rework panning -- Squashed commit of the following:

commit 6f4f4f161b00cb36252727f67ecc4913eb944fd7
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 22:13:09 2014 +0100

    fix panner plugin discovery (prev commit)

commit 26e514f4a80af9192cae3cbd62fde0ae95474dfc
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 18:56:59 2014 +0100

    update panner plugin discovery

    * recurse dirs in 'PANNER_PATH' and 'panner_dir_name' up to 1 level.
    * don't look in ardour_dll_directory() -- no panners are supposed to be in there
    * use .dylib on OSX exclusively.

commit a514c3f1c425dccf3d42eee9d2b183b44fd26a03
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 16:48:34 2014 +0100

    remove debug/devel printf()s

commit d863742ddc69af493ee6a8817bc778968d9b0800
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 16:17:13 2014 +0100

    panner-type: session backward/forward compatibility

commit 25d5e4c663ada34129451b0f9045ab047d6cc2f0
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 16:09:07 2014 +0100

    update URIs -> URLs

commit 00a606a43d9456cfbaf43cae4fb598549326ba71
Merge: 0f1cec1 382eb0f
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 03:29:45 2014 +0100

    Merge branch 'master' into panning

commit 0f1cec19babae538c9697eed4be5d6ddc851b013
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 02:41:15 2014 +0100

    switch panner ID to URI

commit 575282b412c3ae1cd8219cf75f00a1a4239e2813
Author: Robin Gareus <robin@gareus.org>
Date:   Wed Jan 8 00:50:15 2014 +0100

    prepare API for panner URI

commit ea62cd049308859782a7bb16e4f18169d8638b46
Author: Robin Gareus <robin@gareus.org>
Date:   Tue Jan 7 19:57:06 2014 +0100

    update development doc relating to panner selection

commit 586d7de2392e26b9d7f597b1a00b98dfaa42ecdc
Author: Robin Gareus <robin@gareus.org>
Date:   Tue Jan 7 19:56:24 2014 +0100

    clean up PanShell::set_user_selected_panner_type() API

commit 99077886a5a1cacece908d87c29c3be12903027e
Author: Robin Gareus <robin@gareus.org>
Date:   Tue Jan 7 04:46:22 2014 +0100

    panner bypass: visualize & [in]sensitivity

commit 46d688d216f0e67d672376a607157af02b359fb2
Merge: 4e67573 c4cdf61
Author: Robin Gareus <robin@gareus.org>
Date:   Tue Jan 7 02:18:54 2014 +0100

    Merge branch 'master' into panning

commit 4e67573517b3d60ddf65729783687b16cfb2adb7
Author: Robin Gareus <robin@gareus.org>
Date:   Tue Jan 7 01:05:17 2014 +0100

    don't call configure_io() for merely swapping panners

commit d32a4c51f6967f48f7680554866f1f7b311ccde1
Merge: a3226d4 cec3116
Author: Robin Gareus <robin@gareus.org>
Date:   Mon Jan 6 23:49:55 2014 +0100

    Merge branch 'master' into panning

commit a3226d46b598afae54a65ac69320eca84669f347
Author: Robin Gareus <robin@gareus.org>
Date:   Mon Jan 6 17:52:38 2014 +0100

    add notes about panner re-design

commit d1ae2366024605f22b05572a81ee249e6fdbcd2f
Author: Robin Gareus <robin@gareus.org>
Date:   Mon Jan 6 15:06:40 2014 +0100

    add simple stereo-balance panner for testing

commit e0ddd256ff2288b8d8cfad3ad485a916964ce5b5
Author: Robin Gareus <robin@gareus.org>
Date:   Mon Jan 6 17:02:52 2014 +0100

    add frontend/GUI for panner selection

commit 2cb8f846755eb5aea8a2620d31ea981c446c4041
Author: Robin Gareus <robin@gareus.org>
Date:   Mon Jan 6 17:02:20 2014 +0100

    prepare backend for panner selection

9 files changed, 267 insertions, 88 deletions

diff --git a/gtk2_ardour/ardev_common.sh.in b/gtk2_ardour/ardev_common.sh.in
index 850a83c954..8724ff2c7d 100644
--- a/gtk2_ardour/ardev_common.sh.in
+++ b/gtk2_ardour/ardev_common.sh.in
@@ -12,7 +12,7 @@ libs=$TOP/@LIBS@
 
 export ARDOUR_PATH=$TOP/gtk2_ardour/icons:$TOP/gtk2_ardour/pixmaps:$TOP/build/gtk2_ardour:$TOP/gtk2_ardour:.
 export ARDOUR_SURFACES_PATH=$libs/surfaces/osc:$libs/surfaces/generic_midi:$libs/surfaces/tranzport:$libs/surfaces/powermate:$libs/surfaces/mackie:$libs/surfaces/wiimote
-export ARDOUR_PANNER_PATH=$libs/panners/2in2out:$libs/panners/1in2out:$libs/panners/vbap
+export ARDOUR_PANNER_PATH=$libs/panners
 export ARDOUR_DATA_PATH=$TOP:$TOP/build:$TOP/gtk2_ardour:$TOP/build/gtk2_ardour:.
 export ARDOUR_MIDIMAPS_PATH=$TOP/midi_maps:.
 export ARDOUR_MCP_PATH=$TOP/mcp:.
diff --git a/gtk2_ardour/mixer_strip.cc b/gtk2_ardour/mixer_strip.cc
index aa49e20d0c..e7c3f138b8 100644
--- a/gtk2_ardour/mixer_strip.cc
+++ b/gtk2_ardour/mixer_strip.cc
@@ -41,6 +41,7 @@
 #include "ardour/pannable.h"
 #include "ardour/panner.h"
 #include "ardour/panner_shell.h"
+#include "ardour/panner_manager.h"
 #include "ardour/port.h"
 #include "ardour/profile.h"
 #include "ardour/route.h"
@@ -515,7 +516,10 @@ MixerStrip::set_route (boost::shared_ptr<Route> rt)
 	_route->output()->changed.connect (*this, invalidator (*this), boost::bind (&MixerStrip::update_output_display, this), gui_context());
 	_route->route_group_changed.connect (route_connections, invalidator (*this), boost::bind (&MixerStrip::route_group_changed, this), gui_context());
 
+	_route->io_changed.connect (route_connections, invalidator (*this), boost::bind (&MixerStrip::io_changed_proxy, this), gui_context ());
+
 	if (_route->panner_shell()) {
+		update_panner_choices();
 		_route->panner_shell()->Changed.connect (route_connections, invalidator (*this), boost::bind (&MixerStrip::connect_to_pan, this), gui_context());
 	}
 
@@ -1019,9 +1023,48 @@ MixerStrip::connect_to_pan ()
 	p->automation_state_changed.connect (panstate_connection, invalidator (*this), boost::bind (&PannerUI::pan_automation_state_changed, &panners), gui_context());
 	p->automation_style_changed.connect (panstyle_connection, invalidator (*this), boost::bind (&PannerUI::pan_automation_style_changed, &panners), gui_context());
 
-	panners.panshell_changed ();
+	/* This call reduncant, PannerUI::set_panner() connects to _panshell->Changed itself
+	 * However, that only works a panner was previously set.
+	 *
+	 * PannerUI must remain subscribed to _panshell->Changed() in case
+	 * we switch the panner eg. AUX-Send and back
+	 * _route->panner_shell()->Changed() vs _panshell->Changed
+	 */
+	if (panners._panner == 0) {
+		panners.panshell_changed ();
+	}
 }
 
+void
+MixerStrip::update_panner_choices ()
+{
+	ENSURE_GUI_THREAD (*this, &MixerStrip::update_panner_choices)
+	if (!_route->panner_shell()) { return; }
+
+	int in = _route->output()->n_ports().n_audio();
+	int out = in;
+
+	if (_route->panner()) {
+		in = _route->panner()->in().n_audio();
+	}
+
+	if (out < 2 || in == 0) {
+		panners.set_available_panners(_route, std::map<std::string,std::string>());
+		return;
+	}
+
+	std::map<std::string,std::string> panner_list;
+	std::list<PannerInfo*> panner_info = PannerManager::instance().panner_info;
+	/* get available panners for current configuration. */
+	for (list<PannerInfo*>::iterator p = panner_info.begin(); p != panner_info.end(); ++p) {
+		 PanPluginDescriptor* d = &(*p)->descriptor;
+		 if (d->in != -1 && d->in != in) continue;
+		 if (d->out != -1 && d->out != out) continue;
+		 if (d->in == -1 && d->out == -1 && out <= 2) continue;
+		 panner_list.insert(std::pair<std::string,std::string>(d->panner_uri,d->name));
+	}
+	panners.set_available_panners(_route, panner_list);
+}
 
