Add an option to expand the tag browser tree to show the item that was current when the library was closed. The implementation provides an API for plugins to get and set the expansion state.

See https://www.mobileread.com/forums/showthread.php?t=362240

src/calibre/gui2/__init__.py

@@ -411,6 +411,7 @@ def create_defs():
     defs['tag_browser_old_look'] = False
     defs['tag_browser_hide_empty_categories'] = False
     defs['tag_browser_always_autocollapse'] = False
+    defs['tag_browser_restore_tree_expansion'] = False
     defs['tag_browser_allow_keyboard_focus'] = False
     defs['book_list_tooltips'] = True
     defs['show_layout_buttons'] = False

src/calibre/gui2/preferences/look_feel.py

@@ -636,6 +636,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         r('tag_browser_old_look', gprefs)
         r('tag_browser_hide_empty_categories', gprefs)
         r('tag_browser_always_autocollapse', gprefs)
+        r('tag_browser_restore_tree_expansion', gprefs)
         r('tag_browser_show_tooltips', gprefs)
         r('tag_browser_allow_keyboard_focus', gprefs)
         r('bd_show_cover', gprefs)

src/calibre/gui2/preferences/look_feel.ui

@@ -1426,6 +1426,18 @@ also checked then only categories containing a matched item will be shown.</p
             </property>
            </widget>
           </item>
+          <item row="3" column="0">
+           <widget class="QCheckBox" name="opt_tag_browser_restore_tree_expansion">
+            <property name="toolTip">
+             <string>&lt;p&gt;When checked, when a library is opened the Tag browser
+will expand the tree so that the last used item is visible. An item is "used" when
+it is expanded, collapsed, or clicked.&lt;/p&gt;</string>
+            </property>
+            <property name="text">
+             <string>Expand tr&amp;ee to show last used item</string>
+            </property>
+           </widget>
+          </item>
          </layout>
         </item>
         <item row="8" column="0" colspan="3">

src/calibre/gui2/tag_browser/ui.py

@@ -947,8 +947,26 @@ class TagBrowserWidget(QFrame):  # {{{
         self.tags_view.model().prefs['tag_browser_hide_empty_categories'] ^= True
         self.tags_view.recount_with_position_based_index()
 
-    def save_state(self):
+    def save_state(self, gprefs_local=None):
-        gprefs.set('tag browser search box visible', self.toggle_search_button.isChecked())
+        if gprefs_local is None:
+            gprefs_local = gprefs
+        gprefs_local.set('tag browser search box visible', self.toggle_search_button.isChecked())
+
+    def restore_expansion_state(self, state):
+        '''
+        Expands the tag browser tree so that the node specified in state is
+        visible. Use get_expansion_state() to get the state. The intent is that
+        a plugin could restore the state in the library_changed() method.
+        '''
+        if state is not None:
+            self.tags_view.restore_expansion(state)
+
+    def get_expansion_state(self):
+        '''
+        Returns the currently expanded node in the tag browser as a string
+        suitable for restoring using restore_expansion_state.
+        '''
+        return self.tags_view.current_expansion
 
     def toggle_item(self):
         self.tags_view.toggle_current_index()

src/calibre/gui2/tag_browser/view.py

@@ -289,6 +289,7 @@ class TagsView(QTreeView):  # {{{
         self.setDropIndicatorShown(True)
         self.setAutoExpandDelay(500)
         self.pane_is_visible = False
+        self.current_expansion = None
         self.search_icon = QIcon.ic('search.png')
         self.search_copy_icon = QIcon.ic("search_copy_saved.png")
         self.user_category_icon = QIcon.ic('tb_folder.png')
@@ -426,6 +427,7 @@ class TagsView(QTreeView):  # {{{
         self.refresh_signal_processed = True
         db.add_listener(self.database_changed)
         self.expanded.connect(self.item_expanded)
+        self.collapsed.connect(self.item_collapsed)
         self.collapsed.connect(self.collapse_node_and_children)
         db.data.add_marked_listener(self.marked_change_listener)
 
