Add anchor method and fix issue (#100)

adafruit_displayio_layout/layouts/__init__.py

@@ -0,0 +1,61 @@
+# SPDX-FileCopyrightText: 2025 Shubham Patel
+#
+# SPDX-License-Identifier: MIT
+
+from micropython import const
+
+try:
+    from typing import Tuple
+except ImportError:
+    pass
+
+# Anchor point constants for anchor method.
+ANCHOR_TOP_LEFT = const((0.0, 0.0))
+ANCHOR_TOP_CENTER = const((0.5, 0.0))
+ANCHOR_TOP_RIGHT = const((1.0, 0.0))
+ANCHOR_CENTER_LEFT = const((0.0, 0.5))
+ANCHOR_CENTER = const((0.5, 0.5))
+ANCHOR_CENTER_RIGHT = const((1.0, 0.5))
+ANCHOR_BOTTOM_LEFT = const((0.0, 1.0))
+ANCHOR_BOTTOM_CENTER = const((0.5, 1.0))
+ANCHOR_BOTTOM_RIGHT = const((1.0, 1.0))
+
+
+def anchor(obj, anchor: Tuple[float, float], width: int, height: int) -> None:
+    """Helper to position a display object on screen using a defined anchor point.
+
+    Sets `anchor_point` and `anchored_position` for display elements such as `Label`,
+    `Widget`, `AnchoredTileGrid`, or `AnchoredGroup`.
+
+    :param obj: The object to be positioned. Must support `anchor_point` and `anchored_position`.
+    :param anchor: One of the predefined anchor constants (e.g. ANCHOR_TOP_LEFT, ANCHOR_CENTER)
+    :param width: Width of the display in pixels
+    :param height: Height of the display in pixels
+    """
+    if not hasattr(obj, "anchor_point") or not hasattr(obj, "anchored_position"):
+        raise AttributeError(
+            "Object must have both `anchor_point` and `anchored_position` attributes."
+        )
+
+    if anchor not in {
+        ANCHOR_TOP_LEFT,
+        ANCHOR_TOP_CENTER,
+        ANCHOR_TOP_RIGHT,
+        ANCHOR_CENTER_LEFT,
+        ANCHOR_CENTER,
+        ANCHOR_CENTER_RIGHT,
+        ANCHOR_BOTTOM_LEFT,
+        ANCHOR_BOTTOM_CENTER,
+        ANCHOR_BOTTOM_RIGHT,
+    }:
+        raise ValueError(
+            "Anchor must be one of: ANCHOR_TOP_LEFT, ANCHOR_TOP_CENTER, ANCHOR_TOP_RIGHT,\n"
+            "ANCHOR_CENTER_LEFT, ANCHOR_CENTER, ANCHOR_CENTER_RIGHT,\n"
+            "ANCHOR_BOTTOM_LEFT, ANCHOR_BOTTOM_CENTER, ANCHOR_BOTTOM_RIGHT."
+        )
+
+    obj.anchor_point = anchor
+    obj.anchored_position = (
+        int(anchor[0] * width),
+        int(anchor[1] * height),
+    )

adafruit_displayio_layout/layouts/grid_layout.py

@@ -378,6 +378,13 @@ def add_content(
          then the cell_anchor_point from the GridLayout will be used.
         :return: None"""
 
+        grid_x, grid_y = grid_position
+        max_grid_x, max_grid_y = self.grid_size
+        if grid_x >= max_grid_x or grid_y >= max_grid_y:
+            raise ValueError(
+                f"Grid position {grid_position} is out of bounds for grid size {self.grid_size}"
+            )
+
         if cell_anchor_point:
             _this_cell_anchor_point = cell_anchor_point
         else: