root/branch/twedit/CustomLexer.py

import sys
from PyQt4 import QtCore, QtGui, Qsci


class MainWindow(QtGui.QMainWindow):
      def __init__(self):
            QtGui.QMainWindow.__init__(self)
            self.setWindowTitle('Custom Lexer Example')
            self.setGeometry(QtCore.QRect(50,200,400,400))
            self.editor = Qsci.QsciScintilla(self)
            self.editor.setUtf8(True)
            self.editor.setMarginWidth(2, 15)
            self.editor.setFolding(True)
            self.setCentralWidget(self.editor)
            self.lexer = CustomLexer(self.editor)
            self.editor.setLexer(self.lexer)
            self.editor.setText('\n# sample source\n\nfoo = 1\nbar = 2\n')


class CustomLexer(Qsci.QsciLexerCustom):
      def __init__(self, parent):
            Qsci.QsciLexerCustom.__init__(self, parent)
            self._styles = {
                 0: 'Default',
                 1: 'Comment',
                 2: 'Key',
                 3: 'Assignment',
                 4: 'Value',
                 }
            for key,value in self._styles.iteritems():
                 setattr(self, value, key)

      def description(self, style):
            return self._styles.get(style, '')

      def defaultColor(self, style):
            if style == self.Default:
                 return QtGui.QColor('#000000')
            elif style == self.Comment:
                 return QtGui.QColor('#C0C0C0')
            elif style == self.Key:
                 return QtGui.QColor('#0000CC')
            elif style == self.Assignment:
                 return QtGui.QColor('#CC0000')
            elif style == self.Value:
                 return QtGui.QColor('#00CC00')
            return Qsci.QsciLexerCustom.defaultColor(self, style)

      def styleText(self, start, end):
            editor = self.editor()
            if editor is None:
                 return

            # scintilla works with encoded bytes, not decoded characters.
            # this matters if the source contains non-ascii characters and
            # a multi-byte encoding is used (e.g. utf-8)
            source = ''
            if end > editor.length():
                 end = editor.length()
            if end > start:
                 if sys.hexversion >= 0x02060000:
                      # faster when styling big files, but needs python 2.6
                      source = bytearray(end - start)
                      editor.SendScintilla(
                            editor.SCI_GETTEXTRANGE, start, end, source)
                 else:
                      source = unicode(editor.text()
                                            ).encode('utf-8')[start:end]
            if not source:
                 return

            # the line index will also be needed to implement folding
            index = editor.SendScintilla(editor.SCI_LINEFROMPOSITION, start)
            if index > 0:
                 # the previous state may be needed for multi-line styling
                 pos = editor.SendScintilla(
                              editor.SCI_GETLINEENDPOSITION, index - 1)
                 state = editor.SendScintilla(editor.SCI_GETSTYLEAT, pos)
            else:
                 state = self.Default

            set_style = self.setStyling
            self.startStyling(start, 0x1f)

            # scintilla always asks to style whole lines
            for line in source.splitlines(True):
                 length = len(line)
                 if line.startswith('#'):
                      state = self.Comment
                 else:
                      # the following will style lines like "x = 0"
                      pos = line.find('=')
                      if pos > 0:
                            set_style(pos, self.Key)
                            set_style(1, self.Assignment)
                            length = length - pos - 1
                            state = self.Value
                      else:
                            state = self.Default
                 set_style(length, state)
                 # folding implementation goes here
                 index += 1


if __name__ == "__main__":
      app = QtGui.QApplication(sys.argv)
      app.connect(app, QtCore.SIGNAL('lastWindowClosed()'),
                      QtCore.SLOT('quit()'))
      win = MainWindow()
      win.show()
      sys.exit(app.exec_())