Extract magic numbers to named constants

- Add visual effect constants (marker size multipliers, gradient offsets, shadow/border opacity)
- Add connection line constants (color, width, vertical line position)
- Add selected marker color constant
- Replace all magic numbers with named constants for better maintainability
- All visual calculations now use descriptive constant names

Benefits:
- Easier to adjust visual appearance by changing constants
- Better code readability and self-documentation
- Reduced risk of inconsistent values
- Centralized visual configuration

MyTimeline.py

@@ -88,6 +88,24 @@ TOOLTIP_MAX_WIDTH = 500
 LABEL_BACKGROUND_PADDING = 8
 LABEL_BACKGROUND_RADIUS = 5
 
+# Visual Effect Constants
+MARKER_HOVER_SIZE_MULTIPLIER = 1.3
+MARKER_SELECTED_SIZE_MULTIPLIER = 1.2
+GRADIENT_BRIGHTNESS_OFFSET = 0.2
+GRADIENT_DARKNESS_OFFSET = 0.1
+SHADOW_OFFSET_X = 1
+SHADOW_OFFSET_Y = 1
+SHADOW_OPACITY = 0.3
+BORDER_OPACITY = 0.3
+
+# Connection Line Constants
+CONNECTION_LINE_COLOR = (0.2, 0.5, 1.0, 0.75)  # Brighter, more opaque blue
+CONNECTION_LINE_WIDTH = 3.5
+CONNECTION_VERTICAL_LINE_X = 5  # Left of year markers
+
+# Marker State Colors
+SELECTED_MARKER_COLOR = (0.2, 0.4, 0.9)  # Blue highlight for selected person's events
+
 # Logger
 logger = logging.getLogger(__name__)
 
@@ -1371,11 +1389,11 @@ class MyTimelineView(NavigationView):
             size: Size of the marker.
             shape: Shape type ('triangle', 'circle', etc.).
         """
-        context.set_source_rgba(0.0, 0.0, 0.0, 0.3)
+        context.set_source_rgba(0.0, 0.0, 0.0, SHADOW_OPACITY)
-        context.translate(1, 1)
+        context.translate(SHADOW_OFFSET_X, SHADOW_OFFSET_Y)
         self._draw_shape(context, x, y, size, shape)
         context.fill()
-        context.translate(-1, -1)
+        context.translate(-SHADOW_OFFSET_X, -SHADOW_OFFSET_Y)
 
     def _draw_marker_gradient(self, context: cairo.Context, x: float, y: float, 
                              size: float, color: Tuple[float, float, float], 
@@ -1393,8 +1411,14 @@ class MyTimelineView(NavigationView):
         """
         pattern = cairo.RadialGradient(x - size/2, y - size/2, 0, x, y, size)
         r, g, b = color
-        pattern.add_color_stop_rgb(0, min(1.0, r + 0.2), min(1.0, g + 0.2), min(1.0, b + 0.2))
+        pattern.add_color_stop_rgb(0, 
-        pattern.add_color_stop_rgb(1, max(0.0, r - 0.1), max(0.0, g - 0.1), max(0.0, b - 0.1))
+                                   min(1.0, r + GRADIENT_BRIGHTNESS_OFFSET), 
+                                   min(1.0, g + GRADIENT_BRIGHTNESS_OFFSET), 
+                                   min(1.0, b + GRADIENT_BRIGHTNESS_OFFSET))
+        pattern.add_color_stop_rgb(1, 
+                                   max(0.0, r - GRADIENT_DARKNESS_OFFSET), 
+                                   max(0.0, g - GRADIENT_DARKNESS_OFFSET), 
+                                   max(0.0, b - GRADIENT_DARKNESS_OFFSET))
         context.set_source(pattern)
         self._draw_shape(context, x, y, size, shape)
         context.fill()
@@ -1425,13 +1449,13 @@ class MyTimelineView(NavigationView):
         
         # Increase size if hovered or selected
         if is_hovered:
-            marker_size *= 1.3
+            marker_size *= MARKER_HOVER_SIZE_MULTIPLIER
         elif is_selected:
-            marker_size *= 1.2
+            marker_size *= MARKER_SELECTED_SIZE_MULTIPLIER
         
         # Use highlight color if selected
         if is_selected:
-            color = (0.2, 0.4, 0.9)  # Blue highlight for selected person's events
+            color = SELECTED_MARKER_COLOR
         
         # Draw shadow
         self._draw_marker_shadow(context, x, y, marker_size, shape)
@@ -1440,7 +1464,7 @@ class MyTimelineView(NavigationView):
         self._draw_marker_gradient(context, x, y, marker_size, color, shape)
         
         # Draw border
-        context.set_source_rgba(0.0, 0.0, 0.0, 0.3)
+        context.set_source_rgba(0.0, 0.0, 0.0, BORDER_OPACITY)
         context.set_line_width(1)
         self._draw_shape(context, x, y, marker_size, shape)
         context.stroke()
@@ -1686,12 +1710,12 @@ class MyTimelineView(NavigationView):
         
         # Position vertical line to the left of year markers
         # Year labels are positioned at timeline_x - 20 - text_width (around x=90-130)
-        # Position vertical line at x=5 to be clearly left of all year markers
+        # Position vertical line at CONNECTION_VERTICAL_LINE_X to be clearly left of all year markers
-        vertical_line_x = 5  # Left of year markers
+        vertical_line_x = CONNECTION_VERTICAL_LINE_X
         
         # Draw connecting lines - more visible with brighter color and increased opacity
-        context.set_source_rgba(0.2, 0.5, 1.0, 0.75)  # Brighter, more opaque blue
+        context.set_source_rgba(*CONNECTION_LINE_COLOR)
-        context.set_line_width(3.5)  # Increased from 2
+        context.set_line_width(CONNECTION_LINE_WIDTH)
         context.set_line_cap(cairo.LINE_CAP_ROUND)
         context.set_line_join(cairo.LINE_JOIN_ROUND)
         
@@ -1703,15 +1727,15 @@ class MyTimelineView(NavigationView):
             
             # Draw vertical line connecting all events
             if max_y - min_y > EVENT_MARKER_SIZE * 2:
-                context.set_source_rgba(0.2, 0.5, 1.0, 0.75)  # Same opacity as horizontal lines
+                context.set_source_rgba(*CONNECTION_LINE_COLOR)
-                context.set_line_width(3.5)  # Same width as horizontal lines
+                context.set_line_width(CONNECTION_LINE_WIDTH)
                 context.move_to(vertical_line_x, min_y)
                 context.line_to(vertical_line_x, max_y)
                 context.stroke()
         
         # Draw horizontal lines connecting vertical line to each event marker
-        context.set_source_rgba(0.2, 0.5, 1.0, 0.75)  # Brighter, more opaque blue
+        context.set_source_rgba(*CONNECTION_LINE_COLOR)
-        context.set_line_width(3.5)
+        context.set_line_width(CONNECTION_LINE_WIDTH)
         for event_data in person_events:
             # Draw horizontal line from vertical line to event marker
             context.move_to(vertical_line_x, event_data.y_pos)