Enhancement #2017403: Add a preview tab to Markdown "long text" editor (https://bugs.launchpad.net/calibre/+bug/2017403)

src/calibre/gui2/custom_column_widgets.py

@@ -18,6 +18,7 @@ from qt.core import (
 from calibre.ebooks.metadata import title_sort
 from calibre.gui2 import UNDEFINED_QDATETIME, elided_text, error_dialog, gprefs
 from calibre.gui2.comments_editor import Editor as CommentsEditor
+from calibre.gui2.markdown_editor import Editor as MarkdownEditor
 from calibre.gui2.complete2 import EditWithComplete as EWC
 from calibre.gui2.dialogs.tag_editor import TagEditor
 from calibre.gui2.library.delegates import ClearingDoubleSpinBox, ClearingSpinBox
@@ -467,6 +468,41 @@ class Comments(Base):
         self.signals_to_disconnect.append(self._tb.data_changed)
 
 
+class Markdown(Base):
+
+    def setup_ui(self, parent):
+        self._box = QGroupBox(parent)
+        self._box.setTitle(label_string(self.col_metadata['name']))
+        self._layout = QVBoxLayout()
+        self._tb = MarkdownEditor(self._box)
+        self._tb.setSizePolicy(QSizePolicy.Policy.Expanding, QSizePolicy.Policy.Minimum)
+        # self._tb.setTabChangesFocus(True)
+        self._layout.addWidget(self._tb)
+        self._box.setLayout(self._layout)
+        self.widgets = [self._box]
+
+    def setter(self, val):
+        self._tb.markdown = str(val or '').strip()
+
+    def getter(self):
+        val = self._tb.markdown.strip()
+        if not val:
+            val = None
+        return val
+
+    @property
+    def tab(self):
+        return self._tb.tab
+
+    @tab.setter
+    def tab(self, val):
+        self._tb.tab = val
+
+    def connect_data_changed(self, slot):
+        self._tb.editor.textChanged.connect(slot)
+        self.signals_to_disconnect.append(self._tb.editor.textChanged)
+
+
 class MultipleWidget(QWidget):
 
     def __init__(self, parent, only_manage_items=False, widget=EditWithComplete, name=None):
@@ -780,8 +816,10 @@ def comments_factory(db, key, parent):
     ctype = fm.get('display', {}).get('interpret_as', 'html')
     if ctype == 'short-text':
         return SimpleText(db, key, parent)
-    if ctype in ('long-text', 'markdown'):
+    if ctype == 'long-text':
         return LongText(db, key, parent)
+    if ctype == 'markdown':
+        return Markdown(db, key, parent)
     return Comments(db, key, parent)
 
 

src/calibre/gui2/markdown_editor.py

@@ -0,0 +1,122 @@
+#!/usr/bin/env python
+
+
+__license__   = 'GPL v3'
+__copyright__ = '2023, un_pogaz <un.pogaz@gmail.com>'
+__docformat__ = 'restructuredtext en'
+
+from qt.core import (
+    QPlainTextEdit, Qt, QTabWidget, QVBoxLayout, QWidget,
+)
+
+from calibre.gui2.book_details import css
+from calibre.gui2.widgets2 import HTMLDisplay
+from calibre.library.comments import markdown
+
+
+class Editor(QWidget):  # {{{
+
+    def __init__(self, parent=None):
+        QWidget.__init__(self, parent)
+        self._layout = QVBoxLayout(self)
+        self.setLayout(self._layout)
+        self.tabs = QTabWidget(self)
+        self.tabs.setTabPosition(QTabWidget.TabPosition.South)
+        self._layout.addWidget(self.tabs)
+
+        self.editor = QPlainTextEdit(self.tabs)
+
+        self.preview = HTMLDisplay(self.tabs)
+        self.preview.setDefaultStyleSheet(css())
+        self.preview.setTabChangesFocus(True)
+
+        self.tabs.addTab(self.editor, _('&Markdown source'))
+        self.tabs.addTab(self.preview, _('&Preview'))
+
+        self.tabs.currentChanged[int].connect(self.change_tab)
+        self.layout().setContentsMargins(0, 0, 0, 0)
+
+    def set_minimum_height_for_editor(self, val):
+        self.editor.setMinimumHeight(val)
+
+    @property
+    def markdown(self):
+        self.tabs.setCurrentIndex(0)
+        return self.editor.toPlainText().strip()
+
+    @markdown.setter
+    def markdown(self, v):
+        self.editor.setPlainText(str(v or ''))
+
+    def change_tab(self, index):
+        if index == 0:  # changing to source
+            pass
+        if index == 1:  # changing to preview
+            html = markdown(self.editor.toPlainText().strip())
+            val = f'''\
+            <html>
+                <head></head>
+                <body class="vertical">
+                    <div>{html}</div>
+                </body>
+            <html>'''
+            self.preview.setHtml(val)
+
+    @property
+    def tab(self):
+        return 'code' if self.tabs.currentWidget() is self.editor else 'preview'
+
+    @tab.setter
+    def tab(self, val):
+        self.tabs.setCurrentWidget(self.preview if val == 'preview' else self.editor)
+
+    def set_readonly(self, val):
+        self.editor.setReadOnly(bool(val))
+
+    def hide_tabs(self):
+        self.tabs.tabBar().setVisible(False)
+
+    def smarten_punctuation(self):
+        from calibre.ebooks.conversion.preprocess import smarten_punctuation
+        markdown = self.markdown
+        newmarkdown = smarten_punctuation(markdown)
+        if markdown != newmarkdown:
+            self.markdown = newmarkdown
+
+# }}}
+
+
+if __name__ == '__main__':
+    from calibre.gui2 import Application
+    app = Application([])
+    w = Editor()
+    w.resize(800, 600)
+    w.setWindowFlag(Qt.WindowType.Dialog)
+    w.show()
+    w.markdown = '''\
+test *italic* **bold** ***bold-italic*** `code` [link](https://calibre-ebook.com) <span style="font-weight: bold; color:red">span</span>
+
+> Blockquotes
+
+    if '>'+' '*4 in string:
+        pre_block()
+
+1. list 1
+    1. list 1.1
+    2. list 1.2
+2. list 2
+
+***
+
+* list
+- list
+
+# Headers 1
+## Headers 2
+### Headers 3
+#### Headers 4
+##### Headers 5
+###### Headers 6
+'''
+    app.exec()
+    # print(w.markdown)