Additional code quality improvements

- Move datetime imports to module level (follows Python best practices)
  Removed 3 duplicate imports from inside methods

- Extract remaining hardcoded UI constants
  Added FILTER_PAGE_VERTICAL_SPACING, FILTER_CATEGORY_SPACING, FILTER_INDENT_MARGIN
  Added TOOLBAR_SPACING, TOOLBAR_ITEM_MARGIN
  Added TOOLTIP_SEPARATOR_LENGTH
  Replaced all hardcoded spacing/margin values in filter page builders

- Extract common zoom logic into _update_zoom() helper
  Reduces duplication across on_zoom_in, on_zoom_out, on_zoom_reset methods

- Consolidate date handler methods
  Created _sync_year_spin_from_calendar() and _sync_calendar_from_year_spin() helpers
  Created _create_date_from_calendar() helper for date creation
  Reduced ~60 lines of duplicated code in date handlers

- Improve cache management
  Clear event type normalization cache in _invalidate_cache() to prevent stale data

- Improve error messages with more context
  All error messages now specify which operation/component failed
  Makes debugging significantly easier

MyTimeline.py

@@ -29,6 +29,7 @@ MyTimeline View - A vertical timeline showing all events in the database
 # -------------------------------------------------------------------------
 import cairo
 import colorsys
+import datetime
 import logging
 import math
 from dataclasses import dataclass
@@ -104,10 +105,16 @@ DATE_SORT_MONTH_MULTIPLIER = 100  # Month component in date sort value
 # UI Layout Constants
 FILTER_PAGE_MARGIN = 10  # Margin for filter page containers
 FILTER_PAGE_SPACING = 10  # Spacing in filter page containers
+FILTER_PAGE_VERTICAL_SPACING = 5  # Vertical spacing within filter pages
+FILTER_CATEGORY_SPACING = 2  # Spacing within category containers
+FILTER_INDENT_MARGIN = 20  # Indent margin for nested elements
 CALENDAR_CONTAINER_MARGIN = 5  # Margin for calendar containers
 CALENDAR_CONTAINER_SPACING = 5  # Spacing in calendar containers
 CALENDAR_HORIZONTAL_SPACING = 15  # Spacing between calendar frames
 YEAR_SELECTOR_SPACING = 5  # Spacing in year selector boxes
+TOOLBAR_SPACING = 5  # Spacing in toolbar
+TOOLBAR_ITEM_MARGIN = 10  # Margin for toolbar items
+TOOLTIP_SEPARATOR_LENGTH = 30  # Length of tooltip separator line
 
 # Font Constants
 FONT_FAMILY = "Sans"
@@ -551,7 +558,7 @@ class MyTimelineView(NavigationView):
             Gtk.Widget: The main container widget with toolbar and drawing area.
         """
         # Main container
-        main_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=5)
+        main_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=TOOLBAR_SPACING)
         
         # Toolbar with zoom controls
         toolbar = Gtk.Toolbar()
@@ -565,8 +572,8 @@ class MyTimelineView(NavigationView):
         
         # Zoom label
         self.zoom_label = Gtk.Label(label="100%")
-        self.zoom_label.set_margin_start(10)
+        self.zoom_label.set_margin_start(TOOLBAR_ITEM_MARGIN)
-        self.zoom_label.set_margin_end(10)
+        self.zoom_label.set_margin_end(TOOLBAR_ITEM_MARGIN)
         zoom_item = Gtk.ToolItem()
         zoom_item.add(self.zoom_label)
         toolbar.insert(zoom_item, 1)
@@ -796,14 +803,14 @@ class MyTimelineView(NavigationView):
         scrolled = Gtk.ScrolledWindow()
         scrolled.set_policy(Gtk.PolicyType.AUTOMATIC, Gtk.PolicyType.AUTOMATIC)
         
