System.NullReferenceException was unhandled

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System.NullReferenceException was unhandled

Hi!

In my windowed control, whose rendering is done completely in Direct-x, I provide the means for the user to change the font. For this reason, my object includes the function SetupFont(), which is called at least once on startup to set the default font, and then it may be called whenever the user decides to change the font. The mobjFontDirectX and mobjFontGDI objects are defined at class level:

private void SetupFont(System.Drawing.Font objFontGDI)
{
if (!objFontGDI.Equals(mobjFontGDI))

{
if (mobjFontGDI != null)
mobjFontGDI.Dispose();
mobjFontGDI = objFontGDI;
if (mobjFontDirectX != null)
mobjFontDirectX.Dispose();
if (mobjCanvas.objRenderer != null)
mobjFontDirectX = new Microsoft.DirectX.Direct3D.Font(mobjDevice, mobjFontGDI);
}
}

The problem arises when the window is resized after the user changes the font at least once: System.NullReferenceException was unhandled

The stack trace that results follows:

System.NullReferenceException was unhandled
Message="Object reference not set to an instance of an object."
Source="Microsoft.DirectX.Direct3DX"
StackTrace:
at Microsoft.DirectX.Direct3D.Font.OnResetDevice()
at Microsoft.DirectX.Direct3D.Font.OnParentReset(Object sender, EventArgs e)
at System.EventHandler.Invoke(Object sender, EventArgs e)
at Microsoft.DirectX.Direct3D.Device.raise_DeviceReset(Object i1, EventArgs i2)
at Microsoft.DirectX.Direct3D.Device.Reset(PresentParameters[] presentationParameters)
at Microsoft.DirectX.Direct3D.Device.OnParentResized(Object sender, EventArgs e)
at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
at System.Windows.Forms.Control.UpdateBounds()
at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.UserControl.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.SafeNativeMethods.SetWindowPos(HandleRef hWnd, HandleRef hWndInsertAfter, Int32 x, Int32 y, Int32 cx, Int32 cy, Int32 flags)
at System.Windows.Forms.Control.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
at System.Windows.Forms.Control.System.Windows.Forms.Layout.IArrangedElement.SetBounds(Rectangle bounds, BoundsSpecified specified)
at System.Windows.Forms.Layout.DefaultLayout.xLayoutDockedControl(IArrangedElement element, Rectangle newElementBounds, Boolean measureOnly, Size& preferredSize, Rectangle& remainingBounds)
at System.Windows.Forms.Layout.DefaultLayout.LayoutDockedControls(IArrangedElement container, Boolean measureOnly)
at System.Windows.Forms.Layout.DefaultLayout.xLayout(IArrangedElement container, Boolean measureOnly, Size& preferredSize)
at System.Windows.Forms.Layout.DefaultLayout.LayoutCore(IArrangedElement container, LayoutEventArgs args)
at System.Windows.Forms.Layout.LayoutEngine.Layout(Object container, LayoutEventArgs layoutEventArgs)
at System.Windows.Forms.Control.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.ScrollableControl.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.Control.PerformLayout(LayoutEventArgs args)
at System.Windows.Forms.Control.PerformLayout()
at System.Windows.Forms.Control.ResumeLayout(Boolean performLayout)
at System.Windows.Forms.Control.ResumeLayout()
at System.Windows.Forms.SplitContainer.ResizeSplitContainer()
at System.Windows.Forms.SplitContainer.OnLayout(LayoutEventArgs e)
at System.Windows.Forms.Control.PerformLayout(LayoutEventArgs args)
at System.Windows.Forms.Control.System.Windows.Forms.Layout.IArrangedElement.PerformLayout(IArrangedElement affectedElement, String affectedProperty)
at System.Windows.Forms.Layout.LayoutTransaction.DoLayout(IArrangedElement elementToLayout, IArrangedElement elementCausingLayout, String property)
at System.Windows.Forms.Control.OnResize(EventArgs e)
at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
at System.Windows.Forms.Control.UpdateBounds()
at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.SplitContainer.WndProc(Message& msg)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.SafeNativeMethods.SetWindowPos(HandleRef hWnd, HandleRef hWndInsertAfter, Int32 x, Int32 y, Int32 cx, Int32 cy, Int32 flags)
at System.Windows.Forms.Control.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
at System.Windows.Forms.SplitContainer.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
at System.Windows.Forms.Control.System.Windows.Forms.Layout.IArrangedElement.SetBounds(Rectangle bounds, BoundsSpecified specified)
at System.Windows.Forms.Layout.DefaultLayout.xLayoutDockedControl(IArrangedElement element, Rectangle newElementBounds, Boolean measureOnly, Size& preferredSize, Rectangle& remainingBounds)
at System.Windows.Forms.Layout.DefaultLayout.LayoutDockedControls(IArrangedElement container, Boolean measureOnly)
at System.Windows.Forms.Layout.DefaultLayout.xLayout(IArrangedElement container, Boolean measureOnly, Size& preferredSize)
at System.Windows.Forms.Layout.DefaultLayout.LayoutCore(IArrangedElement container, LayoutEventArgs args)
at System.Windows.Forms.Layout.LayoutEngine.Layout(Object container, LayoutEventArgs layoutEventArgs)
at System.Windows.Forms.Control.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.ScrollableControl.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.Control.PerformLayout(LayoutEventArgs args)
at System.Windows.Forms.Control.PerformLayout()
at System.Windows.Forms.Control.ResumeLayout(Boolean performLayout)
at System.Windows.Forms.Control.ResumeLayout()
at System.Windows.Forms.ToolStripContainer.OnSizeChanged(EventArgs e)
at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
at System.Windows.Forms.Control.UpdateBounds()
at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.SafeNativeMethods.SetWindowPos(HandleRef hWnd, HandleRef hWndInsertAfter, Int32 x, Int32 y, Int32 cx, Int32 cy, Int32 flags)
at System.Windows.Forms.Control.SetBoundsCore(Int32 x, Int32 y, Int32 width, Int32 height, BoundsSpecified specified)
at System.Windows.Forms.Control.System.Windows.Forms.Layout.IArrangedElement.SetBounds(Rectangle bounds, BoundsSpecified specified)
at System.Windows.Forms.Layout.DefaultLayout.xLayoutDockedControl(IArrangedElement element, Rectangle newElementBounds, Boolean measureOnly, Size& preferredSize, Rectangle& remainingBounds)
at System.Windows.Forms.Layout.DefaultLayout.LayoutDockedControls(IArrangedElement container, Boolean measureOnly)
at System.Windows.Forms.Layout.DefaultLayout.xLayout(IArrangedElement container, Boolean measureOnly, Size& preferredSize)
at System.Windows.Forms.Layout.DefaultLayout.LayoutCore(IArrangedElement container, LayoutEventArgs args)
at System.Windows.Forms.Layout.LayoutEngine.Layout(Object container, LayoutEventArgs layoutEventArgs)
at System.Windows.Forms.Control.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.ScrollableControl.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.Form.OnLayout(LayoutEventArgs levent)
at System.Windows.Forms.Control.PerformLayout(LayoutEventArgs args)
at System.Windows.Forms.Control.System.Windows.Forms.Layout.IArrangedElement.PerformLayout(IArrangedElement affectedElement, String affectedProperty)
at System.Windows.Forms.Layout.LayoutTransaction.DoLayout(IArrangedElement elementToLayout, IArrangedElement elementCausingLayout, String property)
at System.Windows.Forms.Control.OnResize(EventArgs e)
at System.Windows.Forms.Form.OnResize(EventArgs e)
at GraphicalInterface.frmGraphicalInterface.OnResize(EventArgs e) in C:\Projects\JSR\GraphicalInterface\frmGraphicalInterface.cs:line 396
at System.Windows.Forms.Control.OnSizeChanged(EventArgs e)
at System.Windows.Forms.Control.UpdateBounds(Int32 x, Int32 y, Int32 width, Int32 height, Int32 clientWidth, Int32 clientHeight)
at System.Windows.Forms.Control.UpdateBounds()
at System.Windows.Forms.Control.WmWindowPosChanged(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
at System.Windows.Forms.Form.DefWndProc(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WmSysCommand(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr wndProc, IntPtr hWnd, Int32 msg, IntPtr wParam, IntPtr lParam)
at System.Windows.Forms.NativeWindow.DefWndProc(Message& m)
at System.Windows.Forms.Form.DefWndProc(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
at System.Windows.Forms.ContainerControl.WndProc(Message& m)
at System.Windows.Forms.Form.WmNcButtonDown(Message& m)
at System.Windows.Forms.Form.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 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 GraphicalInterface.Program.Main() in C:\Projects\JSR\GraphicalInterface\Program.cs:line 17
at System.AppDomain.nExecuteAssembly(Assembly 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)
at System.Threading.ThreadHelper.ThreadStart()

