Fix fit tracks

The track-height change needs to be applied so that
vertical_adjustment max range is set correctly.
Otherwise vertical_adjustment.set_value() may fail
or scroll to the wrong position.

In 5b3eacd421 `redisplay_track_views()` was moved from
EditorRoutes to Editor. The call was delegated to the idle
thread, potentially collecting multiple calls before performing
the update.

This resulted in "Fit selection" to set the y-offset before the
height-change was applied.

gtk2_ardour/editor.cc

@@ -5600,6 +5600,22 @@ Editor::queue_redisplay_track_views ()
 	}
 }
 
+void
+Editor::process_redisplay_track_views ()
+{
+	if (_tvl_redisplay_connection.connected ()) {
+		_tvl_redisplay_connection.disconnect ();
+		redisplay_track_views ();
+	}
+}
+
+void
+Editor::redisplay_track_views_now ()
+{
+	_tvl_redisplay_connection.disconnect ();
+	redisplay_track_views ();
+}
+
 void
 Editor::resume_route_redisplay ()
 {
@@ -5882,6 +5898,8 @@ Editor::redisplay_track_views ()
 		return false;
 	}
 
+	_tvl_redisplay_on_resume = false;
+
 	TrackViewStripableSorter cmp;
 	track_views.sort (cmp);
 

gtk2_ardour/editor.h

@@ -1236,8 +1236,11 @@ private:
 	TrackViewList get_tracks_for_range_action () const;
 
 	Gtk::VBox list_vpacker;
+
 	void queue_redisplay_track_views ();
-	bool redisplay_track_views ();
+	void process_redisplay_track_views ();
+	void redisplay_track_views_now ();
+	bool redisplay_track_views (); // do not call this directly, use above wrappers
 
 	bool             _tvl_no_redisplay;
 	bool             _tvl_redisplay_on_resume;

gtk2_ardour/editor_canvas.cc

@@ -957,6 +957,9 @@ Editor::ensure_time_axis_view_is_visible (TimeAxisView const & track, bool at_to
 		return;
 	}
 
+	/* apply any pending [height] changes */
+	process_redisplay_track_views ();
+
 	/* compute visible area of trackview group, as offsets from top of
 	 * trackview group.
 	 */

gtk2_ardour/editor_ops.cc

@@ -8506,6 +8506,9 @@ Editor::fit_tracks (TrackViewList & tracks)
 		}
 	}
 
+	/* apply height changes, so that scrolling works */
+	process_redisplay_track_views ();
+
 	/*
 	   set the controls_layout height now, because waiting for its size
 	   request signal handler will cause the vertical adjustment setting to fail