From 6b5eedca8ed4c761de2202a5d4fe7711af7be198 Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sat, 27 Aug 2016 23:46:20 -0400
Subject: Use template mixins for extensions

---
 lv2/lv2plug.in/ns/lv2core/Plugin.hpp | 36 +++++++++++++++++++++++++++++-------
 plugins/eg-midiamp.lv2/midiamp.cpp   |  9 ++++++---
 2 files changed, 35 insertions(+), 10 deletions(-)

diff --git a/lv2/lv2plug.in/ns/lv2core/Plugin.hpp b/lv2/lv2plug.in/ns/lv2core/Plugin.hpp
index f671640..597dd38 100644
--- a/lv2/lv2plug.in/ns/lv2core/Plugin.hpp
+++ b/lv2/lv2plug.in/ns/lv2core/Plugin.hpp
@@ -1,5 +1,5 @@
 /*
-  Copyright 2015 David Robillard <http://drobilla.net>
+  Copyright 2015-2016 David Robillard <http://drobilla.net>
 
   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
@@ -46,7 +46,7 @@ namespace lv2 {
    The destructor will be called when the host cleans up the plugin.
 */
 template<class Derived>
-class Plugin
+class PluginBase
 {
 public:
 	/**
@@ -79,10 +79,10 @@ public:
 	   @return A handle for the new plugin instance, or NULL if instantiation
 	   has failed.
 	*/
-	Plugin(double                   sample_rate,
-	       const char*              bundle_path,
-	       const LV2_Feature*const* features,
-	       bool*                    valid)
+	PluginBase(double                   sampcle_rate,
+	           const char*              bundle_path,
+	           const LV2_Feature*const* features,
+	           bool*                    valid)
 	{}
 
 	/**
@@ -215,7 +215,7 @@ public:
 		                              &s_run,
 		                              &s_deactivate,
 		                              &s_cleanup,
-		                              &Plugin::extension_data };
+		                              &PluginBase::extension_data };
 		return desc;
 	}
 
@@ -254,6 +254,28 @@ private:
 	}
 };
 
+template<class Derived, template<class S> class First=PluginBase, template<class S> class... Rest>
+struct Plugin : public First< Plugin<Derived, Rest...> > {
+	Plugin(double                    rate,
+	       const char*               bundle_path,
+	       const LV2_Feature* const* features,
+	       bool*                     valid)
+		: First< Plugin<Derived, Rest...> >(rate, bundle_path, features, valid)
+	{}
+
+};
+
+template<class Derived, template<class S> class First>
+struct Plugin<Derived, First> : public First< PluginBase<Derived> > {
+	Plugin(double                    rate,
+	       const char*               bundle_path,
+	       const LV2_Feature* const* features,
+	       bool*                     valid)
+		: First< PluginBase<Derived> >(rate, bundle_path, features, valid)
+	{}
+
+};
+
 } /* namespace lv2 */
 
 #endif /* LV2_PLUGIN_HPP */
diff --git a/plugins/eg-midiamp.lv2/midiamp.cpp b/plugins/eg-midiamp.lv2/midiamp.cpp
index 2fff4e7..ac3d055 100644
--- a/plugins/eg-midiamp.lv2/midiamp.cpp
+++ b/plugins/eg-midiamp.lv2/midiamp.cpp
@@ -1,5 +1,5 @@
 /*
-  Copyright 2015 David Robillard <d@drobilla.net>
+  Copyright 2015-2016 David Robillard <d@drobilla.net>
 
   Permission to use, copy, modify, and/or distribute this software for any
   purpose with or without fee is hereby granted, provided that the above
@@ -23,14 +23,17 @@
 #include "lv2/lv2plug.in/ns/lv2core/Lib.hpp"
 #include "lv2/lv2plug.in/ns/lv2core/Plugin.hpp"
 
+class MidiAmp;
+typedef typename lv2::Plugin<MidiAmp> Base;
+
 /** MIDI-controlled amplifier. */
-class MidiAmp : public lv2::Plugin<MidiAmp> {
+class MidiAmp : public Base {
 public:
 	MidiAmp(double                    rate,
 	        const char*               bundle_path,
 	        const LV2_Feature* const* features,
 	        bool*                     valid)
-		: Plugin(rate, bundle_path, features, valid)
+		: Base(rate, bundle_path, features, valid)
 		, m_map(features, valid)
 		, m_vol(1.0f)
 	{
-- 
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