Question

在lParam的消息WM_NCHITTEST的条件下，哪个值不适合32位整数？

由于我们的WPF应用程序中出现未处理的异常，我们的一位客户看到他的64位计算机出现崩溃，我很难找到原因。从WPF代码引发异常，如堆栈跟踪中所示：

System.OverflowException: Arithmetic operation resulted in an overflow. at Microsoft.Windows.Shell.WindowChromeWorker._HandleNCHitTest(WM uMsg, IntPtr wParam, IntPtr lParam, Boolean& handled) at Microsoft.Windows.Shell.WindowChromeWorker._WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at System.Windows.Interop.HwndSource.PublicHooksFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
 at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

违规方法_HandleNCHitTest的来源是here。

我可以看到抛出溢出异常的唯一方法是将lParam转换为调用IntPtr.ToInt32() here的Point的代码。如果lParam不适合Int32，则会引发此异常。但是，我不能想到这种情况可能发生的情况。是什么让这种情况发生？

Answer 1

简短回答：使用自.NET 4.5以来集成的WindowChrome。

如果你不能切换到.NET 4.5，那么答案很长，这似乎对我有用，请看我对原始问题的评论。你永远无法确定，因为问题有时只出现在某些机器上，而不是所有x64机器上：

我修改了WPF Shell Integration Library v2的源代码。更改的行最后标有<----。

WindowChromeWorker.cs：

    private IntPtr _HandleSize(WM uMsg, IntPtr wParam, IntPtr lParam, out bool handled)
    {
        const int SIZE_MAXIMIZED = 2;

        // Force when maximized.
        // We can tell what's happening right now, but the Window doesn't yet know it's
        // maximized.  Not forcing this update will eventually cause the
        // default caption to be drawn.
        WindowState? state = null;
        if (wParam.ToInt64() == SIZE_MAXIMIZED)  <-----
        {
            state = WindowState.Maximized;
        }
        _UpdateSystemMenu(state);

        // Still let the default WndProc handle this.
        handled = false;
        return IntPtr.Zero;
    }

Utilities.cs：

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static int GET_X_LPARAM(IntPtr lParam)
    {
        return LOWORD(lParam.ToInt64());    <----
    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static int GET_Y_LPARAM(IntPtr lParam)
    {
        return HIWORD(lParam.ToInt64());    <----
    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static int HIWORD(long i)    <----
    {
        return (short)((i >> 16) & 0xFFFF);    <----
    }

    [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
    public static int LOWORD(long i)    <----
    {
        return (short)(i & 0xFFFF);
    }

TaskbarItemInfo.cs：

    private IntPtr _WndProc(IntPtr hwnd, int uMsg, IntPtr wParam, IntPtr lParam, ref bool handled)
    {
        WM message = (WM)uMsg;

        if (message == WM_TASKBARBUTTONCREATED)
        {
            _OnIsAttachedChanged(true);
            _isAttached = true;

            handled = false;
        }
        else
        {
            switch (message)
            {
                case WM.COMMAND:
                    if (Utility.HIWORD(wParam.ToInt64()) == THUMBBUTTON.THBN_CLICKED)  <-----
                    {
                        int index = Utility.LOWORD(wParam.ToInt64());   <----
                        ThumbButtonInfos[index].InvokeClick();
                        handled = true;
                    }
                    break;
                case WM.SIZE:
                    _UpdateThumbnailClipping(_isAttached);
                    handled = false;
                    break;
            }
        }

        return IntPtr.Zero;
    }

什么会导致WM_NCHITTEST lParam溢出32位整数？

1 个答案: