René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: macOS backend reports wrong button for button_release_event","articleBody":"### Bug summary\n\nRun the attached code with the qtagg as well as the macosx backends.\n\nWhile the mouse cursor is over the figure, perform the following:\n\n1. Click mouse. Release mouse\n2. Hold Option: Click mouse. Release mouse.\n3. Hold Control: Click mouse. Release mouse.\n\n### Code for reproduction\n\n```Python\nimport matplotlib.pyplot as plt\n\ndef on_button_press(event):\n    print(f'button press: {event.button}')\ndef on_button_release(event):\n    print(f'button release: {event.button}')\n\nfig = plt.figure()\nfig.canvas.mpl_connect('button_press_event',   on_button_press)\nfig.canvas.mpl_connect('button_release_event', on_button_release)\n\nplt.show()\n```\n\n### Actual outcome\n\nqtagg:\n\n```\nbutton press: 1\nbutton release: 1\nbutton press: 1\nbutton release: 1\nbutton press: 3\nbutton release: 3\n```\n\nmacosx:\n\n```\nbutton press: 1\nbutton release: 1\nbutton press: 2\nbutton release: 1\nbutton press: 3\nbutton release: 1\n```\n\n\n### Expected outcome\n\nBased on these code comments in `_macosx.m`:\n\n```c\nif (modifier \u0026 NSEventModifierFlagControl)\n    /* emulate a right-button click */\n    button = 3;\nelse if (modifier \u0026 NSEventModifierFlagOption)\n    /* emulate a middle-button click */\n    button = 2;\n```\n\nI would expect:\n\n```\nbutton press: 1\nbutton release: 1\nbutton press: 2\nbutton release: 2\nbutton press: 3\nbutton release: 3\n```\n\nHowever, if alt+click should not result in \"middle click\", I would expect macosx to match qtagg.\n\n### Additional information\n\n_No response_\n\n### Operating system\n\nmacOS 14.8.5\n\n### Matplotlib Version\n\ndev\n\n### Matplotlib Backend\n\nqtagg, macosx\n\n### Python version\n\n3.14.5\n\n### Jupyter version\n\n_No response_\n\n### Installation\n\nNone","author":{"url":"https://github.com/iccir","@type":"Person","name":"iccir"},"datePublished":"2026-06-15T03:48:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/31899/matplotlib/issues/31899"}