QTreeView: dragging and dropping items with left mouse button?

Violet Giraffe

I'm unable to get drag and drop working using the left mouse button in a QTreeView. It does work with RMB. But with the LMB the view just selects multiple items that I drag across.

Here are my tree view properties:
http://i.stack.imgur.com/NT07q.png

So, how can I get dragging with a left mouse button to work?

P. S. I have confirmed that with the settings depicted above the "Editable tree model" example demonstrates exactly the same behavior.

SGaist

Hi,

AFAIK, this example doesn't activate the drag and drop feature of QTreeView.

You have the documentation here

Violet Giraffe

That's why I added "with the settings depicted above". I open the example, change those properties and observe the undesired behavior.

SGaist

That's not enough. The example also provides a custom model. The model should also provide the Qt::ItemIsDragEnabled item flag as needed if you want your items to be draggable

Violet Giraffe

This post is deleted!

Violet Giraffe

This post is deleted!

Violet Giraffe

Found what's breaking the drag and drop. It's my code that deselects an item that was single-clicked:

void CFileListView::mousePressEvent(QMouseEvent *e)`
{
	const QModelIndex itemClicked = indexAt(e->pos());

    QTreeView::mousePressEvent(e);

    if (e->button() == Qt::LeftButton && itemClicked.isValid() && e->modifiers() == Qt::NoModifier)
	    selectionModel()->clearSelection();
}

If I comment out the clearSelection call, drag and drop starts working. With clearSelection it's as if D&D is not enabled.
No idea what exactly is happening or how to fix this.

SGaist

To start a drag operation you need to select an index. What you do is that you clear that selection right after it happened so there's nothing to drag anymore.

Violet Giraffe

I see!
Can I somehow start drag manually in the mouseMove event?

SGaist

You would need to re-implement it yourself but why do you do that clear in the pressEvent ?

Violet Giraffe

This is a file manager application, this TreeView is the main file list view. Selection on click really looks horrible, and it's redundant - that's what the cursor is for (the thin dotted frame around an item). And not only that, but this selection upon click breaks other selection management operations.

Violet Giraffe

So, there's no simple way to start dragging a specific item?