matplotlib · thesanatt · Apr 23, 2026 · Apr 23, 2026 · timhoffm · Apr 23, 2026
diff --git a/lib/matplotlib/backends/qt_editor/figureoptions.py b/lib/matplotlib/backends/qt_editor/figureoptions.py
@@ -248,11 +248,34 @@ def apply_callback(data):
         if generate_legend:
             draggable = None
             ncols = 1
+            legend_kwargs = {}
             if axes.legend_ is not None:
                 old_legend = axes.get_legend()
                 draggable = old_legend._draggable is not None
                 ncols = old_legend._ncols
-            new_legend = axes.legend(ncols=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)
+            new_legend = axes.legend(ncols=ncols, **legend_kwargs)
             if new_legend:
                 new_legend.set_draggable(draggable)
 

diff --git a/lib/matplotlib/tests/test_figureoptions_legend.py b/lib/matplotlib/tests/test_figureoptions_legend.py
@@ -0,0 +1,128 @@
+"""Tests for legend preservation in Qt figure options dialog."""
+import matplotlib
+matplotlib.use('Agg')
+import matplotlib.pyplot as plt
+
+
+def test_legend_properties_preserved():
+    """
+    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
+    """
+    fig, ax = plt.subplots()
+    ax.plot(range(5), label='a')
+    ax.plot(range(3)[::-1], label='b')
+
+    ax.legend(
+        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,
+    )
-    ax.legend(
-        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,
-    )
+    initial_props = dict(
+        loc='upper right',
+        fontsize=14,
+        frameon=False,
+        shadow=True,
+        title='My Legend',
+        columnspacing=3.0,
+        labelspacing=1.5,
+        handlelength=4.0,
+        handletextpad=1.2,
+    )
+    legend = ax.legend(ncols=2, **props)
-    ax.legend(
-        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,
-    )
+    initial_props = dict(
+        loc='upper right',
+        fontsize=14,
+        frameon=False,
+        shadow=True,
+        title='My Legend',
+        columnspacing=3.0,
+        labelspacing=1.5,
+        handlelength=4.0,
+        handletextpad=1.2,
+    )
+    legend = ax.legend(ncols=2, **props)
+
+    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
+
+    plt.close(fig)
-    plt.close(fig)
-    plt.close(fig)
+
+
+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')
+
+    assert ax.get_legend() is None
+
+    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)
+
+
+def test_legend_mode_preserved():
+    """
+    Test that mode='expand' is preserved on legend regeneration.
+    """
+    fig, ax = plt.subplots()
+    ax.plot(range(5), label='a')
+    ax.plot(range(3)[::-1], label='b')
+
+    ax.legend(
+        loc='lower left',
+        mode='expand',
+        ncols=2,
+    )
+
+    old_legend = ax.get_legend()
+    old_mode = old_legend._mode
+    old_loc = old_legend._loc
+
+    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
+
+    new_legend = ax.legend(ncols=old_legend._ncols, **legend_kwargs)
+
+    assert new_legend._mode == old_mode
+    assert new_legend._loc == old_loc
+
+    plt.close(fig)