前言
wpf是Direct UI，窗口中只有一个hwnd句柄，大部分控件都是直接在上面绘制的。当我们需要使用不同的渲染方式进行绘制时，就会和控件绘制产生冲突。比如使用opengl渲染3d图形或者视频时，直接在窗口绘制就会出现闪烁，与控件相互覆盖。要解决这个问题就需要，添加一个新的hwnd窗口或控件嵌入wpf窗口中，我们可以通过HwndHost就可以实现这样的功能。
一、如何实现
1、继承HwndHost
public class MyWindowHost : HwndHost
2、实现抽象方法
只需实现下列2个方法
protected override HandleRef BuildWindowCore(HandleRef hwndParent)
{
Handle =创建的窗口句柄
return new HandleRef(this, Handle);
}
protected override void DestroyWindowCore(HandleRef hwnd)
{
hwnd.Handle;//根据句柄销毁窗口
}
3、xaml中使用HwndHost控件
<local:MyWindowHost Width="100" Height="100" > </local:MyWindowHost >
二、具体实现
1、Win32窗口
我们可以通过win32 api创建一个窗口，封装成HwndHost对象，提供给xaml使用。
Win32WindowHost.cs
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
namespace WpfHwndElement
{
/// <summary>
/// 直接通过win32 api创建窗口
/// </summary>
public class Win32WindowHost : HwndHost
{
//重新定义Handle为依赖属性，可以用于绑定
new public IntPtr Handle
{
get { return (IntPtr)GetValue(HandleProperty); }
private set { SetValue(HandleProperty, value); }
}
// Using a DependencyProperty as the backing store for Hwnd. This enables animation, styling, binding, etc...
public static readonly DependencyProperty HandleProperty =
DependencyProperty.Register("Handle", typeof(IntPtr), typeof(Win32WindowHost), new PropertyMetadata(IntPtr.Zero));
protected override HandleRef BuildWindowCore(HandleRef hwndParent)
{
Handle = CreateWindowEx(0, "static", "", WS_CHILD | WS_VISIBLE | LBS_NOTIFY | WS_CLIPSIBLINGS, 0, 0, (int)Width, (int)Height, hwndParent.Handle, IntPtr.Zero, IntPtr.Zero, 0);
return new HandleRef(this, Handle);
}
[DllImport("user32.dll", SetLastError = true)]
static extern System.IntPtr DefWindowProcW(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
protected override void DestroyWindowCore(HandleRef hwnd)
{
DestroyWindow(hwnd.Handle);
}
const int WS_CHILD = 0x40000000;
const int WS_VISIBLE = 0x10000000;
const int LBS_NOTIFY = 0x001;
const int WS_CLIPSIBLINGS = 0x04000000;
[DllImport("user32.dll")]
internal static extern IntPtr CreateWindowEx(int exStyle, string className, string windowName, int style, int x, int y, int width, int height, IntPtr hwndParent, IntPtr hMenu, IntPtr hInstance, [MarshalAs(UnmanagedType.AsAny)] object pvParam);
[DllImport("user32.dll")]
static extern bool DestroyWindow(IntPtr hwnd);
}
}
2、HwndSource窗口
如果不想导入win32 api，则可以使用HwndSource对象创建句柄窗口。
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
namespace WpfHwndElement
{
class HwndSourceHost : HwndHost
{
//重新定义Handle为依赖属性，可以用于绑定
new public IntPtr Handle
{
get { return (IntPtr)GetValue(HandleProperty); }
private set { SetValue(HandleProperty, value); }
}
// Using a DependencyProperty as the backing store for Hwnd. This enables animation, styling, binding, etc...
public static readonly DependencyProperty HandleProperty =
DependencyProperty.Register("Handle", typeof(IntPtr), typeof(HwndSourceHost), new PropertyMetadata(IntPtr.Zero));
HwndSource _source;
protected override HandleRef BuildWindowCore(HandleRef hwndParent)
{
_source = new HwndSource(0, WS_CHILD | WS_VISIBLE | LBS_NOTIFY| WS_CLIPSIBLINGS, 0, 0, 0, (int)Width, (int)Height, "nativeHost", hwndParent.Handle);
Handle = _source.Handle;
return new HandleRef(this, Handle);
}
protected override void DestroyWindowCore(HandleRef hwnd)
{
_source.Dispose();
}
const int WS_CHILD = 0x40000000;
const int WS_VISIBLE = 0x10000000;
const int LBS_NOTIFY = 0x001;
const int WS_CLIPSIBLINGS = 0x04000000;
}
}
3、Wpf窗口
wpf窗口也可以进行嵌入，但需要导入win32对窗口属性进行设置，要设置WS_CHILD 以及父窗口。
using System.Runtime.InteropServices;
using System.Windows;
using System.Windows.Interop;
namespace WpfHwndElement
{
//重新定义Handle为依赖属性，可以用于绑定
public class WpfWindowHost : HwndHost
{
new public IntPtr Handle
{
get { return (IntPtr)GetValue(HandleProperty); }
private set { SetValue(HandleProperty, value); }
}
// Using a DependencyProperty as the backing store for Hwnd. This enables animation, styling, binding, etc...
public static readonly DependencyProperty HandleProperty =
DependencyProperty.Register("Handle", typeof(IntPtr), typeof(WpfWindowHost), new PropertyMetadata(IntPtr.Zero));
const int WS_CHILD = 0x40000000;
const int GWL_STYLE = (-16);
[DllImport("user32.dll", EntryPoint = "GetWindowLongW")]
static extern int GetWindowLong(IntPtr hwnd, int nIndex);
[DllImport("user32.dll", EntryPoint = "SetWindowLongW")]
static extern int SetWindowLong(IntPtr hwnd, int nIndex, int dwNewLong);
[DllImport("user32.dll")]
public static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
protected override HandleRef BuildWindowCore(HandleRef hwndParent)
{
var window = new Window();
var hwnd = new WindowInteropHelper(window).EnsureHandle();
window.Show();
SetWindowLong(hwnd, GWL_STYLE, GetWindowLong(hwnd, GWL_STYLE) | WS_CHILD);
SetParent(hwnd, hwndParent.Handle);
return new HandleRef(this, hwnd);
}
protected override void DestroyWindowCore(HandleRef hwnd)
{
var window = HwndSource.FromHwnd(hwnd.Handle)?.RootVisual as Window;
window?.Close();
}
}
}
三、使用示例
MainWindow.xaml
<Window x:Class="WpfHwndElement.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfHwndElement"
mc:Ignorable="d"
Title="MainWindow" Height="360" Width="640"
>
<StackPanel>
<local:Win32WindowHost Width="100" Height="100"/>
<local:HwndSourceHost Margin="0,10,0,0" Width="100" Height="100"/>
<local:WpfWindowHost Margin="0,10,0,0" Width="100" Height="100"/>
</StackPanel>
</Window>
效果预览
总结
通过HwndHost的方式嵌入hwnd窗口是比较简单易用的，而且也为wpf实现的界面效果提供的更多的可能性，当然嵌入的窗口会覆盖wpf控件，虽然有解决的方法，本文主要还是提供基础的HwndHost用法。
