Using ESC to cancel drag and drop


To escape out of a drag and drop operation we can look for the ESCAPE key in the PreTranslateMessage() and terminate the operation without moving any item..
 

BOOL CTreeCtrlX::PreTranslateMessage(MSG* pMsg)
{
	if( pMsg->message == WM_KEYDOWN && pMsg->wParam == VK_ESCAPE 
					&& m_bLDragging)
	{
		m_bLDragging = 0;
		CImageList::DragLeave(NULL);
		CImageList::EndDrag();
		ReleaseCapture();
		SelectDropTarget(NULL);
		delete m_pDragImage;
		return TRUE;		// DO NOT process further
	}

	return CTreeCtrl::PreTranslateMessage(pMsg);
}

There is one more thing you need to for this to work properly - call SetFocus() in your WM_LBUTTONDOWN handler. If the control doesn't already have focus when the user begins the drag and drop operation, then the control doesn't receive focus and if the control doesn't have the focus, it doesn't receive the WM_KEYDOWN message.



Comments

  • ignore other keys

    Posted by Legacy on 04/22/2002 12:00am

    Originally posted by: real name

    can very useful to ignore all other keys (or maybe left drag with them too) to not get unwanted situations like ctrl-a/del handling during operation
    t!

    Reply
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