/set_surface has two values the user needs to calculate before use. In general these will not be calculated at run time, but beforehand. There may be more than one button with different values to turn various kinds of feedback on or off or to determine which kinds of strips are currently viewed/controlled.
Both feedback and strip-types use bitsets to keep track what they are doing. Any number in a computer is made out of bits that are on or off, but we represent them as normal base 10 numbers. Any one bit turned on will add a unique value to the number as a whole. So for each kind of feedback or strip type to be used, that number should be added to the total.
strip_types is an integer made up of bits. The easy way to deal with this is to think of strip_types items being worth a number and then adding all those numbers together for a value to send. Strip Types will determine What kind of strips will be included in bank. This would include: Audio, MIDI, busses, VCAs, Master, Monitor and hidden or selected strips.
Selected and Hidden bits are normally not needed as Ardour defaults to showing Selected strips and not showing Hidden strips. The purpose of these two flags is to allow showing only Selected strips or only Hidden strips. Using Hidden with other flags will allow Hidden strips to show inline with other strips.
Use Group on will tell ardour that any control on a strip that is part
of a group will affect all strips within that group. Default is off
or the control should only affect the strip the control is applied to.
The /use_group f state command can be used to temporarily
change this on the fly.
Some handy numbers to use might be: 15 (all tracks and busses - 1 + 2 + 4 + 8), 31 (add VCAs to that - 15 + 16). Master or Monitor strips are generally not useful on a surface that has dedicated controls for these strips as there are /master* and /monitor* commands already. However, on a surface with just a bank of fader strips, adding master or monitor would allow access to them within the banks. Selected would be useful for working on a group or a set of user selected strips. Hidden shows strips the GUI has hidden. As such, a control surface will likely have a number of buttons with different strip_types for convenience.
Audio Aux? say what? I am sure most people will have noticed that they can find no Aux strips in the Ardour mixer. There are none. There are busses that can be used a number of ways. From analog days, in OSC, a bus is something that gets used as a sub mix before ending up going to Master. An auxiliary bus is used like a separate mixer and its output goes outside the program or computer to be used as: a monitor mix, a back up recording, or what have you. In OSC where controller strips may be limited, it may be useful not to use up a strip for an aux that is not really a part of the mix. It is also useful to get a list of only aux busses if the control surface is a phone used to provide talent monitor mix control on stage. Each performer would be able to mix their own monitor. The user is free to enable both busses and auxes if they would prefer.
Ardour allows any of it's strips to be hidden so that they do not show up on the GUI mixer or editor. OSC follows the GUI by default and will not show hidden strips. As of Ardour 6.0 the OSC commands include /select/hide y/n for the selected strip and /strip/hide ssid y/n for any strip. This allows the control surface to hide or unhide a strip. What may not be obvious is that hiding a strip makes it disappear and become unselected. So if a selected strip is hidden, it is no longer selected and the select channel will show the default select strip (Master). In order to show a hidden strip, the hidden strips need to be shown first using the /set_surface/strip_types 512 command to show only hidden strips. Then use the /strip/hide SSID 0 or /select/hide 0 to show that strip. Of course, because only hidden strips are showing, the strip you have set to no long hide will seem to vanish. A /set_surface/strip_types 159 will then show the default strip types or replace the 159 with the desired strip_types.
When hiding more than one strip in a row, check the strip name before
hiding as the strips will move as each strip is hidden just as it does
with the GUI mixer. So to hide strips 5, 6 and 7, the hide button
for ssid 5 is pressed 3 times. A more intuitive method
would be to hide strips from right to left (7, 6 and 5) which will
work as expected.
In short, shown strips can only be hidden when they are viewable and hidden strip can only shown (or un-hid) when strip_types include hidden strips.
Feedback is an integer made up of bits. The easy way to deal with this is to think of feedback items being worth a number and then adding all those numbers together for a value to send.
So using a value of 19 (1 + 2 + 16) would turn on feedback for strip and master controls, but leave meters, timecode and bar/beat feedback off.