Signal handles and multi-axis support

[TimonTerBraak]

Maybe you can have a look at this? Not necessarily merge it right away, it probably needs some work / thinking, even if you would like this feature. This branch prototyped multi-axis support, such that signals can individually scaled and panned, as it is quite common that correlated signals have a vast different domain. It also adds 'signal handles' to the left of the plot, similar to most digital oscilloscopes. This handle can be used for both panning and selecting that signal as being 'active'. Note that the vertical axis on the right is then changed to the active signal. While correct, this part needs some visual changes to ensure that it is clear to which signal the vertical axis belongs to. I think something similar to this feature is useful to add the plotting of digital signals. It then allows you to organise the plot area, again similar to digital oscilloscopes. Let me know what you think.

[windelbouwman]

Glad to see this change was possible at all, I think the codebase can be modified fairly easy.

I'm not too sure about this change, one thought I had is how far into the direction of logic analyzer / scope I would like to go. There are good tools such as sigrok which are logic analyzers which usually have this kind of view.

Another idea about the multi axis would be to have an option for the plot to show a seperate axis for each signal in the plot, and allow to select it. Then the vertical zooming/panning will be done for the selected signal. I think at least all axis should be visible, preferably with the color of the signal. Maybe we also require the grid to be present multiple times?

Anyway, good proposal! I'm not sure where this whole thing is going, so I would like to keep this idea around for some time.

[TimonTerBraak]

Glad to see this change was possible at all, I think the codebase can be modified fairly easy.

Yes, it is quite accessible.

I'm not too sure about this change, one thought I had is how far into the direction of logic analyzer / scope I would like to go. There are good tools such as sigrok which are logic analyzers which usually have this kind of view.

The problem of plotting multiple signals with a vast different range remains. If one signal is of orders of magnitude larger than a second one, plotting them in the same area makes little sense for the secondary signal. This is typically resolved by scaling the range of either of the signals (using a dedicated axis).

Another idea about the multi axis would be to have an option for the plot to show a seperate axis for each signal in the plot, and allow to select it. Then the vertical zooming/panning will be done for the selected signal. I think at least all axis should be visible, preferably with the color of the signal. Maybe we also require the grid to be present multiple times?

Note that in the 'legend bar' branch, the selectability of signals has improved and it is always clear what signal is selected. Just to let you know...

The challenge here is to keep the plot area as clean as possible. Not even all decent scopes are good at that. The visuals of the data aggregations are nice, but are at the same time already much more that a single line. Adding multiple grids and axis gives too much clutter, perhaps. The black drawing color is clean. Coloring the axis is not that nice, because you have to be careful on the color usage. When doing so, it works best on a black background; then it requires a switch to a dark-themed tool. The question that remains is how valuable the y-axis actually is. If we have plots with multiple signals, is it not likely that we want to relate some secondary signals to a dominant one (the one with the y-axis)? And we now have the cursor to quickly have the actual value of all signals. If multiple visible axis are important, would it be sufficient to create multiple plots, each having a different y-axis?