From 5d10fd84eb9d95f4176ba1165632d0a60ab7a49f Mon Sep 17 00:00:00 2001
From: Robin Gareus <robin@gareus.org>
Date: Wed, 15 Jun 2022 02:24:03 +0200
Subject: [PATCH] Reduce mixer redraws, and fix scrolling to newly added tracks

PresentationInfo::Change (Properties::selected) is emitted and
handled before Mixer_UI::add_routes() is called. At that point
in time the MixerStrip(s) to be selected may not exist.
Visual selection state was lost.

Furthermore move_stripable_into_view() calling translate_coordinates()
only works after GTK has completed the resize operation.
This lead to the mixer scrolling back to the left edge when creating
new tracks.

Also each selection change caused all tracks to be re-packed.
Now redisplay_track_list() is only called if visibility or order
changes. This signficanly improves performance with large sessions.
---
 gtk2_ardour/mixer_ui.cc | 68 +++++++++++++++++++++++------------------
 1 file changed, 39 insertions(+), 29 deletions(-)

diff --git a/gtk2_ardour/mixer_ui.cc b/gtk2_ardour/mixer_ui.cc
index a64be59b2d..44e462bba2 100644
--- a/gtk2_ardour/mixer_ui.cc
+++ b/gtk2_ardour/mixer_ui.cc
@@ -677,6 +677,7 @@ Mixer_UI::add_stripables (StripableList& slist)
 				}
 
 				strip = new MixerStrip (*this, _session, route);
+				strip->set_selected (route->is_selected ());
 				strips.push_back (strip);
 
 				UIConfiguration::instance().get_default_narrow_ms() ? _strip_width = Narrow : _strip_width = Wide;
@@ -716,14 +717,20 @@ Mixer_UI::add_stripables (StripableList& slist)
 
 	track_display.set_model (track_model);
 
-	/* catch up on selection state, which we left to the editor to set */
-	sync_treeview_from_presentation_info (PropertyChange (Properties::selected));
-
 	if (!from_scratch) {
 		sync_presentation_info_from_treeview ();
 	}
 
 	redisplay_track_list ();
+
+	if (!from_scratch) {
+		/* Mixer_UI::move_stripable_into_view() can only correctly calculate
+		 * the scroll offset after the layout was updated.
+		 * We update update after the resize operation (+10), but before drawing (+20)
+		 * https://docs.gtk.org/glib/const.PRIORITY_HIGH_IDLE.html
+		 */
+		Glib::signal_idle().connect (sigc::bind_return (sigc::bind (sigc::mem_fun (*this, &Mixer_UI::sync_treeview_from_presentation_info), PropertyChange (Properties::selected)), false), G_PRIORITY_HIGH_IDLE + 15);
+	}
 }
 
 void
@@ -891,44 +898,49 @@ Mixer_UI::sync_treeview_from_presentation_info (PropertyChange const & what_chan
 	 * order for the GUI, so reorder the treeview model to match it.
 	 */
 
-	vector<int> neworder;
-	TreeModel::Children rows = track_model->children();
-	uint32_t old_order = 0;
-	bool changed = false;
+	if (what_changed.contains (Properties::order)) {
+		vector<int> neworder;
+		TreeModel::Children rows = track_model->children();
+		uint32_t old_order = 0;
+		bool changed = false;
 
-	if (rows.empty()) {
-		return;
-	}
+		if (rows.empty()) {
+			return;
+		}
 
-	TreeOrderKeys sorted;
-	for (TreeModel::Children::iterator ri = rows.begin(); ri != rows.end(); ++ri, ++old_order) {
-		boost::shared_ptr<Stripable> stripable = (*ri)[stripable_columns.stripable];
-		sorted.push_back (TreeOrderKey (old_order, stripable));
-	}
+		TreeOrderKeys sorted;
+		for (TreeModel::Children::iterator ri = rows.begin(); ri != rows.end(); ++ri, ++old_order) {
+			boost::shared_ptr<Stripable> stripable = (*ri)[stripable_columns.stripable];
+			sorted.push_back (TreeOrderKey (old_order, stripable));
+		}
 
-	TreeOrderKeySorter cmp;
+		TreeOrderKeySorter cmp;
 
-	sort (sorted.begin(), sorted.end(), cmp);
-	neworder.assign (sorted.size(), 0);
+		sort (sorted.begin(), sorted.end(), cmp);
+		neworder.assign (sorted.size(), 0);
 
-	uint32_t n = 0;
+		uint32_t n = 0;
 
-	for (TreeOrderKeys::iterator sr = sorted.begin(); sr != sorted.end(); ++sr, ++n) {
+		for (TreeOrderKeys::iterator sr = sorted.begin(); sr != sorted.end(); ++sr, ++n) {
 
-		neworder[n] = sr->old_display_order;
+			neworder[n] = sr->old_display_order;
 
-		if (sr->old_display_order != n) {
-			changed = true;
+			if (sr->old_display_order != n) {
+				changed = true;
+			}
+		}
+
+		if (changed) {
+			Unwinder<bool> uw (ignore_track_reorder, true);
+			track_model->reorder (neworder);
 		}
 	}
 
-	if (changed) {
-		Unwinder<bool> uw (ignore_track_reorder, true);
-		track_model->reorder (neworder);
+	if (what_changed.contains (Properties::order) || what_changed.contains (Properties::hidden)) {
+		redisplay_track_list ();
 	}
 
 	if (what_changed.contains (Properties::selected)) {
-
 		PresentationInfo::ChangeSuspender cs;
 
 		for (list<MixerStrip *>::const_iterator i = strips.begin(); i != strips.end(); ++i) {
@@ -958,8 +970,6 @@ Mixer_UI::sync_treeview_from_presentation_info (PropertyChange const & what_chan
 			}
 		}
 	}
-
-	redisplay_track_list ();
 }
 
 void