<html> <head> <meta content="text/html; charset=windows-1252" http-equiv="Content-Type"> </head> <body text="#000000" bgcolor="#FFFFFF"> <div class="moz-cite-prefix">On 03/21/2014 02:16 PM, John Clements wrote: </div> <blockquote cite="mid:69077111-4EE9-4F31-B798-A0C68B4CD248@brinckerhoff.org" type="cite"> <pre wrap="">2) upstream, inherit from canvas% and add code to limit the rate of calls to draw. I haven’t looked at the code yet, but this might be my best bet.</pre> </blockquote> I tried overriding "refresh", and there's a tempting mention in the docs that "(Multiple refresh requests before <a href="http://docs.racket-lang.org/gui/canvas___.html#%28meth._%28%28%28lib._mred%2Fmain..rkt%29._canvas%7E3c%7E25%7E3e%29._on-paint%29%29" class="RktValLink" data-pltdoc="x">on-paint</a> can be called are coaleced into a single <a href="http://docs.racket-lang.org/gui/canvas___.html#%28meth._%28%28%28lib._mred%2Fmain..rkt%29._canvas%7E3c%7E25%7E3e%29._on-paint%29%29" class="RktValLink" data-pltdoc="x">on-paint</a> call.)" This does work if you have code that is explicitly calling "refresh". <a class="moz-txt-link-freetext" href="http://docs.racket-lang.org/gui/canvas___.html">http://docs.racket-lang.org/gui/canvas___.html</a> Unfortunately it looks like "refresh" doesn't get called by lower-level stuff like scrollbars. Can anyone confirm this? <blockquote cite="mid:69077111-4EE9-4F31-B798-A0C68B4CD248@brinckerhoff.org" type="cite"> <pre wrap="">3) one other thing occurs to me, though; it looks to me like calls to ‘draw’ are stacking up in an eventspace queue, and that seems like a mistake; if there’s a draw in progress, and calls to draw in the queue, it seems like another ‘draw’ should at a minimum squash the ones in the queue. Perhaps that’s painful to implement, or there’s a good reason for allowing all of the queued calls to complete? </pre> </blockquote> I'm also seeing this (on Linux), or at least, it seems like many paints are happening but the back buffer is not being flushed to the screen. When I run the attached code, and then scroll a lot, then I see more dots printed to the console than frames being shown. When I run it on Windows (from console) then things look much better, and it looks like I'm seeing every paint. When I run it inside DrRacket on Windows I see no updates while scrolling until letting go of the scrollbar (different issue?) What do you see on Mac? Thanks, Dave </body> </html>