Fix weird problem where a menu can be shown on the wrong screen if it is constructed before the first show event. On my test system it is 100% repeatable.

FWIW: I spent several hours trying to find a way to work around this issue. The trigger is clear -- populating the menu for the first time outside of the Qt "show()" process. This commit fixes it by not populating the 'real' menu until the show sequence has started. If something wants the menu before the show process has started then a fake action is returned with the menu.

src/calibre/gui2/actions/sort.py

@@ -5,10 +5,11 @@ __license__ = 'GPL v3'
 __copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 from contextlib import suppress
+from enum import Enum
 from functools import partial
 from qt.core import (
     QAbstractItemView, QAction, QDialog, QDialogButtonBox, QIcon, QListWidget,
-    QListWidgetItem, QSize, Qt, QToolButton, QVBoxLayout, pyqtSignal,
+    QListWidgetItem, QMenu, QSize, Qt, QToolButton, QVBoxLayout, pyqtSignal,
 )
 
 from calibre.gui2.actions import InterfaceAction
@@ -35,6 +36,21 @@ class SortAction(QAction):
         self.sort_requested.emit(self.key, self.ascending)
 
 
+class InitializationEnum(Enum):
+    WaitingInitialization = 0
+    InitializeCalled = 1
+    FullyInitialized = 2
+
+
+class FakeAction(QAction):
+
+    def menu(self):
+        return self.the_menu
+
+    def setMenu(self, menu):
+        self.the_menu = menu
+
+
 class SortByAction(InterfaceAction):
 
     name = 'Sort By'
@@ -43,8 +59,11 @@ class SortByAction(InterfaceAction):
     popup_type = QToolButton.ToolButtonPopupMode.InstantPopup
     action_add_menu = True
     dont_add_to = frozenset(('context-menu-cover-browser', ))
+    init_complete = InitializationEnum.WaitingInitialization
+    menu_shown = False
 
     def genesis(self):
+        self.fake_action = None
         self.sorted_icon = QIcon.ic('ok.png')
         self.qaction.menu().aboutToShow.connect(self.about_to_show)
 
@@ -57,6 +76,45 @@ class SortByAction(InterfaceAction):
         c('reverse_sort_action', _('Reverse current sort'), _('Reverse the current sort order'), self.reverse_sort, 'shift+f5')
         c('reapply_sort_action', _('Re-apply current sort'), _('Re-apply the current sort'), self.reapply_sort, 'f5')
 
+
+    # The property is here because Qt can put the menu on the wrong screen if
+    # the menu is built for the first time outside of the process of showing it.
+    # On Windows this happens if calibre is on screen 2; the menu appears on
+    # screen 1. Why Qt does this I can't say. The problem can be triggered if a
+    # plugin queries the menu during its own initialization. We solve this
+    # problem by giving the caller a fake QAction with the menu, which works for
+    # plugins. We use the "real" action once the user has requested the menu. Of
+    # course, the right fix would be for Qt to show the menu where it should go
+    # even if built previously, but I can't find how to make that happen
+
+    @property
+    def qaction(self):
+        try:
+            # if initialization_complete() hasn't been called or we are fully
+            # initialized then do nothing special
+            if self.init_complete == InitializationEnum.InitializeCalled:
+                if not self.menu_shown:
+                    # This is the problematic case where something wants the
+                    # menu before it's been shown. Construct the fake action
+                    m = QMenu()
+                    self.update_menu(m)
+                    if self.fake_action is None:
+                        self.fake_action = FakeAction()
+                    self.fake_action.setMenu(m)
+                    return self.fake_action
+                else:
+                    # The menu has been shown. No need to construct the fake
+                    # action in the future.
+                    self.init_complete = InitializationEnum.FullyInitialized
+        except Exception:
+            import traceback
+            traceback.print_exc()
+        return self.my_qaction
+
+    @qaction.setter
+    def qaction(self, val):
+        self.my_qaction = val
+
     def reverse_sort(self):
         self.gui.current_view().reverse_sort()
 
@@ -69,13 +127,14 @@ class SortByAction(InterfaceAction):
         self.menuless_qaction.setEnabled(enabled)
 
     def about_to_show(self):
+        self.menu_shown = True
         self.update_menu()
 
     def library_changed(self, db):
         self.update_menu()
 
     def initialization_complete(self):
-        self.update_menu()
+        self.init_complete = InitializationEnum.InitializeCalled
 
     def update_menu(self, menu=None):
         menu = self.qaction.menu() if menu is None else menu
@@ -128,6 +187,8 @@ class SortByAction(InterfaceAction):
                 menu.insertSeparator(before)
             else:
                 menu.addAction(sac)
+        if self.fake_action is not None:
+            self.fake_action.setMenu(menu)
 
     def select_sortable_columns(self):
         db = self.gui.current_db
@@ -166,7 +227,7 @@ class SortByAction(InterfaceAction):
         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)
-            self.update_menu()
+        self.update_menu()
 
     def sort_requested(self, key, ascending):
         if ascending is None: