Distinguishing simple and double clicks

[Richard Gaskin]

Eric Chatonet wrote:
> I just want to make something that was easy with HC: e.g. allow the
> user to use simple and double clicks on the same button but with
> different actions.
> MouseUp is always sent by the engine first then mouseDoubleUp is sent
> if appropriate.

Is that not how HyperCard works?

If HC sends only one message or the other, then it must be adding a
delay to the mouseUp before firing its mouseUp message in order to be 
able to distinguish it from mouseDoubleUp.  :\


As for the task itself, your handlers look good for what you want to do 
so I'd go with those, but the question has me curious:  What is it 
you're working on?

I ask because when I read David Bovill's comment that this is a common 
task, at first glance I thought so too but after thinking about it some 
more I wonder if there's a subtle distinction at play here between 
common and less common use of those two messages in a single control.

--
A little background for those who may not have considered the 
abstraction of the "noun-verb" interaction model:

Most modern GUIs employ a noun-verb model, in which a noun object is 
selected and then a verb object is selected which operates on that noun.

For example, when you select text you're specifying the "noun", and then 
choosing "Bold" from the Style menu selects a "verb" (command) to 
operate on that noun.

The double-click gesture is commonly used as a shortcut to selecting a 
verb, and is generally handled in a noun object  (see 
<http://developer.apple.com/documentation/UserExperience/Conceptual/AppleHIGuidelines/XHIGUserInput/chapter_12_section_2.html#//apple_ref/doc/uid/TP30000361-TPXREF8>).

For example, in the Mac's Finder or Windows' Explorer, you can select an 
icon (the noun) and then select File->Open (the verb), or as a shortcut 
you can double-click the noun object to trigger that most common verb.

We also see this in list controls, where I tend to use mouseDoubleUp 
most frequently, to trigger a default button.

For example, suppose you have a list picker dialog with three controls: 
  list field, "OK" button (default) and "Cancel" button.   The explicit 
way of working with the dialog is to select the item in the list (the 
noun) then click "OK" (the verb), but it's common in many dialogs which 
have a default button to trigger that default button when the user 
double-clicks in the list as a shortcut.

In such selector controls I often have a mouseUp handler, but since it's 
in a noun object it usually just updates the current view to reflect the 
selection, rather than perform an action.

So while I can think of many examples of noun objects that use double 
clicks as a short cut for selecting a verb object, offhand I can't think 
of an example where a verb object handles double-clicks.
--

 From your description it almost sounds like the control in question is
a verb object such as a command button, rather than a noun object such 
as an icon or list item.   Do I understand that correctly?

If so, what is it about the interaction that requires that?

Or to word it in a more solutions-oriented way, might a change to the UI 
  make for an interaction model which maintains the traditional 
noun-verb expectation?

While not every difference between HC and Rev favors Rev, this is one 
where perhaps Dr. Raney's doctorate in cognitive psychology may have 
shown itself well:  while HyperCard eats clicks on double-click (and 
presumably introduces a delay to make that possible), Rev gives the 
developer the freedom to handle them both, confident that in most cases 
it'll be fine since it conforms to the most common interaction model.

Am I wearing rose-colored glasses on this?  Are there common examples of 
verb objects handling double-clicks that I've overlooked?  (Sometimes 
good coffee breeds unwarranted optimism <g>.)

-- 
  Richard Gaskin
  Managing Editor, revJournal
  _______________________________________________________
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