 /*
  * Output port labelling
@@ -1273,6 +1316,12 @@ MixerStrip::diskstream_changed ()
 }
 
 void
+MixerStrip::io_changed_proxy ()
+{
+	Glib::signal_idle().connect_once (sigc::mem_fun (*this, &MixerStrip::update_panner_choices));
+}
+
+void
 MixerStrip::port_connected_or_disconnected (boost::weak_ptr<Port> wa, boost::weak_ptr<Port> wb)
 {
 	boost::shared_ptr<Port> a = wa.lock ();
@@ -1843,6 +1892,8 @@ MixerStrip::show_send (boost::shared_ptr<Send> send)
 	gain_meter().setup_meters ();
 
 	panner_ui().set_panner (_current_delivery->panner_shell(), _current_delivery->panner());
+	panner_ui().set_available_panners(boost::shared_ptr<ARDOUR::Route>(), std::map<std::string,std::string>());
+
 	panner_ui().setup_pan ();
 
 	/* make sure the send has audio output */
@@ -1884,6 +1935,7 @@ MixerStrip::revert_to_default_display ()
 	gain_meter().setup_meters ();
 
 	panner_ui().set_panner (_route->main_outs()->panner_shell(), _route->main_outs()->panner());
+	update_panner_choices();
 	panner_ui().setup_pan ();
 
 	if (has_audio_outputs ()) {
diff --git a/gtk2_ardour/mixer_strip.h b/gtk2_ardour/mixer_strip.h
index fe10070fbb..883bfffdba 100644
--- a/gtk2_ardour/mixer_strip.h
+++ b/gtk2_ardour/mixer_strip.h
@@ -226,6 +226,7 @@ class MixerStrip : public RouteUI, public Gtk::EventBox
 	void edit_output_configuration ();
 
 	void diskstream_changed ();
+	void io_changed_proxy ();
 
 	Gtk::Menu *send_action_menu;
 	Gtk::MenuItem* rename_menu_item;
@@ -237,6 +238,7 @@ class MixerStrip : public RouteUI, public Gtk::EventBox
 	PBD::ScopedConnection panstate_connection;
 	PBD::ScopedConnection panstyle_connection;
 	void connect_to_pan ();
+	void update_panner_choices ();
 
 	void update_diskstream_display ();
 	void update_input_display ();
diff --git a/gtk2_ardour/mono_panner.cc b/gtk2_ardour/mono_panner.cc
index daec1eede1..c1039092c5 100644
--- a/gtk2_ardour/mono_panner.cc
+++ b/gtk2_ardour/mono_panner.cc
@@ -35,6 +35,7 @@
 
 #include "ardour/pannable.h"
 #include "ardour/panner.h"
+#include "ardour/panner_shell.h"
 
 #include "ardour_ui.h"
 #include "global_signals.h"
@@ -57,23 +58,25 @@ static const int top_step = 2;
 MonoPanner::ColorScheme MonoPanner::colors;
 bool MonoPanner::have_colors = false;
 
-MonoPanner::MonoPanner (boost::shared_ptr<ARDOUR::Panner> panner)
-	: PannerInterface (panner)
+MonoPanner::MonoPanner (boost::shared_ptr<ARDOUR::PannerShell> p)
+	: PannerInterface (p->panner())
+	, _panner_shell (p)
 	, position_control (_panner->pannable()->pan_azimuth_control)
-        , drag_start_x (0)
-        , last_drag_x (0)
-        , accumulated_delta (0)
-        , detented (false)
-        , position_binder (position_control)
+	, drag_start_x (0)
+	, last_drag_x (0)
+	, accumulated_delta (0)
+	, detented (false)
+	, position_binder (position_control)
 	, _dragging (false)
 {
-        if (!have_colors) {
-                set_colors ();
-                have_colors = true;
-        }
+	if (!have_colors) {
+		set_colors ();
+		have_colors = true;
+	}
 
-        position_control->Changed.connect (connections, invalidator(*this), boost::bind (&MonoPanner::value_change, this), gui_context());
+	position_control->Changed.connect (connections, invalidator(*this), boost::bind (&MonoPanner::value_change, this), gui_context());
 
+	_panner_shell->Changed.connect (connections, invalidator (*this), boost::bind (&MonoPanner::bypass_handler, this), gui_context());
 	ColorsChanged.connect (sigc::mem_fun (*this, &MonoPanner::color_handler));
 
 	set_tooltip ();
@@ -87,6 +90,10 @@ MonoPanner::~MonoPanner ()
 void
 MonoPanner::set_tooltip ()
 {
+	if (_panner_shell->bypassed()) {
+		_tooltip.set_tip (_("bypassed"));
+		return;
+	}
         double pos = position_control->get_value(); // 0..1
 
         /* We show the position of the center of the image relative to the left & right.
@@ -128,13 +135,17 @@ MonoPanner::on_expose_event (GdkEventExpose*)
 
