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        "%gui qt"
      ]
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        "\n# Update data using timer-based events\n\nUpdate VisPy visualizations from a QTimer in the main GUI thread.\n\n## Data Source\n\nThe important part of this script compared to the previous examples is the\n``DataSource`` class. This class generates new image data in an event-based\nworkflow instead of a ``for`` or ``while`` loop. The events in this case are\ngenerated by a QTimer in the main part of the script. The data generation being\nevent-based works well with Qt's event loop to avoid blocking the main GUI\nthread in basic cases (see below).\n\nNote that this class sends the same numpy array instance every iteration\nto avoid creating unnecessary copies of the data. This should not cause\nissues with Qt or VisPy which will typically not modify data and will copy\narrays if necessary.\n\nThe ``run_data_creation`` method includes a commented piece of code to sleep for\na small but significant amount of time. This is to demonstrate that this\nTimer-based data generation will block the main GUI thread and affect user\nexperience if data generation is not fast. This may also occur if the data\ngenerated is large. Examples of data generation that would not be well-suited\nfor this would be those that require contacting a remote resource\n(database, website, instrument, etc) or a complex algorithm.\n\nThe ``run_data_creation`` uses a Qt signal to notify the VisPy Canvas wrapper\nof new data with which to update the visualization. The function/method being\nconnected to the signal is called a \"slot\". To make use of signals and slots\nrequires ``DataSource`` to be a subclass of ``QObject``. This is also\nneeded if you plan on using the class with a ``QThread`` in the future.\n\n## Timer\n\nThis script uses a ``QTimer`` object to trigger the data creation method every\nN seconds (1.0 seconds by default). If the interval is set to \"auto\" the timer\nwill trigger as fast as possible.\n\n## Other Options\n\nIf this script performs fast enough for your use case and on your users\nsystems then using a QTimer may be the easiest option for generating realtime\ndata for your visualization. If your workflow does not fit well into this\nstructure then a threaded option is likely your best bet. See the other data\nsource scripts in this section of the gallery for other examples.\n"
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        "import time  # noqa\nfrom math import sin, pi\n\nimport numpy as np\nfrom PyQt5 import QtWidgets, QtCore\n\nfrom vispy.scene import SceneCanvas, visuals\nfrom vispy.app import use_app, Timer\n\nIMAGE_SHAPE = (600, 800)  # (height, width)\nCANVAS_SIZE = (800, 600)  # (width, height)\nNUM_LINE_POINTS = 200\n\nCOLORMAP_CHOICES = [\"viridis\", \"reds\", \"blues\"]\nLINE_COLOR_CHOICES = [\"black\", \"red\", \"blue\"]\n\n\nclass Controls(QtWidgets.QWidget):\n    def __init__(self, parent=None):\n        super().__init__(parent)\n        layout = QtWidgets.QVBoxLayout()\n        self.colormap_label = QtWidgets.QLabel(\"Image Colormap:\")\n        layout.addWidget(self.colormap_label)\n        self.colormap_chooser = QtWidgets.QComboBox()\n        self.colormap_chooser.addItems(COLORMAP_CHOICES)\n        layout.addWidget(self.colormap_chooser)\n\n        self.line_color_label = QtWidgets.QLabel(\"Line color:\")\n        layout.addWidget(self.line_color_label)\n        self.line_color_chooser = QtWidgets.QComboBox()\n        self.line_color_chooser.addItems(LINE_COLOR_CHOICES)\n        layout.addWidget(self.line_color_chooser)\n\n        layout.addStretch(1)\n        self.setLayout(layout)\n\n\nclass CanvasWrapper:\n    def __init__(self):\n        self.canvas = SceneCanvas(size=CANVAS_SIZE)\n        self.grid = self.canvas.central_widget.add_grid()\n\n        self.view_top = self.grid.add_view(0, 0, bgcolor='cyan')\n        image_data = _generate_random_image_data(IMAGE_SHAPE)\n        self.image = visuals.Image(\n            image_data,\n            texture_format=\"auto\",\n            cmap=COLORMAP_CHOICES[0],\n            parent=self.view_top.scene,\n        )\n        self.view_top.camera = \"panzoom\"\n        self.view_top.camera.set_range(x=(0, IMAGE_SHAPE[1]), y=(0, IMAGE_SHAPE[0]), margin=0)\n\n        