WebBrowser control keyboard and focus behavior
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 (<body contentEditable='true'>some text</body>) and demonstrates the following:
Tabbing is misbehaving. User needs to hit Tab twice to see the caret (text cursor) inside WebBrowser and be able to type.
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.
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 (
FocusVisualStyle="{x:Null}"does not help).Internally, WebBrowser never receives the focus. That's true for both logical focus (FocusManager) and input focus (Keyboard). The
Keyboard.GotKeyboardFocusEventandFocusManager.GotFocusEventevents 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) andKeyboard.FocusedElementisnull. At the same time,((IKeyboardInputSink)this.webBrowser).HasFocusWithin()returnstrue.
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.
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).
The VS2012 project can be downloaded from here in case someone wants to play with it.
This is XAML:
<Window x:Class="WpfWebBrowserTest.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Width="640" Height="480" Background="LightGray">
<StackPanel Margin="20,20,20,20">
<ToggleButton Name="btnLoad" Focusable="True" IsTabStop="True" Content="Load" Click="btnLoad_Click" Width="100"/>
<WebBrowser Name="webBrowser" Focusable="True" KeyboardNavigation.IsTabStop="True" FocusVisualStyle="{x:Null}" Height="300"/>
<Button Name="btnClose" Focusable="True" IsTabStop="True" Content="Close" Click="btnClose_Click" Width="100"/>
</StackPanel>
</Window>
This is C# code, it has a bunch of diagnostic traces to show how focus/keyboard events are routed and where the focus is:
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("<body contentEditable='true' onload='focus()'>Line 1<br>Line 3<br>Line 3<br></body>");
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):
<StackPanel Margin="20,20,20,20">
<ToggleButton Name="btnLoad" Focusable="True" IsTabStop="True" Content="Load" Click="btnLoad_Click" Width="100"/>
<WebBrowser Name="webBrowser" Focusable="True" KeyboardNavigation.IsTabStop="True" FocusVisualStyle="{x:Null}" Height="150" Margin="10,10,10,10"/>
<WindowsFormsHost Name="wfHost" Focusable="True" Height="150" Margin="10,10,10,10">
<wf:WebBrowser x:Name="wfWebBrowser" />
</WindowsFormsHost>
<Button Name="btnClose" Focusable="True" IsTabStop="True" Content="Close" Click="btnClose_Click" Width="100"/>
</StackPanel>
The only improvement is that I do see focus events on WindowsFormsHost.
[UPDATE] An extreme case: two WebBrowser controls with two carets showing at the same time:
<StackPanel Margin="20,20,20,20">
<ToggleButton Name="btnLoad" Focusable="True" IsTabStop="True" Content="Load" Click="btnLoad_Click" Width="100"/>
<WebBrowser Name="webBrowser" Focusable="True" KeyboardNavigation.IsTabStop="True" FocusVisualStyle="{x:Null}" Height="150" Margin="10,10,10,10"/>
<WebBrowser Name="webBrowser2" Focusable="True" KeyboardNavigation.IsTabStop="True" FocusVisualStyle="{x:Null}" Height="150" Margin="10,10,10,10"/>
<Button Name="btnClose" Focusable="True" IsTabStop="True" Content="Close" Click="btnClose_Click" Width="100"/>
</StackPanel>
this.webBrowser.NavigateToString("<body onload='text.focus()'><textarea id='text' style='width: 100%; height: 100%'>text</textarea></body>");
this.webBrowser2.NavigateToString("<body onload='text.focus()'><textarea id='text' style='width: 100%; height: 100%'>text2</textarea></body>");
This also illustrates that the focus handling issue is not specific to contentEditable=true content.
Answer
For anyone else stumbling upon this post and needing to set keyboard focus to the browser control (not a particular element within the control, necessarily), this bit of code worked for me.
First, add a project reference (under Extensions in VS) for Microsoft.mshtml.
Next, whenever you'd like to focus the browser control (say for example, when the Window loads), simply "focus" the HTML document:
// Constructor
public MyWindow()
{
Loaded += (_, __) =>
{
((HTMLDocument) Browser.Document).focus();
};
}
This will place keyboard focus inside the web browser control, and inside the "invisible" ActiveX window, allowing keys like PgUp / PgDown to work on the HTML page.
If you want to, you might be able to use DOM selection to find a particular element on the page, and try to focus() that particular element. I have not tried this myself.