PyQt4 port of the richtext/syntaxhighlighter example from Qt v4.x

syntax_exmaple.py

#!/usr/bin/env python

"""PyQt4 port of the richtext/syntaxhighlighter example from Qt v4.x"""

from PyQt4 import QtCore, QtGui


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

        self.setupFileMenu()
        self.setupHelpMenu()
        self.setupEditor()

        self.setCentralWidget(self.editor)
        self.setWindowTitle("Syntax Highlighter")

    def about(self):
        QtGui.QMessageBox.about(self, "About Syntax Highlighter",
                "<p>The <b>Syntax Highlighter</b> example shows how to " \
                "perform simple syntax highlighting by subclassing the " \
                "QSyntaxHighlighter class and describing highlighting " \
                "rules using regular expressions.</p>")

    def newFile(self):
        self.editor.clear()

    def openFile(self, path=None):
        if not path:
            path = QtGui.QFileDialog.getOpenFileName(self, "Open File",
                    '', "C++ Files (*.cpp *.h)")

        if path:
            inFile = QtCore.QFile(path)
            if inFile.open(QtCore.QFile.ReadOnly | QtCore.QFile.Text):
                text = inFile.readAll()

                try:
                    # Python v3.
                    text = str(text, encoding='ascii')
                except TypeError:
                    # Python v2.
                    text = str(text)

                self.editor.setPlainText(text)

    def setupEditor(self):
        font = QtGui.QFont()
        font.setFamily('Courier')
        font.setFixedPitch(True)
        font.setPointSize(10)

        self.editor = QtGui.QTextEdit()
        self.editor.setFont(font)

        self.highlighter = Highlighter(self.editor.document())

    def setupFileMenu(self):
        fileMenu = QtGui.QMenu("&File", self)
        self.menuBar().addMenu(fileMenu)

        fileMenu.addAction("&New...", self.newFile, "Ctrl+N")
        fileMenu.addAction("&Open...", self.openFile, "Ctrl+O")
        fileMenu.addAction("E&xit", QtGui.qApp.quit, "Ctrl+Q")

    def setupHelpMenu(self):
        helpMenu = QtGui.QMenu("&Help", self)
        self.menuBar().addMenu(helpMenu)

        helpMenu.addAction("&About", self.about)
        helpMenu.addAction("About &Qt", QtGui.qApp.aboutQt)


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

        keywordFormat = QtGui.QTextCharFormat()
        keywordFormat.setForeground(QtCore.Qt.darkBlue)
        keywordFormat.setFontWeight(QtGui.QFont.Bold)

        keywordPatterns = ["\\bchar\\b", "\\bclass\\b", "\\bconst\\b",
                "\\bdouble\\b", "\\benum\\b", "\\bexplicit\\b", "\\bfriend\\b",
                "\\binline\\b", "\\bint\\b", "\\blong\\b", "\\bnamespace\\b",
                "\\boperator\\b", "\\bprivate\\b", "\\bprotected\\b",
                "\\bpublic\\b", "\\bshort\\b", "\\bsignals\\b", "\\bsigned\\b",
                "\\bslots\\b", "\\bstatic\\b", "\\bstruct\\b",
                "\\btemplate\\b", "\\btypedef\\b", "\\btypename\\b",
                "\\bunion\\b", "\\bunsigned\\b", "\\bvirtual\\b", "\\bvoid\\b",
                "\\bvolatile\\b"]

        self.highlightingRules = [(QtCore.QRegExp(pattern), keywordFormat)
                for pattern in keywordPatterns]

        classFormat = QtGui.QTextCharFormat()
        classFormat.setFontWeight(QtGui.QFont.Bold)
        classFormat.setForeground(QtCore.Qt.darkMagenta)
        self.highlightingRules.append((QtCore.QRegExp("\\bQ[A-Za-z]+\\b"),
                classFormat))

        singleLineCommentFormat = QtGui.QTextCharFormat()
        singleLineCommentFormat.setForeground(QtCore.Qt.red)
        self.highlightingRules.append((QtCore.QRegExp("//[^\n]*"),
                singleLineCommentFormat))

        self.multiLineCommentFormat = QtGui.QTextCharFormat()
        self.multiLineCommentFormat.setForeground(QtCore.Qt.red)

        quotationFormat = QtGui.QTextCharFormat()
        quotationFormat.setForeground(QtCore.Qt.darkGreen)
        self.highlightingRules.append((QtCore.QRegExp("\".*\""),
                quotationFormat))

        functionFormat = QtGui.QTextCharFormat()
        functionFormat.setFontItalic(True)
        functionFormat.setForeground(QtCore.Qt.blue)
        self.highlightingRules.append((QtCore.QRegExp("\\b[A-Za-z0-9_]+(?=\\()"),
                functionFormat))

        self.commentStartExpression = QtCore.QRegExp("/\\*")
        self.commentEndExpression = QtCore.QRegExp("\\*/")

    def highlightBlock(self, text):
        for pattern, format in self.highlightingRules:
            expression = QtCore.QRegExp(pattern)
            index = expression.indexIn(text)
            while index >= 0:
                length = expression.matchedLength()
                self.setFormat(index, length, format)
                index = expression.indexIn(text, index + length)

        self.setCurrentBlockState(0)

        startIndex = 0
        if self.previousBlockState() != 1:
            startIndex = self.commentStartExpression.indexIn(text)

        while startIndex >= 0:
            endIndex = self.commentEndExpression.indexIn(text, startIndex)

            if endIndex == -1:
                self.setCurrentBlockState(1)
                commentLength = len(text) - startIndex
            else:
                commentLength = endIndex - startIndex + self.commentEndExpression.matchedLength()

            self.setFormat(startIndex, commentLength,
                    self.multiLineCommentFormat)
            startIndex = self.commentStartExpression.indexIn(text,
                    startIndex + commentLength);


if __name__ == '__main__':

    import sys

    app = QtGui.QApplication(sys.argv)
    window = MainWindow()
    window.resize(640, 512)
    window.show()
    sys.exit(app.exec_())