Add support for third brush vertical position, for washing the brush

[oskay]

• Will need way to set this height (e.g., a slider in the preferences)
• Will go lower than painting height, so as to mash the bristles into the bottom of the water dish.

[techninja]

Not to open the can of worms... but this kinda opens the can of worms I'd been avoiding for a bit.

The proper way to manage this:

• Use the existing proposal in https://github.com/techninja/cncserver/issues/18, which would take the lowest drop setting as maximum, and the highest lift setting as minimum, then allow for any value from 0 to 1 to be set for height (and/or some named presets as suggested in the ticket linked above)
• Once implemented in cncserver, all references in Robopaint to setting the pen "down" will be manually separated by use case, wherein the value sent for brush cleaning would be "1", the value sent for painting could be "0.7" or some other slider customized value as a percentage between the high and low point.
• This opens up a number of different issues involving assumed heights on "non-interactive" things like tool changes. Chances are the height for washing is not the height you want for getting paint (though it may be a bit closer to the height you want for painting)
• My best guess would be that perhaps we use the named height settings for everything (possibly replacing assumed tool change movements via https://github.com/techninja/cncserver/issues/39), and provide a nice interface with sliders (and appropriate defaults) for all important named heights. Up [0%], Wipe [20%], Paint Paper [60%], Get Paint [70%], Wash [100%]
• If doing this, we may want to consider changing the brush UP and DOWN indicators to be represented by a more absolute value, as they will set the range for all percentage value positions that come after.

The cheap hack for managing this:

• Implement a specialty "just for washing" height setting.
• The "down" position would remain the painting height for set pen "1"
• Washing height would only be available in CNC server for tool changes to water.

[oskay]

Cheaper-yet hack: Do not modify CNCserver.

Use existing functionality of CNCserver to change pen-up and pen-down position when needed. With the present design of CNCserver, these are configured in the settings; so it should be possible to change the setpoints when needed.

Basic idea: When wash cycle initiates, set pen-down height to WASH level. When wash cycle completes, set pen-down height back to PAINT level.

[techninja]

Yes, yes.. that would work. I think I had that in my brain at some point, just got stuck on thinking of it as a CNCserver thing.

I am hesitant to implement this, (though less hesitant if it only touches Robopaint), for the following reasons:

• Brush washing at draw height has been "good enough" for hundreds of paintings, though a lower height would likely improve it, I'm not sure it's worth implementing as a quick hack when a full circle solution is already mostly planned.
• This would be completely unavailable to apps via the API as the current height setting adjustment stuff is actually outside of the API, as the "clientside" app in node-webkit has low-level access to CNCserver and shortcuts this.

One benefit of doing it this way, is retaining simplicity. Adding full height range and named positions adds complexity, but far more control. Though in theory would could operate the API in the exact same v1 spec definition.

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Two options moving forward:

1. Implement this as a quick hack (and optionally add height min/max setting to the API to allow for similar usage in API based apps)
2. Implement this in the proper API way, with named heights and Robopaint adjusted to work with it

[oskay]

For washing, we want to be able to lower the brush as much as possible, so it's probably a good idea, to at least implement it as a quick hack.

I do not think that we need CNCserver to be aware of multiple named positions at this time. Suggested future modification at techninja/cncserver#40

[techninja]

Alright, alright. Issue to manage the "future" modification should be at https://github.com/techninja/cncserver/issues/18 , and the settings API access at https://github.com/techninja/cncserver/issues/40 should be implemented "along with" this hack. Should be very straightforward anyways, thanks to nconf.

One side issue is retained here: When actively setting the height, it helps to see what the height is by changing it on the bot, but there's currently no reset of the pen back to its original state once complete. This actually messes up assumed state in Robopaint as well. Should this be stored on settings entry and reset on settings exit? If so, should be filed under a new issue.

[oskay]

I suggest resetting the pen height back to "up" when closing the settings dialog.

[techninja]

Settings modal dialog currently does not pause progress or spooling/printing, therefore forcing the pen up on settings close willy nilly may be a bad idea. Perhaps only after height adjustment?

[oskay]

So... currently, you can adjust the pen heights while printing? Sounds pretty iffy!

[techninja]

Yes, among other things. It's actually somewhat handy for some things. That one specifically sounds like a recipe for disaster.