Fix: decouple annotation xy from mutable inputs (swev-id: matplotlib__matplotlib-26466)

doc/devel/examples/repro_annotate_xy_mutability.py

@@ -0,0 +1,53 @@
+"""Reproduction script for annotation xy mutability regression (Issue #72).
+
+Run this module to observe how mutating the original ``xy`` or ``xytext``
+arrays changes the rendered annotation position. On affected builds the
+rendered position drifts to the mutated coordinates after the redraw.
+"""
+
+import matplotlib
+
+
+matplotlib.use("Agg")
+
+import matplotlib.pyplot as plt  # noqa: E402
+import numpy as np  # noqa: E402
+
+
+def main() -> None:
+    fig, ax = plt.subplots(layout="constrained")
+
+    xy = np.array([0.25, 0.75], dtype=float)
+    xytext = np.array([24.0, -12.0], dtype=float)
+
+    annotation = ax.annotate(
+        "Mutable source demo",
+        xy=xy,
+        xytext=xytext,
+        textcoords="offset points",
+        arrowprops=dict(arrowstyle="->"),
+    )
+
+    def snapshot(tag: str) -> None:
+        fig.canvas.draw()
+        renderer = fig.canvas.get_renderer()
+        xy_pixels = annotation._get_position_xy(renderer)
+        print(f"{tag} annotation xy (data): {annotation.xy}")
+        print(f"{tag} annotation xy in pixels: {xy_pixels}")
+        print(f"{tag} annotation xytext (offset points): {annotation.get_position()}")
+
+    snapshot("Initial")
+
+    xy[:] = [0.6, 0.2]
+    xytext[:] = [-18.0, 30.0]
+
+    snapshot("After mutation")
+
+    ax.set_xlim(0, 1)
+    ax.set_ylim(0, 1)
+    ax.set_title("Annotation mutability reproduction")
+    fig.savefig("repro_annotate_xy_mutability.png", dpi=150)
+
+
+if __name__ == "__main__":
+    main()

lib/matplotlib/tests/test_text.py

@@ -16,7 +16,7 @@
 import matplotlib.transforms as mtransforms
 from matplotlib.testing.decorators import check_figures_equal, image_comparison
 from matplotlib.testing._markers import needs_usetex
-from matplotlib.text import Text, Annotation
+from matplotlib.text import Text, Annotation, OffsetFrom
 
 pyparsing_version = parse_version(pyparsing.__version__)
 
@@ -676,6 +676,83 @@ def test_annotation_units(fig_test, fig_ref):
     ax.annotate("x", (datetime.now(), 0.5), xycoords=("data", "axes fraction"))
 
 
+def test_annotation_xy_numpy_source_mutation_no_effect():
+    fig, ax = plt.subplots()
+    xy = np.array([0.25, 0.75], dtype=float)
+    ann = ax.annotate("point", xy=xy)
+
+    def current_xy_pixels():
+        fig.canvas.draw()
+        renderer = fig.canvas.get_renderer()
+        return ann._get_position_xy(renderer)
+
+    original_pixels = current_xy_pixels()
+    xy[:] = [0.5, 0.5]
+    mutated_pixels = current_xy_pixels()
+
+    np.testing.assert_allclose(mutated_pixels, original_pixels)
+    assert ann.xy == (0.25, 0.75)
+
+
+def test_annotation_xytext_numpy_source_mutation_no_effect():
+    fig, ax = plt.subplots()
+    xytext = np.array([12.0, -6.0], dtype=float)
+    ann = ax.annotate(
+        "label",
+        xy=(0.4, 0.6),
+        xytext=xytext,
+        textcoords="offset points",
+    )
+
+    def current_text_position():
+        fig.canvas.draw()
+        return ann.get_position()
+
+    original_xytext = current_text_position()
+    xytext[:] = [18.0, -12.0]
+    mutated_xytext = current_text_position()
+
+    assert mutated_xytext == original_xytext
+    assert original_xytext == ann.get_position()
+
+
+def test_annotation_xy_list_source_mutation_no_effect():
+    fig, ax = plt.subplots()
+    xy = [0.1, 0.3]
+    ann = ax.annotate("list", xy=xy)
+
+    def current_xy_pixels():
+        fig.canvas.draw()
+        renderer = fig.canvas.get_renderer()
+        return ann._get_position_xy(renderer)
+
+    original_pixels = current_xy_pixels()
+    xy[0] = 0.9
+    xy[1] = 0.9
+    mutated_pixels = current_xy_pixels()
+
+    np.testing.assert_allclose(mutated_pixels, original_pixels)
+    assert ann.xy == (0.1, 0.3)
+
+
+def test_offsetfrom_ref_coord_numpy_mutation_no_effect():
+    fig, ax = plt.subplots()
+    ref_coord = np.array([0.25, 0.5], dtype=float)
+    offset = OffsetFrom(ax, ref_coord, unit="points")
+
+    fig.canvas.draw()
+    renderer = fig.canvas.get_renderer()
+    original_offset = offset(renderer).transform((0, 0))
+
+    ref_coord[:] = [0.75, 0.2]
+    fig.canvas.draw()
+    renderer = fig.canvas.get_renderer()
+    updated_offset = offset(renderer).transform((0, 0))
+
+    np.testing.assert_allclose(updated_offset, original_offset)
+    assert offset._ref_coord == (0.25, 0.5)
+
+
 @image_comparison(['large_subscript_title.png'], style='mpl20')
 def test_large_subscript_title():
     # Remove this line when this test image is regenerated.

lib/matplotlib/text.py

@@ -1389,7 +1389,7 @@ def __init__(self, artist, ref_coord, unit="points"):
             The screen units to use (pixels or points) for the offset input.
         """
         self._artist = artist
-        self._ref_coord = ref_coord
+        self._ref_coord = tuple(ref_coord)
         self.set_unit(unit)
 
     def set_unit(self, unit):
@@ -1456,7 +1456,7 @@ def __init__(self,
                  xycoords='data',
                  annotation_clip=None):
 
-        self.xy = xy
+        self.xy = tuple(xy)
         self.xycoords = xycoords
         self.set_annotation_clip(annotation_clip)