notepad

notepad.py

import sys
from PyQt5.QtWidgets import (QApplication, QMainWindow, QAction, QFileDialog, QTabWidget,
                             QPlainTextEdit, QWidget, QTextEdit)
from PyQt5.QtGui import QColor, QPainter, QTextFormat
from PyQt5.QtCore import Qt, QRect, QSize

class LineNumberArea(QWidget):
    def __init__(self, editor):
        super().__init__(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.lineNumberArea = LineNumberArea(self)
        self.blockCountChanged.connect(self.updateLineNumberAreaWidth)
        self.updateRequest.connect(self.updateLineNumberArea)
        self.cursorPositionChanged.connect(self.highlightCurrentLine)
        self.updateLineNumberAreaWidth(0)

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

    def updateLineNumberAreaWidth(self, _):
        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.lineNumberArea.width(), rect.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 lineNumberAreaPaintEvent(self, event):
        painter = QPainter(self.lineNumberArea)
        painter.fillRect(event.rect(), Qt.lightGray)
        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(Qt.black)
                painter.drawText(0, int(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 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)

class Notepad(QMainWindow):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setGeometry(100, 100, 800, 600)
        self.setWindowTitle('Notepad')

        # Create tab widget
        self.tabs = QTabWidget()
        self.setCentralWidget(self.tabs)

        # Create first tab
        self.newFile()

        # Create menu bar
        menubar = self.menuBar()
        fileMenu = menubar.addMenu('File')

        # New file action
        newAction = QAction('New', self)
        newAction.setShortcut('Ctrl+N')
        newAction.triggered.connect(self.newFile)
        fileMenu.addAction(newAction)

        # Open file action
        openAction = QAction('Open', self)
        openAction.setShortcut('Ctrl+O')
        openAction.triggered.connect(self.openFile)
        fileMenu.addAction(openAction)

        self.show()

    def newFile(self):
        textEdit = PlainTextEdit()
        self.tabs.addTab(textEdit, f"Untitled {self.tabs.count() + 1}")
        self.tabs.setCurrentWidget(textEdit)

    def openFile(self):
        filename, _ = QFileDialog.getOpenFileName(self, "Open File", "", "Text Files (*.txt);;All Files (*)")
        if filename:
            with open(filename, 'r') as file:
                content = file.read()
                textEdit = PlainTextEdit()
                textEdit.setPlainText(content)
                self.tabs.addTab(textEdit, filename.split('/')[-1])
                self.tabs.setCurrentWidget(textEdit)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Notepad()
    sys.exit(app.exec_())