Add live_view module to qutil.plotting.

The live_view module provides a matplotlib interface for concurrent data viewing using animations and blitting. For line plots without axis rescaling, frame rates of ~100 fps can be reached. A 1080x1920 pixel image can be displayed at ~20 fps. Data sources are pushed to a background thread from where they can fill a queue.

See mjolnir commits a771a5cc..205318e6 for earlier history.

qutil/plotting/core.py

@@ -11,15 +11,23 @@ import dataclasses
 import pathlib
 import warnings
 from contextlib import contextmanager
-from typing import Sequence, Tuple, Mapping, Any, Union, List, Callable
+from typing import Sequence, Tuple, Mapping, Any, Union, List, Callable, Literal
 from weakref import WeakValueDictionary
 
 import matplotlib as mpl
+import matplotlib.pyplot as plt
 import numpy as np
 import numpy.typing as npt
 import pandas as pd
 from cycler import cycler
-from matplotlib import pyplot as plt
+from matplotlib import ticker
+
+from ..typecheck import check_literals
+
+try:
+    import qcodes
+except ImportError:
+    qcodes = None
 
 __all__ = [
     "CoordClicker",
@@ -33,6 +41,7 @@ __all__ = [
     "cycle_plots",
     "update_plot",
     "list_styles",
+    "reformat_axis",
     "get_rwth_color_cycle",
     "rwth_color_cycle",
     "rwth_color_cycle_25",
@@ -707,6 +716,52 @@ def list_styles(include_matplotlib_styles: bool = False) -> List[str]:
         return custom_styles
 
 
+@check_literals
+def reformat_axis(ax_or_cbar: mpl.axes.Axes | mpl.colorbar.Colorbar, data: npt.ArrayLike,
+                  unit: str, which: Literal['x', 'y', 'c']) -> str:
+    """Scales an axis with SI prefixes.
+
+    .. note::
+        This function requires :mod:`qcodes` to be installed.
+
+    Parameters
+    ----------
+    ax_or_cbar :
+        The matplotlib :class:`~matplotlib:matplotlib.axes.Axes` or
+        :class:`~matplotlib:matplotlib.colorbar.Colorbar` to reformat.
+    data :
+        The data to reformat.
+    unit :
+        The unit of the data.
+    which :
+        The type of axis. Either x, y, or c for colorbar axis.
+
+    Returns
+    -------
+    prefix :
+        The SI unit prefix for the reformatted data.
+
+    """
+    if qcodes is None:
+        raise RuntimeError('This function requires qcodes.')
+
+    if np.isnan(data).all():
+        # preempt unhandled exception in find_scale_and_prefix
+        return ''
+
+    prefix, scale = qcodes.plotting.axis_labels.find_scale_and_prefix(data, unit)
+    formatter = ticker.FuncFormatter(lambda value, pos: f"{value * 10 ** (-scale):g}")
+
+    if which == 'x':
+        ax_or_cbar.xaxis.set_major_formatter(formatter)
+    elif which == 'y':
+        ax_or_cbar.yaxis.set_major_formatter(formatter)
+    else:
+        ax_or_cbar.formatter = formatter
+        ax_or_cbar.update_ticks()
+    return prefix
+
+
 @dataclasses.dataclass
 class LaTeXPlotHelper:
     A4_SIZE_INCHES = (8.25, 11.75)