Limited number of plot colors

[bernhardlang]

When developing a plugin for a device with up to eight input channels (activation on demand), the PyMoDAQ machinery got stuck on an IndexError exception when the number of channels exceeded seven. The solution was to add another color in config_pymodaq_utils.toml ... after an interesting journey through the internals :-)

Wouldn't it be better to introduce a fallback mechanism on color indices which wrap around when the end of the list of configured plotting colors is reached?

BTW, shouldn't the definition of the PlotColors class reside in pymodaq_gui rather than in pymodaq_utils?

[seb5g]

Yes a looping mechanisms could be implemented. As for the location, I think I use it also in pymodaq_data matplotlib based data plotter hence a location in the utils module

[seb5g]

actually the looping mechanisms is present:

How do you get an error?

[bernhardlang]

By emitting DataFromPlugins from the plugin callback with data and label arrays having length larger than seven.

The log reads

File "[...]/pymodaq_gui/src/pymodaq_gui/plotting/data_viewers/viewer0D.py", line 109, in update_display_items
self._plot_items.append(pyqtgraph.PlotDataItem(pen=self.colors[ind]))
IndexError: list index out of range

self.colors contained only seven entries before adding one in the config toml, which made the error message disappearing.

It looks like the code snippet you're showing is not taken into account in this location (various other lines around this spot in viewer0D.py use the same direct approach without modulus wrap-around).

[seb5g]

then this should be corrected fro with using the right object and not the direct list from config. Could you work on a PR?

[bernhardlang]

I'll have a look if I can figure out how to catch this.

[seb5g]

whenever there is an import of the list plot_colors directly from the config, replace this by an instance of the PlotColor object

[bernhardlang]

line 22 of Viewer0D.py

PLOT_COLORS = [dict(color=color) for color in utils.plot_colors]

establishes a list of seven dictionaries containing each a PlotColors object to the key 'color'

[{'color': (255, 255, 255)}, {'color': (255, 0, 0)}, ...

The first of these items is used in line 109 to set the color of the first curve, the second of the second etc until the list runs out of members -> ouch. What is the meaning of this list of dicts?

Changing the default argument in the init routine to utils.plot_colors and supplying a dict {'color': self.colors[ind] } where needed instead seems to fix the issue. However, the list of dicts is used also in the add_data_displayer method of View0D. I haven't checked whether that leads to the same kind of bug further down.