bitWalk's: QPlainTextEditor に行番号を付ける～ PySide6 ～

2023-09-22

QPlainTextEditor に行番号を付ける～ PySide6 ～

PySide (Qt for Python) は、Qt（キュート）の Python バインディングで、GUI などを構築するためのクロスプラットフォームなライブラリです。配布ライセンスは LGPL で公開されています（商用ライセンスも有り）。最新のバージョンは Qt6 に対応した PySide6（記事執筆時点で 6.5.2）です。

QPlainTextEdit を利用した、行番号付きのシンプルなテキストエディタのサンプルが下記で紹介されていましたので、興味のある所だけ抜き出してみました^[1]。

なお、等幅フォント (QFontDatabase.FixedFont) を指定しています。

qt_plaintextedit_linenumber.py

	#!/usr/bin/env python
	# coding: utf-8
	# Reference:
	# https://doc.qt.io/qtforpython-6.2/examples/example_widgets__codeeditor.html

	import sys

	from PySide6.QtCore import (
	QRect,
	QSize,
	Qt,
	Slot,
	)
	from PySide6.QtGui import (
	QColor,
	QPainter,
	QTextFormat, QFontDatabase, QFontMetricsF,
	)
	from PySide6.QtWidgets import (
	QApplication,
	QMainWindow,
	QPlainTextEdit,
	QTextEdit,
	QWidget,
	)


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

	def sizeHint(self):
	return QSize(self._editor.lineNumberAreaWidth(), 0)

	def paintEvent(self, event):
	self._editor.lineNumberAreaPaintEvent(event)


	class PlainTextEdit(QPlainTextEdit):
	def __init__(self):
	super().__init__()
	self.setStyleSheet('QPlainTextEdit {background-color: white;}')
	self.setLineWrapMode(QPlainTextEdit.LineWrapMode.NoWrap)
	self.setFontConfig()
	self.lineNumberArea = LineNumberArea(self)
	self.blockCountChanged[int].connect(self.updateLineNumberAreaWidth)
	self.updateRequest[QRect, int].connect(self.updateLineNumberArea)
	self.updateLineNumberAreaWidth(0)
	self.highlightCurrentLine()

	@Slot()
	def highlightCurrentLine(self):
	extra_selections = []

	if not self.isReadOnly():
	selection = QTextEdit.ExtraSelection()

	line_color = QColor(Qt.yellow).lighter(160)
	selection.format.setBackground(line_color)

	selection.format.setProperty(QTextFormat.FullWidthSelection, True)

	selection.cursor = self.textCursor()
	selection.cursor.clearSelection()

	extra_selections.append(selection)

	self.setExtraSelections(extra_selections)

	def lineNumberAreaWidth(self):
	digits = 1
	max_num = max(1, self.blockCount())
	while max_num >= 10:
	max_num *= 0.1
	digits += 1

	space = 3 + self.fontMetrics().horizontalAdvance('9') * digits
	return space

	def lineNumberAreaPaintEvent(self, event):
	painter = QPainter(self.lineNumberArea)
	painter.fillRect(event.rect(), Qt.GlobalColor.white)
	block = self.firstVisibleBlock()
	blockNumber = block.blockNumber()
	offset = self.contentOffset()
	top = self.blockBoundingGeometry(block).translated(offset).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(blockNumber + 1)
	painter.setPen(Qt.black)
	width = self.lineNumberArea.width()
	height = self.fontMetrics().height()
	painter.drawText(0, top, width, height, Qt.AlignRight, number)

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

	# QPainter needs an explicit end().
	painter.end()

	def resizeEvent(self, e):
	super().resizeEvent(e)
	cr = self.contentsRect()
	width = self.lineNumberAreaWidth()
	rect = QRect(cr.left(), cr.top(), width, cr.height())
	self.lineNumberArea.setGeometry(rect)

	@Slot()
	def setFontConfig(self):
	font = QFontDatabase.systemFont(QFontDatabase.FixedFont)
	self.setFont(font)

	fm = QFontMetricsF(font)
	spaceWidth = fm.horizontalAdvance(' ')
	self.setTabStopDistance(spaceWidth * 4)

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

	if rect.contains(self.viewport().rect()):
	self.updateLineNumberAreaWidth(0)

	@Slot()
	def updateLineNumberAreaWidth(self, newBlockCount):
	self.setViewportMargins(self.lineNumberAreaWidth(), 0, 0, 0)


	class Example(QMainWindow):
	def __init__(self):
	super().__init__()
	self.initUI()
	self.setWindowTitle('Simple Editor')

	def initUI(self):
	tedit = PlainTextEdit()
	self.setCentralWidget(tedit)


	def main():
	app = QApplication(sys.argv)
	ex = Example()
	ex.show()
	sys.exit(app.exec())


	if __name__ == '__main__':
	main()