QItemSelectionModel::setCurrentIndex doesn't work

[evgeniy]

My code:

void TreeModel::selectIndex(QModelIndex ix) {
  if (!ix.isValid()) return;
  qDebug() << "name1" << ix.data();
  tree->selectionModel()->clear();
  tree->setExpanded(ix.parent(), true);
  tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);
  tree->scrollTo(ix);
}

void TreeModel::selectIndex(QModelIndex ix) {
  if (!ix.isValid()) return;
  qDebug() << "name1" << ix.data();
  tree->selectionModel()->clear();
  tree->setExpanded(ix.parent(), true);
  tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);
  tree->scrollTo(ix);
}

To copy to clipboard, switch view to plain text mode 

This snippet runs ok after deleting/inserting nodes. But when I try to select the remembered node from previous session in QMainWindow::showEvent the result is:

name1 QVariant(QString, "Highlight elements") 
The program has unexpectedly finished.
C:\Home\develop\qt\arm\designer\Designer exited with code -1073741819

name1 QVariant(QString, "Highlight elements") 
The program has unexpectedly finished.
C:\Home\develop\qt\arm\designer\Designer exited with code -1073741819

To copy to clipboard, switch view to plain text mode 

without

tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);

tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);

To copy to clipboard, switch view to plain text mode 

works well, but I do need to select this item.

Thank you very much in advance!

[ChrisW67]

You cannot store QModelIndexes between sessions, they are create-use-destroy objects.

[evgeniy]

You cannot store QModelIndexes between sessions, they are create-use-destroy objects.

I know it. See qDebug. Read carefully: without "tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);" works well...

[ChrisW67]

Read carefully: without "tree->selectionModel()->setCurrentIndex(ix, QItemSelectionModel::SelectCurrent);" works well...

So what is the problem again?

exited with code -1073741819

-1073741819 == 0xC0000005 Access Violation

Your debug output shows that (with reasonable likelihood) that the index points to an item in a valid model. It does not show that the index is related in any way to the model currently displayed in the tree, but I am willing to assume that it is because that would not lead to a crash anyway. It does not show that tree is a valid pointer. It does not show that tree->selectionModel() is not 0. Either pointer being broken seems reasonably possible given the outcome. Exactly which line is your debugger telling you the crash occurred at? What is the backtrace to that point? What is the value of tree at this point? What does tree->selectionModel() return at that point?

[evgeniy]

tree->selectionModel()->clear(); works
tree->setExpanded(ix.parent(), true); works
tree->scrollTo(ix); works
Could you tell me how to get backtrace from qt creator/gdb?

[ChrisW67]

The "bt" gdb command:

$ gdb ./mydebugexe
(gdb) run
...
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ac5ba7 in ?? () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7ac5ba7 in ?? () from /lib64/libc.so.6
#1  0x0000000000400597 in test () at main.cpp:6
#2  0x00000000004005ad in main (argc=1, argv=0x7fffffffdae8) at main.cpp:10

$ gdb ./mydebugexe
(gdb) run
...
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7ac5ba7 in ?? () from /lib64/libc.so.6
(gdb) bt
#0  0x00007ffff7ac5ba7 in ?? () from /lib64/libc.so.6
#1  0x0000000000400597 in test () at main.cpp:6
#2  0x00000000004005ad in main (argc=1, argv=0x7fffffffdae8) at main.cpp:10

To copy to clipboard, switch view to plain text mode 

If you are using gdb inside Qt Creator then you get a backtrace automatically.

[evgeniy]

debugger log:
>~"\nProgram received signal "
>~"SIGSEGV, Segmentation fault.\n"
>~"0x00438290 in QVariant::Private::Private (this="
>&"warning: (Internal error: pc 0x0 in read in psymtab, but not in symtab.)\n"
(Internal error: pc 0x0 in read in psymtab, but not in symtab.)
>&"\n"
>~"0x0) at ../../../../../../Qt/Qt5.0.2/5.0.2/mingw47_32/include/QtCore/qvariant.h:367\n"
>~"367\t inline Private(): type(Invalid), is_shared(false), is_null(true)\n"

>~"data=[{iname=\"local.node\",name=\"node\",addr=\"0x14384 220\",addr=\"0x14384220\",numchild=\"9\",origaddr= \"0x28d86c\",type=\"DNode\",value=\"{...}\",},{ina me=\"local.this\",name=\"this\",addr=\"0x14341820\ ",addr=\"0x14341820\",numchild=\"5\",origaddr=\"0x 28d890\",type=\"TreeModel\",value=\"{...}\",},{ina me=\"local.index\",name=\"index\",addr=\"0x28dba8\ ",numchild=\"0\",type=\"QModelIndex &\",value=\"(invalid)\",},{iname=\"local.role\",na me=\"role\",addr=\"0x28d898\",numchild=\"0\",type= \"int\",value=\"1\",},],typeinfo=[{name=\"aW50\",size=\"4\"}{name=\"Y29uc3QgUU1vZGVs SW5kZXggJg==\",size=\"4\"}{name=\"RE5vZGUgKg==\",s ize=\"4\"}{name=\"RE5vZGU=\",size=\"36\"}]\n"
>2390^done
dDISCARDING JUNK AT BEGIN OF RESPONSE:
dProgram received signal SIGSEGV, Segmentation fault.
d0x00438290 in QVariant::Private::Private (this=0x0) at ../../../../../../Qt/Qt5.0.2/5.0.2/mingw47_32/include/QtCore/qvariant.h:367
d367 inline Private(): type(Invalid), is_shared(false), is_null(true)
<Rebuild Watchmodel 243>
sFinished retrieving data

[evgeniy]

It's a Qt bug. The only way out:

void MainWindow::showEvent(QShowEvent *event) {
  QMainWindow::showEvent(event);
  QTimer::singleShot(0, this, SLOT(selectLastNode()));
}

void MainWindow::showEvent(QShowEvent *event) {
  QMainWindow::showEvent(event);
  QTimer::singleShot(0, this, SLOT(selectLastNode()));
}

To copy to clipboard, switch view to plain text mode