qt plaintextedit实现选择文本时行号高亮

你可以通过重载QPlainTextEdit的paintEvent()函数，自定义绘制行号的方式，然后在selectionChanged()信号中重新绘制高亮行。以下是一个简单的实现示例：

from PyQt5.QtGui import QTextCursor, QColor, QPainter
from PyQt5.QtWidgets import QPlainTextEdit


class LineNumberTextEdit(QPlainTextEdit):
    def __init__(self, parent=None):
        super(LineNumberTextEdit, self).__init__(parent)
        self.current_line = None
        self.line_number_area_width = 50

    def paintEvent(self, event):
        super(LineNumberTextEdit, self).paintEvent(event)
        if self.current_line:
            painter = QPainter(self.viewport())
            painter.fillRect(0, self.current_line * self.fontMetrics().height(), self.width(), self.fontMetrics().height(), QColor(255, 200, 0))

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

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

    def updateLineNumberAreaWidth(self):
        self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0)

    def lineNumberAreaPaintEvent(self, event):
        painter = QPainter(self.lineNumberArea)
        painter.fillRect(event.rect(), QColor(240, 240, 240))
        block = self.firstVisibleBlock()
        block_number = block.blockNumber()
        top = self.blockBoundingGeometry(block).translated(self.contentOffset()).top()
        bottom = top + self.blockBoundingRect(block).height()
        while block.isValid() and top <= event.rect().bottom():
            if block.isVisible() and bottom >= event.rect().top():
                number = str(block_number + 1)
                painter.setPen(QColor(150, 150, 150))
                painter.drawText(0, top, self.lineNumberArea.width(), self.fontMetrics().height(), Qt.AlignRight, number)
            block = block.next()
            top = bottom
            bottom = top + self.blockBoundingRect(block).height()
            block_number += 1

    def lineNumberAreaMousePressEvent(self, event):
        self.current_line = None
        self.viewport().update()

    def lineNumberAreaMouseMoveEvent(self, event):
        cursor = self.cursorForPosition(event.pos())
        if not cursor.isNull():
            self.current_line = cursor.blockNumber()
            self.viewport().update()

    def lineNumberAreaLeaveEvent(self, event):
        self.current_line = None
        self.viewport().update()

    def lineNumberAreaSizeHint(self):
        return QSize(self.lineNumberAreaWidth(), 0)

    def updateLineNumberArea(self, rect):
        self.lineNumberArea.update(0, rect.y(), self.lineNumberArea.width(), rect.height())

    def resizeLineNumberArea(self):
        self.lineNumberArea.setGeometry(0, 0, self.lineNumberAreaWidth(), self.height())

    def showEvent(self, event):
        super(LineNumberTextEdit, self).showEvent(event)
        if not self.lineNumberArea:
            self.lineNumberArea = LineNumberArea(self)
            self.connect(self.lineNumberArea, SIGNAL('updateLineNumberArea'), self.updateLineNumberArea)
            self.connect(self.lineNumberArea, SIGNAL('resizeLineNumberArea'), self.resizeLineNumberArea)
        self.lineNumberArea.show()

    def hideEvent(self, event):
        super(LineNumberTextEdit, self).hideEvent(event)
        if self.lineNumberArea:
            self.lineNumberArea.hide()

    def scrollContentsBy(self, dx, dy):
        super(LineNumberTextEdit, self).scrollContentsBy(dx, dy)
        self.lineNumberArea.scroll(0, dy)

    def resizeEvent(self, event):
        super(LineNumberTextEdit, self).resizeEvent(event)
        self.lineNumberArea.resizeLineNumberArea()

    def selectionChanged(self):
        super(LineNumberTextEdit, self).selectionChanged()
        self.viewport().update()

    def keyPressEvent(self, event):
        if event.modifiers() == Qt.ControlModifier and event.key() == Qt.Key_C:
            cursor = self.textCursor()
            selected_text = cursor.selectedText()
            lines = selected_text.split('\n')
            if len(lines) > 1:
                for i, line in enumerate(lines):
                    if i == len(lines) - 1:
                        lines[i] = line
                    else:
                        lines[i] = line + '\n'
                QApplication.clipboard().setText(selected_text)
            else:
                super(LineNumberTextEdit, self).keyPressEvent(event)
        else:
            super(LineNumberTextEdit, self).keyPressEvent(event)

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.current_line = None
            self.viewport().update()
        super(LineNumberTextEdit, self).mousePressEvent(event)

    def mouseMoveEvent(self, event):
        cursor = self.cursorForPosition(event.pos())
        if not cursor.isNull():
            self.current_line = cursor.blockNumber()
            self.viewport().update()
        super(LineNumberTextEdit, self).mouseMoveEvent(event)

    def leaveEvent(self, event):
        self.current_line = None
        self.viewport().update()
        super(LineNumberTextEdit, self).leaveEvent(event)

    def focusInEvent(self, event):
        super(LineNumberTextEdit, self).focusInEvent(event)
        self.current_line = None
        self.viewport().update()

    def focusOutEvent(self, event):
        super(LineNumberTextEdit, self).focusOutEvent(event)
        self.current_line = None
        self.viewport().update()

在这个示例中，我们继承了QPlainTextEdit并添加了一些自定义行为。其中，我们使用了一个LineNumberArea类来显示行号，并在编辑器的paintEvent()中绘制高亮行。

在构造函数中，我们初始化了一些变量和信号连接。我们还创建了一个LineNumberArea对象，并将其与updateLineNumberArea()和resizeLineNumberArea()信号连接起来。这样，我们可以在编辑器的大小发生变化时调整行号区域的大小。

在paintEvent()函数中，我们首先调用父类的paintEvent()函数，以便在编辑器中绘制文本。然后，如果当前行不为空，我们绘制黄色矩形来高亮当前行。

在resizeEvent()函数中，我们更新行号区域的宽度，并在updateLineNumberArea()函数中更新行号区域的绘图。

在selectionChanged()函数中，我们重新绘制高亮行。

在mousePressEvent()、mouseMoveEvent()和leaveEvent()函数中，我们设置当前行为None，并在viewport()上调用update()函数，从而清除高亮行。

最后，我们覆盖了QPlainTextEdit的keyPressEvent()函数，以便在按下Ctrl+C键时复制多行文本。我们还覆盖了focusInEvent()和focusOutEvent()函数，以便在编辑器失去焦点时清除高亮行。