markdowneditor#

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document.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause


from PySide6.QtCore import QObject, Property, Signal


class Document(QObject):

    textChanged = Signal(str)

    def __init__(self, parent=None):
        super().__init__(parent)
        self._text = ''

    def text(self):
        return self._text

    def setText(self, t):
        if t != self._text:
            self._text = t
            self.textChanged.emit(t)

    text = Property(str, text, setText, notify=textChanged)

main.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

"""PySide6 Markdown Editor Example"""

import sys

from PySide6.QtCore import QCoreApplication
from PySide6.QtWidgets import QApplication

from mainwindow import MainWindow
import rc_markdowneditor


if __name__ == '__main__':
    app = QApplication(sys.argv)
    QCoreApplication.setOrganizationName("QtExamples")
    window = MainWindow()
    window.show()
    sys.exit(app.exec())

mainwindow.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause


from PySide6.QtCore import QDir, QFile, QIODevice, QUrl, Qt, Slot
from PySide6.QtGui import QFontDatabase
from PySide6.QtWebChannel import QWebChannel
from PySide6.QtWidgets import QDialog, QFileDialog, QMainWindow, QMessageBox

from ui_mainwindow import Ui_MainWindow
from document import Document
from previewpage import PreviewPage


class MainWindow(QMainWindow):

    def __init__(self, parent=None):
        super().__init__(parent)
        self.m_file_path = ''
        self.m_content = Document()
        self._ui = Ui_MainWindow()
        self._ui.setupUi(self)
        font = QFontDatabase.systemFont(QFontDatabase.FixedFont)
        self._ui.editor.setFont(font)
        self._ui.preview.setContextMenuPolicy(Qt.NoContextMenu)
        self._page = PreviewPage(self)
        self._ui.preview.setPage(self._page)

        self._ui.editor.textChanged.connect(self.plainTextEditChanged)

        self._channel = QWebChannel(self)
        self._channel.registerObject("content", self.m_content)
        self._page.setWebChannel(self._channel)

        self._ui.preview.setUrl(QUrl("qrc:/index.html"))

        self._ui.actionNew.triggered.connect(self.onFileNew)
        self._ui.actionOpen.triggered.connect(self.onFileOpen)
        self._ui.actionSave.triggered.connect(self.onFileSave)
        self._ui.actionSaveAs.triggered.connect(self.onFileSaveAs)
        self._ui.actionExit.triggered.connect(self.close)

        self._ui.editor.document().modificationChanged.connect(self._ui.actionSave.setEnabled)

        defaultTextFile = QFile(":/default.md")
        defaultTextFile.open(QIODevice.ReadOnly)
        data = defaultTextFile.readAll()
        self._ui.editor.setPlainText(data.data().decode('utf8'))

    @Slot()
    def plainTextEditChanged(self):
        self.m_content.setText(self._ui.editor.toPlainText())

    @Slot(str)
    def openFile(self, path):
        f = QFile(path)
        name = QDir.toNativeSeparators(path)
        if not f.open(QIODevice.ReadOnly):
            error = f.errorString()
            QMessageBox.warning(self, self.windowTitle(),
                                f"Could not open file {name}: {error}")
            return
        self.m_file_path = path
        data = f.readAll()
        self._ui.editor.setPlainText(data.data().decode('utf8'))
        self.statusBar().showMessage(f"Opened {name}")

    def isModified(self):
        return self._ui.editor.document().isModified()

    @Slot()
    def onFileNew(self):
        if self.isModified():
            m = "You have unsaved changes. Do you want to create a new document anyway?"
            button = QMessageBox.question(self, self.windowTitle(), m)
            if button != QMessageBox.Yes:
                return

        self.m_file_path = ''
        self._ui.editor.setPlainText("## New document")
        self._ui.editor.document().setModified(False)

    @Slot()
    def onFileOpen(self):
        if self.isModified():
            m = "You have unsaved changes. Do you want to open a new document anyway?"
            button = QMessageBox.question(self, self.windowTitle(), m)
            if button != QMessageBox.Yes:
                return
        dialog = QFileDialog(self)
        dialog.setWindowTitle("Open MarkDown File")
        dialog.setMimeTypeFilters(["text/markdown"])
        dialog.setAcceptMode(QFileDialog.AcceptOpen)
        if dialog.exec() == QDialog.Accepted:
            self.openFile(dialog.selectedFiles()[0])