-        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=5)
+        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=FILTER_PAGE_VERTICAL_SPACING)
-        box.set_margin_start(10)
+        box.set_margin_start(FILTER_PAGE_MARGIN)
-        box.set_margin_end(10)
+        box.set_margin_end(FILTER_PAGE_MARGIN)
-        box.set_margin_top(10)
+        box.set_margin_top(FILTER_PAGE_MARGIN)
-        box.set_margin_bottom(10)
+        box.set_margin_bottom(FILTER_PAGE_MARGIN)
         
         # Select All / Deselect All buttons
-        button_box = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL, spacing=5)
+        button_box = Gtk.Box(orientation=Gtk.Orientation.HORIZONTAL, spacing=FILTER_PAGE_VERTICAL_SPACING)
         select_all_btn = Gtk.Button(label=_("Select All"))
         select_all_btn.connect("clicked", self._on_select_all_event_types)
         deselect_all_btn = Gtk.Button(label=_("Deselect All"))
@@ -837,8 +844,8 @@ class MyTimelineView(NavigationView):
             box.pack_start(category_checkbox, False, False, 0)
             
             # Create container for event types in this category
-            category_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=2)
+            category_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=FILTER_CATEGORY_SPACING)
-            category_box.set_margin_start(20)
+            category_box.set_margin_start(FILTER_INDENT_MARGIN)
             category_boxes[category] = category_box
             box.pack_start(category_box, False, False, 0)
             
@@ -877,11 +884,11 @@ class MyTimelineView(NavigationView):
         Returns:
             Gtk.Widget: The category filter page.
         """
-        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=5)
+        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=FILTER_PAGE_VERTICAL_SPACING)
-        box.set_margin_start(10)
+        box.set_margin_start(FILTER_PAGE_MARGIN)
-        box.set_margin_end(10)
+        box.set_margin_end(FILTER_PAGE_MARGIN)
-        box.set_margin_top(10)
+        box.set_margin_top(FILTER_PAGE_MARGIN)
-        box.set_margin_bottom(10)
+        box.set_margin_bottom(FILTER_PAGE_MARGIN)
         
         # Get unique categories
         categories = sorted(set(EVENT_CATEGORIES.values()))
@@ -906,11 +913,11 @@ class MyTimelineView(NavigationView):
         scrolled = Gtk.ScrolledWindow()
         scrolled.set_policy(Gtk.PolicyType.AUTOMATIC, Gtk.PolicyType.AUTOMATIC)
         
-        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=5)
+        box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=FILTER_PAGE_VERTICAL_SPACING)
-        box.set_margin_start(10)
+        box.set_margin_start(FILTER_PAGE_MARGIN)
-        box.set_margin_end(10)
+        box.set_margin_end(FILTER_PAGE_MARGIN)
-        box.set_margin_top(10)
+        box.set_margin_top(FILTER_PAGE_MARGIN)
-        box.set_margin_bottom(10)
+        box.set_margin_bottom(FILTER_PAGE_MARGIN)
         
         # Person checkboxes container - will be populated when dialog is shown
         person_checkboxes = {}
@@ -1022,7 +1029,6 @@ class MyTimelineView(NavigationView):
         calendar_box.set_homogeneous(True)
         
         # Year range for genealogical data
-        import datetime
         current_year = datetime.date.today().year
         min_year = MIN_GENEALOGICAL_YEAR
         max_year = current_year + 10
@@ -1155,10 +1161,10 @@ class MyTimelineView(NavigationView):
                 family_name = self._get_family_display_name(family)
                 
                 # Create container for family members
-                members_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=3)
+                members_box = Gtk.Box(orientation=Gtk.Orientation.VERTICAL, spacing=FILTER_CATEGORY_SPACING + 1)
-                members_box.set_margin_start(20)
+                members_box.set_margin_start(FILTER_INDENT_MARGIN)
-                members_box.set_margin_top(5)
+                members_box.set_margin_top(CALENDAR_CONTAINER_MARGIN)
-                members_box.set_margin_bottom(5)
+                members_box.set_margin_bottom(CALENDAR_CONTAINER_MARGIN)
                 
