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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: macOS backend doesn't always pair key_press_event and key_release_event","articleBody":"### Bug summary\n\nI'm trying to better understand the macOS `key_press_event`/`key_release_event` logic. Should each `key_press_event` be paired with a `key_release_event`?\n\nWhile basic usage works, there are several scenarios where this is not the case.\n\n#### Key Repeats\n\nWhile the figure is the active window, press and hold A:\n```\nyou pressed a None None\nyou pressed a None None\nyou pressed a None None\n```\n\nThis occurs due to `keyDown:` being called on a repeating timer to handle macOS keyboard repeats. Is this the correct behavior, or should only the first press be reported?\n\n\n#### Window loses active focus\n\nWhile the figure is the active window, press Control, Shift, A:\n\n```\nyou pressed control None None\nyou pressed ctrl+shift None None\nyou pressed ctrl+A None None\n```\n\nWhile still holding the keys, use the mouse to select another window. When the keys are released, no event will fire. If a window in a different app was selected, there will be no way to tell when the keys were released. Should the macOS backend send release events if it will no longer receive `keyUp:` messages?\n\n\n#### Window gains active focus\n\nThe inverse of the above. Press control and shift in a different window, then select a Figure and release only shift:\n\n```\nyou pressed control None None\n```\n\nThe is never a \"you released shift\" message posted. Still bugged, but not the exact inverse of the \"loses active\" state.\n\n#### Save Figure Fun\n\nSelect a Figure. Press A. While still holding down A, press S:\n\n```\nyou pressed a None None\n…\nyou pressed a None None\nyou pressed a None None\n```\n\nThe save dialog appears. If you release A, no message will be printed (same case as above).\n\nNow press Escape to cancel the dialog:\n```\nyou pressed s None None\nyou released escape None None\n```\n\nYou now get a single pressed s message (even though you stopped pressing it a long time ago) and an unbalanced \"you released escape\" message.\n\n\n\n\n### Code for reproduction\n\nI'm using the following from PR #21512:\n\n```Python\nimport matplotlib.pyplot as plt\nfig = plt.figure()\n\ndef on_key(event):\n    print('you pressed', event.key, event.xdata, event.ydata)\ndef on_key_release(event):\n    print('you released', event.key, event.xdata, event.ydata)\n\nfig.canvas.mpl_connect('key_press_event', on_key)\nfig.canvas.mpl_connect('key_release_event', on_key_release)\nplt.show()\n```\n\n### Actual outcome\n\nSee cases above.\n\n### Expected outcome\n\n(I'm not sure what the desired outcome is.)\n\n### Additional information\n\n_No response_\n\n### Operating system\n\n_No response_\n\n### Matplotlib Version\n\ndev\n\n### Matplotlib Backend\n\n_No response_\n\n### Python version\n\n_No response_\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\nNone","author":{"url":"https://github.com/iccir","@type":"Person","name":"iccir"},"datePublished":"2026-06-13T02:31:36.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/31886/matplotlib/issues/31886"}