self.view_bot = self.grid.add_view(1, 0, bgcolor='#c0c0c0')\n        line_data = _generate_random_line_positions(NUM_LINE_POINTS)\n        self.line = visuals.Line(line_data, parent=self.view_bot.scene, color=LINE_COLOR_CHOICES[0])\n        self.view_bot.camera = \"panzoom\"\n        self.view_bot.camera.set_range(x=(0, NUM_LINE_POINTS), y=(0, 1))\n\n    def set_image_colormap(self, cmap_name: str):\n        print(f\"Changing image colormap to {cmap_name}\")\n        self.image.cmap = cmap_name\n\n    def set_line_color(self, color):\n        print(f\"Changing line color to {color}\")\n        self.line.set_data(color=color)\n\n    def update_data(self, new_data_dict):\n        print(\"Updating data...\")\n        self.image.set_data(new_data_dict[\"image\"])\n        self.line.set_data(new_data_dict[\"line\"])\n\n\ndef _generate_random_image_data(shape, dtype=np.float32):\n    rng = np.random.default_rng()\n    data = rng.random(shape, dtype=dtype)\n    return data\n\n\ndef _generate_random_line_positions(num_points, dtype=np.float32):\n    rng = np.random.default_rng()\n    pos = np.empty((num_points, 2), dtype=np.float32)\n    pos[:, 0] = np.arange(num_points)\n    pos[:, 1] = rng.random((num_points,), dtype=dtype)\n    return pos\n\n\nclass MyMainWindow(QtWidgets.QMainWindow):\n    def __init__(self, canvas_wrapper: CanvasWrapper, *args, **kwargs):\n        super().__init__(*args, **kwargs)\n\n        central_widget = QtWidgets.QWidget()\n        main_layout = QtWidgets.QHBoxLayout()\n\n        self._controls = Controls()\n        main_layout.addWidget(self._controls)\n        self._canvas_wrapper = canvas_wrapper\n        main_layout.addWidget(self._canvas_wrapper.canvas.native)\n\n        central_widget.setLayout(main_layout)\n        self.setCentralWidget(central_widget)\n\n        self._connect_controls()\n\n    def _connect_controls(self):\n        self._controls.colormap_chooser.currentTextChanged.connect(self._canvas_wrapper.set_image_colormap)\n        self._controls.line_color_chooser.currentTextChanged.connect(self._canvas_wrapper.set_line_color)\n\n\nclass DataSource(QtCore.QObject):\n    \"\"\"Object representing a complex data producer.\"\"\"\n\n    new_data = QtCore.pyqtSignal(dict)\n\n    def __init__(self, num_iterations=1000, parent=None):\n        super().__init__(parent)\n        self._count = 0\n        self._num_iters = num_iterations\n        self._image_data = _generate_random_image_data(IMAGE_SHAPE)\n        self._line_data = _generate_random_line_positions(NUM_LINE_POINTS)\n\n    def run_data_creation(self, timer_event):\n        if self._count >= self._num_iters:\n            return\n\n        # Uncomment to mimic a long-running computation\n        # time.sleep(3)\n        image_data = self._update_image_data(self._count)\n        line_data = self._update_line_data(self._count)\n        self._count += 1\n\n        data_dict = {\n            \"image\": image_data,\n            \"line\": line_data,\n        }\n        self.new_data.emit(data_dict)\n\n    def _update_image_data(self, count):\n        img_count = count % IMAGE_SHAPE[1]\n        self._image_data[:, img_count] = img_count / IMAGE_SHAPE[1]\n        rdata_shape = (IMAGE_SHAPE[0], IMAGE_SHAPE[1] - img_count - 1)\n        self._image_data[:, img_count + 1:] = _generate_random_image_data(rdata_shape)\n        return self._image_data.copy()\n\n    def _update_line_data(self, count):\n        self._line_data[:, 1] = np.roll(self._line_data[:, 1], -1)\n        self._line_data[-1, 1] = abs(sin((count / self._num_iters) * 16 * pi))\n        return self._line_data\n\n\nif __name__ == \"__main__\":\n    app = use_app(\"pyqt5\")\n    app.create()\n    data_source = DataSource()\n    canvas_wrapper = CanvasWrapper()\n    win = MyMainWindow(canvas_wrapper)\n\n    data_source.new_data.connect(canvas_wrapper.update_data)\n    # Change \"1.0\" to \"auto\" to run connected function as quickly as possible\n    timer = Timer(\"1.0\", connect=data_source.run_data_creation, start=True)\n\n    # stop the timer when the window is closed and destroyed\n    # not always needed, but needed for vispy gallery creation\n    win.destroyed.connect(timer.stop)\n\n    win.show()\n    app.run()"
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