wpf-14714-controls-and-libraries-rich-text-editor-examples-automation-how-to-highlight-document-syntax.md
The RichEditControl allows you to create a custom ISyntaxHighlightService implementation to display text in different colors and fonts according to the category of syntax sub-elements. These include keywords, comments, control-flow statements, variables, and other elements. This example describes how to highlight the T-SQL syntax.
Note
The syntax highlight implementation can affect the application’s performance.
A token represents a document range that should be highlighted. You can use third-party libraries or add custom syntax highlight logic to parse a document into tokens and highlight them. You can combine both approaches.
Tip
You can use the DevExpress CodeParser library to parse a document into tokens. Refer to the How to use Syntax Highlight Tokens to implement custom syntax highlighting for a code sample. Note that the library supports limited amount of languages.
Take into account the following requirements when you parse document into tokens:
Follow the steps below to parse the document into tokens:
Call the SubDocument.FindAll method to search for keywords or specific symbols.
Convert all occurrences to SyntaxHighlightToken objects. You can specify a token’s format options in the object constructor.
Check whether the tokens intersect. If not, add them to the tokens collection.
Parse the remaining text into tokens and add them to the same collection.
Sort the objects in the collection according to their position in the original text.
Show Code
Note
A full code example is available here: How to implement T-SQL language syntax highlighting by creating Syntax Highlight Tokens
public class CustomSyntaxHighlightService : ISyntaxHighlightService
{
readonly Document document;
Regex _keywords;
//Declare a regular expression to search text in quotes (including embedded quotes)
Regex _quotedString = new Regex(@"'([^']|'')*'");
//Declare a regular expression to search commented text (including multiline)
Regex _commentedString = new Regex(@"(/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/)");
public CustomSyntaxHighlightService(Document document)
{
this.document = document;
//Declare keywords
string[] keywords = { "INSERT", "SELECT", "CREATE", "TABLE", "USE", "IDENTITY", "ON", "OFF", "NOT", "NULL", "WITH", "SET", "GO", "DECLARE", "EXECUTE", "NVARCHAR", "FROM", "INTO", "VALUES", "WHERE", "AND" };
this._keywords = new Regex(@"\b(" + string.Join("|", keywords.Select(w => Regex.Escape(w))) + @")\b");
}
private List<SyntaxHighlightToken> ParseTokens()
{
List<SyntaxHighlightToken> tokens = new List<SyntaxHighlightToken>();
DocumentRange[] ranges = null;
// Search for quoted strings
ranges = document.FindAll(_quotedString);
for (int i = 0; i < ranges.Length; i++)
{
tokens.Add(CreateToken(ranges[i].Start.ToInt(),ranges[i].End.ToInt(), Color.Red));
}
//Extract all keywords
ranges = document.FindAll(_keywords);
for (int j = 0; j < ranges.Length; j++)
{
//Check whether tokens intersect
if (!IsRangeInTokens(ranges[j], tokens))
tokens.Add(CreateToken(ranges[j].Start.ToInt(), ranges[j].End.ToInt(), Color.Blue));
}
//Find all comments
ranges = document.FindAll(_commentedString);
for (int j = 0; j < ranges.Length; j++)
{
//Check whether tokens intersect
if (!IsRangeInTokens(ranges[j], tokens))
tokens.Add(CreateToken(ranges[j].Start.ToInt(), ranges[j].End.ToInt(), Color.Green));
}
// Sort tokens by their start position
tokens.Sort(new SyntaxHighlightTokenComparer());
// Fill in gaps in document coverage
tokens = CombineWithPlainTextTokens(tokens);
return tokens;
}
//Parse the remaining text into tokens:
List<SyntaxHighlightToken> CombineWithPlainTextTokens(List<SyntaxHighlightToken> tokens)
{
List<SyntaxHighlightToken> result = new List<SyntaxHighlightToken>(tokens.Count * 2 + 1);
int documentStart = this.document.Range.Start.ToInt();
int documentEnd = this.document.Range.End.ToInt();
if (tokens.Count == 0)
result.Add(CreateToken(documentStart, documentEnd, Color.Black));
else
{
SyntaxHighlightToken firstToken = tokens[0];
if (documentStart < firstToken.Start)
result.Add(CreateToken(documentStart, firstToken.Start, Color.Black));
result.Add(firstToken);
for (int i = 1; i < tokens.Count; i++)
{
SyntaxHighlightToken token = tokens[i];
SyntaxHighlightToken prevToken = tokens[i - 1];
if (prevToken.End != token.Start)
result.Add(CreateToken(prevToken.End, token.Start, Color.Black));
result.Add(token);
}
SyntaxHighlightToken lastToken = tokens[tokens.Count - 1];
if (documentEnd > lastToken.End)
result.Add(CreateToken(lastToken.End, documentEnd, Color.Black));
}
return result;
}
//Check whether tokens intersect
private bool IsRangeInTokens(DocumentRange range, List<SyntaxHighlightToken> tokens)
{
return tokens.Any(t => IsIntersect(range, t));
