Preventing inadvertant drag and drop

WEBINAR: On-demand webcast

How to Boost Database Development Productivity on Linux, Docker, and Kubernetes with Microsoft SQL Server 2017 REGISTER >


Have you ever had the experience that you clicked on the Explorer to bring it to the foreground and the directory got moved. This happens if the mouse moves before the mouse button is released. Many of the users of my program had this experience and heres what I did to prevent inadvertant drag - drop. I basically imposed the restriction that after pressing the mouse button the cursor should remain on the item for a few milliseconds before dragging can be initiated.
 

Step 1: Declare member variable

Add a member variable to hold the tick count when the user presses the mouse button.
 
protected:
        DWORD   m_dwDragStart;


Step 2: Define a constant to specify the delay

We define DRAG_DELAY with a value 80. You might want to use a different value.
#define DRAG_DELAY 80


Step 3: Add handler for WM_LBUTTONDOWN

The only interesting thing we do here is initialize the m_dwDragStart variable. GetTickCount() returns the number of milliseconds since Windows was started.
 
void CTreeCtrlX::OnLButtonDown(UINT nFlags, CPoint point) 
{
        m_dwDragStart = GetTickCount();
        CTreeCtrl::OnLButtonDown(nFlags, point);
}


Step 4: Check for sufficient delay in TVN_BEGINDRAG handler

Insert the following code right at the beginning of the TVN_BEGINDRAG handler. In a previous section we have used the name OnBeginDrag() for the handler function. If the delay since the user pressed the left mouse button is not sufficient, we not initiate the drag and drop process.
 
        // This code is to prevent accidental drags.
        if( (GetTickCount() - m_dwDragStart) < DRAG_DELAY )
                return;



Comments

  • Title

    Posted by Legacy on 04/09/2002 12:00am

    Originally posted by: Name

    Comment

    Reply
  • h

    Posted by Legacy on 04/09/2002 12:00am

    Originally posted by: h

    h

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  • Your email address will not be published.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

Top White Papers and Webcasts

  • Many enterprises are working with an IT architecture that's evolved over time. As business needs evolve, IT must decide whether to modernize incrementally, or all at once. Each approach has its benefits and drawbacks. Identity Management is key to modernizing IT; it plays a crucial role in migrating to cloud apps like Office 365 or HR information systems, building web and mobile apps, and opening developer access to business systems. Read how Okta's modern approach to identity management helps business lower …

  • In order for IT service providers to succeed, it's paramount that they find a competitive advantage and continually develop new ways to find additional revenue streams. IT service providers need to be able to do it all for their clients – from managing entire technology infrastructures to responding quickly to a multitude of end-user needs. With a growing number of issues to resolve and limited technicians at hand, how can IT service providers operate efficiently while providing top-notch service …

Most Popular Programming Stories

More for Developers

RSS Feeds

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