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. More…
Synopsis¶
Functions¶
def
currentBlock
()def
currentBlockState
()def
currentBlockUserData
()def
document
()def
format
(pos)def
previousBlockState
()def
setCurrentBlockState
(newState)def
setCurrentBlockUserData
(data)def
setDocument
(doc)def
setFormat
(start, count, color)def
setFormat
(start, count, font)def
setFormat
(start, count, format)
Virtual functions¶
def
highlightBlock
(text)
Slots¶
def
rehighlight
()def
rehighlightBlock
(block)
Detailed Description¶
The
QSyntaxHighlighter
class is a base class for implementingQTextDocument
syntax highlighters. A syntax highligher automatically highlights parts of the text in aQTextDocument
. 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 reimplementhighlightBlock()
.When you create an instance of your
QSyntaxHighlighter
subclass, pass it theQTextDocument
that you want the syntax highlighting to be applied to. For example:editor = QTextEdit() highlighter = MyHighlighter(editor.document())After this your
highlightBlock()
function will be called automatically whenever necessary. Use yourhighlightBlock()
function to apply formatting (e.g. setting the font and color) to the text that is passed to it.QSyntaxHighlighter
provides thesetFormat()
function which applies a givenQTextCharFormat
on the current text block. For example:class MyHighlighter(QSyntaxHighlighter): def highlightBlock(self, text): myClassFormat = QTextCharFormat() myClassFormat.setFontWeight(QFont.Bold) myClassFormat.setForeground(Qt.darkMagenta) pattern = QString("\\bMy[A-Za-z]+\\b") expression = QRegExp(pattern) index = text.indexOf(expression) while index >= 0: length = expression.matchedLength() setFormat(index, length, myClassFormat) index = text.indexOf(expression, 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 thepreviousBlockState()
function. After parsing the block you can save the last state usingsetCurrentBlockState()
.The
currentBlockState()
andpreviousBlockState()
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 thesetCurrentBlockState()
function. Once the state is set theQTextBlock
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”:
multiLineCommentFormat = QTextCharFormat() multiLineCommentFormat.setForeground(Qt.red) startExpression = QRegExp("/\\*") endExpression = QRegExp("\\*/") setCurrentBlockState(0) startIndex = 0 if previousBlockState() != 1: startIndex = text.indexOf(startExpression) while startIndex >= 0: endIndex = text.indexOf(endExpression, startIndex) if endIndex == -1: setCurrentBlockState(1) commentLength = text.length() - startIndex else: commentLength = endIndex - startIndex + endExpression.matchedLength() 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 callingsetCurrentBlockState()
, and make sure that the rest of the block is highlighted.In addition you can query the current formatting and user data using the
format()
andcurrentBlockUserData()
functions respectively. You can also attach user data to the current text block using thesetCurrentBlockUserData()
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 thesetCurrentBlockUserData()
documentation.See also
- class PySide2.QtGui.QSyntaxHighlighter(parent)¶
PySide2.QtGui.QSyntaxHighlighter(parent)
- param parent:
Constructs a
QSyntaxHighlighter
with the givenparent
.If the parent is a
QTextEdit
, it installs the syntax highlighter on the parents document. The specifiedQTextEdit
also becomes the owner of theQSyntaxHighlighter
.Constructs a
QSyntaxHighlighter
and installs it onparent
. The specifiedQTextDocument
also becomes the owner of theQSyntaxHighlighter
.
- PySide2.QtGui.QSyntaxHighlighter.currentBlock()¶
- Return type:
Returns the current text block.
- PySide2.QtGui.QSyntaxHighlighter.currentBlockState()¶
- Return type:
int
Returns the state of the current text block. If no value is set, the returned value is -1.
See also
- PySide2.QtGui.QSyntaxHighlighter.currentBlockUserData()¶
- Return type:
Returns the
QTextBlockUserData
object previously attached to the current text block.See also
- PySide2.QtGui.QSyntaxHighlighter.document()¶
- Return type:
Returns the
QTextDocument
on which this syntax highlighter is installed.See also
- PySide2.QtGui.QSyntaxHighlighter.format(pos)¶
- Parameters:
pos – int
- Return type:
Returns the format at
position
inside the syntax highlighter’s current text block.See also
- PySide2.QtGui.QSyntaxHighlighter.highlightBlock(text)¶
- Parameters:
text – str
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
QSyntaxHighlighter
and reimplement . In your reimplementation you should parse the block’stext
and callsetFormat()
as often as necessary to apply any font and color changes that you require. For example:class MyHighlighter(QSyntaxHighlighter): def highlightBlock(self, text): myClassFormat = QTextCharFormat() myClassFormat.setFontWeight(QFont.Bold) myClassFormat.setForeground(Qt.darkMagenta) pattern = QString("\\bMy[A-Za-z]+\\b") expression = QRegExp(pattern) index = text.indexOf(expression) while index >= 0: length = expression.matchedLength() setFormat(index, length, myClassFormat) index = text.indexOf(expression, index + length)
See the
Detailed Description
for examples of usingsetCurrentBlockState()
,currentBlockState()
andpreviousBlockState()
to handle syntaxes with constructs that span several text blocks
- PySide2.QtGui.QSyntaxHighlighter.previousBlockState()¶
- Return type:
int
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
- PySide2.QtGui.QSyntaxHighlighter.rehighlight()¶
Reapplies the highlighting to the whole document.
See also
- PySide2.QtGui.QSyntaxHighlighter.rehighlightBlock(block)¶
- Parameters:
block –
PySide2.QtGui.QTextBlock
Reapplies the highlighting to the given
QTextBlock
block
.See also
- PySide2.QtGui.QSyntaxHighlighter.setCurrentBlockState(newState)¶
- Parameters:
newState – int
Sets the state of the current text block to
newState
.See also
- PySide2.QtGui.QSyntaxHighlighter.setCurrentBlockUserData(data)¶
- Parameters:
Attaches the given
data
to the current text block. The ownership is passed to the underlying text document, i.e. the providedQTextBlockUserData
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 fromQTextBlockUserData
:class MyHighlighter(QSyntaxHighlighter): def highlightBlock(self, text): myClassFormat = QTextCharFormat() myClassFormat.setFontWeight(QFont.Bold) myClassFormat.setForeground(Qt.darkMagenta) pattern = QString("\\bMy[A-Za-z]+\\b") expression = QRegExp(pattern) index = text.indexOf(expression) while index >= 0: length = expression.matchedLength() setFormat(index, length, myClassFormat) index = text.indexOf(expression, index + length)
During cursor navigation in the associated editor, you can ask the current
QTextBlock
(retrieved using theblock()
function) if it has a user data object set and cast it to yourBlockData
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
- PySide2.QtGui.QSyntaxHighlighter.setDocument(doc)¶
- Parameters:
Installs the syntax highlighter on the given
QTextDocument
doc
. AQSyntaxHighlighter
can only be used with one document at a time.See also
- PySide2.QtGui.QSyntaxHighlighter.setFormat(start, count, color)¶
- Parameters:
start – int
count – int
color –
PySide2.QtGui.QColor
- PySide2.QtGui.QSyntaxHighlighter.setFormat(start, count, font)
- Parameters:
start – int
count – int
font –
PySide2.QtGui.QFont
- PySide2.QtGui.QSyntaxHighlighter.setFormat(start, count, format)
- Parameters:
start – int
count – int
format –
PySide2.QtGui.QTextCharFormat
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