com.trolltech.qt.internal.QSignalEmitterInternal
com.trolltech.qt.QSignalEmitter
com.trolltech.qt.QtJambiObject
com.trolltech.qt.core.QObject
com.trolltech.qt.gui.QSyntaxHighlighter
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java.lang.Object
public abstract class QSyntaxHighlighter
The QSyntaxHighlighter class allows you to define syntax highlighting rules, and in addition you can use the class to query a document's current formatting or user data. The QSyntaxHighlighter class is a base class for implementing QTextEdit syntax highlighters. A syntax highligher automatically highlights parts of the text in a QTextEdit, or more generally in a QTextDocument. Syntax highlighters are often used when the user is entering text in a specific format (for example source code) and help the user to read the text and identify syntax errors.
To provide your own syntax highlighting, you must subclass QSyntaxHighlighter and reimplement highlightBlock().
When you create an instance of your QSyntaxHighlighter subclass, pass it the QTextEdit or QTextDocument that you want the syntax highlighting to be applied to. For example:
QTextEdit editor = new QTextEdit();
MyHighlighter highlighter = new MyHighlighter(editor.document());
After this your highlightBlock() function will be called automatically whenever necessary. Use your highlightBlock() function to apply formatting (e.g. setting the font and color) to the text that is passed to it. QSyntaxHighlighter provides the setFormat() function which applies a given QTextCharFormat on the current text block. For example:
protected void highlightBlock(String text)
{
QTextCharFormat myClassFormat = new QTextCharFormat();
myClassFormat.setFontWeight(QFont.Weight.Bold.value());
myClassFormat.setForeground(new QBrush(QColor.darkMagenta));
String pattern = "\\bMy[A-Za-z]+\\b";
QRegExp expression = new QRegExp(pattern);
int index = expression.indexIn(text);
while (index >= 0) {
int length = expression.matchedLength();
setFormat(index, length, myClassFormat);
index = expression.indexIn(text, index + length);
}
}
Some syntaxes can have constructs that span several text blocks. For example, a C++ syntax highlighter should be able to cope with /*...*/ multiline comments. To deal with these cases it is necessary to know the end state of the previous text block (e.g. "in comment"). Inside your highlightBlock() implementation you can query the end state of the previous text block using the previousBlockState() function. After parsing the block you can save the last state using setCurrentBlockState().
The currentBlockState() and previousBlockState() functions return an int value. If no state is set, the returned value is -1. You can designate any other value to identify any given state using the setCurrentBlockState() function. Once the state is set the QTextBlock keeps that value until it is set set again or until the corresponding paragraph of text is deleted.
For example, if you're writing a simple C++ syntax highlighter, you might designate 1 to signify "in comment":
QTextCharFormat multiLineCommentFormat = new QTextCharFormat();
multiLineCommentFormat.setForeground(new QBrush(QColor.red));
QRegExp startExpression = new QRegExp("/\\*");
QRegExp endExpression = new QRegExp("\\* /");
setCurrentBlockState(0);
int startIndex = 0;
if (previousBlockState() != 1)
startIndex = startExpression.indexIn(text);
while (startIndex >= 0) {
int endIndex = endExpression.indexIn(text, startIndex);
int commentLength;
if (endIndex == -1) {
setCurrentBlockState(1);
commentLength = text.length() - startIndex;
} else {
commentLength = endIndex - startIndex
+ endExpression.matchedLength();
}
setFormat(startIndex, commentLength, multiLineCommentFormat);
startIndex = startExpression.indexIn(text,
startIndex + commentLength);
}
In the example above, we first set the current block state to 0. Then, if the previous block ended within a comment, we higlight from the beginning of the current block (startIndex = 0). Otherwise, we search for the given start expression. If the specified end expression cannot be found in the text block, we change the current block state by calling setCurrentBlockState(), and make sure that the rest of the block is higlighted. In addition you can query the current formatting and user data using the format() and currentBlockUserData() functions respectively. You can also attach user data to the current text block using the setCurrentBlockUserData() function. QTextBlockUserData can be used to store custom settings. In the case of syntax highlighting, it is in particular interesting as cache storage for information that you may figure out while parsing the paragraph's text. For an example, see the setCurrentBlockUserData() documentation.
