Edit book: Allow merging HTML files by drag and drop of the files onto another HTML file

manual/edit.rst

@@ -127,6 +127,9 @@ links and references to the merged files. Note that merging files can sometimes
 cause text styling to change, since the individual files could have used
 different stylesheets.
 
+You can also select text files and then drag and drop the text files onto
+another text file to merge the dropped text files into the target text file.
+
 Changing text file order
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -134,7 +137,8 @@ You can re-arrange the order in which text (HTML) files are opened when reading
 the book by simply dragging and dropping them in the Files browser. For the
 technically inclined, this is called re-ordering the book spine. Note that you
 have to drop the items *between* other items, not on top of them, this can be a
-little fiddly until you get used to it.
+little fiddly until you get used to it. Dropping on top of another file will
+cause the files to be merged.
 
 Marking the cover
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^

src/calibre/gui2/tweak_book/file_list.py

@@ -8,14 +8,14 @@ import posixpath
 import sys
 import textwrap
 from collections import Counter, OrderedDict, defaultdict
-from gettext import pgettext
 from functools import partial
+from gettext import pgettext
 from qt.core import (
-    QApplication, QCheckBox, QDialog, QDialogButtonBox, QFont, QFormLayout, QItemSelectionModel,
+    QAbstractItemView, QApplication, QCheckBox, QDialog, QDialogButtonBox, QFont,
-    QGridLayout, QIcon, QInputDialog, QLabel, QLineEdit, QListWidget, QAbstractItemView,
+    QFormLayout, QGridLayout, QIcon, QInputDialog, QItemSelectionModel, QLabel,
-    QListWidgetItem, QMenu, QPainter, QPixmap, QRadioButton, QScrollArea, QSize,
+    QLineEdit, QListWidget, QListWidgetItem, QMenu, QPainter, QPixmap, QRadioButton,
-    QSpinBox, QStyle, QStyledItemDelegate, Qt, QTimer, QTreeWidget, QTreeWidgetItem,
+    QScrollArea, QSize, QSpinBox, QStyle, QStyledItemDelegate, Qt, QTimer, QTreeView,
-    QVBoxLayout, QWidget, pyqtSignal, sip
+    QTreeWidget, QTreeWidgetItem, QVBoxLayout, QWidget, pyqtSignal, sip
 )
 
 from calibre import human_readable, sanitize_file_name
@@ -43,7 +43,6 @@ from calibre_extensions.progress_indicator import set_no_activate_on_click
 from polyglot.binary import as_hex_unicode
 from polyglot.builtins import iteritems
 
-
 FILE_COPY_MIME = 'application/calibre-edit-book-files'
 TOP_ICON_SIZE = 24
 NAME_ROLE = Qt.ItemDataRole.UserRole
@@ -293,6 +292,63 @@ class FileList(QTreeWidget, OpenWithHandler):
         ans.setData(CONTAINER_DND_MIMETYPE, '\n'.join(filter(None, names)).encode('utf-8'))
         return ans
 
+    def dropMimeData(self, parent, index, data, action):
+        if not parent or not data.hasFormat(CONTAINER_DND_MIMETYPE):
+            return False
+        names = bytes(data.data(CONTAINER_DND_MIMETYPE)).decode('utf-8').splitlines()
+        if not names:
+            return False
+        category = parent.data(0, CATEGORY_ROLE)
+        if category is None:
+            self.handle_reorder_drop(parent, index, names)
+        elif category == 'text':
+            self.handle_merge_drop(parent, names)
+        return False  # we have to return false to prevent Qt's internal machinery from re-ordering nodes
+
+    def handle_merge_drop(self, target_node, names):
+        category_node = target_node.parent()
+        current_order = {category_node.child(i).data(0, NAME_ROLE):i for i in range(category_node.childCount())}
+        names = sorted(names, key=lambda x: current_order.get(x, -1))
+        target_name = target_node.data(0, NAME_ROLE)
+        if len(names) == 1:
+            msg = _('Merge the file {0} into the file {1}?').format(elided_text(names[0]), elided_text(target_name))
+        else:
+            msg = _('Merge the {0} selected files into the file {1}?').format(len(names), elided_text(target_name))
+        if question_dialog(self, _('Merge files'), msg, skip_dialog_name='edit-book-merge-on-drop'):
+            names.append(target_name)
+            names = sorted(names, key=lambda x: current_order.get(x, -1))
+            self.merge_requested.emit(target_node.data(0, CATEGORY_ROLE), names, target_name)
+
+    def handle_reorder_drop(self, category_node, idx, names):
+        current_order = tuple(category_node.child(i).data(0, NAME_ROLE) for i in range(category_node.childCount()))
+        linear_map = {category_node.child(i).data(0, NAME_ROLE):category_node.child(i).data(0, LINEAR_ROLE) for i in range(category_node.childCount())}
+        order_map = {name: i for i, name in enumerate(current_order)}
+        try:
+            insert_before = current_order[idx]
+        except IndexError:
+            insert_before = None
+        names = sorted(names, key=lambda x: order_map.get(x, -1))
+        moved_names = frozenset(names)
+        new_names = [n for n in current_order if n not in moved_names]
+        try:
+            insertion_point = len(new_names) if insert_before is None else new_names.index(insert_before)
+        except ValueError:
+            return
+        new_names = new_names[:insertion_point] + names + new_names[insertion_point:]
+        order = [[name, linear_map[name]] for name in new_names]
+        # Ensure that all non-linear items are at the end, by making any non-linear
+        # items not at the end, linear
+        for i, (name, linear) in tuple(enumerate(order)):
+            if not linear and i < len(order) - 1 and order[i+1][1]:
+                order[i][1] = True
+        self.reorder_spine.emit(order)
+
+    def dropEvent(self, event):
+        # the dropEvent() implementation of QTreeWidget handles InternalMoves
+        # internally and is not suitable for us. QTreeView::dropEvent calls
+        # dropMimeData() where we handle the drop
+        QTreeView.dropEvent(self, event)
+
     @property
     def current_name(self):
         ci = self.currentItem()
@@ -470,7 +526,7 @@ class FileList(QTreeWidget, OpenWithHandler):
             item = QTreeWidgetItem(self.categories['text' if linear is not None else category], 1)
             flags = Qt.ItemFlag.ItemIsEnabled | Qt.ItemFlag.ItemIsSelectable
             if category == 'text':
-                flags |= Qt.ItemFlag.ItemIsDragEnabled
+                flags |= Qt.ItemFlag.ItemIsDragEnabled | Qt.ItemFlag.ItemIsDropEnabled
             if name not in cannot_be_renamed:
                 flags |= Qt.ItemFlag.ItemIsEditable
             item.setFlags(flags)
@@ -479,6 +535,7 @@ class FileList(QTreeWidget, OpenWithHandler):
             item.setData(0, CATEGORY_ROLE, category)
             item.setData(0, LINEAR_ROLE, bool(linear))
             item.setData(0, MIME_ROLE, imt)
+
             set_display_name(name, item)
             tooltips = []
             emblems = []
@@ -815,25 +872,6 @@ class FileList(QTreeWidget, OpenWithHandler):
             ans = list(sorted(ans, key=lambda idx:idx.row()))
         return ans
 
-    def dropEvent(self, event):
-        with self:
-            text = self.categories['text']
-            pre_drop_order = {text.child(i).data(0, NAME_ROLE):i for i in range(text.childCount())}
-            super().dropEvent(event)
-            current_order = {text.child(i).data(0, NAME_ROLE):i for i in range(text.childCount())}
-            if current_order != pre_drop_order:
-                order = []
-                for child in (text.child(i) for i in range(text.childCount())):
-                    name = str(child.data(0, NAME_ROLE) or '')
-                    linear = bool(child.data(0, LINEAR_ROLE))
-                    order.append([name, linear])
-                # Ensure that all non-linear items are at the end, any non-linear
-                # items not at the end will be made linear
-                for i, (name, linear) in tuple(enumerate(order)):
-                    if not linear and i < len(order) - 1 and order[i+1][1]:
-                        order[i][1] = True
-                self.reorder_spine.emit(order)
-
     def item_double_clicked(self, item, column):
         category = str(item.data(0, CATEGORY_ROLE) or '')
         if category: