Distinguish single click from double click C++

double-clickmfcmousevisual c++

I have an application in which double clicking over an image view area changes the layout of the image view. Also on single click a dot will be placed on the image.
My problem is, both functionality is working when double clicked.

Of course I know that, when a double click occurs the control first goes to LButtonDown. I don't want the dot functionality to work when double click occurs. I have been working around this for more than a week. Please help.

Best Answer

The easiest way to solve this is to build a finite-state machine for handling mouse clicks. Basically, this will be a singleton object, which takes input from the mouse click events you're currently using. It's output will be SingleClickDetected, DoubleClickDetected, .... Red arrows indicate events which you are reporting to the rest of your application. Parentheses indicate what event you are reporting.

FSM

Of course, this state machine will have to be modified if you have to deal directly with MouseDown and MouseUp events, instead of MouseClick events. It will be slightly larger, but the idea is basically the same.

EDIT: From the comments, it looks like Windows doesn't cleanly report single- vs double-clicks, and you need to separate them. A state-machine for this scenario: FSM2

This is probably overkill for what you're trying to do, especially since most, if not all GUI-based programs in the history of everything have never ever used a double-click drag. It does show the basic idea, and shows how you can extend your state machine to handle different types of button clicks. Furthermore, if you wanted to, you could handle double-right-clicks, a drag that involves both left and right buttons, or any other scenario you could think of and incorporate into your UI.

Related Solutions

Cocoa – Distinguishing a single click from a double click in Cocoa on the Mac

Delaying the changing of the selection state is (from what I've seen) the recommended way of doing this.

It's pretty simple to implement:

- (void)mouseUp:(NSEvent *)theEvent
{
    if([theEvent clickCount] == 1) {
        [model performSelector:@selector(toggleSelectedState) afterDelay:[NSEvent doubleClickInterval]];
    }
    else if([theEvent clickCount] == 2)
    {
        if([model hasBeenDownloaded])
        {
                [NSRunLoop cancelPreviousPerformRequestsWithTarget: model]; 
                [mainWindowController showPreviewWindowForPicture:model];
        }
    }
}

(Notice that in 10.6, the double click interval is accessible as a class method on NSEvent)

WPF ListView ScrollViewer Double-Click Event

You can't change the behaviour, because the MouseDoubleClick handler is attached to the ListView control, so it has to occur whenever the ListView is clicked -- anywhere. What you can do it detect which element of the ListView first detected the double-click, and figure out from there whether it was a ListViewItem or not. Here's a simple example (omitting error checking):

private void lv_MouseDoubleClick(object sender, MouseButtonEventArgs e)
{
  DependencyObject src = (DependencyObject)(e.OriginalSource);
  while (!(src is Control))
    src = VisualTreeHelper.GetParent(src);
  Debug.WriteLine("*** Double clicked on a " + src.GetType().Name);
}

Note the use of e.OriginalSource to find the actual element that was double-clicked. This will typically be something really low level like a Rectangle or TextBlock, so we use VisualTreeHelper to walk up to the containing control. In my trivial example, I've assumed that the first Control we hit will be the ListViewItem, which may not be the case if you're dealing with CellTemplates that contain e.g. text boxes or check boxes. But you can easily refine the test to look only for ListViewItems -- but in that case don't forget to handle the case there the click is outside any ListViewItem and the search eventually hits the ListView itself.

Best Answer

Related Solutions

Cocoa – Distinguishing a single click from a double click in Cocoa on the Mac

WPF ListView ScrollViewer Double-Click Event

Related Topic