原控件是QPlainTextEdit 移植到了QTextEdit上 使用了借助光标位置进行补偿的方式，来保证滚动行数精确满足要求。
from PyQt5.QtCore import Qt, QRect, QSize, QPoint from PyQt5.QtWidgets import QWidget, QPlainTextEdit, QTextEdit from PyQt5.QtGui import QColor, QPainter, QTextFormat, QKeyEvent, QWheelEvent, QMouseEvent, QTextCursor class QLineNumberArea(QWidget): def __init__(self, editor): super().__init__(editor) self.codeEditor = editor def sizeHint(self): return QSize(self.editor.lineNumberAreaWidth(), 0) def paintEvent(self, event): print('paint!!!!!') self.codeEditor.lineNumberAreaPaintEvent(event) class QCodeEditor(QTextEdit): def __init__(self, parent=None): super().__init__(parent) self.lineNumberArea = QLineNumberArea(self) self.setText('aa\n' * 20) self.document().blockCountChanged.connect(self.updateLineNumberAreaWidth) self.document().cursorPositionChanged.connect(self.highlightCurrentLine) self.verticalScrollBar().sliderMoved.connect(self.on_scroll) # self.verticalScrollBar().sliderPressed.connect(self.on_scroll) self.verticalScrollBar().sliderReleased.connect(self.on_scroll) # self.verticalScrollBar( # self.verticalScrollBar().sliderMoved.connect(self.on_scroll) # self.verticalScrollBar().act # .connect(self.on_scroll) self.updateLineNumberAreaWidth(0) def wheelEvent(self, d: 'QWheelEvent') -> None: self.on_scroll(d) super(QCodeEditor, self).wheelEvent(d) def on_scroll(self, event: QWheelEvent=None): # print('on_scroll', event.x(), event.y()) self.lineNumberArea.update() # scroll(0, None) def keyPressEvent(self, e: QKeyEvent) -> None: super(QCodeEditor, self).keyPressEvent(e) self.updateLineNumberArea(QRect(100, 100, 100, 100), None) self.lineNumberArea.update() # if e==Qt.Key_Return: # self.updateLineNumberAreaWidth(e) def mousePressEvent(self, e: 'QMouseEvent') -> None: block_number = self.cursorForPosition(self.cursor().pos()).blockNumber() print(block_number) super().mousePressEvent(e) # tc = self.textCursor() # # position=self.document.findBlockByNumber(1).position() # tc.setPosition(1, QTextCursor.MoveAnchor) # self.setTextCursor(tc) self.update() def lineNumberAreaWidth(self): digits = 1 block_count = self.document().blockCount() max_value = max(1, block_count) while max_value >= 10: max_value /= 10 digits += 1 space = 3 + self.fontMetrics().width('9') * digits return space def updateLineNumberAreaWidth(self, e): self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0) def updateLineNumberArea(self, rect, dy): # rect = self.height() if dy: self.lineNumberArea.scroll(0, dy) else: self.lineNumberArea.update(0, self.geometry().x(), 10, self.height()) 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 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) def lineNumberAreaPaintEvent(self, event): cursor = QTextCursor(self.document()) painter = QPainter(self.lineNumberArea) painter.fillRect(event.rect(), Qt.lightGray) line_height = self.fontMetrics().height() block_number = self.cursorForPosition(QPoint(0, int(line_height/2))).blockNumber() first_visible_block = self.document().findBlock(block_number) blockNumber = block_number cursor.setPosition(self.cursorForPosition(QPoint(0, int(line_height/2))).position()) rect = self.cursorRect() scroll_compensation = rect.y()-int(rect.y() / line_height)*line_height# 补偿，从光标开始。 print('compensition',scroll_compensation) # print(rect) # self.document().findBlockByLineNumber().document().w top = 0 # QPoint(0, 0)#self.blockBoundingGeometry(first_visible_block).translated(self.contentOffset()).top() last_block_number = self.cursorForPosition(QPoint(0, self.height()-1)).blockNumber() last_visible_block =self.document().findBlock(last_block_number) # print(last_block_number) # self.document().findBlockByLineNumber(). # print(block_number,last_block_number,'height:',line_height) if scroll_compensation<-9: top = 0+18+scroll_compensation else: top=scroll_compensation bottom = top + line_height # self.blockBoundingRect(first_visible_block).height() # Just to make sure I use the right font height = self.fontMetrics().height() block = first_visible_block while block.isValid() and (top <= event.rect().bottom()) and blockNumber<last_block_number: if block.isVisible(): number = str(blockNumber + 1) painter.setPen(Qt.black) # print(top, self.lineNumberArea.width(), height, number) painter.drawText(0, top, self.lineNumberArea.width(), height, Qt.AlignRight, number) block = block.next() top = bottom bottom = top + line_height # self.blockBoundingRect(block).height() blockNumber += 1 if __name__ == '__main__': import sys from PyQt5.QtWidgets import QApplication app = QApplication(sys.argv) codeEditor = QCodeEditor() codeEditor.show() sys.exit(app.exec_())