         /* background */
 
-        context->set_source_rgba (UINT_RGBA_R_FLT(b), UINT_RGBA_G_FLT(b), UINT_RGBA_B_FLT(b), UINT_RGBA_A_FLT(b));
+        if (!_panner_shell->bypassed()) {
+                context->set_source_rgba (UINT_RGBA_R_FLT(b), UINT_RGBA_G_FLT(b), UINT_RGBA_B_FLT(b), UINT_RGBA_A_FLT(b));
+        } else {
+                context->set_source_rgba (0.1, 0.1, 0.1, 0.2);
+        }
         context->rectangle (0, 0, width, height);
         context->fill ();
 
-        double usable_width = width - pos_box_size;
+	double usable_width = width - pos_box_size;
 
-        /* compute the centers of the L/R boxes based on the current stereo width */
+	/* compute the centers of the L/R boxes based on the current stereo width */
 
         if (fmod (usable_width,2.0) == 0) {
                 /* even width, but we need odd, so that there is an exact center.
@@ -158,6 +169,10 @@ MonoPanner::on_expose_event (GdkEventExpose*)
         context->line_to ((pos_box_size/2.0) + (usable_width/2.0), height);
         context->stroke ();
 
+	if (_panner_shell->bypassed()) {
+		return true;
+	}
+
         /* left box */
 
         rounded_rectangle (context,
@@ -250,6 +265,9 @@ MonoPanner::on_button_press_event (GdkEventButton* ev)
 	if (PannerInterface::on_button_press_event (ev)) {
 		return true;
 	}
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
 	
         drag_start_x = ev->x;
         last_drag_x = ev->x;
@@ -319,6 +337,10 @@ MonoPanner::on_button_release_event (GdkEventButton* ev)
                 return false;
         }
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
         _dragging = false;
 	_tooltip.target_stop_drag ();
         accumulated_delta = 0;
@@ -340,6 +362,10 @@ MonoPanner::on_scroll_event (GdkEventScroll* ev)
         double pv = position_control->get_value(); // 0..1.0 ; 0 = left
         double step;
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
         if (Keyboard::modifier_state_contains (ev->state, Keyboard::PrimaryModifier)) {
                 step = one_degree;
         } else {
@@ -365,6 +391,9 @@ MonoPanner::on_scroll_event (GdkEventScroll* ev)
 bool
 MonoPanner::on_motion_notify_event (GdkEventMotion* ev)
 {
+	if (_panner_shell->bypassed()) {
+		_dragging = false;
+	}
         if (!_dragging) {
                 return false;
         }
@@ -406,6 +435,10 @@ MonoPanner::on_key_press_event (GdkEventKey* ev)
         double pv = position_control->get_value(); // 0..1.0 ; 0 = left
         double step;
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
         if (Keyboard::modifier_state_contains (ev->state, Keyboard::PrimaryModifier)) {
                 step = one_degree;
         } else {
@@ -450,6 +483,12 @@ MonoPanner::color_handler ()
 	queue_draw ();
 }
 
+void
+MonoPanner::bypass_handler ()
+{
+	queue_draw ();
+}
+
 PannerEditor*
 MonoPanner::editor ()
 {
diff --git a/gtk2_ardour/mono_panner.h b/gtk2_ardour/mono_panner.h
index 1c387ad32c..523f9731de 100644
--- a/gtk2_ardour/mono_panner.h
+++ b/gtk2_ardour/mono_panner.h
@@ -28,6 +28,10 @@
 
 #include "panner_interface.h"
 
+namespace ARDOUR {
+	class PannerShell;
+}
+
 namespace PBD {
         class Controllable;
 }
@@ -35,7 +39,7 @@ namespace PBD {
 class MonoPanner : public PannerInterface
 {
   public:
-	MonoPanner (boost::shared_ptr<ARDOUR::Panner>);
+	MonoPanner (boost::shared_ptr<ARDOUR::PannerShell>);
 	~MonoPanner ();
 
         boost::shared_ptr<PBD::Controllable> get_controllable() const { return position_control; }
@@ -53,6 +57,7 @@ class MonoPanner : public PannerInterface
 
   private:
 	PannerEditor* editor ();
+	boost::shared_ptr<ARDOUR::PannerShell> _panner_shell;
 	
         boost::shared_ptr<PBD::Controllable> position_control;
         PBD::ScopedConnectionList connections;
@@ -80,6 +85,7 @@ class MonoPanner : public PannerInterface
         static void set_colors ();
         static bool have_colors;
 	void color_handler ();
+	void bypass_handler ();
 };
 
