BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  how to look at paint funciton result immediately when debug          BorlandTalk.com Forum Index -> Delphi VCL Components Writing View previous topic :: View next topic   Author Message Rob Kennedy Guest Posted: Wed Nov 12, 2003 5:34 am    Post subject: Re: how to look at paint funciton result immediately when de chenchang wrote: Quote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! for example: i call TCanvas.LineTo procedure,i want to determine whether it is a right calculated point . so i want to look at result immediately! but i alwarys look at the result after some codes . First, make sure the DoubleBuffered property is False for all components involved. Also, make sure that your form and your component are not covered by any part of the debugger. Otherwise, the debugger will hide the very painting effects you're trying to debug. I usually start my program without any breakpoints set, resize the form to be along the edge of the screen (usually where the Object Inspector used to be) and then re-set the breakpoints and make my component visible. -- Rob Back to top Robert Cerny Guest Posted: Wed Nov 12, 2003 11:18 am    Post subject: Re: how to look at paint funciton result immediately when de Do not use breakpoints at all. Use OutputDebugString() and monitor what comes out. -- Robert Cerny DelphiShaman "chenchang" <baibaichen (AT) sohu (DOT) com> wrote Quote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! for example: i call TCanvas.LineTo procedure,i want to determine whether it is a right calculated point . so i want to look at result immediately! but i alwarys look at the result after some codes . why? how to look at paint funciton result immediately? thanks!!! Back to top Kurt Barthelmess Guest Posted: Wed Nov 12, 2003 1:14 pm    Post subject: Re: how to look at paint funciton result immediately when de "chenchang" <baibaichen (AT) sohu (DOT) com> wrote: Quote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! for example: i call TCanvas.LineTo procedure,i want to determine whether it is a right calculated point . so i want to look at result immediately! but i alwarys look at the result after some codes . Are you looking with your eyes at the screen, or looking programmatically at a pixel on the display? Under some conditions, Windows will cache drawing requests, so you may not see them appear (with your eyes) immediately. Also, as Rob points out, the debugger can interfere with this. Good luck. Kurt Back to top Jens Gruschel Guest Posted: Wed Nov 12, 2003 3:45 pm    Post subject: Re: how to look at paint funciton result immediately when de Quote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! Debugging painting (as well as Windows messages) can be difficult. Often debugging influences the painting itself (remember Heisenberg , especially in timing issues. Jens Back to top Chris Morgan Guest Posted: Wed Nov 12, 2003 3:55 pm    Post subject: Re: how to look at paint funciton result immediately when de Quote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! Debugging painting (as well as Windows messages) can be difficult. Often debugging influences the painting itself (remember Heisenberg , especially in timing issues. When debugging OnPaint events or paint messages you need to arrange your Delphi windows so that they do not overlap at all with your application window, otherwise you will get into a loop where the paint event is fired every time the application window is shown, which will bring your Delphi code window to the front... The other thing you need is lots of patience. OnPaint events get fired A LOT! Cheers, Chris Back to top chenchang Guest Posted: Wed Nov 12, 2003 5:22 pm    Post subject: how to look at paint funciton result immediately when debug now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! for example: i call TCanvas.LineTo procedure,i want to determine whether it is a right calculated point . so i want to look at result immediately! but i alwarys look at the result after some codes . why? how to look at paint funciton result immediately? thanks!!! Back to top chenchang Guest Posted: Thu Nov 13, 2003 3:57 am    Post subject: Re: how to look at paint funciton result immediately when de hi kurt,of course, 1 i set doublebuffered to false 2 do not overlap with other window. it is the top window 3 if possible, i can use remote debug to prevent more paint messages so ,how to eliminate windows cache? "Kurt Barthelmess (TeamB)" <kbarthelmess (AT) compuserve (DOT) com> wrote Quote: "chenchang" <baibaichen (AT) sohu (DOT) com> wrote: now i am writting a Control descendant component,when i debug paint message,i do not look at paint funciton result immediately! for example: i call TCanvas.LineTo procedure,i want to determine whether it is a right calculated point . so i want to look at result immediately! but i alwarys look at the result after some codes . Are you looking with your eyes at the screen, or looking programmatically at a pixel on the