CodeEditor(PyQt4)

#!/usr/bin/python
# -*- coding: utf-8 -*-

import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *
from highlighter import MyHighlighter
from highlighter import HighlightingRule

class CodeEditor(QPlainTextEdit):
    def __init__(self, parent = None):
        QPlainTextEdit.__init__(self, parent)
        self.lineNumberArea = LineNumberArea(self)
        
        self.connect(self, SIGNAL('blockCountChanged(int)'), \
                     self.updateLineNumberAreaWidth)
        self.connect(self, SIGNAL('updateRequest(const QRect &, int)'), \
                     self.updateLineNumberArea)
        self.connect(self, SIGNAL('cursorPositionChanged()'), \
                     self.highlightCurrentLine)
        
        self.updateLineNumberAreaWidth(0)
        self.highlightCurrentLine()
    def highlightCurrentLine(self):
        extraSelections = QTextEdit.extraSelections(QTextEdit())
        if not self.isReadOnly():
            selection = QTextEdit.ExtraSelection()
            lineColor = QColor(Qt.yellow).lighter(160)
            selection.format.setBackground(lineColor)
            selection.format.setProperty(QTextFormat.FullWidthSelection, True)
            selection.cursor = self.textCursor()
            selection.cursor.clearSelection()
            extraSelections.append(selection)
        self.setExtraSelections(extraSelections)
    def lineNumberAreaWidth(self):
        digits = 1
        Max = max(1, self.blockCount())
        while (Max >= 10) :
            Max /= 10
            digits += 1
        space = 3 + self.fontMetrics().width('9') * digits 
        return space
    def updateLineNumberAreaWidth(self, newBlockCount):
        self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0)
    def updateLineNumberArea(self, rect, dy):
        if dy:
            self.lineNumberArea.scroll(0, dy)
        else:
            self.lineNumberArea.update(0, rect.y(), \
                                       self.lineNumberAreaWidth(), \
                                       rect.height())
        if (rect.contains(self.viewport().rect())):
            self.updateLineNumberAreaWidth(0)
    def resizeEvent(self, e):
        QPlainTextEdit.resizeEvent(self, e)
        cr = self.contentsRect()
        self.lineNumberArea.setGeometry(QRect(cr.left(), cr.top(), \
                                              self.lineNumberAreaWidth(), \
                                              cr.height()))
    def lineNumberAreaPaintEvent(self, event):
        painter = QPainter(self.lineNumberArea)
        rect = event.rect()
        painter.fillRect(rect, Qt.lightGray)
        block = self.firstVisibleBlock()
        blockNumber = block.blockNumber()
        top = int(self.blockBoundingGeometry(block).translated(\
            self.contentOffset()).top())
        bottom = top + int(self.blockBoundingRect(block).height())
        while (block.isValid() and top <= rect.bottom()):
            if (block.isVisible() and bottom >= rect.top()):
                number = QString.number(blockNumber + 1)
                painter.setPen(Qt.black)
                painter.drawText(0, top, self.lineNumberArea.width(), \
                                 self.fontMetrics().height(), \
                                 Qt.AlignRight, number)
            block = block.next()
            top = bottom
            bottom = top + int(self.blockBoundingRect(block).height())
            blockNumber += 1

class LineNumberArea(QWidget):
    def __init__(self, editor):
        QWidget.__init__(self, editor)
        self.codeEditor = editor
    def sizeHint(self):
        return QSize(codeEditor.lineNumberAreaWidth(), 0)
    def paintEvent(self, event):
        self.codeEditor.lineNumberAreaPaintEvent(event)

def main():
    app = QApplication(sys.argv)
    editor = CodeEditor()
    editor.setWindowTitle('Code Editor Example')
    editor.show()
    app.exec_()
    
if __name__ == '__main__':
    main()