Syntax Highlighter Example

The Syntax Highlighter example shows how to perform simple syntax highlighting.

syntaxhighlighter.py

# Copyright (C) 2013 Riverbank Computing Limited.
# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

"""PySide6 port of the widgets/richtext/syntaxhighlighter example from Qt v5.x"""

import os
from pathlib import Path
import sys
import re
from PySide6.QtCore import (QFile, Qt, QTextStream)
from PySide6.QtGui import (QColor, QFont, QFontDatabase, QKeySequence,
                           QSyntaxHighlighter, QTextCharFormat)
from PySide6.QtWidgets import (QApplication, QFileDialog, QMainWindow,
    QPlainTextEdit)


class MainWindow(QMainWindow):
    def __init__(self, parent=None):
        QMainWindow.__init__(self, parent)

        self._highlighter = Highlighter()

        self.setup_file_menu()
        self.setup_editor()

        self.setCentralWidget(self._editor)
        self.setWindowTitle(self.tr("Syntax Highlighter"))

    def new_file(self):
        self._editor.clear()

    def open_file(self, path=""):
        file_name = path

        if not file_name:
            file_name, _ = QFileDialog.getOpenFileName(self, self.tr("Open File"), "",
                                                       "Python Files (*.py)")

        if file_name:
            in_file = QFile(file_name)
            if in_file.open(QFile.ReadOnly | QFile.Text):
                stream = QTextStream(in_file)
                self._editor.setPlainText(stream.readAll())

    def setup_editor(self):
        class_format = QTextCharFormat()
        class_format.setFontWeight(QFont.Bold)
        class_format.setForeground(Qt.blue)
        pattern = r'^\s*class\s+\w+\(.*$'
        self._highlighter.add_mapping(pattern, class_format)

        function_format = QTextCharFormat()
        function_format.setFontItalic(True)
        function_format.setForeground(Qt.blue)
        pattern = r'^\s*def\s+\w+\s*\(.*\)\s*:\s*$'
        self._highlighter.add_mapping(pattern, function_format)

        comment_format = QTextCharFormat()
        comment_format.setBackground(QColor("#77ff77"))
        self._highlighter.add_mapping(r'^\s*#.*$', comment_format)

        font = QFontDatabase.systemFont(QFontDatabase.FixedFont)
        self._editor = QPlainTextEdit()
        self._editor.setFont(font)
        self._highlighter.setDocument(self._editor.document())

    def setup_file_menu(self):
        file_menu = self.menuBar().addMenu(self.tr("&File"))

        new_file_act = file_menu.addAction(self.tr("&New..."))
        new_file_act.setShortcut(QKeySequence(QKeySequence.New))
        new_file_act.triggered.connect(self.new_file)

        open_file_act = file_menu.addAction(self.tr("&Open..."))
        open_file_act.setShortcut(QKeySequence(QKeySequence.Open))
        open_file_act.triggered.connect(self.open_file)

        quit_act = file_menu.addAction(self.tr("E&xit"))
        quit_act.setShortcut(QKeySequence(QKeySequence.Quit))
        quit_act.triggered.connect(self.close)

        help_menu = self.menuBar().addMenu("&Help")
        help_menu.addAction("About &Qt", qApp.aboutQt)


class Highlighter(QSyntaxHighlighter):
    def __init__(self, parent=None):
        QSyntaxHighlighter.__init__(self, parent)

        self._mappings = {}

    def add_mapping(self, pattern, format):
        self._mappings[pattern] = format

    def highlightBlock(self, text):
        for pattern, format in self._mappings.items():
            for match in re.finditer(pattern, text):
                start, end = match.span()
                self.setFormat(start, end - start, format)


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MainWindow()
    window.resize(640, 512)
    window.show()
    window.open_file(os.fspath(Path(__file__).resolve()))
    sys.exit(app.exec())