    @Slot()
    def onFileSave(self):
        if not self.m_file_path:
            self.onFileSaveAs()
        if not self.m_file_path:
            return

        f = QFile(self.m_file_path)
        name = QDir.toNativeSeparators(self.m_file_path)
        if not f.open(QIODevice.WriteOnly | QIODevice.Text):
            error = f.errorString()
            QMessageBox.warning(self, self.windowTitle(),
                                f"Could not write to file {name}: {error}")
            return
        text = self._ui.editor.toPlainText()
        f.write(bytes(text, encoding='utf8'))
        f.close()
        self._ui.editor.document().setModified(False)
        self.statusBar().showMessage(f"Wrote {name}")

    @Slot()
    def onFileSaveAs(self):
        dialog = QFileDialog(self)
        dialog.setWindowTitle("Save MarkDown File")
        dialog.setMimeTypeFilters(["text/markdown"])
        dialog.setAcceptMode(QFileDialog.AcceptSave)
        dialog.setDefaultSuffix("md")
        if dialog.exec() != QDialog.Accepted:
            return
        path = dialog.selectedFiles()[0]
        self.m_file_path = path
        self.onFileSave()

    def closeEvent(self, event):
        if self.isModified():
            m = "You have unsaved changes. Do you want to exit anyway?"
            button = QMessageBox.question(self, self.windowTitle(), m)
            if button != QMessageBox.Yes:
                event.ignore()
            else:
                event.accept()

mainwindow.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>800</width>
    <height>600</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MarkDown Editor</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <layout class="QHBoxLayout" name="horizontalLayout">
    <item>
     <widget class="QSplitter" name="splitter">
      <property name="orientation">
       <enum>Qt::Horizontal</enum>
      </property>
      <widget class="QPlainTextEdit" name="editor"/>
      <widget class="QWebEngineView" name="preview" native="true"/>
     </widget>
    </item>
   </layout>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>800</width>
     <height>26</height>
    </rect>
   </property>
   <widget class="QMenu" name="menu_File">
    <property name="title">
     <string>&amp;File</string>
    </property>
    <addaction name="actionNew"/>
    <addaction name="actionOpen"/>
    <addaction name="actionSave"/>
    <addaction name="actionSaveAs"/>
    <addaction name="separator"/>
    <addaction name="actionExit"/>
   </widget>
   <addaction name="menu_File"/>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
  <action name="actionOpen">
   <property name="text">
    <string>&amp;Open...</string>
   </property>
   <property name="toolTip">
    <string>Open document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+O</string>
   </property>
  </action>
  <action name="actionSave">
   <property name="text">
    <string>&amp;Save</string>
   </property>
   <property name="toolTip">
    <string>Save current document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+S</string>
   </property>
  </action>
  <action name="actionExit">
   <property name="text">
    <string>E&amp;xit</string>
   </property>
   <property name="toolTip">
    <string>Exit editor</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+Q</string>
   </property>
  </action>
  <action name="actionSaveAs">
   <property name="text">
    <string>Save &amp;As...</string>
   </property>
   <property name="toolTip">
    <string>Save document under different name</string>
   </property>
  </action>
  <action name="actionNew">
   <property name="text">
    <string>&amp;New</string>
   </property>
   <property name="toolTip">
    <string>Create new document</string>
   </property>
   <property name="shortcut">
    <string>Ctrl+N</string>
   </property>
  </action>
 </widget>
 <resources/>
 <connections/>
</ui>

previewpage.py

# Copyright (C) 2022 The Qt Company Ltd.
# SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

from PySide6.QtGui import QDesktopServices
from PySide6.QtWebEngineCore import QWebEnginePage


class PreviewPage(QWebEnginePage):

    def __init__(self, parent=None):
        super().__init__(parent)

    def acceptNavigationRequest(self, url, type, isMainFrame):
        # Only allow qrc:/index.html.
        if url.scheme() == "qrc":
            return True
        QDesktopServices.openUrl(url)
        return False

resources/markdowneditor.qrc

<RCC>
    <qresource prefix="/">
        <file>default.md</file>
        <file>index.html</file>
        <file>3rdparty/markdown.css</file>
        <file>3rdparty/marked.js</file>
    </qresource>
</RCC>