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Oct 26, 2023
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Improve legend picking example #27205

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39 changes: 26 additions & 13 deletions galleries/examples/event_handling/legend_picking.py
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Original file line number Diff line number Diff line change
Expand Up @@ -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()