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POWhat could cause Double Buffering to kill my app?
 

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  1. POWhat could cause Double Buffering to kill my app?
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    <p>I have a few custom (winforms) components that draw to the screen using GDI+.</p> <p>To prevent flickering on repaint, I decided to enable double buffering, so I added a line to my constructor:</p> <pre><code>public ColourWheel() { InitializeComponent(); this.DoubleBuffered = true; } </code></pre> <p>Which works fine on this component (ColourWheel). When I add the same line to the constructor of either of my other two (similarly structured) components, I get a couple of strange symptoms:</p> <ol> <li>When I try to run a form with the component on, I get an Argument Exception on <code>Application.Run(new Form());</code>.</li> <li>If I switch to design mode, I get an error about the component having an unhandled exception to do with a parameter.</li> </ol> <p>It doesn't seem to matter whether I turn double buffering on one or all of them, it still works on the ColourWheel, but not the others.</p> <p><em>For the record, I've also tried a few other <a href="https://stackoverflow.com/a/77233/50151">double</a> <a href="https://stackoverflow.com/a/181384/50151">buffering</a> techniques.</em></p> <p>What could be causing double buffering to work on one component, but not others?</p> <hr> <p><strong>EDIT:</strong> Here's the exception detail from the run-time symptom:</p> <blockquote> <p>System.ArgumentException was unhandled Message=Parameter is not valid. Source=System.Drawing StackTrace: at System.Drawing.Graphics.GetHdc() at System.Drawing.BufferedGraphics.RenderInternal(HandleRef refTargetDC, BufferedGraphics buffer) at System.Drawing.BufferedGraphics.Render() at System.Windows.Forms.Control.WmPaint(Message&amp; m) at System.Windows.Forms.Control.WndProc(Message&amp; m) at System.Windows.Forms.ScrollableControl.WndProc(Message&amp; m) at System.Windows.Forms.UserControl.WndProc(Message&amp; m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message&amp; m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message&amp; m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG&amp; msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(Form mainForm) at TestForm.Program.Main() in D:\Documents and Settings\Tom Wright\My Documents\Visual Studio 2010\Projects\ColourPicker\TestForm\Program.cs:line 18 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:</p> </blockquote> <hr> <p><strong>EDIT 2:</strong> The OnPaint handler from one (the more complicated) of the two components that are causing problems:</p> <pre><code>private void ValueSlider_Paint(object sender, PaintEventArgs e) { using (Graphics g = e.Graphics) { g.DrawImage(this.gradientImage, new Rectangle(0, 0, paintArea.Width, paintArea.Height)); if (this.showmarker) { ColourHandler.HSV alt = ColourHandler.RGBtoHSV(new ColourHandler.RGB(this.SelectedColour.R, this.SelectedColour.G, this.SelectedColour.B)); alt.Saturation = 0; alt.value = 255 - alt.value; using (Pen pen = new Pen(ColourHandler.HSVtoColour(alt))) { pen.Width = (float)MARKERWIDTH; g.DrawRectangle(pen, 0 - pen.Width, this.brightnessPoint.Y - MARKERWIDTH, this.paintArea.Width + (pen.Width * 2), MARKERWIDTH * 2); } } } } </code></pre>
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    1. USTom Wright
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    1. COPlease share the exception.
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    2. CO@roken All yours my friend.
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    3. COAre you overriding OnPaint() in the offending controls? If so, what does that look like?
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