Flickering mouse pointer

[guiQt]

An extremely simple text editor accepts external file drop changing its title:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
setAcceptDrops(true);
}

void MainWindow::dragEnterEvent(QDragEnterEvent *event)
{
event->accept();
}

void MainWindow::dragMoveEvent(QDragMoveEvent *event)
{
event->accept();
}

void MainWindow::dropEvent(QDropEvent *event)
{
if (event->mimeData()->hasFormat("text/uri-list")) {
QList<QUrl> urls = event->mimeData()->urls();
if (urls.isEmpty())
return;
QString fileName = urls.first().toLocalFile();
if (fileName.isEmpty())
return;
setWindowTitle(tr("%1 - %2").arg(fileName).arg(tr("Drag File")));
}
}
MainWindow has just one widget, textEdit, defined by:

MyTextEdit::MyTextEdit(QWidget *parent)
: QTextEdit(parent)
{
setAcceptDrops(true);
}

void MyTextEdit::dragEnterEvent(QDragEnterEvent *e)
{
if (e->source()) {
if (e->source() == viewport()) {
e->accept();
}
}
}
textEdit accepts only "self" drops, so inserted text can then be moved or copied.
What is the reason of the pointer flickering? How can i remove it?
Thanks.

[guiQt]

Bump :confused:

[guiQt]

Looking for an answer :(

[guiQt]

Rebump :confused:

[Lykurg]

I can't see any problem in your code, so can you please provide a minimal compilable example reproducing your problem.

[guiQt]

droptest example
Problem shows up when you try to move/copy any entered word by dragging/Ctrl+dragging.

[Lykurg]

Can't reproduce it here on Mac. Where did you see it, Linux (which) or Windows or both?

[guiQt]

Ubuntu 10.04. Not tested on Windows.

[Zlatomir]

I have tested on kubuntu 10.4 and there is no "flicker", and can test on ubuntu, but a little bit later

LE:tested on ubuntu 10.4 and didn't flicker.

[guiQt]

Well, I'm pleased with the correctness of the code, but astonished with the configuration of my system.
Can't think about anything correlated...

[tbscope]

Try playing with performance settings.

- Update your graphics driver
- Try disabling some desktop effects

[guiQt]

Tried playing with some Compiz effects, following tbscope's hint.
However I think it's not a performance matter.
The problem seems to be correlated to MyTextEdit widget itself. To prove that, I added a second QTextEdit to MainWindow: flicker shows up only when dragging over MyTextEdit.
P.S. Short video included

[Lykurg]

Ok, on my console I get
Qt: Internal error: WH0A, unexpected condition reached? Not sure what goes wrong here.

[Lykurg]

Ehm, I found it: you have forgot to forward the drag to the base class:
void MyTextEdit::dragEnterEvent(QDragEnterEvent *e)
{
if (e->source()) {
if (e->source() == viewport()) {
e->accept();
}
}
QTextEdit::dragEnterEvent(e);
}Also use the Q_OBJECT macro in your own text edit class.

[guiQt]

The solution proposed by Lykurg removes the flicker, but the drag is not forwarded to the MainWindow when text editor accepts external file drop.
So the code that meets initial requests is:

void MyTextEdit::dragEnterEvent(QDragEnterEvent *e)
{
if (e->source()) {
if (e->source() == viewport()) {
e->accept();
QTextEdit::dragEnterEvent(e);
return;
}
}
e->ignore();
}

[wysota]

Hmm.... You mean you don't want the text editor to accept any drags apart the ones that originated in itself? Some strange text editor :)

[guiQt]

:D It's a pure theoretical (and trivial, obviously) case (described above in detail).
The final goal is to develop a lot more complex custom widget (MyTextEdit class with extended QTextEdit functionalities) that besides accepting normal drag and drop originated in itself, it sends external drops to its parent.
This way it's reusable: each application using MyTextEdit class is allowed to manage external drops in its own way.

[wysota]

I would still want to be able to drop some text snippet into the text editor without having to implement that in the parent/subclass of the editor... Especially if that was part of the original behaviour of the text editor.

[guiQt]

I would still want to be able to drop some text snippet into the text editor without having to implement that in the parent/subclass of the editor...
Perhaps you'll use YourTextEdit class ;)

[wysota]

Perhaps I would simply block only those events I explicitly don't want instead of blocking everything which is not what I am interested in at the moment.