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List: kde-panel-devel
Subject: Re: Review Request 125433: kcm_kamera: Double calls to load() lead to strange scrollbars after savin
From: "Marcus Meissner" <marcus () jet ! franken ! de>
Date: 2015-09-28 18:47:33
Message-ID: 20150928184733.8863.4877 () mimi ! kde ! org
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> On Sept. 28, 2015, 7:02 a.m., Marcus Meissner wrote:
> > according to git blame I added this to help autoload the camera list ... although I have not much \
> > recall of this :/
>
> Christian Butcher wrote:
> A run of 'gdb systemsettings5' with 'break KKameraConfig::load()' and corresponding calls to 'bt' \
> informs me that with the load() call inside displayGPSuccessDialogue, first it is called by the \
> displayGPSuccessDialogue: ```
> #0 KKameraConfig::load (this=0x9d3310) at \
> /home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:203 #1 0x00007fffd3e08bec in \
> KKameraConfig::displayGPSuccessDialogue (this=0x9d3310) at \
> /home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:171 #2 0x00007fffd3e07c04 in \
> KKameraConfig::KKameraConfig (this=0x9d3310, parent=0x9c3240) at \
> /home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:67 #3 0x00007fffd3e0c89e in \
> KPluginFactory::createInstance<KKameraConfig, QWidget> (parentWidget=0x0, parent=0x9c3240, args=...) at \
> /opt/kde/include/KF5/KCoreAddons/kpluginfactory.h:477 #4 0x00007ffff34df827 in \
> KPluginFactory::create(char const*, QWidget*, QObject*, QList<QVariant> const&, QString const&) () from \
> /opt/kde/lib64/libKF5CoreAddons.so.5 #5 0x00007ffff798ed10 in KCModuleLoader::loadModule(KCModuleInfo \
> const&, KCModuleLoader::ErrorReporting, QWidget*, QStringList const&) () from \
> /opt/kde/lib64/libKF5KCMUtils.so.5 #6 0x00007ffff799785c in KCModuleProxyPrivate::loadModule() () from \
> /opt/kde/lib64/libKF5KCMUtils.so.5
> ...
> #67 0x00.... in main ()
> ```
>
> and then again by KCModule::qt_static_metacall:
> ```
> #0 KKameraConfig::load (this=0x9d3310) at \
> /home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:203 #1 0x00007ffff6a4e9d9 in \
> KCModule::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () from \
> /opt/kde/lib64/libKF5ConfigWidgets.so.5 #2 0x00007ffff3075832 in QObject::event(QEvent*) () from \
> /opt/qt5/lib64/libQt5Core.so.5 #3 0x00007ffff4be74c7 in QWidget::event(QEvent*) () from \
> /opt/qt5/lib64/libQt5Widgets.so.5 #4 0x00007ffff4ba699c in \
> QApplicationPrivate::notify_helper(QObject*, QEvent*) () from /opt/qt5/lib64/libQt5Widgets.so.5 #5 \
> 0x00007ffff4babb40 in QApplication::notify(QObject*, QEvent*) () from /opt/qt5/lib64/libQt5Widgets.so.5 \
> #6 0x00007ffff3046ae3 in QCoreApplication::notifyInternal(QObject*, QEvent*) () from \
> /opt/qt5/lib64/libQt5Core.so.5 #7 0x00007ffff3048d53 in \
> QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from \
> /opt/qt5/lib64/libQt5Core.so.5 #8 0x00007ffff309bac3 in ?? () from /opt/qt5/lib64/libQt5Core.so.5
> #9 0x00007fffed7b778d in g_main_dispatch (context=0x7fffdc0016f0) at ../../glib/gmain.c:3122
> #10 g_main_context_dispatch (context=context@entry=0x7fffdc0016f0) at ../../glib/gmain.c:3737
> #11 0x00007fffed7b7a38 in g_main_context_iterate (context=context@entry=0x7fffdc0016f0, \
> block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../../glib/gmain.c:3808
> #12 0x00007fffed7b7adc in g_main_context_iteration (context=0x7fffdc0016f0, may_block=1) at \
> ../../glib/gmain.c:3869 #13 0x00007ffff309beb7 in \
> QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from \
> /opt/qt5/lib64/libQt5Core.so.5 #14 0x00007ffff3044682 in \
> QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /opt/qt5/lib64/libQt5Core.so.5 #15 \
> 0x00007ffff304c18d in QCoreApplication::exec() () from /opt/qt5/lib64/libQt5Core.so.5 #16 \
> 0x000000000040f108 in main () ```
>
> I would guess that the second call occurs immediately after (but I didn't step through, so I could be \
> horribly wrong).