}
bool IsIntersect(DocumentRange range, SyntaxHighlightToken token)
{
int start = range.Start.ToInt();
if (start >= token.Start && start < token.End)
return true;
int end = range.End.ToInt() - 1;
if (end >= token.Start && end < token.End)
return true;
if (start < token.Start && end >= token.End)
return true;
return false;
}
}
//Compare token's initial positions to sort them
public class SyntaxHighlightTokenComparer : IComparer<SyntaxHighlightToken>
{
public int Compare(SyntaxHighlightToken x, SyntaxHighlightToken y)
{
return x.Start - y.Start;
}
}
Public Class CustomSyntaxHighlightService
Implements ISyntaxHighlightService
Private ReadOnly document As Document
Private _keywords As Regex
' Declare a regular expression to search text in quotes (including embedded quotes)
Private _quotedString As New Regex("'([^']|'')*'")
' Declare a regular expression to search commented text (including multiline)
Private _commentedString As New Regex("(/\*([^*]|[\r\n]|(\*+([^*/]|[\r\n])))*\*+/)")
Public Sub New(ByVal document As Document)
Me.document = document
' Declare keywords
Dim keywords() As String = { "INSERT", "SELECT", "CREATE", "TABLE", "USE", "IDENTITY", "ON", "OFF", "NOT", "NULL", "WITH", "SET", "GO", "DECLARE", "EXECUTE", "NVARCHAR", "FROM", "INTO", "VALUES", "WHERE", "AND" }
Me._keywords = New Regex("\b(" & String.Join("|", keywords.Select(Function(w) Regex.Escape(w))) & ")\b")
End Sub
Private Function ParseTokens() As List(Of SyntaxHighlightToken)
Dim tokens As New List(Of SyntaxHighlightToken)()
Dim ranges() As DocumentRange = Nothing
' Search for quoted strings
ranges = document.FindAll(_quotedString)
For i As Integer = 0 To ranges.Length - 1
tokens.Add(CreateToken(ranges(i).Start.ToInt(),ranges(i).End.ToInt(), Color.Red))
Next i
'Extract all keywords
ranges = document.FindAll(_keywords)
For j As Integer = 0 To ranges.Length - 1
'Check whether tokens intersect
If Not IsRangeInTokens(ranges(j), tokens) Then
tokens.Add(CreateToken(ranges(j).Start.ToInt(), ranges(j).End.ToInt(), Color.Blue))
End If
Next j
'Find all comments
ranges = document.FindAll(_commentedString)
For j As Integer = 0 To ranges.Length - 1
' Check whether tokens intersect
If Not IsRangeInTokens(ranges(j), tokens) Then
tokens.Add(CreateToken(ranges(j).Start.ToInt(), ranges(j).End.ToInt(), Color.Green))
End If
Next j
' Sort tokens by their start position
tokens.Sort(New SyntaxHighlightTokenComparer())
' Fill in gaps in document coverage
tokens = CombineWithPlainTextTokens(tokens)
Return tokens
End Function
'Parse the remaining text into tokens:
Private Function CombineWithPlainTextTokens(ByVal tokens As List(Of SyntaxHighlightToken)) As List(Of SyntaxHighlightToken)
Dim result As New List(Of SyntaxHighlightToken)(tokens.Count * 2 + 1)
Dim documentStart As Integer = Me.document.Range.Start.ToInt()
Dim documentEnd As Integer = Me.document.Range.End.ToInt()
If tokens.Count = 0 Then
result.Add(CreateToken(documentStart, documentEnd, Color.Black))
Else
Dim firstToken As SyntaxHighlightToken = tokens(0)
If documentStart < firstToken.Start Then
result.Add(CreateToken(documentStart, firstToken.Start, Color.Black))
End If
result.Add(firstToken)
For i As Integer = 1 To tokens.Count - 1
Dim token As SyntaxHighlightToken = tokens(i)
Dim prevToken As SyntaxHighlightToken = tokens(i - 1)
If prevToken.End <> token.Start Then
result.Add(CreateToken(prevToken.End, token.Start, Color.Black))
End If
result.Add(token)
Next i
Dim lastToken As SyntaxHighlightToken = tokens(tokens.Count - 1)
If documentEnd > lastToken.End Then
result.Add(CreateToken(lastToken.End, documentEnd, Color.Black))
End If
End If
Return result
End Function
'Check whether tokens intersect
Private Function IsRangeInTokens(ByVal range As DocumentRange, ByVal tokens As List(Of SyntaxHighlightToken)) As Boolean
Return tokens.Any(Function(t) IsIntersect(range, t))
End Function
Private Function IsIntersect(ByVal range As DocumentRange, ByVal token As SyntaxHighlightToken) As Boolean
Dim start As Integer = range.Start.ToInt()
If start >= token.Start AndAlso start < token.End Then
Return True
End If
Dim [end] As Integer = range.End.ToInt() - 1
If [end] >= token.Start AndAlso [end] < token.End Then
Return True
End If
If start < token.Start AndAlso [end] >= token.End Then
Return True
End If
Return False
End Function
End Class
'Compare token's initial positions to sort them
Public Class SyntaxHighlightTokenComparer
Implements IComparer(Of SyntaxHighlightToken)
Public Function Compare(ByVal x As SyntaxHighlightToken, ByVal y As SyntaxHighlightToken) As Integer Implements IComparer(Of SyntaxHighlightToken).Compare
Return x.Start - y.Start
End Function
End Class
Note
You can use the DocumentRange.Freeze() or DocumentRangeExtensions class methods to improve performance during syntax highlight.
