Fix gain inc/dec with multiple-selection spanning groups

When tracks in a gain-sharing group are selected, stepping gain
up/down affected the tracks N times:
   for-each selected track inc/dec gain w/grouping.

When a mix of grouped and un-grouped tracks is selected, this lead to
inconsistent gain changes.

The new approach expands the groups first. Ignoring groups is not correct
either for single selection.

1 files changed, 1 insertions, 0 deletions

diff --git a/gtk2_ardour/mixer_ui.h b/gtk2_ardour/mixer_ui.h
index 27c8f0bce6..24e457cf72 100644
--- a/gtk2_ardour/mixer_ui.h
+++ b/gtk2_ardour/mixer_ui.h
@@ -129,6 +129,7 @@ public:
 
 protected:
 	void set_axis_targets_for_operation ();
+	ARDOUR::AutomationControlSet selected_gaincontrols ();
 
 private:
 	Mixer_UI ();