How to disable the automatic selectioning in a QGraphicsscene? [Solved]

  • Hi,

    when I put some QGraphicItems in a QGraphicsscene and give this Items the ItemIsSelectible flag, one item can be selected with a mouse click (all other items are deselected automatically then). If I hold down CTRL key while clicking, the other items hold their selection state. But how can I achive this with another key than CTRL or for example in a special mode, where I do not need to hold down a key for adding items to the selection with clicking on it. I tried nearly everything, but I do not know where to catch and avoid this automatic deselection behaviour. Does anyone know how this could be done?


  • Override the QGraphicsScene::mousePressEvent() and implement your own selection scheme. Have a look at the QGraphicsScene::mousePressEvent() implementation for ideas.

  • I tried this but it does not work, even if I do not propagate the mousePressEvent to QGraphicsScene::mousePressEvent() the deselection occurs. :(

  • OK, found it. The item itself does the selectioning and unselectioning in both it's mousePressEvent and mouseReleaseEvent. QGraphicsScene::mousePressEvent() does only a deselection of all items if there is no item under the cursor. So finally reimplementing QGraphicsItem::mousePressEvent() (and mouseReleaseEvent) and not propagate the event to the base class solved the problem.
    It is worthwhile to have a look at the source of QGraphicsItem::mousePressEvent().

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