0010429: Mackie Control: "single fader follows selection" only works for the first 8 stripables (X-Touch One) - MantisBT

ID	Project	Category	View Status	Date Submitted	Last Update

0010429	ardour	bugs	public	2026-07-04 20:29	2026-07-04 20:30

Reporter	bourrinlepoulpe	Assigned To
Priority	normal	Severity	minor	Reproducibility	always
Status	new	Resolution	open
Platform	Microsoft	OS	Windows	OS Version	11
Product Version	9.7

Summary	0010429: Mackie Control: "single fader follows selection" only works for the first 8 stripables (X-Touch One)
Description	On devices using <SingleFaderFollowsSelection value="yes"/> (e.g. the Behringer X-Touch One), the fader only follows GUI track selection for stripables within the first n_strips() (8) positions of the session. Selecting any track/bus beyond that: the fader drops to -inf and the scribble strip goes blank. This matches an older unresolved forum report: https://discourse.ardour.org/t/behringer-x-touch-one-channel-banking-issue/107252 Cause : In MackieControlProtocol::stripable_selection_changed() (libs/surfaces/mackie/mackie_control_protocol.cc), the loop that collects selected stripables increments 'added' for every stripable SCANNED instead of every stripable MAPPED, so the search never looks past the first n_strips() entries of the sorted list: for (; r != sorted.end() && added < (si)->n_strips (false); ++r, ++added) { if ((r)->is_selected()) { stripables.push_back (r); } } If the selected stripable sits beyond position 8, 'stripables' stays empty and map_stripables() nulls every strip. Fix Only count stripables actually retained, so the scan covers the whole session while still mapping at most n_strips() per surface: for (; r != sorted.end() && added < (si)->n_strips (false); ++r) { if ((r)->is_selected()) { stripables.push_back (r); ++added; } } Tested with an X-Touch One (MC standard mode, "X-Touch One" device file): selection following now works for any track/bus in a session with more than 8 stripables.
Steps To Reproduce	1. Connect an X-Touch One, enable Mackie Control, device "X-Touch One". 2. Create a session with more than 8 tracks/busses. 3. In the GUI, select a track beyond the 8th position. 4. Observed: fader drops to -inf, display blank. Expected: fader and display follow the selected track.
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Date Modified	Username	Field	Change
2026-07-04 20:29	bourrinlepoulpe	New Issue