> load() does indeed call populateDeviceListView(), then gp_list_free(list). gp_list_new(&list) is called \
> in the same function, so I don't think there's any risk of double free, but something strange happens.
> If I watch carefully, sometimes the correct kcm loads and is then replaced by the scrollbars between \
> debug statements to 'kamera.kcontrol' in ~/.xsession-errors (these debug statements aren't in the git \
> repository since they're fairly useless for general use I imagine). I'm sure the reliability of 'tail \
> -f' for judging timing is pretty non-existent but I find it qualitatively convincing.
I tried to comment it out, it does not seem to change behaviour so it seems good.
(the config dialog is broken though... :( )
- Marcus
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
https://git.reviewboard.kde.org/r/125433/#review86025
-----------------------------------------------------------
On Sept. 28, 2015, 5:09 a.m., Christian Butcher wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> https://git.reviewboard.kde.org/r/125433/
> -----------------------------------------------------------
>
> (Updated Sept. 28, 2015, 5:09 a.m.)
>
>
> Review request for KDE Graphics and Plasma.
>
>
> Repository: kamera
>
>
> Description
> -------
>
> The displayGPSuccessDialogue(void) function calls load() as its last statement currently.
>
> Documentation for the KCModule api (both \
> [kde4](http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKCModule.html) and \
> [frameworks](http://api.kde.org/frameworks-api/frameworks5-apidocs/kconfigwidgets/html/classKCModule.html)) \
> informs the reader that load() is called at the end of construction - consequently it seems that the \
> additional load() call leads to the function (which is implemented as KKameraConfig::load() ) being \
> called twice.
> [Bug 236844](https://bugs.kde.org/show_bug.cgi?id=236844) may be related but at least on my KF5 based \
> system, this does not cause or prevent a crash, which is referenced in the bug.
> Separately, COPYING-CMAKE-SCRIPTS is referenced by the FindGphoto2.cmake file, and seems to have missed \
> the commit in [RR-125230](https://git.reviewboard.kde.org/r/125230/). If this was intentional, then my \
> apologies for readding here, but if so, the FindGphoto2.cmake file will need changing in some way.
>
> Diffs
> -----
>
> COPYING-CMAKE-SCRIPTS PRE-CREATION
> kcontrol/kamera.cpp 2d8f61449a5a6f2650d864c864652ebea780a422
> kcontrol/kameradevice.h b0ecb974f8fcb765228afe1965aeebab8e7656ed
>
> Diff: https://git.reviewboard.kde.org/r/125433/diff/
>
>
> Testing
> -------
>
> When the call is present, opening the Kamera KCM within systemsettings after saving changes and going \
> back to the main systemsettings view leads to a strange set of scrollbars.
> With the additional call removed, the KCM-Kamera opens properly on the second attempt, after saving \
> changes.
