WebBrowser控制键盘和焦点行为-WebBrowsercontrolkeyboardandfocusbehavior

Apparently, there are some serious keyboard and focus issues with WPF WebBrowser control. I've put together a trivial WPF app, just a WebBrowser and two buttons. The app loads a very basic editable HTML markup (some text) and demonstrates the following:

显然，WPF WebBrowser控件存在一些严重的键盘和焦点问题。我整合了一个微不足道的WPF应用程序，一个网络浏览器和两个按钮。该应用程序加载一个非常基本的可编辑HTML标记(一些文本)，并演示以下内容:

• Tabbing is misbehaving. User needs to hit Tab twice to see the caret (text cursor) inside WebBrowser and be able to type.

  跨栏是行为不端。用户需要按Tab键两次，才能在WebBrowser中看到caret(文本光标)，并能够键入。

• When user switches away from the app (e.g., with Alt-Tab), then goes back, the caret is gone and she is unable to type at all. A physical mouse click into the WebBrowser's window client area is required to get back the caret and keystrokes.

  当用户离开应用程序时(例如，使用Alt-Tab)，然后返回，插入符号就消失了，她根本无法输入。要取回插入符号和击键，需要在WebBrowser的窗口客户端区域中单击一个物理鼠标。

• Inconsistently, a dotted focus rectangle shows up around WebBrowser (when tabbing, but not when clicking). I could not find a way to get rid of it (FocusVisual does not help).

  不一致的是，在WebBrowser周围会出现一个虚线焦点矩形(在制表时显示，但在单击时不显示)。我找不到摆脱它的方法(FocusVisual没有帮助)。

• Internally, WebBrowser never receives the focus. That's true for both logical focus (FocusManager) and input focus (Keyboard). The Keyboard.GotKeyboardFocusEvent and FocusManager.GotFocusEvent events never get fired for WebBrowser (although they both do for buttons in the same focus scope). Even when the caret is inside WebBrowser, FocusManager.GetFocusedElement(mainWindow) points to a previously focused element (a button) and Keyboard.FocusedElement is null. At the same time, ((IKeyboardInputSink)this.webBrowser).HasFocusWithin() returns true.

  在内部，WebBrowser不会收到焦点。对于逻辑焦点(FocusManager)和输入焦点(键盘)都是如此。键盘。GotKeyboardFocusEvent FocusManager。GotFocusEvent事件不会因为WebBrowser而被触发(尽管它们都在同一个焦点范围内对按钮进行操作)。即使插入符号在WebBrowser中，FocusManager.GetFocusedElement(mainWindow)也指向一个先前聚焦的元素(一个按钮)和键盘。FocusedElement是null。同时，((IKeyboardInputSink)this.webBrowser). hasfocuswithin()返回true。

I'd say, such behaviour is almost too dysfunctional to be true, but that's how it works. I could probably come up with some hacks to fix it and bring it in row with native WPF controls like TextBox. Still I hope, maybe I'm missing something obscure yet simple here. Has anyone dealt with a similar problem? Any suggestions on how to fix this would be greatly appreciated.

我得说，这种行为几乎是不正常的，不可能是真的，但它就是这样运作的。我可能会想出一些技巧来修复它，并将它与文本框之类的本地WPF控件放在一起。我仍然希望，也许我在这里漏掉了一些模糊但简单的东西。有人处理过类似的问题吗?对于如何解决这一问题，我们将非常感谢。

At this point, I'm inclined to develop an in-house WPF wrapper for WebBrowser ActiveX Control, based upon HwndHost. We are also considering other alternatives to WebBrowser, such as Chromium Embedded Framework (CEF).

在这一点上，我倾向于开发基于HwndHost的WebBrowser ActiveX控件的内部WPF包装器。我们还在考虑web浏览器的其他替代品，比如Chromium嵌入式框架(CEF)。

The VS2012 project can be downloaded from here in case someone wants to play with it.

