Reticule lines to extend through the whole window.

They are mostly meant to help locate the focus when scrolling through
the large star map: scroll x (or y) until you see the line then scroll y
(or x) to find the focus; so they should extend to the scrollregion.

reticule.py

@@ -22,19 +22,16 @@
 
 class Reticule:
 
-    def __init__(self, canvas, radius_x=35, radius_y=20, color='green'):
+    def __init__(self, canvas, width, height, radius_x=35, radius_y=20, color='green'):
         self.canvas = canvas
+        self.width = width
+        self.height = height
         self.radius_x = radius_x
         self.radius_y = radius_y
         self.color = color
         self.item_ids = []
         self.init_reticule()
         self.xy_cache = 0, 0
-        self.canvas.bind(
-            '<Configure>',
-            self.handle_canvas_resize,
-            add='+',
-            )
 
     def get_reticule_coords(self, x, y):
         '''
@@ -42,8 +39,8 @@ class Reticule:
         rectangle yield coords for four lines and an oval suitable for
         passing to canvas.coords() method.
         '''
-        width = int(self.canvas['width'])
+        width = self.width
-        height = int(self.canvas['height'])
+        height = self.height
 
         top = y - self.radius_y
         left = x - self.radius_x
@@ -58,7 +55,7 @@ class Reticule:
 
     def init_reticule(self):
         append = self.item_ids.append
-        w, h = int(self.canvas['width']), int(self.canvas['height'])
+        w, h = self.width, self.height
         coords = self.get_reticule_coords(w >> 1, h >> 1)  # Center.
 
         append(canvas.create_line(*next(coords), fill=self.color))
@@ -76,36 +73,15 @@ class Reticule:
     def handle_set_event(self, event):
         self.set_reticule(event.x, event.y)
 
-    def handle_canvas_resize(self, _event):
-        # We're going to assume that some other callback has updated the
-        # canvas values.  Otherwise we could get the new width and height
-        # from the Configure event.
-        self.set_reticule(*self.xy_cache)
-
 
 if __name__ == '__main__':
     from tkinter import *
 
-    def handle_canvas_resize(event):
-        # I don't know why the Tk system doesn't update these values.
-        canvas['width'] = event.width
-        canvas['height'] = event.height
-        # update reticule here/now?
-        # If the canvas window has enlarged then some of the lines will have
-        # to be extended.
-
     canvas = Canvas(bg='black')
 
-    canvas.bind('<Configure>', handle_canvas_resize)
     canvas.pack(expand=True, fill=BOTH)
-    canvas.update()
 
-    # Let the configure event propagate and trigger the
+    reticule = Reticule(canvas, 1024, 768)
-    # handle_canvas_resize() callback to set the width
-    # and height values of the canvas correctly so that
-    # the reticule lines get drawn correctly.
-
-    reticule = Reticule(canvas)
     canvas.bind('<Button-1>', reticule.handle_set_event)
     canvas.bind('<B1-Motion>', reticule.handle_set_event)