Refactor: move legend property extraction to Legend._get_properties()

Sanat Gupta · Sanat Gupta · commit da680ddf160c · 2026-04-23T12:47:57.000-04:00
Address review feedback from @timhoffm: - Added Legend._get_properties() method that returns a dict of legend properties needed for recreation - figureoptions.py now calls old_legend._get_properties() instead of extracting properties inline - Updated tests to directly test _get_properties() method - Tests cover basic properties, mode/bbox_to_anchor, roundtrip recreation, and no-existing-legend edge case
diff --git a/lib/matplotlib/backends/qt_editor/figureoptions.py b/lib/matplotlib/backends/qt_editor/figureoptions.py
@@ -253,28 +253,7 @@ def apply_callback(data):
                 old_legend = axes.get_legend()
                 draggable = old_legend._draggable is not None
                 ncols = old_legend._ncols
-                # Preserve location and positioning
-                legend_kwargs['loc'] = old_legend._loc
-                if old_legend._bbox_to_anchor is not None:
-                    legend_kwargs['bbox_to_anchor'] = (
-                        old_legend._bbox_to_anchor.bounds)
-                # Preserve styling
-                legend_kwargs['fontsize'] = old_legend._fontsize
-                legend_kwargs['frameon'] = old_legend.get_frame_on()
-                legend_kwargs['shadow'] = old_legend.shadow
-                legend_kwargs['framealpha'] = (
-                    old_legend.get_frame().get_alpha())
-                legend_kwargs['title'] = (
-                    old_legend.get_title().get_text())
-                # Preserve layout settings
-                if old_legend._mode is not None:
-                    legend_kwargs['mode'] = old_legend._mode
-                legend_kwargs['columnspacing'] = (
-                    old_legend.columnspacing)
-                legend_kwargs['labelspacing'] = old_legend.labelspacing
-                legend_kwargs['handlelength'] = old_legend.handlelength
-                legend_kwargs['handletextpad'] = (
-                    old_legend.handletextpad)
+                legend_kwargs = old_legend._get_properties()
             new_legend = axes.legend(ncols=ncols, **legend_kwargs)
             if new_legend:
                 new_legend.set_draggable(draggable)
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -1098,6 +1098,34 @@ def set_frame_on(self, b):
 
     draw_frame = set_frame_on  # Backcompat alias.
 
+    def _get_properties(self):
+        """
+        Return a dictionary of legend properties for recreation.
+
+        This is used by the Qt figure options dialog to preserve legend
+        settings when regenerating the legend.
+        """
+        props = {
+            'loc': self._loc,
+            'fontsize': self._fontsize,
+            'frameon': self.get_frame_on(),
+            'shadow': self.shadow,
+            'framealpha': self.get_frame().get_alpha(),
+            'title': self.get_title().get_text(),
+            'columnspacing': self.columnspacing,
+            'labelspacing': self.labelspacing,
+            'handlelength': self.handlelength,
+            'handletextpad': self.handletextpad,
+            'borderpad': self.borderpad,
+            'borderaxespad': self.borderaxespad,
+            'markerscale': self.markerscale,
+        }
+        if self._bbox_to_anchor is not None:
+            props['bbox_to_anchor'] = self._bbox_to_anchor.bounds
+        if self._mode is not None:
+            props['mode'] = self._mode
+        return props
+
     def get_bbox_to_anchor(self):
         """Return the bbox that the legend will be anchored to."""
         if self._bbox_to_anchor is None:
diff --git a/lib/matplotlib/tests/test_figureoptions_legend.py b/lib/matplotlib/tests/test_figureoptions_legend.py
@@ -1,15 +1,12 @@
-"""Tests for legend preservation in Qt figure options dialog."""
+"""Tests for legend property preservation."""
 import matplotlib
 matplotlib.use('Agg')
 import matplotlib.pyplot as plt
 
 
-def test_legend_properties_preserved():
+def test_get_properties_basic():
     """
-    Test that legend properties are preserved when the legend is
-    regenerated via the Qt figure options dialog.
-
-    Regression test for https://github.com/matplotlib/matplotlib/issues/17775
+    Test that Legend._get_properties() returns the correct properties.
     """
     fig, ax = plt.subplots()
     ax.plot(range(5), label='a')
@@ -28,101 +25,102 @@ def test_legend_properties_preserved():
         handletextpad=1.2,
     )
 