                 # Collect all child checkboxes for this family
                 child_checkboxes = []
@@ -1224,7 +1230,7 @@ class MyTimelineView(NavigationView):
             
             container.show_all()
         except (AttributeError, KeyError) as e:
-            logger.warning(f"Error updating person filter: {e}", exc_info=True)
+            logger.warning(f"Error updating person filter widgets in filter dialog: {e}", exc_info=True)
 
     def _update_date_range_widgets(self) -> None:
         """
@@ -1256,7 +1262,6 @@ class MyTimelineView(NavigationView):
             self._update_year_spin_button('date_to_year_spin', to_year, self._on_to_year_changed)
         else:
             # Reset to current date
-            import datetime
             now = datetime.date.today()
             from_calendar.select_month(now.month - 1, now.year)
             to_calendar.select_month(now.month - 1, now.year)
@@ -1342,49 +1347,42 @@ class MyTimelineView(NavigationView):
             # For now, we'll always use calendar dates if they're valid
             # The "Clear Dates" button will reset the explicit flag
             
-            # Get selected dates from calendars
+            # Get Date objects from calendar selections
-            # Gtk.Calendar.get_date() returns (year, month, day) where month is 0-11
+            from_date = self._create_date_from_calendar(from_calendar)
-            from_year, from_month, from_day = from_calendar.get_date()
+            to_date = self._create_date_from_calendar(to_calendar)
-            to_year, to_month, to_day = to_calendar.get_date()
             
-            try:
+            if from_date is None or to_date is None:
-                # Create Date objects from calendar selections
+                # Show error message for invalid dates
-                # Note: month from calendar is 0-11, Date.set_yr_mon_day expects 1-12
-                from_date = Date()
-                from_date.set_yr_mon_day(from_year, from_month + 1, from_day)
-                min_sort = from_date.get_sort_value()
-                
-                to_date = Date()
-                to_date.set_yr_mon_day(to_year, to_month + 1, to_day)
-                max_sort = to_date.get_sort_value()
-                
-                # Validate date range
-                if min_sort > max_sort:
-                    # Show error message
-                    if hasattr(self, 'date_validation_label'):
-                        self.date_validation_label.set_markup(
-                            f"<span color='red'>{_('Error: From date must be before To date')}</span>"
-                        )
-                    self.date_range_filter = None
-                    self.date_range_explicit = False
-                    return
-                else:
-                    # Clear error message
-                    if hasattr(self, 'date_validation_label'):
-                        self.date_validation_label.set_text("")
-                    
-                    # Set filter - user has selected dates in calendars
-                    self.date_range_filter = (min_sort, max_sort)
-                    self.date_range_explicit = True
-                    
-            except (ValueError, AttributeError, TypeError) as e:
-                logger.warning(f"Error parsing date range: {e}", exc_info=True)
-                self.date_range_filter = None
-                self.date_range_explicit = False
                 if hasattr(self, 'date_validation_label'):
                     self.date_validation_label.set_markup(
-                        f"<span color='red'>{_('Error: Invalid date')}</span>"
+                        f"<span color='red'>{_('Error: Invalid date in date range filter')}</span>"
                     )
+                logger.warning("Error parsing date range in filter dialog: invalid date from calendar")
+                self.date_range_filter = None
+                self.date_range_explicit = False
+                return
+            
+            min_sort = from_date.get_sort_value()
+            max_sort = to_date.get_sort_value()
+            
+            # Validate date range
+            if min_sort > max_sort:
+                # Show error message
+                if hasattr(self, 'date_validation_label'):
+                    self.date_validation_label.set_markup(
+                        f"<span color='red'>{_('Error: From date must be before To date')}</span>"
+                    )
+                self.date_range_filter = None
+                self.date_range_explicit = False
+                return
+            else:
+                # Clear error message
+                if hasattr(self, 'date_validation_label'):
+                    self.date_validation_label.set_text("")
+                
+                # Set filter - user has selected dates in calendars
+                self.date_range_filter = (min_sort, max_sort)
+                self.date_range_explicit = True
         else:
             # No calendar widgets, clear filter
             self.date_range_filter = None
@@ -1435,6 +1433,56 @@ class MyTimelineView(NavigationView):
             for checkbox in self._filter_widgets['event_type_checkboxes'].values():
                 checkbox.set_active(False)
 
