filer-qt --desktop segfaults when stylesheet.qss exists and is not empty #2

probonopd · 2020-10-19T20:21:47Z

Why?

Is it a fault of https://github.com/helloSystem/Filer or a fault of QtPlugin?

probonopd · 2020-10-29T20:21:31Z

Working around filer-qt --desktop specifically now by not loading the qss for it...

probonopd · 2021-02-15T17:36:39Z

Working around filer-qt --desktop specifically now by not loading the qss for it...

3bd2f1b

As a result, Filer and the Desktop Preferences are not styled using the stylesheet.
So the question is, why does filer-qt --desktop crash when the workaround is not there.

probonopd · 2021-04-04T08:12:21Z

When it is crashing (this currently can be forced by running Filer without --desktop (then our crude workaround is not used and it is loading stylestheet.css) and then running Filer with --desktop while the other one is still running:

recvmsg(4,{NULL,0,[{"\M-! \M-Q\^B\M-9\^N\M^@\^AT\^A\0"...,4096}],1,{},0,0},0) = 32 (0x20)
write(9,"\^A",1)                                 = 1 (0x1)
poll({ 8/POLLIN 21/POLLIN 30/POLLIN },3,49)      = 1 (0x1)
read(8,"\^A",16)                                 = 1 (0x1)
poll({ 4/POLLIN },1,-1)                          = 1 (0x1)
recvmsg(4,{NULL,0,[{"\M-! \M-Q\^B\M-9\^N\M^@\^AT\^A\0"...,4096}],1,{},0,0},0) = 32 (0x20)
write(9,"\^A",1)                                 = 1 (0x1)
poll({ 8/POLLIN 21/POLLIN 30/POLLIN },3,35)      = 1 (0x1)
read(8,"\^A",16)                                 = 1 (0x1)
poll({ 8/POLLIN 21/POLLIN 30/POLLIN },3,35)      = 0 (0x0)
getfsstat(0x0,0,MNT_NOWAIT)                      = 16 (0x10)
getfsstat(0x809716300,37504,MNT_NOWAIT)          = 16 (0x10)
poll({ 17/POLLIN 19/POLLIN },2,-1)               = 1 (0x1)
recvmsg(19,{NULL,0,[{"l\^A\0\^A\0\0\0\0\^C\0\0\0\M^F\0"...,2048}],1,{},0,0x40000},0x40000) = 152 (0x98)
recvmsg(19,0x7fffdf7f9780,0x40000)               ERR#35 'Resource temporarily unavailable'
write(18,"\^A",1)                                = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
poll({ 8/POLLIN 21/POLLIN 30/POLLIN },3,2996)    = 1 (0x1)
read(8,"\^A",16)                                 = 1 (0x1)
poll({ 17/POLLIN 19/POLLIN },2,0)                = 1 (0x1)
read(17,"\^A",16)                                = 1 (0x1)
sendmsg(19,{NULL,0,[{"l\^B\^A\^A.\t\0\0\M-\\0\0\0\^_\0"...,48},{")\t\0\0<!DOCTYPE node PUBLIC "-/"...,2350}],2,{},0,0},MSG_NOSIGNAL) = 2398 (0x95e)
poll({ 17/POLLIN 19/POLLIN },2,-1)               = 1 (0x1)
read(17,"\^A",16)                                = 1 (0x1)
write(18,"\^A",1)                                = 1 (0x1)
poll({ 17/POLLIN 19/POLLIN },2,-1)               = 1 (0x1)
recvmsg(19,{NULL,0,[{"l\^A\0\^A\^D\0\0\0\^F\0\0\0~\0\0"...,2048}],1,{},0,0x40000},0x40000) = 148 (0x94)
recvmsg(19,0x7fffdf7f9780,0x40000)               ERR#35 'Resource temporarily unavailable'
write(18,"\^A",1)                                = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
poll({ 17/POLLIN 19/POLLIN },2,0)                = 1 (0x1)
read(17,"\^A",16)                                = 1 (0x1)
poll({ 8/POLLIN 21/POLLIN 30/POLLIN },3,1973)    = 1 (0x1)
read(8,"\^A",16)                                 = 1 (0x1)
desktopManager: 1
write(2,"desktopManager: 1\n",18)                = 18 (0x12)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
write(9,"\^A",1)                                 = 1 (0x1)
probono: FolderItemDelegate::FolderItemDelegate created
write(2,"probono: FolderItemDelegate::Fol"...,56) = 56 (0x38)
probono: FileLauncher created
write(2,"probono: FileLauncher created\n",30)    = 30 (0x1e)
SIGNAL 11 (SIGSEGV) code=SEGV_MAPERR trapno=12 addr=0x8
poll({ 4/POLLIN },1,-1)                          ERR#4 'Interrupted system call'
<thread 100638 exited>
<thread 100640 exited>
<thread 100650 exited>
<thread 100642 exited>
<thread 100643 exited>
process killed, signal = 11

