Xojo Conferences
| XDC | May | 2019 | Miami | USA |
Canvas.Paint difference between Mac OS X and Windows XP platforms (Real Studio network user group Mailinglist archive)
Back to the thread list
Previous thread: App not responding
Next thread: Really nasty problems with overlapping controls - in particular cross-platform.
| Canvas.Paint difference between Mac OS X and Windows XP platforms |
| Date: 19.08.05 11:50 (Fri, 19 Aug 2005 12:50:50 +0200) |
| From: Emile Schwarz |
|
Hi all,
REALbasic 5.5.5 and 2005R2 Mac OS X 10.4.2 Windows XP SP2 Found in a Canvas.Paint event: Sub Paint(g As Graphics) If OffscreenPict = Nil Then Else Me.Backdrop = OffscreenPict End If End Sub Works fine under Mac OS X and flicked like hell (who said that Hell flick ?) when running under Windows XP SP2. The solution is to assign the OffscreenPict out of the Paint event [but I have that wrong habbit]. What I called in the previous paragraph 'wrong habbit' is nice under some circumstances (everywhere I do not run that project under Windows)... ... and so the question is: Is it a bad idea to assign to a Canvas' Backdrop (or Window background) an offscreen Picture ? TIA, Emile _______________________________________________ Unsubscribe or switch delivery mode: <http://www.realsoftware.com/support/listmanager/> Search the archives of this list here: <http://support.realsoftware.com/listarchives/lists.html> |
| Re: Canvas.Paint difference between Mac OS X and Windows XP platforms |
| Date: 19.08.05 17:21 (Fri, 19 Aug 2005 10:21:06 -0600) |
| From: Joseph J. Strout |
|
At 12:50 PM +0200 8/19/05, Emile Schwarz wrote:
>Found in a Canvas.Paint event: > >Sub Paint(g As Graphics) > If OffscreenPict = Nil Then > > Else > Me.Backdrop = OffscreenPict > End If >End Sub Zow! This is a bit like finding an abandoned land mine in your back yard. It's dangerous and you want to get rid of it ASAP. In particular, one should never assign to the Backdrop of a canvas in the Paint event. Either assign the backdrop somewhere else, and don't touch it in the Paint event (perhaps you don't need anything at all in your Paint event), or forget about the Backdrop property, and instead simply do g.DrawPicture OffscreenPict, 0, 0. The latter is what I usually do, but I know some people prefer using Backdrop. >The solution is to assign the OffscreenPict out of the Paint event >[but I have that wrong habit]. Right. You'll want to fix that habit as soon as you can. >What I called in the previous paragraph 'wrong habbit' is nice under >some circumstances (everywhere I do not run that project under >Windows)... No, it's not. It's dangerous and incorrect anywhere. >Is it a bad idea to assign to a Canvas' Backdrop (or Window >background) an offscreen Picture ? In the Paint event (or any method called by that), yes. Anywhere else is fine. Best, - Joe |