+    def _sync_year_spin_from_calendar(self, calendar: Gtk.Calendar, spin_key: str, handler: Callable) -> None:
+        """
+        Update year spin button to match calendar date.
+        
+        Args:
+            calendar: The calendar widget.
+            spin_key: Key to find the spin button in _filter_widgets.
+            handler: Handler function to block/unblock during update.
+        """
+        if spin_key in self._filter_widgets:
+            year, month, day = calendar.get_date()
+            year_spin = self._filter_widgets[spin_key]
+            year_spin.handler_block_by_func(handler)
+            year_spin.set_value(year)
+            year_spin.handler_unblock_by_func(handler)
+
+    def _sync_calendar_from_year_spin(self, calendar_key: str, new_year: int) -> None:
+        """
+        Update calendar to match year spin button value.
+        
+        Args:
+            calendar_key: Key to find the calendar in _filter_widgets.
+            new_year: The new year value to set.
+        """
+        if calendar_key in self._filter_widgets:
+            calendar = self._filter_widgets[calendar_key]
+            current_year, current_month, current_day = calendar.get_date()
+            # Update calendar to new year, keeping same month and day
+            calendar.select_month(current_month, new_year)
+
+    def _create_date_from_calendar(self, calendar: Gtk.Calendar) -> Optional[Date]:
+        """
+        Create a Date object from calendar selection.
+        
+        Args:
+            calendar: The calendar widget.
+            
+        Returns:
+            Optional[Date]: Date object if successful, None otherwise.
+        """
+        try:
+            year, month, day = calendar.get_date()
+            # Note: month from calendar is 0-11, Date.set_yr_mon_day expects 1-12
+            date_obj = Date()
+            date_obj.set_yr_mon_day(year, month + 1, day)
+            return date_obj
+        except (ValueError, AttributeError, TypeError) as e:
+            logger.debug(f"Error creating date from calendar: {e}")
+            return None
+
     def _on_from_date_selected(self, calendar: Gtk.Calendar) -> None:
         """
         Handle From date calendar selection.
@@ -1442,14 +1490,7 @@ class MyTimelineView(NavigationView):
         Args:
             calendar: The calendar widget that was selected.
         """
-        # Update year spin button to match calendar
+        self._sync_year_spin_from_calendar(calendar, 'date_from_year_spin', self._on_from_year_changed)
-        if 'date_from_year_spin' in self._filter_widgets:
-            year, month, day = calendar.get_date()
-            year_spin = self._filter_widgets['date_from_year_spin']
-            year_spin.handler_block_by_func(self._on_from_year_changed)
-            year_spin.set_value(year)
-            year_spin.handler_unblock_by_func(self._on_from_year_changed)
-        
         self._validate_date_range()
 
     def _on_to_date_selected(self, calendar: Gtk.Calendar) -> None:
@@ -1459,14 +1500,7 @@ class MyTimelineView(NavigationView):
         Args:
             calendar: The calendar widget that was selected.
         """
-        # Update year spin button to match calendar
+        self._sync_year_spin_from_calendar(calendar, 'date_to_year_spin', self._on_to_year_changed)
-        if 'date_to_year_spin' in self._filter_widgets:
-            year, month, day = calendar.get_date()
-            year_spin = self._filter_widgets['date_to_year_spin']
-            year_spin.handler_block_by_func(self._on_to_year_changed)
-            year_spin.set_value(year)
-            year_spin.handler_unblock_by_func(self._on_to_year_changed)
-        
         self._validate_date_range()
 