When it is not loading the stylesheet because it was directly invoked with with --desktop, then it looks like this:

desktopManager: 1
write(2,"desktopManager: 1\n",18)		 = 18 (0x12)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
write(9,"\^A",1)				 = 1 (0x1)
probono: FolderItemDelegate::FolderItemDelegate created
write(2,"probono: FolderItemDelegate::Fol"...,56) = 56 (0x38)
access("/usr/local/etc/fonts/fonts.conf",R_OK)	 = 0 (0x0)
access("/usr/local/etc/fonts/fonts.conf",R_OK)	 = 0 (0x0)
readlink("/usr/local/etc/fonts/fonts.conf",0x7fffffffc180,1023) ERR#22 'Invalid argument'
fstatat(AT_FDCWD,"/usr/local/etc/fonts/fonts.conf",{ mode=-rw-r--r-- ,inode=132655,size=2852,blksize=4096 },0x0) = 0 (0x0)
openat(AT_FDCWD,"/usr/local/etc/fonts/fonts.conf",O_RDONLY|O_CLOEXEC,00) = 22 (0x16)
read(22,"<?xml version="1.0"?>\n<!DOCTYPE"...,1024) = 1024 (0x400)
read(22,"s.\n\n\tKeith Packard\n-->\n\n<!"...,1024) = 1024 (0x400)
read(22,"string>sans-serif</string>\n\t\t"...,1024) = 804 (0x324)
read(22,0x7fffffffca90,1024)			 = 0 (0x0)
close(22)					 = 0 (0x0)
getrandom("&\M-4h\240\M-A 8\M^O\M-v\M-_F"...,40,0) = 40 (0x28)
mmap(0x0,1104,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0x0) = 34461900800 (0x80616e000)
minherit(0x80616e000,1104,INHERIT_ZERO)		 = 0 (0x0)
access("/usr/local/etc/fonts/conf.d",R_OK)	 = 0 (0x0)
access("/usr/local/etc/fonts/conf.d",R_OK)	 = 0 (0x0)

So when it does not crash, it does some font loading related work. Is this the part that is crashing when there is a stylesheet.qss file?

Looking at the code, there is an invocation of QStyledItemDelegate near probono: FolderItemDelegate::FolderItemDelegate created - coincidence?

probonopd · 2021-04-04T08:28:41Z

We have some calls to the obsolete QStyleOptionViewItemV4 which probably should be ported to QStyleOptionViewItem.

However, we have those in both folderitemdelegate.cpp and in desktopitemdelegate.cpp. The crash only happens when the desktop is being shown. So most likely what is causing it must be in the latter but not the former...

We have a QStyleOptionViewItemV4 there.

Replacing the V4s does not prevent the crash. They are probably just aliases anyway https://doc.qt.io/archives/qt-5.11/qstyleoptionviewitem-obsolete.html.

probonopd · 2021-04-04T10:13:28Z

This can be reproduced with a way simpler style plugin, based on the Qt example "SimpleStyle" that comes with Qt Creator, with only one method in simplestyle.cpp:

void SimpleStyle::polish(QApplication* app)
{
    qDebug() << "probono: SimpleStyle::polish(QApplication* app)";

    QCommonStyle::polish(app);

    app->setPalette(standardPalette());

    // probono: Use ~/.config/stylesheet.qss or /etc/xdg/tylesheet.qss if exists
    QString qsspath;
    qsspath = QStandardPaths::locate(QStandardPaths::ConfigLocation, QStringLiteral("stylesheet.qss"), QStandardPaths::LocateFile);
    if(qsspath.isEmpty() == false) {
        QMessageBox *msgBox = new QMessageBox(QMessageBox::NoIcon, "Title", qsspath);
        msgBox->exec();
        QFile File(qsspath);
        File.open(QFile::ReadOnly);
        QString StyleSheet = QLatin1String(File.readAll());
        app->setStyleSheet(StyleSheet);
    }
}

If we build this, then

sudo cp ~/build-styleplugin-Desktop-Debug/styles/libsimplestyleplugin.so /usr/local/lib/qt5/plugins/styles/

and then run QT_QPA_PLATFORMTHEME="" QT_STYLE_OVERRIDE=simplestyle /System/Filer.AppDir/AppRun followed by QT_QPA_PLATFORMTHEME="" QT_STYLE_OVERRIDE=simplestyle /System/Filer.AppDir/AppRun --desktop, then we also get the crash.

