Strip::notify_property_changed accesses _stripable without verifying
that is not null. However it is possible for this to be null, so
add a null check.
Only enable the master display and meter modes for Qcon devices if this
surface is in the master position. Extenders don't have master meters
or master displays.
Logic to detect an extender has to be based on if this surface object is
the master position. Has master fader is true for all surfaces in this
"device".
Old and new strings are compared before sending to keep traffic down. To
ensure that we send all the required characters be sure to init the last
value to characters that are never going to appear in a real string.
Space is a bad choice since it is a valid character. Use NUL instead.
The device info file allows key names and values to be configured in each
device file. Use that information when building the Functions Keys tab in
the Mackie protocol setup dialog.
While surfaces are being created it is possible to have surfaces, but
not have a master surface yet. This happens when the config calls
for extenders to the left of the master section. Don't assume that
if we have surfaces, the master surface is available.
This resolves a PBD vs ARDOUR namespace error for some compilers:
```
error: reference to 'microseconds_t' is ambiguous
libs/pbd/pbd/microseconds.h:29:19: error: candidates are: typedef uint64_t PBD::microseconds_t
libs/ardour/ardour/types.h:81:29: error: typedef PBD::microseconds_t ARDOUR::microseconds_t
```
If the wrong device profile is selected (ex Xtouch One) but another device
is connected (Xtouch), it is possible to have a master fader on the
device, but not in the code. This would then cause a crash when the
master fader was touched.
This just protects from a wrong configuration.
In some cases old and/or conflicting port names were saved
with the session (e.g. "Faderport" for FP1,8). Loading old sessions
then merges this state into the config, which could lead to
port-registration failure when the surfaces was enabled.
Follow Session::setup_bundles() lead for single channel
MIDI bundles. This cleans-up the port-matrix display and
removes redundant names. The underlying engine port-name
is not of interest to the user.
