René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: Draggable legend with use_blit hides legend after legend picking","articleBody":"### Bug summary\n\nUsing the legend picking example (https://matplotlib.org/stable/gallery/event_handling/legend_picking.html) and changing the next last line from leg.set_draggable(True) to leg.set_draggable(True, use_blit=True) then legend is not showing after picking it. Clicking again over its position makes it visible again.\r\nSetting the legend draggable again (after being picked/clicked) with use_blit=False does not help.\r\nBest regards, Daniel\n\n### Code for reproduction\n\n```Python\n# https://matplotlib.org/stable/gallery/event_handling/legend_picking.html\r\n\r\nimport matplotlib.pyplot as plt\r\nimport numpy as np\r\n\r\nt = np.linspace(0, 1)\r\ny1 = 2 * np.sin(2 * np.pi * t)\r\ny2 = 4 * np.sin(2 * np.pi * 2 * t)\r\n\r\nfig, ax = plt.subplots()\r\nax.set_title('Click on legend line to toggle line on/off')\r\n(line1, ) = ax.plot(t, y1, lw=2, label='1 Hz')\r\n(line2, ) = ax.plot(t, y2, lw=2, label='2 Hz')\r\nleg = ax.legend(fancybox=True, shadow=True)\r\n\r\nlines = [line1, line2]\r\nmap_legend_to_ax = {}  # Will map legend lines to original lines.\r\n\r\npickradius = 5  # Points (Pt). How close the click needs to be to trigger an event.\r\n\r\nfor legend_line, ax_line in zip(leg.get_lines(), lines):\r\n    legend_line.set_picker(pickradius)  # Enable picking on the legend line.\r\n    map_legend_to_ax[legend_line] = ax_line\r\n\r\n\r\ndef on_pick(event):\r\n    # On the pick event, find the original line corresponding to the legend\r\n    # proxy line, and toggle its visibility.\r\n    legend_line = event.artist\r\n\r\n    # Do nothing if the source of the event is not a legend line.\r\n    if legend_line not in map_legend_to_ax:\r\n        return\r\n\r\n    ax_line = map_legend_to_ax[legend_line]\r\n    visible = not ax_line.get_visible()\r\n    ax_line.set_visible(visible)\r\n    # Change the alpha on the line in the legend, so we can see what lines\r\n    # have been toggled.\r\n    legend_line.set_alpha(1.0 if visible else 0.2)\r\n    fig.canvas.draw()\r\n\r\n\r\nfig.canvas.mpl_connect('pick_event', on_pick)\r\n\r\n# Works even if the legend is draggable. This is independent from picking legend lines.\r\nleg.set_draggable(True, use_blit=True)\r\n\r\nplt.show()\n```\n\n\n### Actual outcome\n\nThe legend is not showing after picking it. Clicking again over its position makes it visible again.\n\n### Expected outcome\n\nLegend is visible at all times.\n\n### Additional information\n\n_No response_\n\n### Operating system\n\nWindows\n\n### Matplotlib Version\n\n3.8.1\n\n### Matplotlib Backend\n\nTkAgg\n\n### Python version\n\n3.9.7\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\npip","author":{"url":"https://github.com/dallas74","@type":"Person","name":"dallas74"},"datePublished":"2024-04-24T10:36:40.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/28129/matplotlib/issues/28129"}