Underline not detected after reloading RTF

问题

I'm currently trying to get a RichTextBox with basic formatting working for my new beta notes software, Lilly Notes. Brian Lagunas' article on the subject put me in the right direction, however I'm having a bit of an issue. If you click on underlined text, the Underline button becomes pressed, so the state is being recognised. However if I serialize it to RTF and then deserialize it back into the RichTextBox, then it doesn't get detected. Since the code in Lilly Notes is not trivial to demonstrate here, I have created a SSCCE to demonstrate the problem.

First, MainWindow.xaml:

<Window x:Class="WpfRichTextBoxUnderline.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow"
        Height="350"
        Width="525">
    <DockPanel LastChildFill="True">
        <Button Name="SaveAndReloadButton"
                Content="Save and Reload"
                DockPanel.Dock="Bottom"
                Click="SaveAndReloadButton_Click" />
        <ToggleButton Name="UnderlineButton"
                      DockPanel.Dock="Top"
                      Width="20"
                      Command="{x:Static EditingCommands.ToggleUnderline}"
                      CommandTarget="{Binding ElementName=RichText}">
            <ToggleButton.Content>
                <TextBlock Text="U"
                           TextDecorations="Underline" />
            </ToggleButton.Content>
        </ToggleButton>
        <RichTextBox Name="RichText"
                     SelectionChanged="RichTextBox_SelectionChanged" />
    </DockPanel>
</Window>

This is what it looks like:

In the codebehind, I have code to detect the state of the formatting when the selection changes, and update the state of the Underline button accordingly. This is no different from Brian Lagunas' method.

private void RichTextBox_SelectionChanged(object sender, RoutedEventArgs e)
{
    if (this.RichText.Selection != null)
    {
        object currentValue = this.RichText.Selection.GetPropertyValue(Inline.TextDecorationsProperty);
        this.UnderlineButton.IsChecked = (currentValue == DependencyProperty.UnsetValue) ? false : currentValue != null && currentValue.Equals(TextDecorations.Underline);
    }
}

Then I have a method (and another helper method) which saves the RTF to a string and then applies it to the RichTextBox. Again I'm doing this just to keep it simple - in Lilly Notes, I'm saving that string to a database, and then loading it back when the the application is run again.

public Stream GenerateStreamFromString(string s)
{
    MemoryStream stream = new MemoryStream();
    StreamWriter writer = new StreamWriter(stream);
    writer.Write(s);
    writer.Flush();
    stream.Position = 0;
    return stream;
}

private async void SaveAndReloadButton_Click(object sender, RoutedEventArgs e)
{
    string data = null;
    var range = new TextRange(this.RichText.Document.ContentStart, this.RichText.Document.ContentEnd);
    using (var memoryStream = new MemoryStream())
    {
        range.Save(memoryStream, DataFormats.Rtf);
        memoryStream.Position = 0;

        using (StreamReader reader = new StreamReader(memoryStream))
        {
            data = await reader.ReadToEndAsync();
        }
    }

    // load

    var stream = GenerateStreamFromString(data);
    range = new TextRange(this.RichText.Document.ContentStart, this.RichText.Document.ContentEnd);
    range.Load(stream, DataFormats.Rtf);
}

After I click the Save and Reload button, and the RTF gets serialized to a string and deserialized back into the RichTextBox, underline detection does not work any more, and when I click the underlined text, the button remains as if the underline was not working:

Now, when I debugged this, I noticed this:

Initially, when you click on a piece of underlined text, you get a TextDecorationCollection with a Count of 1. But after saving and reloading, you get a Count of zero, which is why the detection is not working.

Note that this problem applies only to underline/strikethrough, which belong to the TextDecorationCollection in WPF. Bold and Italic do not exhibit this issue.

Is this happening because I am doing something wrong, or is this a bug with the RichTextBox?

You can find the SSCCE code here at my BitBucket repo.

回答1:

Inline.TextDecorations is a Collection, so probably comparing it directly is not a good idea.

