Set DoubleClickInterval very low!

Mark Waddingham mark at livecode.com
Thu Aug 4 03:02:06 EDT 2016 

In order for you to be able to do completely different things on click and double click you need to wait and see if a double click occurs before the doubleClickInterval and if it does not *then* do the single click action. After all, the engine is not clairvoyant.

This is why click then double click should always be an incremental and related action - unless you want a pause in processing the single click.

Mark.

Sent from my iPhone

> On 4 Aug 2016, at 03:14, Peter M. Brigham <pmbrig at gmail.com> wrote:
> 
> So I must not be understanding this. If you want something to happen on mouseup and something else to happen on mousedoubleup, then how do you do it?
> 
> If I put this into a button script:
> 
> on mousedown
>   put "mousedown" & cr after fld "text"
> end mousedown
> 
> on mouseUp
>   put "mouseup" & cr after fld "text"
> end mouseUp
> 
> on mousedoubledown
>   put "mousedoubledown" & cr after fld "text"
> end mousedoubledown
> 
> on mousedoubleup
>   put "mousedoubleup" & cr after fld "text"
> end mousedoubleup
> 
> and I then do a doubleclick, I get 
> 
> mousedown
> mouseup
> mousedoubledown
> mousedoubleup
> 
> in fld "text". So far so good. if I comment out the actions in the mousedown and mouseup handlers, so they are effectively blocking those messages, I get
> 
> mousedoubledown
> mousedoubleup
> 
> in the field. But how do I get
> 
> mousedown
> mouseup
> 
> on a single click and *only*
> 
> mousedoubledown
> mousedoubleup
> 
> on a doubleclick?
> 
> It seems to me that if a doubleclick always produces both a mousedown/up and mousedoubledown/up set of messages, there is no way of preventing the mousedown/up actions happening in addition to the mousedoubledown/up actions. To make it clearer:
> 
> on mouseup
>   show grc "test1"
> end mouseup
> 
> on mousedoubleup
>   show grc "test2"
> end mousedoubleup
> 
> the mousedoubleup action will always show both graphics, but I want it to only show grc "test2".
> 
> ???
> 
> -- Peter
> 
> Peter M. Brigham
> pmbrig at gmail.com
> 
> 
> 
>> On Aug 3, 2016, at 7:55 PM, Mark Waddingham wrote:
>> 
>>> On 2016-08-04 01:32, Sannyasin Brahmanathaswami wrote:
>>> How is it a bug? logically the engine must wait for the double click
>>> interval before responding or double clicks could never be passed?
>>> N'est ce pas?
>> 
>> No - that isn't how double clicks work in LiveCode.
>> 
>> On the first mouseDown the engine:
>> 
>> 1) Stores the time of the mouseDown (last-click-time)
>> 2) Stores the location of the mouseDown (last-click-loc)
>> 3) Dispatches mouseDown
>> 
>> On a subsequent mouseDown the engine does the following:
>> 
>> if current-click-time - last-click-time < doubleClickInterval and \
>>      abs(current-click-loc.x - click-loc.x) < doubleClickDelta and \
>>         abs(current-click-loc.y - click-loc.y) < doubleClickDelta then
>>     dispatch mouseDoubleDown
>> else
>>     dispatch mouseDown
>> end if
>> 
>> i.e. If a click is within the doubleClickInterval time-wise since the last click, and within the doubleClickDelta distance since the last click a mouseDoubleDown message is sent instead of mouseDown.
>> 
>> (Note that if a mouse down event results in a mouseDown message, then you will receive a mouseUp message when the mouse is released, and if a mouse down even results in a mouseDoubleDown message, then you will receive a mouseDoubleUp message when the mouse is released).
>> 
>> What you are seeing is the fact that if you tap quickly (i.e. each one within the doubleClickInterval and close to each other on the screen) then you will receive:
>> 
>> mouseDown
>> mouseUp
>> mouseDoubleDown
>> mouseDoubleUp
>> mouseDown
>> mouseUp
>> mouseDoubleDown
>> mouseDoubleUp
>> 
>> i.e. You will get an alternating sequence of down/up and doubleDown/doubleUp pairs.
>> 
>> Solution: If you don't need to handle double clicks do:
>> 
>> on mouseDoubleDown
>>   mouseDown
>> end mouseDoubleDown
>> 
>> on mouseDoubleUp
>>   mouseUp
>> end mouseDoubleUp
>> 
>> This is a long standing (i.e. forever!) 'the way things work' in LiveCode - although I think there is a way it could be a great deal better, and more intuitive.
>> 
>> The only use of multi-click 'gestures' (which is what 'double clicks' are) which makes sense from a UI interaction point of view is where each click builds upon the action of the previous one.
>> 
>> e.g. In Finder:
>> 
>> 1) The first click selects a file
>> 2) The second click runs the file (which is already selected at this point)
>> 
>> e.g. In Text Editors:
>> 
>> 1) The first click places the caret
>> 2) The second click selects the word the caret is in
>> 3) The third click selects the line the word is in
>> 
>> Thus, one possible improvement would be to ditch the 'double' messages entirely, and add a 'clickCount' event property (a bit like the clickLoc) which returns the number of subsequent clicks. This would mean that (in a mouseDown / Up) handler you just choose what you do based on the clickCount. This means you can easily handle single, double or triple click sequences (which, I think is pretty much as far as you can stretch that particular bit of physical interaction - unless you want to cause the user significant problems in using your UI). i.e. In a double click scenario you would get:
>> 
>> mouseDown (clickCount == 1)
>> mouseUp (clickCount == 1)
>> mouseDown (clickCount == 2)
>> mouseUp (clickCount == 2)
>> 
>> This can be further built upon by introducing the idea of gestures. A 'click' is actually a gesture, not an event - i.e. it is a precise sequence of events which can be interpreted as a specific type of action. Introducing gestures you'd get the following message sequence:
>> 
>> mouseDown (clickCount == 1)
>> mouseUp (clickCount == 1)
>> click (clickCount == 1)
>> mouseDown (clickCount == 2)
>> mouseUp (clickCount == 2)
>> doubleClick (clickCount == 2)
>>   if passed then click (clickCount == 2)
>> 
>> For what its worth, LiveCode Builder uses the clickCount model (i.e. no double messages) - although we haven't added 'gestures' there yet.
>> 
>> Warmest Regards,
>> 
>> Mark.
>> 
>> -- 
>> Mark Waddingham ~ mark at livecode.com ~ http://www.livecode.com/
>> LiveCode: Everyone can create apps
>> 
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