issues:
> 
> 
> 
> With Qt 5.5, there was lots of work on this issue. It did not get fixed,
> though - at least on my system. I came up with a patch against Qt 5.5
> that fixes the problem here, it's linked from the 2nd bugreport above
> and currently under review at the Qt project.
> 
> There's hope at the horizon :D (at least once Qt 5.5 lands in Debian ;-).

Once the patch gets accepted by upstream :)

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Lisandro Damián Nicanor Pérez Meyer
http://perezmeyer.com.ar/
http://perezmeyer.blogspot.com/


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Bug#787680: Qt5: Applications disappear or crash when screen is switched

[Ralf Jung]

For the record, there's two more related upstream issues:



With Qt 5.5, there was lots of work on this issue. It did not get fixed,
though - at least on my system. I came up with a patch against Qt 5.5
that fixes the problem here, it's linked from the 2nd bugreport above
and currently under review at the Qt project.

There's hope at the horizon :D (at least once Qt 5.5 lands in Debian ;-).

Kind regards,
Ralf


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