 #endif /* __gtk_ardour_mono_panner_h__ */
diff --git a/gtk2_ardour/panner_ui.cc b/gtk2_ardour/panner_ui.cc
index c82a44f399..3ee794e578 100644
--- a/gtk2_ardour/panner_ui.cc
+++ b/gtk2_ardour/panner_ui.cc
@@ -51,6 +51,7 @@ PannerUI::PannerUI (Session* s)
 	, _current_nins (-1)
 	, pan_automation_style_button ("")
 	, pan_automation_state_button ("")
+	, _panner_list()
 {
 	set_session (s);
 
@@ -203,7 +204,7 @@ PannerUI::~PannerUI ()
 void
 PannerUI::panshell_changed ()
 {
-        set_panner (_panshell, _panshell->panner());
+	set_panner (_panshell, _panshell->panner());
 	setup_pan ();
 }
 
@@ -233,73 +234,51 @@ PannerUI::setup_pan ()
 		return;
 	}
 
-	if (nouts == 0 || nouts == 1) {
+	if (_panshell->panner_gui_uri() == "http://ardour.org/plugin/panner_2in2out#ui")
+	{
+		boost::shared_ptr<Pannable> pannable = _panner->pannable();
 
-		/* stick something into the panning viewport so that it redraws */
-
-		EventBox* eb = manage (new EventBox());
-		pan_vbox.pack_start (*eb, false, false);
-
-		delete big_window;
-		big_window = 0;
-
-	} else if (nouts == 2) {
-
-                if (nins == 2) {
-
-                        /* add integrated 2in/2out panner GUI */
-
-                        boost::shared_ptr<Pannable> pannable = _panner->pannable();
-
-                        _stereo_panner = new StereoPanner (_panner);
-                        _stereo_panner->set_size_request (-1, pan_bar_height);
-                        pan_vbox.pack_start (*_stereo_panner, false, false);
-
-                        boost::shared_ptr<AutomationControl> ac;
+		_stereo_panner = new StereoPanner (_panshell);
+		_stereo_panner->set_size_request (-1, pan_bar_height);
+		pan_vbox.pack_start (*_stereo_panner, false, false);
 
-                        ac = pannable->pan_azimuth_control;
-                        _stereo_panner->StartPositionGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
-                                                                                  boost::weak_ptr<AutomationControl> (ac)));
-                        _stereo_panner->StopPositionGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
-                                                                                 boost::weak_ptr<AutomationControl>(ac)));
+		boost::shared_ptr<AutomationControl> ac;
 
-                        ac = pannable->pan_width_control;
-                        _stereo_panner->StartWidthGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
-                                                                               boost::weak_ptr<AutomationControl> (ac)));
-                        _stereo_panner->StopWidthGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
-                                                                              boost::weak_ptr<AutomationControl>(ac)));
-                        _stereo_panner->signal_button_release_event().connect (sigc::mem_fun(*this, &PannerUI::pan_button_event));
+		ac = pannable->pan_azimuth_control;
+		_stereo_panner->StartPositionGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
+					boost::weak_ptr<AutomationControl> (ac)));
+		_stereo_panner->StopPositionGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
+					boost::weak_ptr<AutomationControl>(ac)));
 
-                } else if (nins == 1) {
-                        /* 1-in/2out */
-
-                        boost::shared_ptr<Pannable> pannable = _panner->pannable();
-                        boost::shared_ptr<AutomationControl> ac = pannable->pan_azimuth_control;
-
-                        _mono_panner = new MonoPanner (_panner);
-			
-                        _mono_panner->StartGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
-                                                                      boost::weak_ptr<AutomationControl> (ac)));
-                        _mono_panner->StopGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
-                                                             boost::weak_ptr<AutomationControl>(ac)));
-
-                        _mono_panner->signal_button_release_event().connect (sigc::mem_fun(*this, &PannerUI::pan_button_event));
-
-                        _mono_panner->set_size_request (-1, pan_bar_height);
+		ac = pannable->pan_width_control;
+		_stereo_panner->StartWidthGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
+					boost::weak_ptr<AutomationControl> (ac)));
+		_stereo_panner->StopWidthGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
+					boost::weak_ptr<AutomationControl>(ac)));
+		_stereo_panner->signal_button_release_event().connect (sigc::mem_fun(*this, &PannerUI::pan_button_event));
+	}
+	else if (_panshell->panner_gui_uri() == "http://ardour.org/plugin/panner_1in2out#ui"
+			|| _panshell->panner_gui_uri() == "http://ardour.org/plugin/panner_balance#ui")
+	{
+		boost::shared_ptr<Pannable> pannable = _panner->pannable();
+		boost::shared_ptr<AutomationControl> ac = pannable->pan_azimuth_control;
 
