How to detect Drops outside of the target

sandro4912

Let me explain my issue with a simplified explanation:

I want to transfer something from Widget A to Widget B via drag and drop.

So far so good I understand how to do it.

Just one issue I face. I want to take something out of Widget A as soon as the drag is started (Before it reaches its destination). That something should get dropped on Widget B.

If the drop is released on the way (outside of Widget B) the contend should be transferred back to Widget A.

How can I achieve that?

To give some more details:

Widget A and Widget B are both derrived from QGraphicsWidget placed into a QGraphicsScene.

I implemented all the drag and drop operations in Widget A and Widget B.

My idea would be:

Derrive QGraphicsScene itself and implement dropEvent there.

Is that the right way or is there a better one?

SGaist

Hi,

Shouldn't you rather hide it until done and just show it again on drop failure ?

Christian Ehrlicher

Do you implement your own dnd handlers or use the Qt default ones?

sandro4912

I use QDrop with QMimeData.

And true in the real app something just gets hidden in the Widget A. But how to i report to it that the drop failed?

Christian Ehrlicher

My question was more - how do you begin the drag operation? Normally you call QDrag::exec() or something similar which returns the drop action used.

sandro4912

@Christian-Ehrlicher said in How to detect Drops outside of the target:

QDrag::exec()

A yes i call QDrag::exec() in mouseMoveEvent of Widget A

SGaist

As @Christian-Ehrlicher already suggested, check the result of exec and act accordingly.

sandro4912

I checked the result like this:

    // do change here

    // do the drag
    auto result = drag->exec();

    if (result == Qt::IgnoreAction) {
        // revert change here
    }

So that should be it