If I comment out the app->setStyleSheet(StyleSheet); above then it does not crash.

If I replace the line with app->setStyleSheet(""); then it does not crash.

If I replace the line with app->setStyleSheet("QObject { font-size: 14pt; }"); or with app->setStyleSheet("QObject { }"); then it also crashes.

Interesting: When setStyleSheet to anything but "" then SimpleStyle::polish(QApplication* app) seems to get called twice. Maybe polish is not the correct place to hook this in?

probonopd · 2021-04-04T11:19:54Z

If we apply the same stylesheet not through this plugin but in Filer filer.cpp as shown below, then it does not crash and the qss does get applied (but as soon as there is anything in the qss file, even a comment, then the desktop background is always white, the font-related settings of Filer are ignored and the stylesheet always "wins").

This shows that one can set a stylesheet without Filer crashing when the desktop is rendered, but with weird side effects and not in the way we are trying to do it in this plugin... so it may well be that we need to turn out attention the Filer's desktop drawing code (as well)...

#include <libfm/fm.h>
#include "application.h"
#include "libfmqt.h"
#include <QStandardPaths>
#include <QMessageBox>

int main(int argc, char** argv) {
  // ensure that glib integration of Qt is not turned off
  // This fixes #168: https://github.com/lxde/filer-qt/issues/168
  qunsetenv("QT_NO_GLIB");

  Filer::Application app(argc, argv);
  app.init();

  // ----------------------------------------------------------------------------------------
  // probono: Use ~/.config/stylesheet.qss or /etc/xdg/stylesheet.qss if exists
  // FIXME: This is a workaround for the workaround in
  // https://github.com/helloSystem/QtPlugin/commit/3bd2f1b6d6e6fb3a6fcdf972871165e46de2011f
  // to temporarily fix https://github.com/helloSystem/Utilities/issues/48 until
  // https://github.com/helloSystem/QtPlugin/issues/2
  // is properly resolved.
  QString qsspath;
  qsspath = QStandardPaths::locate(QStandardPaths::ConfigLocation, QStringLiteral("stylesheet.qss"), QStandardPaths::LocateFile);
  if(qsspath.isEmpty() == false) {
      QFile File(qsspath);
      File.open(QFile::ReadOnly);
      QString StyleSheet = QLatin1String(File.readAll());
      app.setStyleSheet(StyleSheet);
  }
  // ----------------------------------------------------------------------------------------

  return app.exec();
}

probonopd · 2021-04-09T17:08:26Z

Another application where this can be reproduced with:

https://github.com/mildred/qfm

When using QT_QPA_PLATFORMTHEME=panda (as is the default on helloSystem), then

It segfaults immediately when /usr/local/etc/xdg/stylesheet.qss exists
When I move that file away, it does not exist

So it's definitely not a Filer bug.

kettle-7 · 2021-05-26T08:46:16Z

Closed then?

probonopd · 2021-05-26T16:47:35Z

Hesitant to close this as long the bug can be reproduced with
https://github.com/mildred/qfm. While it is possible that it is not a QtPlugin bug it seems like it gets triggered when QtPlugin and a non-empty qss file are used.

probonopd added the bug Something isn't working label Oct 29, 2020

probonopd changed the title ~~Some applications segfault when stylesheet.css exists and is not empty~~ Some applications segfault when stylesheet.qss exists and is not empty Oct 29, 2020

probonopd mentioned this issue Feb 15, 2021

Desktop: Not in Hello System Style helloSystem/Utilities#48

Closed

probonopd mentioned this issue Feb 21, 2021

Uniform styles helloSystem/hello#133

Closed

probonopd changed the title ~~Some applications segfault when stylesheet.qss exists and is not empty~~ filer-qt --desktop segfaults when stylesheet.qss exists and is not empty Apr 4, 2021

probonopd pinned this issue Apr 4, 2021

probonopd added the help wanted Extra attention is needed label Apr 4, 2021

This was referenced Apr 10, 2021

desktopwindow: fix crash on stylesheet loading helloSystem/Filer#76

Merged

desktopwindow: switch to updating stylesheet for background helloSystem/Filer#77

Merged

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filer-qt --desktop segfaults when stylesheet.qss exists and is not empty #2

filer-qt --desktop segfaults when stylesheet.qss exists and is not empty #2

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filer-qt --desktop segfaults when stylesheet.qss exists and is not empty #2

filer-qt --desktop segfaults when stylesheet.qss exists and is not empty #2

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