-                        update_pan_sensitive ();
-                        pan_vbox.pack_start (*_mono_panner, false, false);
+		_mono_panner = new MonoPanner (_panshell);
 
-                } else {
-                        warning << string_compose (_("No panner user interface is currently available for %1-in/2out tracks/busses"),
-                                                   nins) << endmsg;
-                }
+		_mono_panner->StartGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::start_touch),
+					boost::weak_ptr<AutomationControl> (ac)));
+		_mono_panner->StopGesture.connect (sigc::bind (sigc::mem_fun (*this, &PannerUI::stop_touch),
+					boost::weak_ptr<AutomationControl>(ac)));
 
-		delete big_window;
-		big_window = 0;
+		_mono_panner->signal_button_release_event().connect (sigc::mem_fun(*this, &PannerUI::pan_button_event));
 
-	} else {
+		_mono_panner->set_size_request (-1, pan_bar_height);
 
+		update_pan_sensitive ();
+		pan_vbox.pack_start (*_mono_panner, false, false);
+	}
+	else if (_panshell->panner_gui_uri() == "http://ardour.org/plugin/panner_vbap#ui")
+	{
 		if (!twod_panner) {
 			twod_panner = new Panner2d (_panshell, 61);
 			twod_panner->set_name ("MixerPanZone");
@@ -309,17 +288,26 @@ PannerUI::setup_pan ()
 
 		update_pan_sensitive ();
 		twod_panner->reset (nins);
- 		if (big_window) {
- 			big_window->reset (nins);
- 		}
+		if (big_window) {
+			big_window->reset (nins);
+		}
 		twod_panner->set_size_request (-1, 61);
 
 		/* and finally, add it to the panner frame */
 
-                pan_vbox.pack_start (*twod_panner, false, false);
+		pan_vbox.pack_start (*twod_panner, false, false);
+	}
+	else
+	{
+		/* stick something into the panning viewport so that it redraws */
+		EventBox* eb = manage (new EventBox());
+		pan_vbox.pack_start (*eb, false, false);
+
+		delete big_window;
+		big_window = 0;
 	}
 
-        pan_vbox.show_all ();
+	pan_vbox.show_all ();
 }
 
 void
@@ -388,8 +376,27 @@ PannerUI::build_pan_menu ()
 	bypass_menu_item->set_active (_panshell->bypassed());
 	bypass_menu_item->signal_toggled().connect (sigc::mem_fun(*this, &PannerUI::pan_bypass_toggle));
 
-	items.push_back (MenuElem (_("Reset"), sigc::mem_fun (*this, &PannerUI::pan_reset)));
-	items.push_back (MenuElem (_("Edit..."), sigc::mem_fun (*this, &PannerUI::pan_edit)));
+	if (!_panshell->bypassed()) {
+		items.push_back (MenuElem (_("Reset"), sigc::mem_fun (*this, &PannerUI::pan_reset)));
+		items.push_back (MenuElem (_("Edit..."), sigc::mem_fun (*this, &PannerUI::pan_edit)));
+	}
+
+	if (_route && _panner_list.size() > 1 && !_panshell->bypassed()) {
+		RadioMenuItem::Group group;
+		items.push_back (SeparatorElem());
+
+		assert(_panshell->user_selected_panner_uri() == ""
+				||  _panshell->user_selected_panner_uri() == _panshell->current_panner_uri());
+
+		_suspend_menu_callbacks = true;
+		for (std::map<std::string,std::string>::const_iterator p = _panner_list.begin(); p != _panner_list.end(); ++p) {
+			items.push_back (RadioMenuElem (group, p->second,
+						sigc::bind(sigc::mem_fun (*this, &PannerUI::pan_set_custom_type), p->first)));
+			RadioMenuItem* i = dynamic_cast<RadioMenuItem *> (&items.back ());
+			i->set_active (_panshell->current_panner_uri() == p->first);
+		}
+		_suspend_menu_callbacks = false;
+	}
 }
 
 void
@@ -403,6 +410,9 @@ PannerUI::pan_bypass_toggle ()
 void
 PannerUI::pan_edit ()
 {
+	if (_panshell->bypassed()) {
+		return;
+	}
 	if (_mono_panner) {
 		_mono_panner->edit ();
 	} else if (_stereo_panner) {
@@ -413,10 +423,21 @@ PannerUI::pan_edit ()
 void
 PannerUI::pan_reset ()
 {
+	if (_panshell->bypassed()) {
+		return;
+	}
 	_panner->reset ();
 }
 
