Lmms: SIGSEGV on cloning pattern

[StinaIsNormallyDistributed]

When ctrl-clicking to drag-clone any pattern (beat, pianoroll or automation), lmms segfaults without further error.

lmms 1.2.0-rc7.42
qt5 5.12.0-3

[Cangle50]

Looks a little like what was reported in #4738 .

@megahertz commented

Fixed in Arch Linux in qt5-base 5.12.0-2

Looks like qt5 5.12.0-3 has broken it again.

[dvzrv]

@StinaIsNormallyDistributed seems this is happening on exit:

QPixmap::grabWidget is deprecated, use QWidget::grab() instead
[1]    1168 segmentation fault (core dumped)  lmms

[dvzrv]

Looking at the QPixmap documentation, this is obsolete since 5.12 and needs to be changed within lmms in these files.
However, this should not lead to a crash (at least not intentionally).
FWIW, it's the same problem with 5.12.0-2.

[dvzrv]

This seems to trickle down to Qcursor:

Thread 1 "lmms" received signal SIGSEGV, Segmentation fault.
QCursor::shape (this=this@entry=0x0) at kernel/qcursor.cpp:539
539     kernel/qcursor.cpp: No such file or directory.

Don't have much time for a debug build, but might do that in the coming days

[ghost]

While dragging a leaveEvent in TrackContentObjectView is triggered that calls QApplication::restoreOverrideCursor(), that is what is causing the crash.

It won't crash with this patch:

include/Track.h

--- a/include/Track.h
+++ b/include/Track.h
@@ -311,6 +311,7 @@
    bool m_gradient;

    bool m_needsUpdate;
+   bool m_isDragging;
    inline void setInitialMousePos( QPoint pos )
    {
        m_initialMousePos = pos;

src/core/Track.cpp

--- a/src/core/Track.cpp
+++ b/src/core/Track.cpp
@@ -275,7 +275,8 @@
    m_textShadowColor( 0, 0, 0 ),
    m_BBPatternBackground( 0, 0, 0 ),
    m_gradient( true ),
-   m_needsUpdate( true )
+   m_needsUpdate( true ),
+   m_isDragging( false )
 {
    if( s_textFloat == NULL )
    {
@@ -598,9 +599,12 @@
  */
 void TrackContentObjectView::leaveEvent( QEvent * e )
 {
-   while( QApplication::overrideCursor() != NULL )
-   {
-       QApplication::restoreOverrideCursor();
+   if ( ! m_isDragging )
+   {
+       while( QApplication::overrideCursor() != NULL )
+       {
+           QApplication::restoreOverrideCursor();
+       }
    }
    if( e != NULL )
    {
@@ -868,6 +872,8 @@
            // Write the TCOs to the DataFile for copying
            DataFile dataFile = createTCODataFiles( tcoViews );

+           m_isDragging = true;
+
            // TODO -- thumbnail for all selected
            QPixmap thumbnail = grab().scaled(
                128, 128,
@@ -876,6 +882,8 @@
            new StringPairDrag( QString( "tco_%1" ).arg(
                                m_tco->getTrack()->type() ),
                                dataFile.toString(), thumbnail, this );
+
+           m_isDragging = false;
        }
    }

[PhysSong]

Looks similar to #3926 to me.

[tresf]

@CYBERDEViLNL can you test against #4870 and confirm that it fixes this bug? If so, we'll close it as duplicate of #3926.

[ghost]

@tresf nope https://github.com/LMMS/lmms/pull/4870 won’t solve this issue. src/core/Track.cpp should be updated for that.

Here is a list of files that probably should be updated to. Only Track.cpp causes troubles with Qt 5.12 but for more clean code I think they all should get a update. I'm willing to work on that, all I need is some time :-P, should a new issue be opened or just continue here for all these files?

src/gui/widgets/LcdSpinBox.cpp:102:     QApplication::setOverrideCursor( Qt::BlankCursor );
src/gui/widgets/Knob.cpp:603:       QApplication::setOverrideCursor( Qt::BlankCursor );
src/gui/editors/PianoRoll.cpp:1602:                 QApplication::setOverrideCursor( c );
src/gui/editors/PianoRoll.cpp:1616:                 QApplication::setOverrideCursor( c );
src/gui/editors/PianoRoll.cpp:2021:         QApplication::setOverrideCursor(
src/gui/editors/PianoRoll.cpp:2239:                     QApplication::setOverrideCursor(QCursor(cursorShape));
src/gui/editors/PianoRoll.cpp:2244:                 QApplication::setOverrideCursor(QCursor(cursorShape));
src/gui/editors/AutomationEditor.cpp:587:               QApplication::setOverrideCursor( c );
src/gui/editors/AutomationEditor.cpp:820:                       QApplication::setOverrideCursor(
src/gui/editors/AutomationEditor.cpp:827:                   QApplication::setOverrideCursor( c );
src/core/Track.cpp:707:         QApplication::setOverrideCursor( c );
src/core/Track.cpp:729:         QApplication::setOverrideCursor( c );
src/core/Track.cpp:941:         QApplication::setOverrideCursor( c );
src/core/Track.cpp:2728:            QApplication::setOverrideCursor( c );
src/core/Track.cpp:2735:            QApplication::setOverrideCursor( c );