VS2012项目可以从这里下载，以防有人想玩它。

This is XAML:

这是XAML:

This is C# code, it has a bunch of diagnostic traces to show how focus/keyboard events are routed and where the focus is:

这是c#代码，它有许多诊断跟踪，显示焦点/键盘事件是如何路由的，焦点在哪里:

using System;
using System.Diagnostics;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows;
using System.Windows.Input;
using System.Windows.Navigation;

namespace WpfWebBrowserTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();

            // watch these events for diagnostics
            EventManager.RegisterClassHandler(typeof(UIElement), Keyboard.PreviewKeyDownEvent, new KeyEventHandler(MainWindow_PreviewKeyDown));
            EventManager.RegisterClassHandler(typeof(UIElement), Keyboard.GotKeyboardFocusEvent, new KeyboardFocusChangedEventHandler(MainWindow_GotKeyboardFocus));
            EventManager.RegisterClassHandler(typeof(UIElement), FocusManager.GotFocusEvent, new RoutedEventHandler(MainWindow_GotFocus));
        }

        private void btnLoad_Click(object sender, RoutedEventArgs e)
        {
            // load the browser
            this.webBrowser.NavigateToString("Line 1
Line 3
Line 3
");
            this.btnLoad.IsChecked = true;
        }

        private void btnClose_Click(object sender, RoutedEventArgs e)
        {
            // close the form
            if (MessageBox.Show("Close it?", this.Title, MessageBoxButton.YesNo) == MessageBoxResult.Yes)
                this.Close();
        }

        // Diagnostic events

        void MainWindow_GotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
        {
            Debug.Print("{0}, source: {1}, {2}", FormatMethodName(), FormatType(e.Source), FormatFocused());
        }

        void MainWindow_GotFocus(object sender, RoutedEventArgs e)
        {
            Debug.Print("{0}, source: {1}, {2}", FormatMethodName(), FormatType(e.Source), FormatFocused());
        }

        void MainWindow_PreviewKeyDown(object sender, KeyEventArgs e)
        {
            Debug.Print("{0}, key: {1}, source: {2}, {3}", FormatMethodName(), e.Key.ToString(), FormatType(e.Source), FormatFocused());
        }

        // Debug output formatting helpers

        string FormatFocused()
        {
            // show current focus and keyboard focus
            return String.Format("Focus: {0}, Keyboard focus: {1}, webBrowser.HasFocusWithin: {2}",
                FormatType(FocusManager.GetFocusedElement(this)),
                FormatType(Keyboard.FocusedElement),
                ((System.Windows.Interop.IKeyboardInputSink)this.webBrowser).HasFocusWithin());
        }

        string FormatType(object p)
        {
            string result = p != null ? String.Concat('*', p.GetType().Name, '*') : "null";
            if (p == this.webBrowser )
                result += "!!";
            return result;
        }

        static string FormatMethodName()
        {
            return new StackTrace(true).GetFrame(1).GetMethod().Name;
        }

    }
}

[UPDATE] The situation doesn't get better if I host WinForms WebBrowser (in place of, or side-by-side with WPF WebBrowser):

[更新]如果我托管WinForms WebBrowser(代替WPF WebBrowser，或与WPF WebBrowser并行)，情况不会变得更好:

The only improvement is that I do see focus events on WindowsFormsHost.

唯一的改进是，我确实看到了WindowsFormsHost上的焦点事件。

[UPDATE] An extreme case: two WebBrowser controls with two carets showing at the same time:

[更新]一个极端的情况:两个WebBrowser控件同时显示两个carets:

    

    
    

    


this.webBrowser.NavigateToString("text");
this.webBrowser2.NavigateToString("text2");

This also illustrates that the focus handling issue is not specific to cOntentEditable=true content.

这也说明了焦点处理问题并不是针对cOntentEditable=true content的。

2 个解决方案

// Constructor
public MyWindow()
{
    Loaded += (_, __) =>
    {
        ((HTMLDocument) Browser.Document).focus();
    };
}