 void
+PannerUI::pan_set_custom_type (std::string uri) {
+	if (_suspend_menu_callbacks) return;
+	if (_route) {
+		_route->set_custom_panner_uri(uri);
+	}
+}
+
+void
 PannerUI::effective_pan_display ()
 {
         if (_stereo_panner) {
@@ -609,3 +630,10 @@ void
 PannerUI::position_adjusted ()
 {
 }
+
+void
+PannerUI::set_available_panners(boost::shared_ptr<ARDOUR::Route> r, std::map<std::string,std::string> p)
+{
+	_route = r;
+	_panner_list = p;
+}
diff --git a/gtk2_ardour/panner_ui.h b/gtk2_ardour/panner_ui.h
index de93d49956..dca24451d1 100644
--- a/gtk2_ardour/panner_ui.h
+++ b/gtk2_ardour/panner_ui.h
@@ -73,6 +73,7 @@ class PannerUI : public Gtk::HBox, public ARDOUR::SessionHandlePtr
 
 	void set_width (Width);
 	void setup_pan ();
+	void set_available_panners(boost::shared_ptr<ARDOUR::Route>, std::map<std::string,std::string>);
 
 	void effective_pan_display ();
 
@@ -141,6 +142,7 @@ class PannerUI : public Gtk::HBox, public ARDOUR::SessionHandlePtr
 	void pan_reset ();
 	void pan_bypass_toggle ();
 	void pan_edit ();
+	void pan_set_custom_type (std::string type);
 
 	void pan_automation_state_changed();
 	void pan_automation_style_changed();
@@ -158,6 +160,10 @@ class PannerUI : public Gtk::HBox, public ARDOUR::SessionHandlePtr
 
         void start_touch (boost::weak_ptr<ARDOUR::AutomationControl>);
         void stop_touch (boost::weak_ptr<ARDOUR::AutomationControl>);
+
+	boost::shared_ptr<ARDOUR::Route> _route;
+	std::map<std::string,std::string> _panner_list;
+	bool _suspend_menu_callbacks;
 };
 
 #endif /* __ardour_gtk_panner_ui_h__ */
diff --git a/gtk2_ardour/stereo_panner.cc b/gtk2_ardour/stereo_panner.cc
index 721567bf10..c2b38867ab 100644
--- a/gtk2_ardour/stereo_panner.cc
+++ b/gtk2_ardour/stereo_panner.cc
@@ -34,6 +34,7 @@
 
 #include "ardour/pannable.h"
 #include "ardour/panner.h"
+#include "ardour/panner_shell.h"
 
 #include "ardour_ui.h"
 #include "global_signals.h"
@@ -58,8 +59,9 @@ bool StereoPanner::have_colors = false;
 
 using namespace ARDOUR;
 
-StereoPanner::StereoPanner (boost::shared_ptr<Panner> panner)
-	: PannerInterface (panner)
+StereoPanner::StereoPanner (boost::shared_ptr<PannerShell> p)
+	: PannerInterface (p->panner())
+	, _panner_shell (p)
 	, position_control (_panner->pannable()->pan_azimuth_control)
 	, width_control (_panner->pannable()->pan_width_control)
 	, dragging_position (false)
@@ -80,6 +82,7 @@ StereoPanner::StereoPanner (boost::shared_ptr<Panner> panner)
 
 	position_control->Changed.connect (connections, invalidator(*this), boost::bind (&StereoPanner::value_change, this), gui_context());
 	width_control->Changed.connect (connections, invalidator(*this), boost::bind (&StereoPanner::value_change, this), gui_context());
+	_panner_shell->Changed.connect (connections, invalidator (*this), boost::bind (&StereoPanner::bypass_handler, this), gui_context());
 
 	ColorsChanged.connect (sigc::mem_fun (*this, &StereoPanner::color_handler));
 
@@ -94,6 +97,10 @@ StereoPanner::~StereoPanner ()
 void
 StereoPanner::set_tooltip ()
 {
+	if (_panner_shell->bypassed()) {
+		_tooltip.set_tip (_("bypassed"));
+		return;
+	}
 	double pos = position_control->get_value(); // 0..1
 
 	/* We show the position of the center of the image relative to the left & right.
@@ -145,7 +152,11 @@ StereoPanner::on_expose_event (GdkEventExpose*)
 
