BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  paintbox background painting issue          BorlandTalk.com Forum Index -> Delphi Graphics View previous topic :: View next topic   Author Message Joe Guest Posted: Wed Feb 01, 2006 5:30 pm    Post subject: paintbox background painting issue Hello everybody I have derived a custom paintobx from TPaintbox. now i wish to paint a background bitmap so i have added a Background (TPicture) property (linked with a fBackground private member) and put the paint stuff into the Paint procedure (see below) and trying 2 solutions. It seemed to works but in the test application i put a MyPaintbox object inside a scrollbox and although the background is correctly displayed at first, as soon as i scroll down or upwards the scrollbox's scrollbars the background gets temporarily messed up until i call again the paint routine (for example with Invalidate). How could I solve in order to keep the bitmap, say, always perfecty stretched inside the whole paintbox boundsrect even when scrolling down/up the scrollbox's scrollbars? thanks in advance for any help/tip about the above Joe --- procedure TMyPaintBox.Paint; var Graphic: TGraphic; R: TRect; begin Canvas.Lock; try { draw background image } if Background.Graphic <> nil then begin Graphic := Background.Graphic; R := Canvas.ClipRect; // solution 1 // Canvas.StretchDraw(R, Graphic); // solution 2 Canvas.StretchDraw(BoundsRect, Graphic); end; { do other paint stuff } ..... finally Canvas.UnLock; end; inherited; end; Back to top Peter Below (TeamB) Guest Posted: Wed Feb 01, 2006 7:15 pm    Post subject: Re: paintbox background painting issue In article <43e0ef77 (AT) newsgroups (DOT) borland.com>, Joe wrote: Quote: I have derived a custom paintobx from TPaintbox. now i wish to paint a background bitmap so i have added a Background (TPicture) property (linked with a fBackground private member) and put the paint stuff into the Paint procedure (see below) and trying 2 solutions. It seemed to works but in the test application i put a MyPaintbox object inside a scrollbox and although the background is correctly displayed at first, as soon as i scroll down or upwards the scrollbox's scrollbars the background gets temporarily messed up until i call again the paint routine (for example with Invalidate). How could I solve in order to keep the bitmap, say, always perfecty stretched inside the whole paintbox boundsrect even when scrolling down/up the scrollbox's scrollbars? if Background.Graphic <> nil then begin Graphic := Background.Graphic; R := Canvas.ClipRect; // solution 1 // Canvas.StretchDraw(R, Graphic); // solution 2 Canvas.StretchDraw(BoundsRect, Graphic); You are making a faulty assumption here: that the Canvas.Cliprect will be the area of the paintbox (it's clientrect). That is not the case, if the scrollbox is scrolled the cliprect of the next paint request will just be the area uncovered by the scrolling. That is why your first approach fails. Using Boundsrect is also not correct, you should use Clientrect. Have you set the Align property of the paintbox instance you dropped on the scrollbox to anything other than alNone, by the way? -- Peter Below (TeamB) Use the newsgroup archives : http://www.mers.com/searchsite.html http://www.tamaracka.com/search.htm http://groups.google.com http://www.prolix.be Back to top Joe Guest Posted: Thu Feb 02, 2006 11:58 am    Post subject: Re: paintbox background painting issue Thank you Peter yes i agree, solution 1 was just a test using your suggestion, ClientRect in place of BoundsRect works fine yes the Align property is alNone thanks again Joe "Peter Below (TeamB)" <100113.1101 (AT) compuXXserve (DOT) com> wrote: Quote: You are making a faulty assumption here: that the Canvas.Cliprect will be the area of the paintbox (it's clientrect). That is not the case, if the scrollbox is scrolled the cliprect of the next paint request will just be the area uncovered by the scrolling. That is why your first approach fails. Using Boundsrect is also not correct, you should use Clientrect. Have you set the Align property of the paintbox instance you dropped on the scrollbox to anything other than alNone, by the way? 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