pyqt 中的代码编辑器示例

我尝试学习一些Qt（PyQt）。为此，我使用了代码编辑器示例 http://doc.qt.io/qt-4.8/qt-widgets-codeeditor-example.html的文档。当前行的突出显示效果很好。但行号不显示。

实际上LineNumberArea.paintEvent甚至没有被调用。后来也没有CodeEditor.lineNumberAreaPaintEvent。据我了解，数字栏的paintEvent应该定期调用。或者至少当有一个updateRequest或滚动事件（由调用CodeEditor.updateLineNumberArea).

以下是我将代码从 C++ 移植到 Python 的方法：

import sys
from PyQt4.QtGui import *
from PyQt4.QtCore import *

import numpy as np

class LineNumberArea(QWidget):
    def __init__(self, editor):
        super().__init__()
        self.editor = editor


    def sizeHint(self):
        return Qsize(self.editor.lineNumberAreaWidth(), 0)


    def paintEvent(self, event):
        print('LineNumberArea.paintEvent')
        self.editor.lineNumberAreaPaintEvent(event)


class CodeEditor(QPlainTextEdit):
    def __init__(self):
        super().__init__()
        self.lineNumberArea = LineNumberArea(self)

        self.connect(self, SIGNAL('blockCountChanged(int)'), self.updateLineNumberAreaWidth)
        self.connect(self, SIGNAL('updateRequest(QRect,int)'), self.updateLineNumberArea)
        self.connect(self, SIGNAL('cursorPositionChanged()'), self.highlightCurrentLine)

        self.updateLineNumberAreaWidth(0)


    def lineNumberAreaWidth(self):
        """ This method has been slightly modified (use of log and uses actual
        font rather than standart.) """
        n_lines = self.blockCount()
        digits = np.ceil(np.log10(n_lines)) + 1
        return digits * QFontMetrics(self.font()).width('9') + 3


    def updateLineNumberAreaWidth(self, _):
        print('CodeEditor.updateLineNumberAreaWidth: margin = {}'.format(self.lineNumberAreaWidth()))
        self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0)


    def updateLineNumberArea(self, rect, dy):
        print('CodeEditor.updateLineNumberArea: rect = {}, dy = {}'.format(rect, dy))

        if dy:
            self.lineNumberArea.scroll(0, dy)
        else:
            self.lineNumberArea.update(0, rect.y(), self.lineNumberArea.width(),
                                       rect.height())

        print('CodeEditor.updateLineNumberArea: rect.contains(self.viewport().rect()) = {}'.format(rect.contains(self.viewport().rect())))
        if rect.contains(self.viewport().rect()):
            self.updateLineNumberAreaWidth(0)


    def resizeEvent(self, event):
        super().resizeEvent(event)

        cr = self.contentsRect();
        self.lineNumberArea.setGeometry(QRect(cr.left(), cr.top(),
                                        self.lineNumberAreaWidth(), cr.height()))

    def lineNumberAreaPaintEvent(self, event):
        print('CodeEditor.lineNumberAreaPaintEvent')
        painter(self.lineNumberArea)
        painter.fillRect(event.rect(), Qt.lightGray)

        block = self.firstVisibleBlock()
        blockNumber = block.blockNumber()
        top = self.blockBoundingGeometry(block).translated(self.contentOffset()).top()
        bottom = top + self.blockBoundingRect(block).height()

        # Just to make sure I use the right font
        height = QFontMetrics(self.font()).height()
        while block.isValid() and (top <= event.rect().bottom()):
            if block.isVisible() and (bottom >= event.rect().top()):
                number = str(blockNumber + 1)
                painter.setPen(Qt.black)
                painter.drawText(0, top, lineNumberArea.width(), height,
                                 Qt.AlignRight, number)

            block = block.next()
            top = bottom
            bottom = top + self.blockBoundingRect(block).height()
            blockNumber += 1


    def highlightCurrentLine(self):
        extraSelections = []

        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)


if __name__ == "__main__":
    app = QApplication(sys.argv)

    txt = CodeEditor()
    txt.show()

    sys.exit(app.exec_())

任何帮助将不胜感激。

如果重要的话： 蟒蛇：3.4.3，PyQt：4.8.6，操作系统：RHEL 6

你的例子看起来大部分是正确的。缺少绘制事件的问题是由于未在LineNumberArea小部件。所以你只需要：

class LineNumberArea(QWidget):
    def __init__(self, editor):
        super().__init__(editor)

另外，lineNumberAreaPaintEvent方法有一些问题，但很容易修复：

def lineNumberAreaPaintEvent(self, event):
    # missing constructor
    painter = QPainter(self.lineNumberArea)
    ...
    # no need to use QFontMetrics
    height = self.fontMetrics().height()
    ...
            # missing self
            painter.drawText(0, top, self.lineNumberArea.width(), height,
                             Qt.AlignRight, number)

我不确定你想用你的实现来做什么lineNumberAreaWidth，因为它似乎没有给出正确的结果。不过，最初的实现完全按照预期工作（而且速度也快得多）：

def lineNumberAreaWidth(self):
    digits = 1
    count = max(1, self.blockCount())
    while count >= 10:
        count /= 10
        digits += 1
    space = 3 + self.fontMetrics().width('9') * digits
    return space