Drag-n-Drop with cut and not copy

[KjellKod]

QDropEvent drop(event->pos(), Qt::MoveAction, event->mimeData(), 
		event->mouseButtons(), Qt::ShiftModifier, event->type()); // <-- Qt::ShiftModifier is important
}

QDropEvent drop(event->pos(), Qt::MoveAction, event->mimeData(), 
		event->mouseButtons(), Qt::ShiftModifier, event->type()); // <-- Qt::ShiftModifier is important
}

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Why is Qt::ShiftModifier important? Wouldn't it be better to use the actual modifiers for the event? I.e.

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

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[wysota]

Wouldn't it be better to use the actual modifiers for the event? I.e.

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

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The whole point of the "hack" is to make Shift the modifier. This will change the event to move instead of copy. If you use keyboardModifiers(), you might "inherit" some other modifier which would make it a link instead of move.

[jpn]

Why is Qt::ShiftModifier important? Wouldn't it be better to use the actual modifiers for the event? I.e.

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

event->keyboardModifiers()
// instead of
Qt::ShiftModifier

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It's important because the inner QTextControl ends up using QDropEvent::proposedAction(). The proposed action is determined by a private Qt class called QDragManager according to the modifiers (QDragManager::defaultAction() in src/gui/kernel/qdnd.cpp). I found all this out by simply debugging through the dropEvent() code.

[KjellKod]

I see what you mean - the shift modifier makes it into cut-n-paste rather than copy-n-paste

I've been a bit hesitant to look at Qt's code but I see now that when encountering problems like this that's definitely worthwhile

Thanks again J-P.

[jpn]

I see what you mean - the shift modifier makes it into cut-n-paste rather than copy-n-paste

Yep, exactly.

I've been a bit hesitant to look at Qt's code but I see now that when encountering problems like this that's definitely worthwhile

Please don't hesitate to do so, it's definitely the most powerful way to find out why something works like it does.

The sources throughout Qt are pretty clean and understandable. However, one confusing thing when looking into the sources of Qt for the first time might be the usage of Pimpl. Whether it's a new concept or not, one gets quickly used to the way it's used in Qt.

Thanks again J-P.

No problem at all, happy hacking with Qt!