It seems to me as if when re-defining the font, the font object that was originally created is somehow still there, though the function makes sure to politely dispose of it before creating the new directx font.

I already tried to isolate the problem in a smaller project wihout success.

Any ideas



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System.NullReferenceException was unhandled

  • MarkusEilers

    I implemented the solution number 3 and it worked indeed.

    Thanks, Ralph. I've been for three days trying to fix it before I decided to post it!

  • Loane Sharp

    Maybe override the form's resize and check' and just dispose it and re-create

    I had some weirdness with the DirectX3d.fonts on Form closing. I kept getting a null refernce until I overrid the forms exit and added a font.dispose();



  • baka_deshi

    Well, yes it might work, but I'd need also the form to properly resize its child controls. A weird thing to me is the fact that the problem does not show when using *almost* the same code in a small project created just to prove the malfunction.

    There must be another factor not considered yet.

  • JP 360

    The default behavior of managed Direct3D is to reset the device after the window is resized. This is done to make sure that the back buffer has the same size as your window. Unfortunately such a reset will invalidate some of your DirectX objects. Mainly everything that was created in the default pool or use a state block. Your Font object is part of this invalidation, too.

    There are at least three possible solutions for this problem.

    1. Disable the managed Direct3D event handling. Look for the Device.IsUsingEventHandlers property

    2. You can handle the Device.DeviceResizing event and cancel it. If the device is not reset your font object will not lost.

    3. Handle the Device.DeviceLost and Device.DeviceReset event. Dispose your font object during the lost and recreate at the reset event.

    I don’t recommend the second solution because there are other reasons that will cause a device reset.

    If you look for a fast solution use the third one. As the event handlers have some other drawbacks solution one would be the best but force you to handle device lost situations and back buffer scaling fully by your own.



  • System.NullReferenceException was unhandled
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