-    old_legend = ax.get_legend()
-    old_loc = old_legend._loc
-    old_fontsize = old_legend._fontsize
-    old_frameon = old_legend.get_frame_on()
-    old_shadow = old_legend.shadow
-    old_title = old_legend.get_title().get_text()
-    old_ncols = old_legend._ncols
-    old_columnspacing = old_legend.columnspacing
-    old_labelspacing = old_legend.labelspacing
-    old_handlelength = old_legend.handlelength
-    old_handletextpad = old_legend.handletextpad
-
-    # Simulate what the patched figureoptions code does
-    draggable = old_legend._draggable is not None
-    ncols = old_legend._ncols
-    legend_kwargs = {}
-    legend_kwargs['loc'] = old_legend._loc
-    if old_legend._bbox_to_anchor is not None:
-        legend_kwargs['bbox_to_anchor'] = (
-            old_legend._bbox_to_anchor.bounds)
-    legend_kwargs['fontsize'] = old_legend._fontsize
-    legend_kwargs['frameon'] = old_legend.get_frame_on()
-    legend_kwargs['shadow'] = old_legend.shadow
-    legend_kwargs['framealpha'] = old_legend.get_frame().get_alpha()
-    legend_kwargs['title'] = old_legend.get_title().get_text()
-    if old_legend._mode is not None:
-        legend_kwargs['mode'] = old_legend._mode
-    legend_kwargs['columnspacing'] = old_legend.columnspacing
-    legend_kwargs['labelspacing'] = old_legend.labelspacing
-    legend_kwargs['handlelength'] = old_legend.handlelength
-    legend_kwargs['handletextpad'] = old_legend.handletextpad
-
-    new_legend = ax.legend(ncols=ncols, **legend_kwargs)
-    if new_legend:
-        new_legend.set_draggable(draggable)
-
-    assert new_legend._loc == old_loc
-    assert new_legend._fontsize == old_fontsize
-    assert new_legend.get_frame_on() == old_frameon
-    assert new_legend.shadow == old_shadow
-    assert new_legend.get_title().get_text() == old_title
-    assert new_legend._ncols == old_ncols
-    assert new_legend.columnspacing == old_columnspacing
-    assert new_legend.labelspacing == old_labelspacing
-    assert new_legend.handlelength == old_handlelength
-    assert new_legend.handletextpad == old_handletextpad
+    legend = ax.get_legend()
+    props = legend._get_properties()
+
+    assert props['loc'] == legend._loc
+    assert props['fontsize'] == 14
+    assert props['frameon'] is False
+    assert props['shadow'] is True
+    assert props['title'] == 'My Legend'
+    assert props['columnspacing'] == 3.0
+    assert props['labelspacing'] == 1.5
+    assert props['handlelength'] == 4.0
+    assert props['handletextpad'] == 1.2
+    assert 'bbox_to_anchor' not in props
+    assert 'mode' not in props
 
     plt.close(fig)
 
 
-def test_legend_regeneration_no_existing_legend():
+def test_get_properties_with_mode_and_bbox():
     """
-    Test that regenerating a legend when none exists still works.
+    Test that _get_properties() includes mode and bbox_to_anchor
+    when they are set.
     """
     fig, ax = plt.subplots()
     ax.plot(range(5), label='a')
 
-    assert ax.get_legend() is None
+    ax.legend(
+        bbox_to_anchor=(0, 1.02, 1, 0.2),
+        loc='lower left',
+        mode='expand',
+        ncols=2,
+    )
 
-    new_legend = ax.legend(ncols=1)
-    assert new_legend is not None
-    assert len(new_legend.get_texts()) == 1
-    assert new_legend.get_texts()[0].get_text() == 'a'
+    legend = ax.get_legend()
+    props = legend._get_properties()
+
+    assert props['mode'] == 'expand'
+    assert 'bbox_to_anchor' in props
 
     plt.close(fig)
 
 
-def test_legend_mode_preserved():
+def test_get_properties_roundtrip():
     """
-    Test that mode='expand' is preserved on legend regeneration.
+    Test that properties from _get_properties() can be used to
+    recreate a legend with the same settings.
     """
     fig, ax = plt.subplots()
     ax.plot(range(5), label='a')
     ax.plot(range(3)[::-1], label='b')
 
     ax.legend(
-        loc='lower left',
-        mode='expand',
+        loc='upper right',
+        fontsize=14,
+        frameon=False,
+        shadow=True,
+        title='My Legend',
         ncols=2,
+        columnspacing=3.0,
+        labelspacing=1.5,
+        handlelength=4.0,
+        handletextpad=1.2,
     )
 
     old_legend = ax.get_legend()
-    old_mode = old_legend._mode
-    old_loc = old_legend._loc
+    props = old_legend._get_properties()
+    ncols = old_legend._ncols
+
+    # Recreate legend using extracted properties
+    new_legend = ax.legend(ncols=ncols, **props)
+
+    assert new_legend._fontsize == 14
+    assert new_legend.get_frame_on() is False
+    assert new_legend.shadow is True
+    assert new_legend.get_title().get_text() == 'My Legend'
+    assert new_legend._ncols == 2
+    assert new_legend.columnspacing == 3.0
+    assert new_legend.labelspacing == 1.5
+    assert new_legend.handlelength == 4.0
+    assert new_legend.handletextpad == 1.2
+
+    plt.close(fig)
+
 
-    legend_kwargs = {}
-    legend_kwargs['loc'] = old_legend._loc
-    legend_kwargs['fontsize'] = old_legend._fontsize
-    legend_kwargs['frameon'] = old_legend.get_frame_on()
-    if old_legend._mode is not None:
-        legend_kwargs['mode'] = old_legend._mode
+def test_legend_regeneration_no_existing_legend():
+    """
+    Test that regenerating a legend when none exists still works.
+    """
+    fig, ax = plt.subplots()
+    ax.plot(range(5), label='a')
 
-    new_legend = ax.legend(ncols=old_legend._ncols, **legend_kwargs)
+    assert ax.get_legend() is None
 
-    assert new_legend._mode == old_mode
-    assert new_legend._loc == old_loc
+    new_legend = ax.legend(ncols=1)
+    assert new_legend is not None
+    assert len(new_legend.get_texts()) == 1
+    assert new_legend.get_texts()[0].get_text() == 'a'
 
     plt.close(fig)
