Minimal Canvas with larger Y values on the top of the screen.

Author: tmontes

src/aturtle/canvas.py

@@ -0,0 +1,59 @@
+# ----------------------------------------------------------------------------
+# Python A-Turtle
+# ----------------------------------------------------------------------------
+# Copyright (c) Tiago Montes.
+# See LICENSE for details.
+# ----------------------------------------------------------------------------
+
+import tkinter
+
+
+
+class InvertedYTkCanvas(tkinter.Canvas):
+
+    def __init__(self, master, background):
+
+        super().__init__(
+            master,
+            highlightthickness=0,
+            background=background,
+        )
+
+
+    def _inverted_y(self, coords):
+
+        return [
+            -value if offset % 2 else value
+            for offset, value in enumerate(coords)
+        ]
+
+
+    def create_polygon(self, coords, *, fill, outline, width):
+
+        return super().create_polygon(
+            self._inverted_y(coords),
+            fill=fill,
+            outline=outline,
+            width=width,
+        )
+
+
+    def move(self, item_id, dx, dy):
+
+        return super().move(item_id, dx, -dy)
+
+
+    def create_line(self, coords, *, fill, width, capstyle):
+
+        return super().create_line(
+            self._inverted_y(coords),
+            fill=fill,
+            width=width,
+            capstyle=capstyle,
+        )
+
+
+    def coords(self, item_id, coords):
+
+        return super().coords(item_id, self._inverted_y(coords))
+

src/aturtle/window.py

@@ -7,6 +7,8 @@
 
 import tkinter
 
+from . import canvas
+
 
 
 class Window:
@@ -18,7 +20,8 @@ class Window:
     _windows = []
 
     def __init__(self, width=320, height=320, x=None, y=None,
-                 fill_color='white', title='A-Turtle'):
+                 fill_color='white', title='A-Turtle',
+                 canvas_factory=canvas.InvertedYTkCanvas):
         """
         Initialize a Window with the given `width` and `height`, filled in
         `fill_color`, with the given `title`.
@@ -47,9 +50,8 @@ def __init__(self, width=320, height=320, x=None, y=None,
         y = (tk_window.winfo_screenheight() - height) // 2 if y is None else y
 
         tk_window.geometry(f'{width}x{height}+{x}+{y}')
-        canvas = tkinter.Canvas(
+        canvas = canvas_factory(
             tk_window,
-            highlightthickness=0,
             background=fill_color,
         )
         canvas.pack(expand=True, fill='both')