 	/* background */
 
-	context->set_source_rgba (UINT_RGBA_R_FLT(b), UINT_RGBA_G_FLT(b), UINT_RGBA_B_FLT(b), UINT_RGBA_A_FLT(b));
+	if (!_panner_shell->bypassed()) {
+		context->set_source_rgba (UINT_RGBA_R_FLT(b), UINT_RGBA_G_FLT(b), UINT_RGBA_B_FLT(b), UINT_RGBA_A_FLT(b));
+	} else {
+		context->set_source_rgba (0.1, 0.1, 0.1, 0.2);
+	}
 	cairo_rectangle (context->cobj(), 0, 0, width, height);
 	context->fill ();
 
@@ -183,6 +194,10 @@ StereoPanner::on_expose_event (GdkEventExpose*)
 	context->set_source_rgba (UINT_RGBA_R_FLT(r), UINT_RGBA_G_FLT(r), UINT_RGBA_B_FLT(r), UINT_RGBA_A_FLT(r));
 	context->stroke ();
 
+	if (_panner_shell->bypassed()) {
+		return true;
+	}
+
 	/* compute & draw the line through the box */
 
 	context->set_line_width (2);
@@ -267,6 +282,10 @@ StereoPanner::on_button_press_event (GdkEventButton* ev)
 	if (PannerInterface::on_button_press_event (ev)) {
 		return true;
 	}
+
+	if (_panner_shell->bypassed()) {
+		return true;
+	}
 	
 	drag_start_x = ev->x;
 	last_drag_x = ev->x;
@@ -412,6 +431,10 @@ StereoPanner::on_button_release_event (GdkEventButton* ev)
 		return false;
 	}
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
 	bool const dp = dragging_position;
 
 	_dragging = false;
@@ -443,6 +466,10 @@ StereoPanner::on_scroll_event (GdkEventScroll* ev)
 	double wv = width_control->get_value(); // 0..1.0 ; 0 = left
 	double step;
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
 	if (Keyboard::modifier_state_contains (ev->state, Keyboard::PrimaryModifier)) {
 		step = one_degree;
 	} else {
@@ -474,6 +501,9 @@ StereoPanner::on_scroll_event (GdkEventScroll* ev)
 bool
 StereoPanner::on_motion_notify_event (GdkEventMotion* ev)
 {
+	if (_panner_shell->bypassed()) {
+		_dragging = false;
+	}
 	if (!_dragging) {
 		return false;
 	}
@@ -566,6 +596,10 @@ StereoPanner::on_key_press_event (GdkEventKey* ev)
 	double wv = width_control->get_value(); // 0..1.0 ; 0 = left
 	double step;
 
+	if (_panner_shell->bypassed()) {
+		return false;
+	}
+
 	if (Keyboard::modifier_state_contains (ev->state, Keyboard::PrimaryModifier)) {
 		step = one_degree;
 	} else {
@@ -641,6 +675,12 @@ StereoPanner::color_handler ()
 	queue_draw ();
 }
 
+void
+StereoPanner::bypass_handler ()
+{
+	queue_draw ();
+}
+
 PannerEditor*
 StereoPanner::editor ()
 {
diff --git a/gtk2_ardour/stereo_panner.h b/gtk2_ardour/stereo_panner.h
index 8b62b7d82a..bb4687d209 100644
--- a/gtk2_ardour/stereo_panner.h
+++ b/gtk2_ardour/stereo_panner.h
@@ -24,6 +24,10 @@
 #include "gtkmm2ext/binding_proxy.h"
 #include "panner_interface.h"
 
+namespace ARDOUR {
+	class PannerShell;
+}
+
 namespace PBD {
         class Controllable;
 }
@@ -35,7 +39,7 @@ namespace ARDOUR {
 class StereoPanner : public PannerInterface
 {
   public:
-	StereoPanner (boost::shared_ptr<ARDOUR::Panner>);
+	StereoPanner (boost::shared_ptr<ARDOUR::PannerShell>);
 	~StereoPanner ();
 
         boost::shared_ptr<PBD::Controllable> get_position_controllable() const { return position_control; }
@@ -56,6 +60,7 @@ class StereoPanner : public PannerInterface
 
   private:
 	PannerEditor* editor ();
+	boost::shared_ptr<ARDOUR::PannerShell> _panner_shell;
 		   
         boost::shared_ptr<PBD::Controllable> position_control;
         boost::shared_ptr<PBD::Controllable> width_control;
@@ -94,6 +99,7 @@ class StereoPanner : public PannerInterface
         static void set_colors ();
         static bool have_colors;
 	void color_handler ();
+	void bypass_handler ();
 };
 
 #endif /* __gtk_ardour_stereo_panner_h__ */