Perhaps this will work better:

TextDecorationCollection currentValue = this.RichText.Selection.GetPropertyValue(Inline.TextDecorationsProperty) as TextDecorationCollection;
this.UnderlineButton.IsChecked = (currentValue == DependencyProperty.UnsetValue) ? false : currentValue != null && currentValue.Contains(TextDecorations.Underline);

EDIT

After going through the code provided, I discovered the probable cause:

This image was done before saving and reloading as RTF.

In the image above, notice that the inlines of the paragraph are Run and the parent of the caret is also a Run and both have TextDecorations in place.

Now lets save and reload!

In the image above, notice that the the inlines of paragraph are now Span and the parent of the caret is Run. but the weird thing is that the Span has the TextDecoration in place, but the parent Run does not have any TextDecoration in it.

Solution

Here is a possible solution, or better said a workaround:

    private void RichTextBox_SelectionChanged(object sender, RoutedEventArgs e)
    {
        var caret = RichText.CaretPosition;
        Paragraph paragraph = RichText.Document.Blocks.FirstOrDefault(x => x.ContentStart.CompareTo(caret) == -1 && x.ContentEnd.CompareTo(caret) == 1) as Paragraph;

        if (paragraph != null)
        {
            Inline inline = paragraph.Inlines.FirstOrDefault(x => x.ContentStart.CompareTo(caret) == -1 && x.ContentEnd.CompareTo(caret) == 1) as Inline;
            if (inline != null)
            {
                TextDecorationCollection decorations = inline.TextDecorations;
                this.UnderlineButton.IsChecked = (decorations == DependencyProperty.UnsetValue) ? false : decorations != null && decorations.Contains(TextDecorations.Underline[0]);
            }
        }
    }

In the solution above, I tried to get the underlying Run or Span, by using the current caret position. The rest remains similar.

回答2:

There seems to be a bug in GetCharacterValueFromPosition being used by RichTextBox.Selection.GetPropertyValue. Have a look at this post: link

When that method is getting the TextDecorationsProperty, it is walking up the logical tree to find an element which has a non-null value for the property. When it finds such a value, it returns it. The problem is that it should be checking for both a null value and an empty TextDecorationCollection.

If you use the suggested implementation it will fix the checked state issue on your toggle button. However there is still the issue that it doesn't set/unset underlines properly.

回答3:

Try changing your selection event handler to the following:

private void RichTextBox_SelectionChanged(object sender, RoutedEventArgs e)
{
    if (this.RichText.Selection != null)
    {
        var currentValue = new TextRange(this.RichText.Selection.Start, this.RichText.Selection.End);
        if (currentValue.GetPropertyValue(Inline.TextDecorationsProperty) == TextDecorations.Underline)
        {
            this.UnderlineButton.IsChecked = true;
        }
        else
        {
            this.UnderlineButton.IsChecked = false;
        }
}

回答4:

I know this is an old question, and already has an accepted answer, but not exactly the right answer, and having the same problem, I write for future users of the solution that I found. Is in VB...

    Dim TextRange = New TextRange(richTxtEditor.Selection.Start, richTxtEditor.Selection.End)
Dim textDecor As TextDecorationCollection
Dim DecorationFound as Boolean = false
If TextRange.IsEmpty Then
    textDecor = txtRange.GetPropertyValue(Inline.TextDecorationsProperty)

    If textDecor.Equals(TextDecorations.Underline) Then
        MsgBox("Is Underline, and it only works on a new document, not a document loaded.")
        DecorationFound = true
    End If

    If textDecor.Equals(TextDecorations.Strikethrough) Then
        MsgBox("Is Strikethrough, and it only works on a new document, not a document loaded.")
        DecorationFound = true
    End If

    ' ### START # From here starts the solution to the problem !!! ###

    If NOT DecorationFound Then
        For i = 0 To textDecor.Count - 1
            If textDecor.Item(i).Location = TextDecorationLocation.Underline Then
                MsgBox("Is Underline, and it works on a loaded document.")
            ElseIf textDecor.Item(i).Location = TextDecorationLocation.Strikethrough Then
                MsgBox("Is Strikethrough, and it works on a loaded document.") 
            End If
        Next
    End If

    ' ### END SOLUTION ###

End If

来源：https://stackoverflow.com/questions/25217557/underline-not-detected-after-reloading-rtf

标签

wpf

serialization

richtextbox

rtf