> As a camera to test, the first (in the scroll list) serial port camera is 'Achiever Digital Adc65'. \
> 'Barbie' may be easier to find as the first entry for 'B', and is also more memorable... I used a \
> serial camera, since then the kcm will load images even without a camera connected
>
> File Attachments
> ----------------
>
> scrollbars
> https://git.reviewboard.kde.org/media/uploaded/files/2015/09/28/74e8bd93-4c4a-4103-9fb1-7bd106258058__kcm1.png
>
>
> Thanks,
>
> Christian Butcher
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="https://git.reviewboard.kde.org/r/125433/">https://git.reviewboard.kde.org/r/125433/</a>
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<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<p style="margin-top: 0;">On September 28th, 2015, 7:02 a.m. UTC, <b>Marcus Meissner</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: \
-o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">according to git blame I added this to help autoload the camera list ... \
although I have not much recall of this :/</p></pre> </blockquote>
<p>On September 28th, 2015, 7:30 a.m. UTC, <b>Christian Butcher</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: 10px;">
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: \
-o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">A run of 'gdb systemsettings5' with 'break KKameraConfig::load()' and \
corresponding calls to 'bt' informs me that with the load() call inside displayGPSuccessDialogue, first \
it is called by the displayGPSuccessDialogue:</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;"><div class="codehilite" style="background: #f8f8f8"><pre \
style="line-height: 125%">#0 KKameraConfig::load (this=0x9d3310) at \
/home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:203 #1 0x00007fffd3e08bec in \
KKameraConfig::displayGPSuccessDialogue (this=0x9d3310) at \
/home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:171 #2 0x00007fffd3e07c04 in \
KKameraConfig::KKameraConfig (this=0x9d3310, parent=0x9c3240) at \
/home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:67 #3 0x00007fffd3e0c89e in \
KPluginFactory::createInstance<KKameraConfig, QWidget> (parentWidget=0x0, parent=0x9c3240, \
args=...) at /opt/kde/include/KF5/KCoreAddons/kpluginfactory.h:477
#4 0x00007ffff34df827 in KPluginFactory::create(char const*, QWidget*, QObject*, QList<QVariant> \
const&, QString const&) () from /opt/kde/lib64/libKF5CoreAddons.so.5
#5 0x00007ffff798ed10 in KCModuleLoader::loadModule(KCModuleInfo const&, \
KCModuleLoader::ErrorReporting, QWidget*, QStringList const&) () from \
/opt/kde/lib64/libKF5KCMUtils.so.5 #6 0x00007ffff799785c in KCModuleProxyPrivate::loadModule() () from \
/opt/kde/lib64/libKF5KCMUtils.so.5
...
#67 0x00.... in main ()
</pre></div>
</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">and \
then again by KCModule::qt_static_metacall:</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;"><div class="codehilite" style="background: #f8f8f8"><pre \
style="line-height: 125%">#0 KKameraConfig::load (this=0x9d3310) at \
/home/christian/kde-git/Extras/kamera/kcontrol/kamera.cpp:203 #1 0x00007ffff6a4e9d9 in \
KCModule::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) () from \
/opt/kde/lib64/libKF5ConfigWidgets.so.5 #2 0x00007ffff3075832 in QObject::event(QEvent*) () from \
/opt/qt5/lib64/libQt5Core.so.5 #3 0x00007ffff4be74c7 in QWidget::event(QEvent*) () from \
/opt/qt5/lib64/libQt5Widgets.so.5 #4 0x00007ffff4ba699c in QApplicationPrivate::notify_helper(QObject*, \
QEvent*) () from /opt/qt5/lib64/libQt5Widgets.so.5 #5 0x00007ffff4babb40 in \
QApplication::notify(QObject*, QEvent*) () from /opt/qt5/lib64/libQt5Widgets.so.5 #6 0x00007ffff3046ae3 \
in QCoreApplication::notifyInternal(QObject*, QEvent*) () from /opt/qt5/lib64/libQt5Core.so.5 #7 \
0x00007ffff3048d53 in QCoreApplicationPrivate::sendPostedEvents(QObject*, int, QThreadData*) () from \
/opt/qt5/lib64/libQt5Core.so.5 #8 0x00007ffff309bac3 in ?? () from /opt/qt5/lib64/libQt5Core.so.5
#9 0x00007fffed7b778d in g_main_dispatch (context=0x7fffdc0016f0) at ../../glib/gmain.c:3122
#10 g_main_context_dispatch (context=context@entry=0x7fffdc0016f0) at ../../glib/gmain.c:3737
#11 0x00007fffed7b7a38 in g_main_context_iterate (context=context@entry=0x7fffdc0016f0, \
block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../../glib/gmain.c:3808
#12 0x00007fffed7b7adc in g_main_context_iteration (context=0x7fffdc0016f0, may_block=1) at \
../../glib/gmain.c:3869 #13 0x00007ffff309beb7 in \
QEventDispatcherGlib::processEvents(QFlags<QEventLoop::ProcessEventsFlag>) () from \
/opt/qt5/lib64/libQt5Core.so.5 #14 0x00007ffff3044682 in \
QEventLoop::exec(QFlags<QEventLoop::ProcessEventsFlag>) () from /opt/qt5/lib64/libQt5Core.so.5 #15 \
0x00007ffff304c18d in QCoreApplication::exec() () from /opt/qt5/lib64/libQt5Core.so.5 #16 \
0x000000000040f108 in main () </pre></div>
</p>
<p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: inherit;">I \
would guess that the second call occurs immediately after (but I didn't step through, so I could be \
