QSyntaxHighlighter Class▲
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Header: QSyntaxHighlighter
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CMake:
find_package(Qt6 REQUIRED COMPONENTS Gui)
target_link_libraries(mytarget PRIVATE Qt6::Gui)
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qmake: QT += gui
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Inherits: https://
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Group: QSyntaxHighlighter is part of https://
Detailed Description▲
The https:// class is a base class for implementing https:// syntax highlighters. A syntax highligher automatically highlights parts of the text in a https://. 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 https:// and reimplement https://().
When you create an instance of your https:// subclass, pass it the https:// 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 https://() function will be called automatically whenever necessary. Use your https://() function to apply formatting (e.g. setting the font and color) to the text that is passed to it. https:// provides the https://() function which applies a given https:// on the current text block. For example:
void MyHighlighter::highlightBlock(const QString &text)
{
QTextCharFormat myClassFormat;
myClassFormat.setFontWeight(QFont::Bold);
myClassFormat.setForeground(Qt::darkMagenta);
QRegularExpression expression("\\bMy[A-Za-z]+\\b");
QRegularExpressionMatchIterator i = expression.globalMatch(text);
while (i.hasNext()) {
QRegularExpressionMatch match = i.next();
setFormat(match.capturedStart(), match.capturedLength(), myClassFormat);
}
}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 https://() implementation you can query the end state of the previous text block using the https://() function. After parsing the block you can save the last state using https://().
The https://() and https://() 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 https://() function. Once the state is set the https:// 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;
multiLineCommentFormat.setForeground(Qt::red);
QRegularExpression startExpression("/\\*");
QRegularExpression endExpression("\\*/");
setCurrentBlockState(0);
int startIndex = 0;
if (previousBlockState() != 1)
startIndex = text.indexOf(startExpression);
while (startIndex >= 0) {
QRegularExpressionMatch endMatch;
int endIndex = text.indexOf(endExpression, startIndex, &endMatch);
int commentLength;
if (endIndex == -1) {
setCurrentBlockState(1);
commentLength = text.length() - startIndex;
} else {
commentLength = endIndex - startIndex
+ endMatch.capturedLength();
}
setFormat(startIndex, commentLength, multiLineCommentFormat);
startIndex = text.indexOf(startExpression,
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 highlight 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 https://(), and make sure that the rest of the block is highlighted.
In addition you can query the current formatting and user data using the https://() and https://() functions respectively. You can also attach user data to the current text block using the https://() function. https:// 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 https://() documentation.
See Also▲
See also https://, Syntax Highlighter Example
Member Function Documentation▲
[explicit] QSyntaxHighlighter::QSyntaxHighlighter(QObject *parent)▲
Constructs a https:// with the given parent.
If the parent is a QTextEdit, it installs the syntax highlighter on the parents document. The specified QTextEdit also becomes the owner of the https://.
[explicit] QSyntaxHighlighter::QSyntaxHighlighter(QTextDocument *parent)▲
Constructs a https:// and installs it on parent. The specified https:// also becomes the owner of the https://.
[virtual] QSyntaxHighlighter::~QSyntaxHighlighter()▲
Destructor. Uninstalls this syntax highlighter from the text document.
[protected] QTextBlock QSyntaxHighlighter::currentBlock() const▲
Returns the current text block.
[protected] int QSyntaxHighlighter::currentBlockState() const▲
Returns the state of the current text block. If no value is set, the returned value is -1.
See Also▲
See also https://()
[protected] QTextBlockUserData *QSyntaxHighlighter::currentBlockUserData() const▲
Returns the https:// object previously attached to the current text block.
See Also▲
See also https://(), https://()
QTextDocument *QSyntaxHighlighter::document() const▲
[protected] QTextCharFormat QSyntaxHighlighter::format(int position) const▲
Returns the format at position inside the syntax highlighter's current text block.
See Also▲
See also https://()
[pure virtual protected] void QSyntaxHighlighter::highlightBlock(const QString &text)▲
Highlights the given text block. This function is called when necessary by the rich text engine, i.e. on text blocks which have changed.
To provide your own syntax highlighting, you must subclass https:// and reimplement highlightBlock(). In your reimplementation you should parse the block's text and call https://() as often as necessary to apply any font and color changes that you require. For example:
void MyHighlighter::highlightBlock(const QString &text)
{
QTextCharFormat myClassFormat;
myClassFormat.setFontWeight(QFont::Bold);
myClassFormat.setForeground(Qt::darkMagenta);
QRegularExpression expression("\\bMy[A-Za-z]+\\b");
QRegularExpressionMatchIterator i = expression.globalMatch(text);
while (i.hasNext()) {
QRegularExpressionMatch match = i.next();
setFormat(match.capturedStart(), match.capturedLength(), myClassFormat);
}
}See the https:// for examples of using https://(), https://() and https://() to handle syntaxes with constructs that span several text blocks
See Also▲
See also https://(), https://(), https://()
[protected] int QSyntaxHighlighter::previousBlockState() const▲
Returns the end state of the text block previous to the syntax highlighter's current block. If no value was previously set, the returned value is -1.
See Also▲
See also https://(), https://()
void QSyntaxHighlighter::rehighlight()▲
void QSyntaxHighlighter::rehighlightBlock(const QTextBlock &block)▲
[protected] void QSyntaxHighlighter::setCurrentBlockState(int newState)▲
[protected] void QSyntaxHighlighter::setCurrentBlockUserData(QTextBlockUserData *data)▲
Attaches the given data to the current text block. The ownership is passed to the underlying text document, i.e. the provided https:// object will be deleted if the corresponding text block gets deleted.
https:// 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 https:// in a simple class derived from https://:
struct ParenthesisInfo
{
QChar character;
int position;
};
struct BlockData : public QTextBlockUserData
{
QList<ParenthesisInfo> parentheses;
};During cursor navigation in the associated editor, you can ask the current https:// (retrieved using the https://() 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.
See Also▲
See also https://(), https://()
void QSyntaxHighlighter::setDocument(QTextDocument *doc)▲
Installs the syntax highlighter on the given https:// doc. A https:// can only be used with one document at a time.
See Also▲
See also https://()
[protected] void QSyntaxHighlighter::setFormat(int start, int count, const QTextCharFormat &format)▲
This function is applied to the syntax highlighter's current text block (i.e. the text that is passed to the https://() 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 https://'s functions. Note that the document itself remains unmodified by the format set through this function.
See Also▲
See also https://(), https://()
[protected] void QSyntaxHighlighter::setFormat(int start, int count, const QColor &color)▲
This is an overloaded function.
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.
See Also▲
See also https://(), https://()
[protected] void QSyntaxHighlighter::setFormat(int start, int count, const QFont &font)▲
This is an overloaded function.
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.
See Also▲
See also https://(), https://()