René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[Bug]: DPI keeps doubling when creating a new MatPlotLib QtWidget in qt6","articleBody":"### Bug summary\r\n\r\nI ran into this bizarre bug, I am not sure if it's a skill issue on my end, but I am trying to embed a plot in my qt6 application. Allowing the user to plot and replot for some reason keeps increasing the sizes of my chart elements, but *only* when I have display scaling on (e.g. 125%, 150% etc). To illustrate:\r\n\r\n![wat](https://github.com/matplotlib/matplotlib/assets/59785388/286c07a7-e217-4fea-82db-817f7c3b3b10)\r\n\r\nSee below for the code, basically I am creating a new plot every time there is a mouse click on that row. Embedding `print(self.chart.figure.dpi)` shows that my plot's dpi keeps doubling every other time I trigger a click. Console output:\r\n\r\n```\r\n100.0\r\n100.0\r\n200.0\r\n200.0\r\n400.0\r\n400.0\r\n```\r\n\r\nI can workaround this by explicitly setting the figure DPI, e.g. figure.dpi = 100 when creating it. But I assume that means I'm giving up display scaling\r\n        \r\n\r\n### Code for reproduction\r\n\r\n```python\r\nimport matplotlib\r\n\r\nmatplotlib.use(\"Qt5Agg\")\r\nfrom matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg\r\nfrom matplotlib.figure import Figure\r\nfrom PyQt6.QtWidgets import (\r\n    QWidget,\r\n    QVBoxLayout, QFrame\r\n)\r\n\r\nclass GraphView(QWidget):\r\n    def __init__(self):\r\n        super().__init__()\r\n        self.layout = QVBoxLayout()\r\n        self.separator = None\r\n        self.chart = MplCanvas()\r\n\r\n        self.figures = None\r\n\r\n        self.init_widget()\r\n\r\n    def init_widget(self):\r\n        self.init_separator()\r\n        self.layout.addWidget(self.separator)\r\n        self.layout.addWidget(self.chart)\r\n        self.setLayout(self.layout)\r\n    ...\r\n    # Note this is the code that triggers when I click a row.\r\n    def update_graph(self, figure):\r\n\r\n        self.chart.deleteLater()\r\n        self.chart = MplCanvas(fig=figure)\r\n    \r\n        self.layout.addWidget(self.chart)\r\n        self.layout.update()\r\n\r\nclass MplCanvas(FigureCanvasQTAgg):\r\n    def __init__(self, fig=Figure()):\r\n        super(MplCanvas, self).__init__(fig)\r\n\r\n```\r\n\r\n\r\n### Actual outcome\r\n\r\nFigure DPI keeps dynamically doubling\r\n\r\n### Expected outcome\r\n\r\nDPI shouldn't double like that, it's madness :frowning_face: \r\n\r\n### Additional information\r\n\r\n_No response_\r\n\r\n### Operating system\r\n\r\nWindows, Linux\r\n\r\n### Matplotlib Version\r\n\r\n3.6.3\r\n\r\n### Matplotlib Backend\r\n\r\nQtAgg\r\n\r\n### Python version\r\n\r\n3.11.4\r\n\r\n### Jupyter version\r\n\r\n_No response_\r\n\r\n### Installation\r\n\r\npip","author":{"url":"https://github.com/hydroEng","@type":"Person","name":"hydroEng"},"datePublished":"2023-07-24T10:38:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":12},"url":"https://github.com/26380/matplotlib/issues/26380"}