horribly wrong). </p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">load() does indeed call populateDeviceListView(), then gp_list_free(list). \
gp_list_new(&list) is called in the same function, so I don't think there's any risk of double free, \
but something strange happens.</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">If I watch carefully, sometimes the correct kcm loads and is then replaced \
by the scrollbars between debug statements to 'kamera.kcontrol' in ~/.xsession-errors (these debug \
statements aren't in the git repository since they're fairly useless for general use I imagine). I'm sure \
the reliability of 'tail -f' for judging timing is pretty non-existent but I find it qualitatively \
convincing.</p></pre> </blockquote>
</blockquote>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: -pre-wrap; white-space: \
-o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">I tried to comment it out, it does not seem to change behaviour so it \
seems good.</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
inherit;">(the config dialog is broken though... :( )</p></pre> <br />
<p>- Marcus</p>
<br />
<p>On September 28th, 2015, 5:09 a.m. UTC, Christian Butcher wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="12" style="border: 1px #888a85 solid; \
border-radius: 6px; -moz-border-radius: 6px; -webkit-border-radius: 6px;"> <tr>
<td>
<div>Review request for KDE Graphics and Plasma.</div>
<div>By Christian Butcher.</div>
<p style="color: grey;"><i>Updated Sept. 28, 2015, 5:09 a.m.</i></p>
<div style="margin-top: 1.5em;">
<b style="color: #575012; font-size: 10pt;">Repository: </b>
kamera
</div>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid \
#b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">The displayGPSuccessDialogue(void) function \
calls load() as its last statement currently.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">Documentation for the KCModule api (both <a \
href="http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKCModule.html" style="padding: \
0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: normal;">kde4</a> and <a \
href="http://api.kde.org/frameworks-api/frameworks5-apidocs/kconfigwidgets/html/classKCModule.html" \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">frameworks</a>) informs the reader that load() is called at the end of construction - \
consequently it seems that the additional load() call leads to the function (which is implemented as \
KKameraConfig::load() ) being called twice.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;"><a href="https://bugs.kde.org/show_bug.cgi?id=236844" \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: normal;">Bug \
236844</a> may be related but at least on my KF5 based system, this does not cause or prevent a crash, \
which is referenced in the bug.</p> <p style="padding: 0;text-rendering: inherit;margin: 0;line-height: \
inherit;white-space: inherit;">Separately, COPYING-CMAKE-SCRIPTS is referenced by the FindGphoto2.cmake \
file, and seems to have missed the commit in <a href="https://git.reviewboard.kde.org/r/125230/" \
style="padding: 0;text-rendering: inherit;margin: 0;line-height: inherit;white-space: \
normal;">RR-125230</a>. If this was intentional, then my apologies for readding here, but if so, the \
FindGphoto2.cmake file will need changing in some way.</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: 1px solid #b8b5a0">
<tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;"><p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">When the call is present, opening the \
Kamera KCM within systemsettings after saving changes and going back to the main systemsettings view \
leads to a strange set of scrollbars.</p> <p style="padding: 0;text-rendering: inherit;margin: \
0;line-height: inherit;white-space: inherit;">With the additional call removed, the KCM-Kamera opens \
properly on the second attempt, after saving changes.</p> <p style="padding: 0;text-rendering: \
inherit;margin: 0;line-height: inherit;white-space: inherit;">As a camera to test, the first (in the \
scroll list) serial port camera is 'Achiever Digital Adc65'. 'Barbie' may be easier to find as the first \
entry for 'B', and is also more memorable... I used a serial camera, since then the kcm will load images \
even without a camera connected</p></pre> </td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>COPYING-CMAKE-SCRIPTS <span style="color: grey">(PRE-CREATION)</span></li>
<li>kcontrol/kamera.cpp <span style="color: grey">(2d8f61449a5a6f2650d864c864652ebea780a422)</span></li>
<li>kcontrol/kameradevice.h <span style="color: \
grey">(b0ecb974f8fcb765228afe1965aeebab8e7656ed)</span></li>
</ul>
<p><a href="https://git.reviewboard.kde.org/r/125433/diff/" style="margin-left: 3em;">View Diff</a></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">File Attachments </h1>
<li><a href="https://git.reviewboard.kde.org/media/uploaded/files/2015/09/28/74e8bd93-4c4a-4103-9fb1-7bd106258058__kcm1.png">scrollbars</a></li>
</ul>
</td>
</tr>
</table>
</div>
</body>
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