QTextEdit, and Syntax Highlighter Example.
| Nested Class Summary |
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| Nested classes/interfaces inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
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com.trolltech.qt.internal.QSignalEmitterInternal.AbstractSignalInternal |
| Field Summary |
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| Fields inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
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currentSender |
| Constructor Summary | |
|---|---|
QSyntaxHighlighter(QObject parent)
Constructs a QSyntaxHighlighter with the given parent. |
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QSyntaxHighlighter(QTextDocument parent)
Constructs a QSyntaxHighlighter and installs it on parent. |
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QSyntaxHighlighter(QTextEdit parent)
Constructs a QSyntaxHighlighter and installs it on parent 's QTextDocument. |
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| Method Summary | |
|---|---|
protected QTextBlock |
currentBlock()
Returns the current text block. |
protected int |
currentBlockState()
Returns the state of the current text block. |
protected QTextBlockUserData |
currentBlockUserData()
Returns the QTextBlockUserData object previously attached to the current text block. |
QTextDocument |
document()
Returns the QTextDocument on which this syntax highlighter is installed. |
protected QTextCharFormat |
format(int pos)
Returns the format at position inside the syntax highlighter's current text block. |
protected abstract void |
highlightBlock(java.lang.String text)
Highlights the given text block. |
protected int |
previousBlockState()
Returns the end state of the text block previous to the syntax highlighter's current block. |
void |
rehighlight()
Redoes the highlighting of the whole document. |
protected void |
setCurrentBlockState(int newState)
Sets the state of the current text block to newState. |
protected void |
setCurrentBlockUserData(QTextBlockUserData data)
Attaches the given data to the current text block. |
void |
setDocument(QTextDocument doc)
Installs the syntax highlighter on the given QTextDocumentdoc. |
protected void |
setFormat(int start,
int count,
QColor color)
This is an overloaded member function, provided for convenience. |
protected void |
setFormat(int start,
int count,
QFont font)
This is an overloaded member function, provided for convenience. |
protected void |
setFormat(int start,
int count,
QTextCharFormat format)
This function is applied to the syntax highlighter's current text block (i. |
| Methods inherited from class com.trolltech.qt.core.QObject |
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childEvent, children, connectSlotsByName, customEvent, disposeLater, dumpObjectInfo, dumpObjectTree, dynamicPropertyNames, event, eventFilter, findChild, findChild, findChild, findChildren, findChildren, findChildren, findChildren, indexOfProperty, installEventFilter, isWidgetType, killTimer, moveToThread, objectName, parent, properties, property, removeEventFilter, setObjectName, setParent, setProperty, startTimer, timerEvent, toString, userProperty |
| Methods inherited from class com.trolltech.qt.QtJambiObject |
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dispose, disposed, equals, finalize, reassignNativeResources, tr, tr, tr |
| Methods inherited from class com.trolltech.qt.QSignalEmitter |
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blockSignals, disconnect, disconnect, signalsBlocked, signalSender, thread |
| Methods inherited from class com.trolltech.qt.internal.QSignalEmitterInternal |
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__qt_signalInitialization |
| Methods inherited from class java.lang.Object |
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clone, getClass, hashCode, notify, notifyAll, wait, wait, wait |
| Methods inherited from interface com.trolltech.qt.QtJambiInterface |
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disableGarbageCollection, nativeId, nativePointer, reenableGarbageCollection, setJavaOwnership |
| Constructor Detail |
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public QSyntaxHighlighter(QObject parent)
public QSyntaxHighlighter(QTextDocument parent)
QTextDocument also becomes the owner of the QSyntaxHighlighter.
public QSyntaxHighlighter(QTextEdit parent)
QTextDocument. The specified QTextEdit also becomes the owner of the QSyntaxHighlighter.
| Method Detail |
|---|
protected final QTextBlock currentBlock()
protected final int currentBlockState()
setCurrentBlockState().
protected final QTextBlockUserData currentBlockUserData()
QTextBlockUserData object previously attached to the current text block. QTextBlock::userData(), and setCurrentBlockUserData().
public final QTextDocument document()
QTextDocument on which this syntax highlighter is installed. setDocument().
protected final QTextCharFormat format(int pos)
setFormat().
protected final int previousBlockState()
highlightBlock(), and setCurrentBlockState().
public final void rehighlight()
protected final void setCurrentBlockState(int newState)
currentBlockState(), and highlightBlock().
protected final void setCurrentBlockUserData(QTextBlockUserData data)
QTextBlockUserData object will be deleted if the corresponding text block gets deleted. QTextBlockUserData can be used to store custom settings. In the case of syntax highlighting, it is in particular interesting as cache storage for information that you may figure out while parsing the paragraph's text.
