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
Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • On-demand Event Event Date: February 12, 2015 The evolution of systems engineering with the SysML modeling language has resulted in improved requirements specification, better architectural definition, and better hand-off to downstream engineering. Agile methods have proven successful in the software domain, but how can these methods be applied to systems engineering? Check out this webcast and join Bruce Powel Douglass, author of Real-Time Agility, as he discusses how agile methods have had a tremendous …

  • Remember getting your first box of LEGOS as a kid? How fun it was putting the pieces together, collaborating with your friends to create something new? Now, as an IT professional, assembling and maintaining a Lego-like collaboration infrastructure isn't what you signed up for. Piecing together disparate systems of record for email, web meetings and other applications is about as painful as stepping on a pile of Legos. Download the e-book to learn how implementing a collaboration system connects systems of …

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date