From 130cfd2e08f694b3a87bba543a6237c31f776e1d Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Fri, 2 May 2025 09:40:38 -0600
Subject: [PATCH] catch hscroll in pianoroll appropriately

Some thought might be put into thinking about why/whether EditingContext
ought to do this instead, since Editor does almost the same thing, but
without using the horizontal_adjustment owned by EditingContext
---
 gtk2_ardour/pianoroll.cc | 10 ++++++++++
 gtk2_ardour/pianoroll.h  |  1 +
 2 files changed, 11 insertions(+)

diff --git a/gtk2_ardour/pianoroll.cc b/gtk2_ardour/pianoroll.cc
index bbb70210d6..9f5d91c832 100644
--- a/gtk2_ardour/pianoroll.cc
+++ b/gtk2_ardour/pianoroll.cc
@@ -265,9 +265,19 @@ Pianoroll::add_multi_controller_item (Gtk::Menu_Helpers::MenuList&,
 }
 
 
+void
+Pianoroll::scrolled ()
+{
+	pending_visual_change.add (VisualChange::TimeOrigin);
+	pending_visual_change.time_origin = horizontal_adjustment.get_value() * samples_per_pixel;
+	ensure_visual_change_idle_handler ();
+}
+
 void
 Pianoroll::build_lower_toolbar ()
 {
+	horizontal_adjustment.signal_value_changed().connect (sigc::mem_fun (*this, &Pianoroll::scrolled));
+
 	ArdourButton::Element elements = ArdourButton::Element (ArdourButton::Text|ArdourButton::Indicator|ArdourButton::Edge|ArdourButton::Body);
 
 	_canvas_hscrollbar = manage (new Gtk::HScrollbar (horizontal_adjustment));
diff --git a/gtk2_ardour/pianoroll.h b/gtk2_ardour/pianoroll.h
index 82ea8df40f..4762f1db53 100644
--- a/gtk2_ardour/pianoroll.h
+++ b/gtk2_ardour/pianoroll.h
@@ -346,4 +346,5 @@ class Pianoroll : public CueEditor
 
 	bool bbt_ruler_event (GdkEvent*);
 	void ruler_locate (GdkEventButton*);
+	void scrolled ();
 };