After one of these methods is called, RichEditControl stops tracking the actual document position for this range, and the target ranges cannot be modified. The frozen document ranges become invalid after the document is modified. Don’t use these ranges for further document processing operations.
The SyntaxHighlightProperties class represents a token’s format settings. You can pass this class’s object to the SyntaxHighlightToken object constructor or use it as the SyntaxHighlightToken.Properties property value.
The code sample below converts keywords occurrences to the highlight tokens and specifies their foreground color:
SyntaxHighlightToken CreateToken(int start, int end, Color foreColor)
{
SyntaxHighlightProperties properties = new SyntaxHighlightProperties();
properties.ForeColor = foreColor;
return new SyntaxHighlightToken(start, end - start, properties);
}
Private Function CreateToken(ByVal start As Integer, ByVal [end] As Integer, ByVal foreColor As Color) As SyntaxHighlightToken
Dim properties As SyntaxHighlightProperties = New SyntaxHighlightProperties()
properties.ForeColor = foreColor
Return New SyntaxHighlightToken(start, [end] - start, properties)
End Function
Note
The RichEditControl highlights unformatted text syntax only.
Call the SubDocument.ApplySyntaxHighlight within the ISyntaxHighlightService.Execute method to enable syntax highlighting.
The code sample below uses the ParseTokens method shown above to create a list of SyntaxHighlightToken objects and pass it to the ApplySyntaxHighlight method.
public void Execute()
{
List<SyntaxHighlightToken> tSqltokens = ParseTokens();
document.ApplySyntaxHighlight(tSqltokens);
}
public void ForceExecute()
{
Execute();
}
Private Sub Execute() Implements ISyntaxHighlightService.Execute
Dim tSqltokens As List(Of SyntaxHighlightToken) = ParseTokens()
document.ApplySyntaxHighlight(tSqltokens)
End Sub
Public Sub ForceExecute() Implements ISyntaxHighlightService.ForceExecute
Execute()
End Sub
In the main class, use the RichEditControl.ReplaceService<T>(T) method to register the created implementation.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
//Register the created service and load the document
richEditControl1.ReplaceService<ISyntaxHighlightService>(new CustomSyntaxHighlightService(richEditControl1.Document));
richEditControl1.LoadDocument("CarsXtraScheduling.sql");
//Specify the richEdit's layout settings
richEditControl1.Document.Sections[0].Page.Width = Units.InchesToDocumentsF(80f);
richEditControl1.Document.DefaultCharacterProperties.FontName = "Courier New";
}
Public Partial Class Form1
Inherits Form
Public Sub New()
InitializeComponent()
' Register the created service and load the document
richEditControl1.ReplaceService(Of ISyntaxHighlightService)(New CustomSyntaxHighlightService(richEditControl1.Document))
richEditControl1.LoadDocument("CarsXtraScheduling.sql")
' Specify the richEdit's layout settings
richEditControl1.Document.Sections(0).Page.Width = Units.InchesToDocumentsF(80F)
richEditControl1.Document.DefaultCharacterProperties.FontName = "Courier New"
End Sub
End Class
See Also
Syntax highlighting using DevExpress CodeParser and Syntax Highlight tokens
How to use Syntax Highlight Tokens to implement custom syntax highlighting