Merge branch 'lazy-operations-look_feel' of https://github.com/un-pogaz/calibre

src/calibre/gui2/preferences/look_feel.py

@@ -36,6 +36,7 @@ from qt.core import (
     Qt,
     QTableWidget,
     QTableWidgetItem,
+    QTabWidget,
     QVBoxLayout,
     QWidget,
     pyqtSignal,
@@ -692,8 +693,16 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         self.css_highlighter = get_highlighter('css')()
         self.css_highlighter.apply_theme(get_theme(None))
         self.css_highlighter.set_document(self.opt_book_details_css.document())
+        self.lazy_tabs = {}
         for i in range(self.tabWidget.count()):
             self.sections_view.addItem(QListWidgetItem(self.tabWidget.tabIcon(i), self.tabWidget.tabText(i).replace('&', '')))
+            # retrieve tabs and subtabs of look & feel to load their content later when clicking of them
+            w = self.tabWidget.widget(i).widget()
+            self.lazy_tabs[(i, None)] = w
+            if isinstance(w, QTabWidget):
+                w.currentChanged.connect(partial(self.lazy_tab_operations, i))
+                for ii in range(w.count()):
+                    self.lazy_tabs[(i, ii)] = w.widget(ii)
         self.sections_view.setCurrentRow(self.tabWidget.currentIndex())
         self.sections_view.currentRowChanged.connect(self.tabWidget.setCurrentIndex)
         self.sections_view.setMaximumWidth(self.sections_view.sizeHintForColumn(0) + 16)
@@ -854,6 +863,7 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
         self.tb_focus_label.setVisible(self.opt_tag_browser_allow_keyboard_focus.isChecked())
         self.update_color_palette_state()
         self.opt_gui_layout.setCurrentIndex(0 if self.gui.layout_container.is_wide else 1)
+        self.lazy_tab_operations(self.tabWidget.currentIndex(), None)
 
     def open_cg_cache(self):
         open_local_file(self.gui.grid_view.thumbnail_cache.location)
@@ -863,9 +873,20 @@ class ConfigWidget(ConfigWidgetBase, Ui_Form):
             _('Current space used: %s') % human_readable(size))
 
     def tab_changed(self, index):
+        self.lazy_tab_operations(index, None)
         if self.tabWidget.currentWidget() is self.cover_grid_tab:
             self.show_current_cache_usage()
 
+    def lazy_tab_operations(self, idx_section, idx_subtab):
+        '''
+        Check if the tab has lazy operations.
+        Perfom the lazy operations only once, the first time the tab is selected.
+        '''
+        tab = self.lazy_tabs.get((idx_section, idx_subtab), None)
+        if hasattr(tab, 'lazy_populate_content'):
+            tab.lazy_populate_content()
+        self.lazy_tabs.pop((idx_section, idx_subtab), None)
+
     def show_current_cache_usage(self):
         t = Thread(target=self.calc_cache_size)
         t.daemon = True

src/calibre/gui2/preferences/look_feel_tabs/tb_icon_rules.py

@@ -141,8 +141,14 @@ class TbIconRulesTab(ConfigTabWidget, Ui_Form):
         self.tb_icon_rules_groupbox.setContentsMargins(0, 0, 0, 0)
         self.tb_icon_rules_gridlayout.setContentsMargins(2, 2, 2, 2)
 
-        field_metadata = gui.current_db.field_metadata
+        try:
-        category_icons = gui.tags_view.model().category_custom_icons
+            self.table_column_widths = gprefs.get('tag_browser_rules_dialog_table_widths', None)
+        except Exception:
+            pass
+
+    def lazy_populate_content(self):
+        field_metadata = self.gui.current_db.field_metadata
+        category_icons = self.gui.tags_view.model().category_custom_icons
         v = gprefs['tags_browser_value_icons']
         row = 0
         for category,vdict in v.items():
@@ -170,11 +176,6 @@ class TbIconRulesTab(ConfigTabWidget, Ui_Form):
         self.do_sort(VALUE_COLUMN)
         self.do_sort(CATEGORY_COLUMN)
 
-        try:
-            self.table_column_widths = gprefs.get('tag_browser_rules_dialog_table_widths', None)
-        except Exception:
-            pass
-
     def show_context_menu(self, point):
         clicked_item = self.rules_table.itemAt(point)
         if clicked_item is None: