I'm implementing a basic shape drawing tool using a custom subclass of Qt's QGraphicsScene and several QGraphicsItem. Now there are several situations where I don't want any "global" actions to be executed:
For example, while dragging items around, the user should not be allowed to create a new file or to undo the last action (by pressing Ctrl-Z for example) since this would lead to several problems that would have to be handled separately (if the user is currently drawing an edge between two nodes, what should happen if he presses Ctrl-Z with the last recorded action being the creation of the first node?)
I noticed that several commercial applications like Microsoft Word and Adobe Photoshop just seem to ignore any usual keyboard shortcuts while being in such an "intermediate" state. Furthermore, when dragging items out of the viewport, these tools display a "forbidden" cursor and do not allow any mouse press events to reach the outer window (like a right click on the toolbar, for example).
How should I implement this in my case, when using QGraphicsScene? I already tried to add the following override:
void MyGraphicsScene::keyPressEvent(QKeyEvent* keyEvent)
{
keyEvent->accept();
}
But any pressed keys were still delivered to the main window. In addition to that, I'm not sure if filtering just keyboard events is safe enough, since there might be other input events that could trigger forbidden actions.
Is there any generic approach to this problem that I could use in my software?
