[FR]: Allow adjusting probe area bounds

[Thynix]

Is your feature request related to a problem? Please describe.

The XY coordinates assume the probe points are spread uniformly throughout the entire bed. For things like the BLTouch, or other probes where a margin from the edge is either advisable or physically required, this isn't true. This makes it harder to add aluminum foil to compensate for deviations from flatness because the edge of the visualization isn't actually the edge of the bed, and all the XY coordinate numbers are wrong.

Describe the solution you'd like

I'd like to be able to specify the bounds of the area probed within the bed, be that explicitly or with a margin from the edge.

Describe alternatives you've considered

I can determine the actual probe points and consider the claimed coordinates to be their actual equivalents when making decisions, but that doesn't help much with eyeballing the visualization to see where things are.

Additional context

My printer sends leveling reports like

Recv: Bilinear Leveling Grid:
Recv:       0      1      2      3      4
Recv:  0 +0.010 +0.037 +0.020 -0.029 +0.000
Recv:  1 +0.020 -0.010 -0.068 +0.006 +0.014
Recv:  2 -0.019 +0.010 -0.012 +0.020 +0.034
Recv:  3 +0.003 -0.017 -0.038 +0.079 +0.010
Recv:  4 -0.013 +0.038 -0.032 -0.014 -0.012

which I notice doesn't specify coordinates.

As to specifying custom_box for the printer, it could help, but won't exactly solve it. The edge of the visualization will still be the edge of the probe area instead of the edge of the bed. It'd be a workable improvement, though as the bounds are intended to be larger than the printable area, not smaller, it'd be annoying to get warnings when printing close to the edges of the bed.

[jneilliii]

You are correct, the plugin calculates x/y positional data from the number of probe points and bed size when that positional data is not reported, as you found out is rare. Adding a matching offset/margin setting would make sense to use but would "shrink" the visualization to that newly inset bed perimeter, wo would not represent the entire bed. There's no good way to counter that without loads of math calculations, so I felt it better to give the rough approximation and still see the full bed size versus clipping the bed in the visualization. If I could find a good way to do both I would, but nothing has popped up yet.

[Thynix]

Ah, so Unified Bed Leveling will specify coordinates. I didn't realize that. I was using bilinear.

[jneilliii]

Going to track this one under revived issue #130.

[jneilliii]

Added the option to define probe margin/offset in above commit and is available in version 1.1.2rc2. You can change the plugin's release channel in OctoPrint's Software Update settings to Release Candidate and update when prompted if you want to try it out.