QTreeView: a few clicks crash

[mentalmushroom]

Hello

I’ve noticed a strange thing happens with QTreeView. In order to demonstrate it I created a small application. The program has one and only window that is actually a QTreeView instance. This tree contains several rows, each row has a sub-branch, and inside the sub-branch there are several sub-items (see the first image attached).

To see what I mean run the app, expand the last item of the tree and its sub-branch, click the down arrow of the vertical scrollbar to scroll it a little bit down, then click 4 times quickly on the collapse/expand button (see the red circle on the image).
click_place.png

After doing that you get assertion failed.
crash.png

Seems like QTreeView can’t find an item for the mouse position, because it moved when the branch was collapsed. I’ve attached two screenshots that show the stack state (perhaps, useful).
callstack_coordinateForItem.jpgcallstack_viewportEvent.jpg

My question – is there any solution/workaround for that or should I report a bug?

Here goes the complete application code.

#include <QtCore>
#include <QtGui>
 
int main(int argc, char ** argv)
{
	QApplication app(argc, argv);
 
	QStandardItemModel dataModel;
 
	//	populate data model
	for (int i = 0; i < 5; ++i)
	{
		QList<QStandardItem *> primaryItems;
		primaryItems.append(new QStandardItem(QString("primary item %1").arg(i)));
		primaryItems.append(new QStandardItem("info"));
 
		QStandardItem *dBranch = new QStandardItem("branch 1");
 
		for (int f = 0; f < 10; ++f)	//	add sub-items to the branch 1
		{
			QList<QStandardItem*> subItems;
			subItems.append(new QStandardItem(QString("sub-item %1").arg(f)));
			subItems.append(new QStandardItem("sub-item info"));
 
			dBranch->appendRow(subItems);
		}
 
		primaryItems.first()->appendRow(dBranch);
 
		dataModel.appendRow(primaryItems);
	}	//	over i
 
	QTreeView treeView;
	treeView.setModel(&dataModel);
	treeView.setEditTriggers(QAbstractItemView::NoEditTriggers);
	treeView.header()->setResizeMode(QHeaderView::ResizeToContents);
	treeView.resize(300, 350);
	treeView.show();
 
	return app.exec();
}

#include <QtCore>
#include <QtGui>

int main(int argc, char ** argv)
{
	QApplication app(argc, argv);

	QStandardItemModel dataModel;

	//	populate data model
	for (int i = 0; i < 5; ++i)
	{
		QList<QStandardItem *> primaryItems;
		primaryItems.append(new QStandardItem(QString("primary item %1").arg(i)));
		primaryItems.append(new QStandardItem("info"));

		QStandardItem *dBranch = new QStandardItem("branch 1");
		
		for (int f = 0; f < 10; ++f)	//	add sub-items to the branch 1
		{
			QList<QStandardItem*> subItems;
			subItems.append(new QStandardItem(QString("sub-item %1").arg(f)));
			subItems.append(new QStandardItem("sub-item info"));

			dBranch->appendRow(subItems);
		}

		primaryItems.first()->appendRow(dBranch);

		dataModel.appendRow(primaryItems);
	}	//	over i

	QTreeView treeView;
	treeView.setModel(&dataModel);
	treeView.setEditTriggers(QAbstractItemView::NoEditTriggers);
	treeView.header()->setResizeMode(QHeaderView::ResizeToContents);
	treeView.resize(300, 350);
	treeView.show();

	return app.exec();
}

To copy to clipboard, switch view to plain text mode 

[stampede]

Can't reproduce (tested on windows 7), I scroll down and click on it many times and nothing interesting happens. Do you have maybe another system to test it ? What Qt version are you using ?

[mentalmushroom]

I am using Windows 7 x64, Qt 4.7.2 + Visual Studio 2008 SP1. I've also tested it on another machine with Vista x86 - also crashed.

Perhaps, it somehow depends on hardware and speed of events processing, so it may happen more or less often on other machines. I noticed sometimes I had to wait a few seconds before it crashed. Sometimes it appeared only when I moved a mouse after clicking. I can try to make a video if needed.

Also I noticed it very rarely happens when you delete items, but this crash I don't know how to reproduce either.

[janton]

I tested this and have the same issue (Vista x86)
Here a video how to reproduce

[stampede]

Don't know if this matter, but I have all the graphics effects disabled (aero composition etc, all is set to "best performance"). You may try with that setting too.

[mentalmushroom]

I tried to turn off Aero and it seems like it doesn't affect the crash. The crash still happens and it is pretty simple to make it to appear. If you can't reproduce it make sure you do exactly the same. Expand the last row (and sub-branch), not something else. Don't scroll totally down - do only one click on the scrollbar down arrow. When you are clicking it needs to be done VERY QUICKLY. When you finish clicking you should get the mouse positioned on the "primary item 4". Then move a mouse and the crash should appear.

I didn't try it with the newer versions of Qt, but there is high chance it was not fixed there. I hope the issue will be addressed and resolved.

[stampede]

I see that both of you are using Visual Studio, I'm using mingw (gcc 4.5.2). Can you try that ? Can anyone using mingw verify this crash ?

[wysota]

Did anyone check what is contained in the line reported by Visual Studio or are you just limiting yourself to "hey, my app crashed, is it a bug in Qt?"

[mentalmushroom]

I see that both of you are using Visual Studio, I'm using mingw (gcc 4.5.2). Can you try that ? Can anyone using mingw verify this crash ?

I've never used mingw, so I am afraid I can't help with that. Perhaps, somebody else can.

Did anyone check what is contained in the line reported by Visual Studio or are you just limiting yourself to "hey, my app crashed, is it a bug in Qt?"

What should I check? That was a qt code. I don't understand it really well, but as far as I understood it can't find an item at the mouse position, because it was moved when the branch was collapsed and scrollbar disappeared.

[wysota]

What should I check? That was a qt code.

So have a look at it. And see why Qt aborted your app.

I don't understand it really well, but as far as I understood it can't find an item at the mouse position, because it was moved when the branch was collapsed and scrollbar disappeared.

Code aborts at an assert which means two things. One is that there is a problem here somewhere you need to either address or work around, and two that if you build your app in release mode there is a good chance it won't crash.

[mentalmushroom]

You are right, in release mode it doesn't crash (at least I could not make it to appear). But still failed assertion is a little bit "boo".
On Mac OS X Lion 10.7.1 + Qt 4.7.4 (Qt Creator) it doesn't crash in debug mode either.