我在 WPF 应用程序中有一个 WinForms 控件。幸运的是，在 WPF 中，鼠标滚轮事件通常由鼠标光标下的控件处理......但如果它是 WinForms 控件，我必须先单击该控件以使其获得键盘焦点。当 WinForms 控件没有焦点时，如何绕过此行为并将鼠标滚轮事件发送到它？
（注意：MouseWheel 和PreviewMouseWheelevents 似乎不适用于 WindowsFormsHost。如果PreviewMouseWheel在 WindowsFormsHost 的父级中添加处理程序，则当鼠标位于非 WPF 控件顶部时不会调用它。显然，WinForms 控件也没有得到MouseWheel事件；事件似乎完全消失了。）
一种可能的解决方案是手动处理所有WM_MOUSEWHEEL消息并引发MouseWheel未聚焦控件的事件。我的附加行为实现了这个想法：
public static class CaptureMouseWheelWhenUnfocusedBehavior
{
private static readonly HashSet<WindowsFormsHost> TrackedHosts =
new HashSet<WindowsFormsHost>();
private static readonly System.Windows.Forms.IMessageFilter MessageFilter =
new MouseWheelMessageFilter();
private sealed class MouseWheelMessageFilter : System.Windows.Forms.IMessageFilter
{
[DllImport("User32.dll"), SuppressUnmanagedCodeSecurity]
private static extern IntPtr WindowFromPoint(System.Drawing.Point point);
private static System.Drawing.Point LocationFromLParam(IntPtr lParam)
{
int x = (int)((((long)lParam) >> 0) & 0xffff);
int y = (int)((((long)lParam) >> 16) & 0xffff);
return new System.Drawing.Point(x, y);
}
private static bool ConsiderRedirect(WindowsFormsHost host)
{
var control = host.Child;
return control != null &&
!control.IsDisposed &&
control.IsHandleCreated &&
control.Visible &&
!control.Focused;
}
private static int DeltaFromWParam(IntPtr wParam)
{
return (short)((((long)wParam) >> 16) & 0xffff);
}
private static System.Windows.Forms.MouseButtons MouseButtonsFromWParam(IntPtr wParam)
{
const int MK_LBUTTON = 0x0001;
const int MK_MBUTTON = 0x0010;
const int MK_RBUTTON = 0x0002;
const int MK_XBUTTON1 = 0x0020;
const int MK_XBUTTON2 = 0x0040;
int buttonFlags = (int)((((long)wParam) >> 0) & 0xffff);
var buttons = System.Windows.Forms.MouseButtons.None;
if(buttonFlags != 0)
{
if((buttonFlags & MK_LBUTTON) == MK_LBUTTON)
{
buttons |= System.Windows.Forms.MouseButtons.Left;
}
if((buttonFlags & MK_MBUTTON) == MK_MBUTTON)
{
buttons |= System.Windows.Forms.MouseButtons.Middle;
}
if((buttonFlags & MK_RBUTTON) == MK_RBUTTON)
{
buttons |= System.Windows.Forms.MouseButtons.Right;
}
if((buttonFlags & MK_XBUTTON1) == MK_XBUTTON1)
{
buttons |= System.Windows.Forms.MouseButtons.XButton1;
}
if((buttonFlags & MK_XBUTTON2) == MK_XBUTTON2)
{
buttons |= System.Windows.Forms.MouseButtons.XButton2;
}
}
return buttons;
}
public bool PreFilterMessage(ref System.Windows.Forms.Message m)
{
const int WM_MOUSEWHEEL = 0x020A;
if(m.Msg == WM_MOUSEWHEEL)
{
var location = LocationFromLParam(m.LParam);
var hwnd = WindowFromPoint(location);
foreach(var host in TrackedHosts)
{
if(!ConsiderRedirect(host)) continue;
if(hwnd == host.Child.Handle)
{
var delta = DeltaFromWParam(m.WParam);
{
// raise event for WPF control
var mouse = InputManager.Current.PrimaryMouseDevice;
var args = new MouseWheelEventArgs(mouse, Environment.TickCount, delta);
args.RoutedEvent = WindowsFormsHost.MouseWheelEvent;
host.RaiseEvent(args);
}
{
// raise event for winforms control
var buttons = MouseButtonsFromWParam(m.WParam);
var args = new System.Windows.Forms.MouseEventArgs(
buttons, 0, location.X, location.Y, delta);
var method = typeof(System.Windows.Forms.Control).GetMethod(
"OnMouseWheel",
System.Reflection.BindingFlags.Instance |
System.Reflection.BindingFlags.NonPublic);
method.Invoke(host.Child, new object[] { args });
}
return true;
}
}
}
return false;
}
}
public static bool GetIsEnabled(DependencyObject obj)
{
return (bool)obj.GetValue(IsEnabledProperty);
}
public static void SetIsEnabled(DependencyObject obj, bool value)
{
obj.SetValue(IsEnabledProperty, value);
}
public static readonly DependencyProperty IsEnabledProperty =
DependencyProperty.RegisterAttached(
"IsEnabled",
typeof(bool),
typeof(CaptureMouseWheelWhenUnfocusedBehavior),
new PropertyMetadata(false, OnIsEnabledChanged));
private static void OnIsEnabledChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
{
var wfh = o as WindowsFormsHost;
if(wfh == null) return;
if((bool)e.NewValue)
{
wfh.Loaded += OnHostLoaded;
wfh.Unloaded += OnHostUnloaded;
if(wfh.IsLoaded && TrackedHosts.Add(wfh))
{
if(TrackedHosts.Count == 1)
{
System.Windows.Forms.Application.AddMessageFilter(MessageFilter);
}
}
}
else
{
wfh.Loaded -= OnHostLoaded;
wfh.Unloaded -= OnHostUnloaded;
if(TrackedHosts.Remove(wfh))
{
if(TrackedHosts.Count == 0)
{
System.Windows.Forms.Application.RemoveMessageFilter(MessageFilter);
}
}
}
}
private static void OnHostLoaded(object sender, EventArgs e)
{
var wfh = (WindowsFormsHost)sender;
if(TrackedHosts.Add(wfh))
{
if(TrackedHosts.Count == 1)
{
System.Windows.Forms.Application.AddMessageFilter(MessageFilter);
}
}
}
private static void OnHostUnloaded(object sender, EventArgs e)
{
var wfh = (WindowsFormsHost)sender;
if(TrackedHosts.Remove(wfh))
{
if(TrackedHosts.Count == 0)
{
System.Windows.Forms.Application.RemoveMessageFilter(MessageFilter);
}
}
}
}
它可以在 XAML 中使用：
<WindowsFormsHost namespace:CaptureMouseWheelWhenUnfocusedBehavior.IsEnabled="True" />
和后面的代码：
CaptureMouseWheelWhenUnfocusedBehavior.SetIsEnabled(host, true);
更新：添加代码以引发 WinForms 控件的事件