Click Event

[elset191]

I would like a click event (Mouse down followed by Mouse up) in addition to the separate mouse down and mouse up.  You can fire a mouse up event without having mouse downed inside a control.  Likewise, you can fire a mouse down event by clicking and dragging and releasing outside of the event.  There have been numerous occasions where I want a click event rather than individual down and up events.

[altenbach]

So, how long should it have to wait after a mouse down to decide if it is a "mouse down" or "mouse click" event? I think you should implement this yourself by e.g. placing a TRUE in a shift register at the "mouse down" event and check it in the mouse "up event" case. Any other event clears the the state boolean.

[GregSands]

I'm not sure if the shift-register suggestion will always work.  Firstly, it's pretty easy for a Mouse Move event (or even several) to get in between Down and Up (also possibly user-generated events or dynamic events if there's parallel code).  And secondly, if there is a need to distinguish Mouse Down separately from Down-Up, then putting the action into the Mouse Up event won't do anything if it's just Mouse Down.  Nesting event cases to detect a Mouse Up within the Mouse Down event doesn't work.

Two other possible ways to detect a Click:

1) Use the Input Device Control under the Connectivity palette to wait in the Mouse Down event and see if the button goes up again.

2) Use a producer-consumer queue-based framework (or similar) to wait after a Mouse Down to see if there's a Mouse Up (event times get passed as data), meanwhile storing other actions to process otherwise.  But I think this checking needs to happen outside the event loop.

Both of these do require a click-length - 250ms seems to be reasonable.

[JackDunaway]

altenbach's suggestion was quickly written, but fundamentally correct.

You can get clever with shifting event data between events, and I would use the time field of the mouse down event shifted to the mouse up event. Compare the difference to the click time threshold, and you have a mouse click event, unaffected by the number of events fired in between. The two suggestions by GregS are arguably unnecessarily complex, but it depends on your app!

I have never missed the full down-up mouse "click" event, and cannot forsee a use in the future for it. (Buttons have this feature already built in based on the button action.)

Message Edited by mechelecengr on 06-19-2009 08:10 AM

[elset191]

Good Comments guys.  I figured there'd be some issues with it. 

Meche,

As for a use case.  I'm writing a small search utility and have controls that are disabled, which are used to filter the results.  If the user wants to filter a result based on a particular parameter I want him to be able to click inside the control to enable it and begin typing.  Right now I use mouse down, and it works okay.  Just, like you stated, doesn't work as a boolean button would.

[GregSands]

My suggestions were for the case where you want to distinguish Down-Up from Mouse Down-and-hold - and therefore want to do something before you receive a Mouse Up event.  One example I can think is to build and display a custom popup menu, which you may not want to display if there is an "immediate" Mouse Up.  Double-click detection (and distinguishing from Single-click) would also be difficult without an external process (e.g. consumer loop) which was checking for a particular sequence of events.