Feature: relative position helpers

arcade/application.py

@@ -915,6 +915,30 @@ def on_mouse_leave(self, x: int, y: int):
         """
         pass
 
+    def absolute(self, fractional_pos: tuple[float, float]) -> tuple[float, float]:
+        """Convert a relative fractional pair to absolute screen pixels.
+
+        As in the rest of arcade and OpenGL, the default coordinate system
+        places the origin at the bottom left.
+
+        :param fractional_pos: A position where the x and y are fractional
+            values of the window size.
+        :returns: A tuple of absolute pixel X and Y relative to bottom left.
+        """
+        w, h = self.size
+        frac_x, frac_y = fractional_pos
+        return frac_x * w, frac_y * h
+
+    def relative(self, pixel_pos: tuple[float, float]) -> tuple[float, float]:
+        """Convert absolute screen pixels to a relative fractional pair.
+
+        :param pixel_pos: a tuple of X and Y pixel positions within the window.
+        :returns: A tuple of fractional X and Y relative to the bottom left.
+        """
+        w, h = self.size
+        pixel_x, pixel_y = pixel_pos
+        return pixel_x / w, pixel_y / h
+
 
 def open_window(
     width: int,