     def _on_from_calendar_changed(self, calendar: Gtk.Calendar) -> None:
@@ -1476,13 +1510,7 @@ class MyTimelineView(NavigationView):
         Args:
             calendar: The calendar widget that changed.
         """
-        # Update year spin button to match calendar
+        self._sync_year_spin_from_calendar(calendar, 'date_from_year_spin', self._on_from_year_changed)
-        if 'date_from_year_spin' in self._filter_widgets:
-            year, month, day = calendar.get_date()
-            year_spin = self._filter_widgets['date_from_year_spin']
-            year_spin.handler_block_by_func(self._on_from_year_changed)
-            year_spin.set_value(year)
-            year_spin.handler_unblock_by_func(self._on_from_year_changed)
 
     def _on_to_calendar_changed(self, calendar: Gtk.Calendar) -> None:
         """
@@ -1491,13 +1519,7 @@ class MyTimelineView(NavigationView):
         Args:
             calendar: The calendar widget that changed.
         """
-        # Update year spin button to match calendar
+        self._sync_year_spin_from_calendar(calendar, 'date_to_year_spin', self._on_to_year_changed)
-        if 'date_to_year_spin' in self._filter_widgets:
-            year, month, day = calendar.get_date()
-            year_spin = self._filter_widgets['date_to_year_spin']
-            year_spin.handler_block_by_func(self._on_to_year_changed)
-            year_spin.set_value(year)
-            year_spin.handler_unblock_by_func(self._on_to_year_changed)
 
     def _on_from_year_changed(self, spin_button: Gtk.SpinButton) -> None:
         """
@@ -1506,14 +1528,9 @@ class MyTimelineView(NavigationView):
         Args:
             spin_button: The year spin button that changed.
         """
-        if 'date_from_calendar' in self._filter_widgets:
+        new_year = int(spin_button.get_value())
-            calendar = self._filter_widgets['date_from_calendar']
+        self._sync_calendar_from_year_spin('date_from_calendar', new_year)
-            new_year = int(spin_button.get_value())
+        self._validate_date_range()
-            current_year, current_month, current_day = calendar.get_date()
-            # Update calendar to new year, keeping same month and day
-            calendar.select_month(current_month, new_year)
-            # Trigger validation
-            self._validate_date_range()
 
     def _on_to_year_changed(self, spin_button: Gtk.SpinButton) -> None:
         """
@@ -1522,14 +1539,9 @@ class MyTimelineView(NavigationView):
         Args:
             spin_button: The year spin button that changed.
         """
-        if 'date_to_calendar' in self._filter_widgets:
+        new_year = int(spin_button.get_value())
-            calendar = self._filter_widgets['date_to_calendar']
+        self._sync_calendar_from_year_spin('date_to_calendar', new_year)
-            new_year = int(spin_button.get_value())
+        self._validate_date_range()
-            current_year, current_month, current_day = calendar.get_date()
-            # Update calendar to new year, keeping same month and day
-            calendar.select_month(current_month, new_year)
-            # Trigger validation
-            self._validate_date_range()
 
     def _on_clear_date_range(self, button: Gtk.Button) -> None:
         """
@@ -1544,7 +1556,6 @@ class MyTimelineView(NavigationView):
             
             # Reset to current date (calendars always show a date)
             # Get current date and set calendars to it
-            import datetime
             now = datetime.date.today()
             from_calendar.select_month(now.month - 1, now.year)  # month is 0-11
             from_calendar.select_day(now.day)
@@ -1682,6 +1693,8 @@ class MyTimelineView(NavigationView):
         self._cached_min_date = None
         self._cached_max_date = None
         self._event_to_person_cache.clear()  # Clear event-to-person cache
+        # Clear event type normalization cache to prevent stale data
+        self._event_type_normalization_cache.clear()
 
     def _calculate_timeline_height(self) -> None:
         """Calculate and set timeline height based on number of events and zoom."""
@@ -1798,7 +1811,7 @@ class MyTimelineView(NavigationView):
                 except (AttributeError, KeyError):
                     continue
         except (AttributeError, KeyError) as e:
-            logger.warning(f"Error building event-to-person index: {e}", exc_info=True)
+            logger.warning(f"Error building event-to-person index from database: {e}", exc_info=True)
 
     def _find_person_for_event(self, event: 'Event') -> Optional['Person']:
         """
@@ -1893,7 +1906,7 @@ class MyTimelineView(NavigationView):
                     self.all_events.append(timeline_event)
 
         except (AttributeError, KeyError) as e:
-            logger.warning(f"Error collecting events: {e}", exc_info=True)
+            logger.warning(f"Error collecting events from database: {e}", exc_info=True)
             return
 
