Allow creating sorts based on multiple columns (Add the Sort action to the toolbar via Preferences->Toolbars & menus)

Fixes #1945891 [[Enhancement] Select sortable columns in a separate window](https://bugs.launchpad.net/calibre/+bug/1945891)

src/calibre/gui2/actions/sort.py

@@ -7,10 +7,10 @@ __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from contextlib import suppress
 from functools import partial
-from qt.core import QAction, QIcon, QToolButton, pyqtSignal
+from qt.core import QAction, QDialog, QIcon, QToolButton, pyqtSignal
 
 from calibre.gui2.actions import InterfaceAction
-from calibre.utils.icu import sort_key
+from calibre.utils.icu import primary_sort_key
 from polyglot.builtins import iteritems
 
 SORT_HIDDEN_PREF = 'sort-action-hidden-fields'
@@ -98,8 +98,9 @@ class SortByAction(InterfaceAction):
         name_map = {v:k for k, v in iteritems(fm.ui_sortable_field_keys())}
         hidden = frozenset(db.new_api.pref(SORT_HIDDEN_PREF, default=()) or ())
         hidden_items_menu = menu.addMenu(_('Select sortable columns'))
+        menu.addAction(_('Sort on multiple columns'), self.choose_multisort)
         menu.addSeparator()
-        all_names = sorted(name_map, key=sort_key)
+        all_names = sorted(name_map, key=primary_sort_key)
         for name in all_names:
             key = name_map[name]
             ac = hidden_items_menu.addAction(name)
@@ -124,6 +125,12 @@ class SortByAction(InterfaceAction):
             sac.sort_requested.connect(self.sort_requested)
             menu.addAction(sac)
 
+    def choose_multisort(self):
+        from calibre.gui2.dialogs.multisort import ChooseMultiSort
+        d = ChooseMultiSort(self.gui.current_db, parent=self.gui, is_device_connected=self.gui.device_connected)
+        if d.exec_() == QDialog.DialogCode.Accepted:
+            self.gui.library_view.multisort(d.current_sort_spec)
+
     def sort_requested(self, key, ascending):
         if ascending is None:
             self.gui.library_view.intelligent_sort(key, True)

src/calibre/gui2/dialogs/multisort.py

@@ -0,0 +1,123 @@
+#!/usr/bin/env python
+# vim:fileencoding=utf-8
+# License: GPL v3 Copyright: 2021, Kovid Goyal <kovid at kovidgoyal.net>
+
+
+from qt.core import (
+    QAbstractItemView, QHBoxLayout, QLabel, QListWidget, QListWidgetItem, QSize, Qt,
+    QVBoxLayout
+)
+
+from calibre import prepare_string_for_xml
+from calibre.gui2 import error_dialog
+from calibre.gui2.actions.sort import SORT_HIDDEN_PREF
+from calibre.gui2.widgets2 import Dialog
+from calibre.utils.icu import primary_sort_key
+
+ascending_symbol = '⏷'
+descending_symbol = '⏶'
+
+
+class ChooseMultiSort(Dialog):
+
+    def __init__(self, db, is_device_connected=False, parent=None, hidden_pref=SORT_HIDDEN_PREF):
+        self.db = db.new_api
+        self.hidden_fields = set(self.db.pref(SORT_HIDDEN_PREF, default=()) or ())
+        if not is_device_connected:
+            self.hidden_fields.add('ondevice')
+        fm = self.db.field_metadata
+        self.key_map = fm.ui_sortable_field_keys().copy()
+        self.name_map = {v:k for k, v in self.key_map.items()}
+        self.all_names = sorted(self.name_map, key=primary_sort_key)
+        self.sort_order_map = dict.fromkeys(self.key_map, True)
+        super().__init__(_('Sort by multiple columns'), 'multisort-chooser', parent=parent)
+
+    def sizeHint(self):
+        return QSize(600, 400)
+
+    def setup_ui(self):
+        self.vl = vl = QVBoxLayout(self)
+        self.hl = hl = QHBoxLayout()
+        self.la = la = QLabel(_(
+            'Pick multiple columns to sort by. Drag and drop to re-arrange. Higher columns are more important.'
+            ' Ascending or descending order can be toggled by clicking the column name at the bottom'
+            ' of this dialog, after having selected it.'))
+        la.setWordWrap(True)
+        vl.addWidget(la)
+        vl.addLayout(hl)
+        self.order_label = la = QLabel('')
+        la.setTextFormat(Qt.TextFormat.RichText)
+        la.setWordWrap(True)
+        la.linkActivated.connect(self.link_activated)
+        vl.addWidget(la)
+        vl.addWidget(self.bb)
+
+        self.column_list = cl = QListWidget(self)
+        hl.addWidget(cl)
+        for name in self.all_names:
+            i = QListWidgetItem(cl)
+            i.setText(name)
+            i.setData(Qt.ItemDataRole.UserRole, self.name_map[name])
+            cl.addItem(i)
+            i.setCheckState(Qt.CheckState.Unchecked)
+            if self.name_map[name] in self.hidden_fields:
+                i.setHidden(True)
+        cl.setDragDropMode(QAbstractItemView.DragDropMode.InternalMove)
+        cl.currentRowChanged.connect(self.current_changed)
+        cl.itemDoubleClicked.connect(self.item_double_clicked)
+        cl.setCurrentRow(0)
+        cl.itemChanged.connect(self.update_order_label)
+        cl.model().rowsMoved.connect(self.update_order_label)
+
+    def item_double_clicked(self, item):
+        cs = item.checkState()
+        item.setCheckState(Qt.CheckState.Checked if cs == Qt.CheckState.Unchecked else Qt.CheckState.Unchecked)
+
+    def current_changed(self):
+        self.update_order_label()
+
+    @property
+    def current_sort_spec(self):
+        ans = []
+        cl = self.column_list
+        for item in (cl.item(r) for r in range(cl.count())):
+            if item.checkState() == Qt.CheckState.Checked:
+                k = item.data(Qt.ItemDataRole.UserRole)
+                ans.append((k, self.sort_order_map[k]))
+        return ans
+
+    def update_order_label(self):
+        t = ''
+        for i, (k, ascending) in enumerate(self.current_sort_spec):
+            name = self.key_map[k]
+            symbol = ascending_symbol if ascending else descending_symbol
+            if i != 0:
+                t += ' :: '
+            q = bytes.hex(k.encode('utf-8'))
+            dname = prepare_string_for_xml(name).replace(" ", "&nbsp;")
+            t += f' <a href="{q}" style="text-decoration: none">{dname}&nbsp;{symbol}</a>'
+        if t:
+            t = _('Effective sort') + ': ' + t
+        self.order_label.setText(t)
+
+    def link_activated(self, url):
+        key = bytes.fromhex(url).decode('utf-8')
+        self.sort_order_map[key] ^= True
+        self.update_order_label()
+
+    def accept(self):
+        if not self.current_sort_spec:
+            return error_dialog(self, _('No sort selected'), _(
+                'You must select at least one column on which to sort'), show=True)
+        super().accept()
+
+
+if __name__ == '__main__':
+    from calibre.gui2 import Application
+    app = Application([])
+    from calibre.library import db
+    d = ChooseMultiSort(db())
+    d.exec_()
+    print(d.current_sort_spec)
+    del d
+    del app