Drag-scrolling a group

[Roger Eller]

Can it be done math-free?  If you nest a group inside the scrollable locked
group, and set the nested group to a simple "grab me" in a mouseDown or
mouseStillDown handler...

~Roger

On Thu, Jul 11, 2013 at 2:00 PM, Devin Asay wrote:

> Hi all,
>
> Has anyone worked out  a method for drag-scrolling a group? I have a
> simple game in which play area may be smaller than the working screenrect
> on some screens. I lock the group so that it's always the same size as the
> stack window, then I just set the scroll of the group to show part of the
> play area that is in view. I've worked out how to do it using the scroll
> wheel on the mouse, but I also want to be able to drag the play area around
> with the mouse. It's "sort of" working, but is moving very jerkily.
>
> I'm doing this:
>
> local sDragging, sMouseV, sMouseH
>
> on mouseUp
>     put false into sDragging
> end mouseUp
>
> on mouseRelease
>     put false into sDragging
> end mouseRelease
>
> on mouseDown
>     if the height of this stack < the maxHeight of this stack OR  \
>           the height of this stack < the maxHeight of this stack then
>         put true into sDragging
>     else
>         put false into sDragging
>     end if
>     put the mouseV into sMouseV
>     put the mouseH into sMouseH
> end mouseDown
>
> on mouseMove pNewMouseH, pNewMouseV
>     if sDragging then
>         set the hScroll of me to the hScroll of me - (pNewMouseH -sMouseH)
>         set the vScroll of me to the vScroll of me - (pNewMouseV - sMouseV)
>     end if
> end mouseMove
>
> My math brain is not very sharp today. Ideas?
>
> Thanks,
>
> Devin
>
>
> Devin Asay
> Learn to code with LiveCode University
> http://university.livecode.com
>
>
>
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