From f647ac7daea3d5ae8bfb2903bff67fffcc6197df Mon Sep 17 00:00:00 2001
From: Johannes Mueller <github@johannes-mueller.org>
Date: Tue, 15 Aug 2017 21:05:13 +0200
Subject: [PATCH] Allow plugin inline displays to shrink
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Plugin inline displays were forbidden to shrink as this might cause a deadlock
when the shrinkage causes the scrollbar to disappear.

display shrink → scrollbar unneeded → scrollbar disappears →
more horizontal space -> display grows -> scrollbar appears →
less horizontal space -> display shrink and so forth

This was formerly avoided by not allowing display shrinkage.

The solution proposed here sets the maximum height of the display to the
current height, if a scrollbar is present during resizing and has not been
present during the last resizing. So if this scrollbar disappears (after
resizing it might no longer be needed), the display would have the possibility
to grow, but it does not grow vertically as the maximum height is limited to
the current height.
---
 gtk2_ardour/processor_box.cc | 9 +++++++--
 gtk2_ardour/processor_box.h  | 1 +
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/gtk2_ardour/processor_box.cc b/gtk2_ardour/processor_box.cc
index 504ad10f32..9beb733617 100644
--- a/gtk2_ardour/processor_box.cc
+++ b/gtk2_ardour/processor_box.cc
@@ -1568,6 +1568,7 @@ ProcessorEntry::PluginInlineDisplay::PluginInlineDisplay (ProcessorEntry& e, boo
 	: PluginDisplay (p, max_height)
 	, _entry (e)
 	, _scroll (false)
+	, _given_max_height (max_height)
 {
 	std::string postfix = string_compose(_("\n%1+double-click to toggle inline-display"), Keyboard::tertiary_modifier_name ());
 
@@ -1639,11 +1640,15 @@ ProcessorEntry::PluginInlineDisplay::update_height_alloc (uint32_t inline_height
 	}
 
 	if (shm != _cur_height) {
-		if (_scroll == sc || _cur_height < shm) {
-			queue_resize ();
+		queue_resize ();
+		if (!_scroll && sc) {
+			_max_height = shm;
+		} else {
+			_max_height = _given_max_height;
 		}
 		_cur_height = shm;
 	}
+
 	_scroll = sc;
 }
 
diff --git a/gtk2_ardour/processor_box.h b/gtk2_ardour/processor_box.h
index 5772e6dbd1..81c5c8e20f 100644
--- a/gtk2_ardour/processor_box.h
+++ b/gtk2_ardour/processor_box.h
@@ -258,6 +258,7 @@ private:
 
 		ProcessorEntry& _entry;
 		bool _scroll;
+		const uint32_t _given_max_height;
 	};
 
 	class LuaPluginDisplay : public PluginInlineDisplay {