For example while parsing the text, you can keep track of parenthesis characters that you encounter ('{[(' and the like), and store their relative position and the actual QChar in a simple class derived from QTextBlockUserData:
class ParenthesisInfo
{
char character;
int position;
}
class BlockData extends QTextBlockUserData
{
List<ParenthesisInfo> parentheses;
}
During cursor navigation in the associated editor, you can ask the current QTextBlock (retrieved using the QTextCursor::block() function) if it has a user data object set and cast it to your BlockData object. Then you can check if the current cursor position matches with a previously recorded parenthesis position, and, depending on the type of parenthesis (opening or closing), find the next opening or closing parenthesis on the same level. In this way you can do a visual parenthesis matching and highlight from the current cursor position to the matching parenthesis. That makes it easier to spot a missing parenthesis in your code and to find where a corresponding opening/closing parenthesis is when editing parenthesis intensive code.
currentBlockUserData(), and QTextBlock::setUserData().
public final void setDocument(QTextDocument doc)
QTextDocumentdoc. A QSyntaxHighlighter can only be used with one document at a time. document().
protected final void setFormat(int start,
int count,
QColor color)
The specified color is applied to the current text block from the start position for a length of count characters.
The other attributes of the current text block, e.g. the font and background color, are reset to default values.
format(), and highlightBlock().
protected final void setFormat(int start,
int count,
QFont font)
The specified font is applied to the current text block from the start position for a length of count characters.
The other attributes of the current text block, e.g. the font and background color, are reset to default values.
format(), and highlightBlock().
protected final void setFormat(int start,
int count,
QTextCharFormat format)
highlightBlock() function). The specified format is applied to the text from the start position for a length of count characters (if count is 0, nothing is done). The formatting properties set in format are merged at display time with the formatting information stored directly in the document, for example as previously set with QTextCursor's functions. Note that the document itself remains unmodified by the format set through this function.
format(), and highlightBlock().
protected abstract void highlightBlock(java.lang.String text)
To provide your own syntax highlighting, you must subclass QSyntaxHighlighter and reimplement highlightBlock(). In your reimplementation you should parse the block's text and call setFormat() as often as necessary to apply any font and color changes that you require. For example:
protected void highlightBlock(String text)
{
QTextCharFormat myClassFormat = new QTextCharFormat();
myClassFormat.setFontWeight(QFont.Weight.Bold.value());
myClassFormat.setForeground(new QBrush(QColor.darkMagenta));
String pattern = "\\bMy[A-Za-z]+\\b";
QRegExp expression = new QRegExp(pattern);
int index = expression.indexIn(text);
while (index >= 0) {
int length = expression.matchedLength();
setFormat(index, length, myClassFormat);
index = expression.indexIn(text, index + length);
}
}
Some syntaxes can have constructs that span several text blocks. For example, a C++ syntax highlighter should be able to cope with /*...*/ multiline comments. To deal with these cases it is necessary to know the end state of the previous text block (e.g. "in comment"). Inside your highlightBlock() implementation you can query the end state of the previous text block using the previousBlockState() function. After parsing the block you can save the last state using setCurrentBlockState().
The currentBlockState() and previousBlockState() functions return an int value. If no state is set, the returned value is -1. You can designate any other value to identify any given state using the setCurrentBlockState() function. Once the state is set the QTextBlock keeps that value until it is set set again or until the corresponding paragraph of text gets deleted.
For example, if you're writing a simple C++ syntax highlighter, you might designate 1 to signify "in comment". For a text block that ended in the middle of a comment you'd set 1 using setCurrentBlockState, and for other paragraphs you'd set 0. In your parsing code if the return value of previousBlockState() is 1, you would highlight the text as a C++ comment until you reached the closing */.
previousBlockState(), setFormat(), and setCurrentBlockState().
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