@@ -1434,6 +1436,7 @@ class TagsView(QTreeView):  # {{{
         ci = self.currentIndex()
         if not ci.isValid():
             ci = self.indexAt(QPoint(10, 10))
+        item_is_expanded = True if ci.isValid() and self.isExpanded(ci) else False
         use_pos = self._model.use_position_based_index_on_next_recount
         self._model.use_position_based_index_on_next_recount = False
         if use_pos:
@@ -1454,6 +1457,10 @@ class TagsView(QTreeView):  # {{{
                 index = self._model.index_for_named_path(path)
                 if index.isValid():
                     self.show_item_at_index(index)
+                    if not item_is_expanded:
+                        # show_item_at_index() will expand the target node.
+                        # Collapse it if it wasn't expanded before the recount.
+                        self.collapse(index)
         self.blockSignals(False)
 
     def show_item_at_path(self, path, box=False,
@@ -1490,5 +1497,26 @@ class TagsView(QTreeView):  # {{{
         Called by the expanded signal
         '''
         self.setCurrentIndex(idx)
+        self.current_expansion = (self.isExpanded(idx), self._model.named_path_for_index(idx))
+
+    def item_collapsed(self, idx):
+        '''
+        Called by the collapsed signal
+        '''
+        self.current_expansion = (self.isExpanded(idx), self._model.named_path_for_index(idx))
+
+    def currentChanged(self, idx, prev_idx):
+        self.current_expansion = (self.isExpanded(idx), self._model.named_path_for_index(idx))
+        super().currentChanged(idx, prev_idx)
+
+    def restore_expansion(self, expansion):
+        self.current_expansion = None
+        if expansion is not None and len(expansion) == 2:
+            idx = self._model.index_for_named_path(expansion[1])
+            if idx.isValid():
+                self.show_item_at_index(idx)
+                if not expansion[0]:
+                    self.collapse(idx)
+
 
     # }}}

src/calibre/gui2/ui.py

@@ -983,6 +983,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
                             return
                     else:
                         return
+            self._save_tb_state(gprefs)
             for action in self.iactions.values():
                 try:
                     action.library_about_to_change(olddb, db)
@@ -1009,6 +1010,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
             if db.new_api.pref('virtual_lib_on_startup'):
                 self.apply_virtual_library(db.new_api.pref('virtual_lib_on_startup'))
             self.rebuild_vl_tabs()
+            self._restore_tb_expansion_state() # Do this before plugins library_changed()
             for action in self.iactions.values():
                 try:
                     action.library_changed(db)
@@ -1167,16 +1169,29 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
                     _('<b>Failed</b>')+': '+str(job.description),
                     det_msg=job.details, retry_func=retry_func)
 
+    def _save_tb_state(self, gprefs):
+        self.tb_widget.save_state(gprefs)
+        if gprefs['tag_browser_restore_tree_expansion']:
+            tv_saved_expansions = gprefs.get('tags_view_saved_expansions', {})
+            tv_saved_expansions.update({self.current_db.library_id: self.tb_widget.get_expansion_state()})
+            gprefs['tags_view_saved_expansions'] = tv_saved_expansions
+
+    def _restore_tb_expansion_state(self):
+        if gprefs['tag_browser_restore_tree_expansion']:
+            tv_saved_expansions = gprefs.get('tags_view_saved_expansions', {})
+            self.tb_widget.restore_expansion_state(tv_saved_expansions.get(self.current_db.library_id))
+
     def read_settings(self):
         self.restore_geometry(gprefs, 'calibre_main_window_geometry', get_legacy_saved_geometry=lambda: config['main_window_geometry'])
         self.read_layout_settings()
+        self._restore_tb_expansion_state()
 
     def write_settings(self):
         with gprefs:  # Only write to gprefs once
             self.save_geometry(gprefs, 'calibre_main_window_geometry')
             dynamic.set('sort_history', self.library_view.model().sort_history)
             self.save_layout_state()
-            self.tb_widget.save_state()
+            self._save_tb_state(gprefs)
 
     def restart(self):
         self.quit(restart=True)