use-revolution digest, Vol 1 #1315 - 11 msgs

[Bob Rasmussen]

Dave Cragg <dcragg at lacscentre.co.uk> wrote:

>  A mouseMove event is always sent in combination with (and before) a
>  mouseDown event. I think this may be what you are referring to. It's
>  been part of the engine behavior as far back as I can remember.
>
>  You can check with the following script in a button. Keep the mouse
>  still, and then click it. (In fact, there now seem to be two
>  mouseMove messages sent prior to a mouseDown.)
>
>  local lvEvents

>  on mouseUp
>      put "mouseUp" & cr after lvEvents
>      put lvEvents
>      put empty into lvEvents
>  end mouseUp
>
>  on mouseMove
>      if the mouse is down then put "mouseMove" & cr after lvEvents
>  end mouseMove
>
>  on mousedown
>      put "mouseDown" & cr after lvEvents
>  end mouseDown
>
>  I'm not defending the rationality of this, but one good outcome is
>  that it discourages use of "the mouse" function to determine whether
>  the mouse is down when you want to track mouse movement.
>
>  For those new to the list (this issue crops up regularly), the
>  "proper" way is to set a flag (as a script local or custom property)
>  on mouseDown and reset it on mouseUp. Then in the mouseMove handler,
>  check the state of the flag, and *not* the mouse function.
>
>  Cheers
>  Dave



I genuinely appreciate the effort Dave, but that's still not the case I
reported.  The "mouseMove" message that your example demonstrates does indeed
occur before the "mouseDown".  However, the extra one I observed occurred
*after* the "mouseDown" had already executed several statements and before the
remaining statements in the "mouseDown" handler completed.  It happened, in
fact, coincident with a "hide" statement *inside* the "mouseDown" handler.  I
know this, because my handlers looks something like the following after a few
diagnostic items are added akin to your example:

    local lvEvents, mouseIsDown


    on mouseDown
      put true into mouseIsDown
      put "mouseDown enter" & cr after lvEvents

      -- several statements, which among other things makes a new group within
an existing group using a "copy" command

      put "before hide" & cr after lvEvents
      hide anObject
      put "after hide" & cr after lvEvents

      -- several more statements

      put "mouseDown exit" & cr after lvEvents
    end mouseDown


    on mouseMove h, v
      if mouseIsDown then
        put "mouseMove     <--" & cr after lvEvents

        -- several more statements

      end if
    end mouseMove


    on mouseUp
      put false into mouseIsDown
      put "mouseUp" & cr after lvEvents
      put lvEvents
      put empty into lvEvents

      -- several more statements

    end mouseUp


What shows up in the message box is this:

    mouseDown enter
    before hide
    mouseMove     <--
    after hide
    mouseDown exit
    mouseMove     <--
    mouseMove     <--
    mouseMove     <--
    mouseUp


Take a look at the third line.  I hope this makes my situation clearer now.

Thanks,

RR