display? Under some conditions, Windows will cache drawing requests, so you may not see them appear (with your eyes) immediately. Also, as Rob points out, the debugger can interfere with this. Good luck. Kurt Back to top Kurt Barthelmess Guest Posted: Thu Nov 13, 2003 11:47 am    Post subject: Re: how to look at paint funciton result immediately when de "chenchang" <baibaichen (AT) sohu (DOT) com> wrote: Quote: hi kurt,of course, 1 i set doublebuffered to false 2 do not overlap with other window. it is the top window 3 if possible, i can use remote debug to prevent more paint messages so ,how to eliminate windows cache? You can not prevent Windows caching. I suspect that is the problem here. I can reproduce the problem even when I am painting direcly to the canvas/screen: procedure TForm1.Button1Click(Sender: TObject); begin with Canvas do begin if B then Brush.Color := clRed else Brush.Color := clBlue; FillRect(ClientRect); end; B := not B; end; Setting a breakpoint on the FillRect statement and stepping does not cause the painting to occur until I let it run. It does happen eventually, but there is no other painting code, so Windows is caching on me. I can force an immediate update of the display by calling Update right after the call to FillRect. You might want to do that for debugging your painting code, but I would not leave it in for production. Good luck. Kurt Back to top chenchang Guest Posted: Fri Nov 14, 2003 12:31 am    Post subject: Re: how to look at paint funciton result immediately when de i doubt this is causeed by TCancas? and what do u think? "Kurt Barthelmess (TeamB)" <kbarthelmess (AT) compuserve (DOT) com> wrote Quote: "chenchang" <baibaichen (AT) sohu (DOT) com> wrote: hi kurt,of course, 1 i set doublebuffered to false 2 do not overlap with other window. it is the top window 3 if possible, i can use remote debug to prevent more paint messages so ,how to eliminate windows cache? You can not prevent Windows caching. I suspect that is the problem here. I can reproduce the problem even when I am painting direcly to the canvas/screen: procedure TForm1.Button1Click(Sender: TObject); begin with Canvas do begin if B then Brush.Color := clRed else Brush.Color := clBlue; FillRect(ClientRect); end; B := not B; end; Setting a breakpoint on the FillRect statement and stepping does not cause the painting to occur until I let it run. It does happen eventually, but there is no other painting code, so Windows is caching on me. I can force an immediate update of the display by calling Update right after the call to FillRect. You might want to do that for debugging your painting code, but I would not leave it in for production. Good luck. Kurt Back to top Kurt Barthelmess Guest Posted: Fri Nov 14, 2003 1:14 am    Post subject: Re: how to look at paint funciton result immediately when de "chenchang" <baibaichen (AT) sohu (DOT) com> wrote: Quote: i doubt this is causeed by TCancas? and what do u think? It has nothing to do with TCanvas. You'll get the same caching doing operations with the HDC directly. Good luck. Kurt Back to top Rob Kennedy Guest Posted: Fri Nov 14, 2003 1:17 am    Post subject: Re: how to look at paint funciton result immediately when de Kurt Barthelmess (TeamB) wrote: Quote: It has nothing to do with TCanvas. You'll get the same caching doing operations with the HDC directly. Do you suppose the GDIFlush API function would be of any use? -- Rob Back to top chenchang Guest Posted: Fri Nov 14, 2003 6:48 am    Post subject: Re: how to look at paint funciton result immediately when de what's mean? rob "Rob Kennedy" <.> wrote Quote: Kurt Barthelmess (TeamB) wrote: It has nothing to do with TCanvas. You'll get the same caching doing operations with the HDC directly. Do you suppose the GDIFlush API function would be of any use? -- Rob Back to top chenchang Guest Posted: Fri Nov 14, 2003 8:42 am    Post subject: Re: how to look at paint funciton result immediately when de oh, rob, i know what u say!!! if i want to look at result immeduately, i can call Windows.GDiSetBatchLimit(1). that will disable Cache!!!!!! thanks !!!!!!!!!! "Rob Kennedy" <.> wrote Quote: Kurt Barthelmess (TeamB) wrote: It has nothing to do with TCanvas. You'll get the same caching doing operations with the HDC directly. Do you suppose the GDIFlush API function would be of any use? -- Rob Back to top Kurt Barthelmess Guest Posted: Fri Nov 14, 2003 11:30 am    Post subject: Re: how to look at paint funciton result immediately when de Rob Kennedy <.> wrote: Quote: Do you suppose the GDIFlush API function would be of any use? Yes, it might. It certainly will cause Windows to flush the cache. Or you could disable the caching. I'd think you'd only want to do that when debugging, to avoid the loss to drawing optimizations though. Then the question becomes one of "Does flushing the cache so as to observe the effect of an operation interfere with the operation itself?" Sort of a Heisenberg Uncertainty Principle as applied to GDI<g>. 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