         # Sort events by date
@@ -2395,6 +2408,19 @@ class MyTimelineView(NavigationView):
         self._adjusted_events_cache = None
         self._cache_key = None
 
+    def _update_zoom(self, level: float) -> None:
+        """
+        Update zoom level and refresh the display.
+        
+        Args:
+            level: The new zoom level to set.
+        """
+        self.zoom_level = level
+        self.update_zoom_display()
+        self._recalculate_timeline_height()
+        if self.drawing_area:
+            self.drawing_area.queue_draw()
+
     def on_zoom_in(self, widget: Gtk.Widget) -> None:
         """
         Zoom in.
@@ -2403,11 +2429,8 @@ class MyTimelineView(NavigationView):
             widget: The widget that triggered the zoom (unused).
         """
         if self.zoom_level < self.max_zoom:
-            self.zoom_level = min(self.zoom_level + self.zoom_step, self.max_zoom)
+            new_level = min(self.zoom_level + self.zoom_step, self.max_zoom)
-            self.update_zoom_display()
+            self._update_zoom(new_level)
-            self._recalculate_timeline_height()  # Only recalculate height, not events
-            if self.drawing_area:
-                self.drawing_area.queue_draw()
 
     def on_zoom_out(self, widget: Gtk.Widget) -> None:
         """
@@ -2417,11 +2440,8 @@ class MyTimelineView(NavigationView):
             widget: The widget that triggered the zoom (unused).
         """
         if self.zoom_level > self.min_zoom:
-            self.zoom_level = max(self.zoom_level - self.zoom_step, self.min_zoom)
+            new_level = max(self.zoom_level - self.zoom_step, self.min_zoom)
-            self.update_zoom_display()
+            self._update_zoom(new_level)
-            self._recalculate_timeline_height()  # Only recalculate height, not events
-            if self.drawing_area:
-                self.drawing_area.queue_draw()
 
     def on_zoom_reset(self, widget: Gtk.Widget) -> None:
         """
@@ -2430,11 +2450,7 @@ class MyTimelineView(NavigationView):
         Args:
             widget: The widget that triggered the reset (unused).
         """
-        self.zoom_level = 1.0
+        self._update_zoom(1.0)
-        self.update_zoom_display()
-        self._recalculate_timeline_height()  # Only recalculate height, not events
-        if self.drawing_area:
-            self.drawing_area.queue_draw()
 
     def on_scroll(self, widget: Gtk.Widget, event: Gdk.Event) -> bool:
         """
@@ -2695,7 +2711,7 @@ class MyTimelineView(NavigationView):
             if place:
                 return place.get_title()
         except (AttributeError, KeyError) as e:
-            logger.debug(f"Error accessing place for event: {e}")
+            logger.debug(f"Error accessing place information for event in tooltip: {e}")
         return None
 
     def _format_person_tooltip(self, person: 'Person', person_events: List[TimelineEvent]) -> str:
@@ -2711,7 +2727,7 @@ class MyTimelineView(NavigationView):
         """
         person_name = name_displayer.display(person)
         tooltip_text = f"<b>{person_name}</b>\n"
-        tooltip_text += "─" * 30 + "\n"
+        tooltip_text += "─" * TOOLTIP_SEPARATOR_LENGTH + "\n"
         
         # Sort by date
         person_events_sorted = sorted(person_events, key=lambda x: x.date_sort)
@@ -3237,7 +3253,7 @@ class MyTimelineView(NavigationView):
                     if max_year is None or year > max_year:
                         max_year = year
             except (AttributeError, ValueError) as e:
-                logger.debug(f"Error accessing year from date: {e}")
+                logger.debug(f"Error extracting year from date for timeline year marker: {e}")
         
         return (min_year, max_year)