Merge pull request #27206 from meeseeksmachine/auto-backport-of-pr-27205-on-v3.8.x

ksunden · web-flow · commit 2521750b0df2 · 2023-10-26T12:34:35.000-05:00
Backport PR #27205 on branch v3.8.x (Improve legend picking example)
diff --git a/galleries/examples/event_handling/legend_picking.py b/galleries/examples/event_handling/legend_picking.py
@@ -18,33 +18,46 @@
 import numpy as np
 
 t = np.linspace(0, 1)
-y1 = 2 * np.sin(2*np.pi*t)
-y2 = 4 * np.sin(2*np.pi*2*t)
+y1 = 2 * np.sin(2 * np.pi * t)
+y2 = 4 * np.sin(2 * np.pi * 2 * t)
 
 fig, ax = plt.subplots()
 ax.set_title('Click on legend line to toggle line on/off')
-line1, = ax.plot(t, y1, lw=2, label='1 Hz')
-line2, = ax.plot(t, y2, lw=2, label='2 Hz')
+(line1, ) = ax.plot(t, y1, lw=2, label='1 Hz')
+(line2, ) = ax.plot(t, y2, lw=2, label='2 Hz')
 leg = ax.legend(fancybox=True, shadow=True)
 
 lines = [line1, line2]
-lined = {}  # Will map legend lines to original lines.
-for legline, origline in zip(leg.get_lines(), lines):
-    legline.set_picker(True)  # Enable picking on the legend line.
-    lined[legline] = origline
+map_legend_to_ax = {}  # Will map legend lines to original lines.
+
+pickradius = 5  # Points (Pt). How close the click needs to be to trigger an event.
+
+for legend_line, ax_line in zip(leg.get_lines(), lines):
+    legend_line.set_picker(pickradius)  # Enable picking on the legend line.
+    map_legend_to_ax[legend_line] = ax_line
 
 
 def on_pick(event):
     # On the pick event, find the original line corresponding to the legend
     # proxy line, and toggle its visibility.
-    legline = event.artist
-    origline = lined[legline]
-    visible = not origline.get_visible()
-    origline.set_visible(visible)
+    legend_line = event.artist
+
+    # Do nothing if the source of the event is not a legend line.
+    if legend_line not in map_legend_to_ax:
+        return
+
+    ax_line = map_legend_to_ax[legend_line]
+    visible = not ax_line.get_visible()
+    ax_line.set_visible(visible)
     # Change the alpha on the line in the legend, so we can see what lines
     # have been toggled.
-    legline.set_alpha(1.0 if visible else 0.2)
+    legend_line.set_alpha(1.0 if visible else 0.2)
     fig.canvas.draw()
 
+
 fig.canvas.mpl_connect('pick_event', on_pick)
+
+# Works even if the legend is draggable. This is independent from picking legend lines.
+leg.set_draggable(True)
+
 plt.show()
