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Re: Using DUIM's <viewport>

On Thu, 23 Mar 2000 16:45:02   Andrew W Armstrong wrote:
> 
>--
>
>On Thu, 23 Mar 2000 07:15:02   Chris Double 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:
>
>Nice trick, Chris! A possibility that might work is to add a single drawing pane as the window to be scrolled, and to then add the list boxes to that.
>
>Here's an approximate sketch, I haven't tried this (I'll try and post a real version when I'm at home, unless Chris beats me to it):

OK, here's the real version (it turns out 'define pane' no longer uses <drawing-pane>, so I had to use a different solution):

define frame <scrolling-test> (<simple-frame>)
  pane %column (pane)
    make(<column-layout>, 
         children: vector(make(<push-button>, label: "Hello"),
                          make(<list-box>, items: #(1, 2, 3)),
                          make(<list-box>, items: #(4, 5, 6))));
  layout (frame)
    scrolling ()
      make(<drawing-pane>,
           children: vector(frame.%column),
           foreground: #f)
    end;
end frame <scrolling-test>;

define method main () => ()
  start-frame(make(<scrolling-test>));
end method main;

The only problem with this solution is that the background of the scrolling area is now white instead of the default Windows color. I can't seem to find a way to ask a drawing pane to pick up the default color, if that is a problem for your application I'll try and find a way.

Just for the record, the bugs I'd like to see fixed are:

1. <viewport> does inappropriate bitblt'ing when scrolling collections of gadgets.

2. <drawing-pane> cannot pick up the correct default background color, because it is overriden with $white. Maybe we need another class (<gadget-pane>?) that uses the default gadget color, or maybe we need a way to override this behavior (:background $default-background, or something).

I hope this helps, 

Andy

---------------------------
Andy Armstrong
andrewa@functionalobjects.com



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