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POMulti-threading Delphi synchronization using Critical Sections between a Timer and other threads
 

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    <p>It is a problem of synchronization. I made a simplification for my problem so I have a VCL Timer and a few threads. The threads are trying to write things in two bitmaps, and the timer is trying to draw the bitmaps into Images(TImage). Here is a modification of my code to be easier to understand(this paste code is very vague).</p> <pre><code>//------------------------------------------------------------------------------ Procedure TMyForm.Add(iX,iY,iNr:integer); begin EnterCriticalSection(csCriticalSection); bmRed.Canvas.Lock; bmBlue.Canvas.Lock; //.... drawing etc... bmRed.Canvas.TextOut(iX,iY,IntToStr(iNr)); bmBlue.Canvas.TextOut(iX,iY,IntToSTr(iNr)); bmRed.Canvas.Unlock; bmBlue.Canvas.Unlock; LeaveCriticalSection(csCriticalSection); end; //------------------------------------------------------------------------------ procedure TMyForm.tmTimer(...); begin EnterCriticalSection(csCriticalSection); bmRed.Canvas.Lock; bmBlue.Canvas.Lock; //Drawing on bmRed and bmBlue imBlue.Canvas.Draw(bmBlue); imRed.Canvas.Draw(bmBlue); bmRed.Canvas.Unlock; bmBlue.Canvas.Unlock; LeaveCriticalSection(csCriticalSection); end; //------------------------------------------------------------------------------ Procedure TMyThread.Execute(); begin Randomize; while not terminated do begin MyFormInstance.Add(Random(100),Random(100),Random(100)); Sleep(20); end; end; initialization InitializeCriticalSection(csCriticalSection); finalization DeleteCriticalSection(csCriticalSection); </code></pre> <p>Usually the threads gives me errors when entering in the critical section or after a few seconds the timer will no longer draw me anything.</p>
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