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Re: Using DUIM's <viewport>

In article <wku2hxaofu.fsf@double.co.nz>, Chris Double 
<chris@double.co.nz> wrote:

> Dustin Voss <agent_@mindspring.com> writes:
> 
> > Can you (or anyone) think of a way to automatically repaint this?
> > Maybe hook into some event somewhere?
> 
> If you don't mind a bit of flicker when scrolling, adding the
> following method will do the trick:
> 
> -----------------8<-----------------
> define method note-viewport-position-changed( 
>     frame :: <scroll-test-frame>,
>     sheet :: <sheet>, x, y) => ()
>   next-method();
> 
>   let region = frame.lists-pane.sheet-region; 
>   with-sheet-medium (medium = sheet)
>     clear-box*(medium, region)
>   end;
>   repaint-sheet(sheet, region);
> 
>   do-sheet-children(update-gadget, frame.lists-pane);  
> end; 
> -----------------8<-----------------
> 
> The method note-viewport-position-changed gets called when the
> scrolling area is scrolled. It is called by scroll-viewport-child. It
> looks like the redraw problem is somewhere in scroll-viewport-child or
> something it calls. The method above erases the list panes and then
> forces them to update again after scroll-viewport-child is called.
> 
> It is specialised on the frame so you'll have to add this method for
> each frame where you do this sort of thing.
> 
> Hope that helps,
> Chris.

That seems to work fine (aside from the flicker) for list boxes.  I had 
intended to use list controls, though, and this technique doesn't work 
for that.  I poked around in the source code, but couldn't figure out 
what was different.

Interestingly, if I do this (IIRC)...

define method note-position-changed (frame :: <frame>, sheet :: <sheet>)
  next-method();
  sheet.sheet-mapped? := #f;
  sheet.sheet-mapped? := #t;
end;

...it works correctly for list controls as well as list boxes.  But it 
still flickers, and the control loses focus -- I tried to save and reset 
the focus to no avail.

I dug through the DUIM source and tried to find why this works.  My best 
guess is that relayout-parent or relayout-children is responsible, but I 
called those functions manually and the controls didn't repaint properly.

I think I'll try to make my own control.  Wish me luck! -- I'm sure I'll 
need it.

Thanks for everyone's help!
References: