gui_session: distinguish view-stacking operations

This patch eliminates the use of invalid view handles as special
Session::Command arguments. The TO_FRONT and TO_BACK operations
interpreted as invalid neighbor as top-most or back-most position.
Those corner cases are now expressed via dedicated commands. The
new stacking commands are FRONT, BACK, FRONT_OF, and BEHIND_OF.

While changing the command interface, the patch removes the OP_
prefix from the opcode values.

Issue #5242

repos/demo/include/scout/graphics_backend_impl.h

@@ -163,9 +163,7 @@ class Scout::Graphics_backend_impl : public Graphics_backend
 
 		void bring_to_front() override
 		{
-			using Command     = Gui::Session::Command;
+			_gui.enqueue<Gui::Session::Command::Front>(_view);
-			using View_handle = Gui::Session::View_handle;
-			_gui.enqueue<Command::To_front>(_view, View_handle());
 			_gui.execute();
 		}
 

repos/demo/src/server/nitlog/main.cc

@@ -375,7 +375,7 @@ class Log_view
 
 		void top()
 		{
-			_gui.enqueue<Command::To_front>(_handle, View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/gems/include/nano3d/scene.h

@@ -279,11 +279,9 @@ class Nano3d::Scene
 		:
 			_env(env), _pos(pos), _size(size)
 		{
-			using View_handle = Gui::Session::View_handle;
-
 			Gui::Rect rect(_pos, _size);
 			_gui.enqueue<Command::Geometry>(_view_handle, rect);
-			_gui.enqueue<Command::To_front>(_view_handle, View_handle());
+			_gui.enqueue<Command::Front>(_view_handle);
 			_gui.execute();
 
 			_gui.input.sigh(_input_handler);

repos/gems/src/app/backdrop/main.cc

@@ -115,13 +115,12 @@ struct Backdrop::Main
 	void _update_view()
 	{
 		/* display view behind all others */
-		using Command     = Gui::Session::Command;
+		using Command = Gui::Session::Command;
-		using View_handle = Gui::Session::View_handle;
 
 		_gui.enqueue<Command::Background>(_view_handle);
 		Gui::Rect rect(Gui::Point(), _buffer->size());
 		_gui.enqueue<Command::Geometry>(_view_handle, rect);
-		_gui.enqueue<Command::To_back>(_view_handle, View_handle());
+		_gui.enqueue<Command::Back>(_view_handle);
 		_gui.execute();
 	}
 

repos/gems/src/app/decorator/window.h

@@ -67,13 +67,12 @@ class Decorator::Window : public Window_base
 
 			void stack(View_handle neighbor)
 			{
-				_gui.enqueue<Command::To_front>(_handle, neighbor);
+				_gui.enqueue<Command::Front_of>(_handle, neighbor);
 			}
 
-			void stack_back_most()
+			void stack_front_most() { _gui.enqueue<Command::Front>(_handle); }
-			{
+
-				_gui.enqueue<Command::To_back>(_handle, View_handle());
+			void stack_back_most()  { _gui.enqueue<Command::Back>(_handle); }
-			}
 
 			void place(Rect rect)
 			{
@@ -445,7 +444,7 @@ class Decorator::Window : public Window_base
 
 		void stack_front_most() override
 		{
-			_content_view.stack(View_handle());
+			_content_view.stack_front_most();
 			_stack_decoration_views();
 		}
 

repos/gems/src/app/menu_view/dialog.h

@@ -107,12 +107,11 @@ struct Menu_view::Dialog : List_model<Dialog>::Element
 		 && _view_geometry.area == geometry.area)
 			return;
 
-		using Command     = Gui::Session::Command;
+		using Command = Gui::Session::Command;
-		using View_handle = Gui::Session::View_handle;
 
 		_view_geometry = geometry;
 		_gui.enqueue<Command::Geometry>(_view_handle, _view_geometry);
-		_gui.enqueue<Command::To_front>(_view_handle, View_handle());
+		_gui.enqueue<Command::Front>(_view_handle);
 		_gui.execute();
 	}
 

repos/gems/src/app/osci/main.cc

@@ -59,7 +59,7 @@ struct Osci::Main
 		{
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_handle, Rect(position, size));
-			_gui.enqueue<Command::To_front>(_handle, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/gems/src/app/rom_osci/main.cc

@@ -96,7 +96,7 @@ struct Osci::Main
 		{
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_handle, Rect(position, size));
-			_gui.enqueue<Command::To_front>(_handle, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/gems/src/app/screenshot_trigger/main.cc

@@ -62,7 +62,7 @@ struct Screenshot_trigger::Main
 		{
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_handle, Rect(position, size));
-			_gui.enqueue<Command::To_front>(_handle, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/gems/src/app/themed_decorator/window.h

@@ -199,13 +199,12 @@ class Decorator::Window : public Window_base, public Animator::Item
 
 			void stack(View_handle neighbor)
 			{
-				_gui.enqueue<Command::To_front>(_handle, neighbor);
+				_gui.enqueue<Command::Front_of>(_handle, neighbor);
 			}
 
-			void stack_back_most()
+			void stack_front_most() { _gui.enqueue<Command::Front>(_handle); }
-			{
+
-				_gui.enqueue<Command::To_back>(_handle, View_handle());
+			void stack_back_most()  { _gui.enqueue<Command::Back>(_handle); }
-			}
 
 			void place(Rect rect, Point offset)
 			{
@@ -390,7 +389,7 @@ class Decorator::Window : public Window_base, public Animator::Item
 		}
 		void stack_front_most() override
 		{
-			_content_view.stack(View_handle());
+			_content_view.stack_front_most();
 			_stack_decoration_views();
 		}
 

repos/gems/src/server/gui_fader/main.cc

@@ -393,7 +393,7 @@ class Gui_fader::Gui_session_component
 
 				bool forward_command = true;
 
-				if (command.opcode == Gui::Session::Command::OP_GEOMETRY) {
+				if (command.opcode == Gui::Session::Command::GEOMETRY) {
 
 					/* remember view geometry as defined by the client */
 					_view_geometry = command.geometry.rect;

repos/gems/src/server/terminal/main.cc

@@ -163,7 +163,7 @@ struct Terminal::Main : Character_consumer
 
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_view, Rect(Point(0, 0), _fb_mode.area));
-			_gui.enqueue<Command::To_front>(_view, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_view);
 			_gui.execute();
 
 			_flushed_fb_mode = _fb_mode;

repos/gems/src/server/wm/decorator_gui.h

@@ -233,7 +233,7 @@ struct Wm::Decorator_gui_session : Genode::Rpc_object<Gui::Session>,
 	{
 		switch (cmd.opcode) {
 
-		case Command::OP_TITLE:
+		case Command::TITLE:
 			{
 				unsigned id = 0;
 				Genode::ascii_to(cmd.title.title.string(), id);
@@ -244,14 +244,15 @@ struct Wm::Decorator_gui_session : Genode::Rpc_object<Gui::Session>,
 				return;
 			}
 
-		case Command::OP_TO_FRONT:
+		case Command::FRONT:
-		case Command::OP_TO_BACK:
+		case Command::BACK:
+		case Command::FRONT_OF:
+		case Command::BEHIND_OF:
 
 			try {
 
-				View_handle const view_handle = (cmd.opcode == Command::OP_TO_FRONT)
+				/* the first argument is the same for all stacking operations */
-				                              ?  cmd.to_front.view
+				View_handle const view_handle = cmd.front.view;
-				                              :  cmd.to_back.view;
 
 				/*
 				 * If the content view is re-stacked, replace it by the real
@@ -287,7 +288,7 @@ struct Wm::Decorator_gui_session : Genode::Rpc_object<Gui::Session>,
 
 			return;
 
-		case Command::OP_GEOMETRY:
+		case Command::GEOMETRY:
 
 			try {
 
@@ -306,7 +307,7 @@ struct Wm::Decorator_gui_session : Genode::Rpc_object<Gui::Session>,
 			_gui.enqueue(cmd);
 			return;
 
-		case Command::OP_OFFSET:
+		case Command::OFFSET:
 
 			try {
 
@@ -321,8 +322,8 @@ struct Wm::Decorator_gui_session : Genode::Rpc_object<Gui::Session>,
 			}
 			return;
 
-		case Command::OP_BACKGROUND:
+		case Command::BACKGROUND:
-		case Command::OP_NOP:
+		case Command::NOP:
 
 			_gui.enqueue(cmd);
 			return;

repos/gems/src/server/wm/gui.h

@@ -158,10 +158,17 @@ class Wm::Gui::View : private Genode::Weak_object<View>,
 					[&] (auto) { warning("unable to obtain real_neighbor_handle"); }
 				);
 
-			if (_neighbor_behind)
+			if (real_neighbor_handle.valid()) {
-				_real_gui.enqueue<Command::To_front>(_real_handle, real_neighbor_handle);
+				if (_neighbor_behind)
-			else
+					_real_gui.enqueue<Command::Front_of>(_real_handle, real_neighbor_handle);
-				_real_gui.enqueue<Command::To_back>(_real_handle, real_neighbor_handle);
+				else
+					_real_gui.enqueue<Command::Behind_of>(_real_handle, real_neighbor_handle);
+			} else {
+				if (_neighbor_behind)
+					_real_gui.enqueue<Command::Front>(_real_handle);
+				else
+					_real_gui.enqueue<Command::Back>(_real_handle);
+			}
 
 			_real_gui.execute();
 
@@ -730,7 +737,7 @@ class Wm::Gui::Session_component : public Rpc_object<Gui::Session>,
 		{
 			switch (command.opcode) {
 
-			case Command::OP_GEOMETRY:
+			case Command::GEOMETRY:
 				{
 					Locked_ptr<View> view(_view_handle_registry.lookup(command.geometry.view));
 					if (view.valid())
@@ -738,7 +745,7 @@ class Wm::Gui::Session_component : public Rpc_object<Gui::Session>,
 					return;
 				}
 
-			case Command::OP_OFFSET:
+			case Command::OFFSET:
 				{
 					Locked_ptr<View> view(_view_handle_registry.lookup(command.offset.view));
 					if (view.valid())
@@ -747,35 +754,30 @@ class Wm::Gui::Session_component : public Rpc_object<Gui::Session>,
 					return;
 				}
 
-			case Command::OP_TO_FRONT:
+			case Command::FRONT:
 				{
-					Locked_ptr<View> view(_view_handle_registry.lookup(command.to_front.view));
+					Locked_ptr<View> view(_view_handle_registry.lookup(command.front.view));
+					if (view.valid())
+						view->stack(Weak_ptr<View>(), true);
+					return;
+				}
+
+			case Command::FRONT_OF:
+				{
+					Locked_ptr<View> view(_view_handle_registry.lookup(command.front_of.view));
 					if (!view.valid())
 						return;
 
-					/* bring to front if no neighbor is specified */
+					if (!command.front_of.neighbor.valid())
-					if (!command.to_front.neighbor.valid()) {
-						view->stack(Weak_ptr<View>(), true);
 						return;
-					}
 
 					/* stack view relative to neighbor */
-					view->stack(_view_handle_registry.lookup(command.to_front.neighbor),
+					view->stack(_view_handle_registry.lookup(command.front_of.neighbor),
 					            true);
 					return;
 				}
 
-			case Command::OP_TO_BACK:
+			case Command::TITLE:
-				{
-					return;
-				}
-
-			case Command::OP_BACKGROUND:
-				{
-					return;
-				}
-
-			case Command::OP_TITLE:
 				{
 					char sanitized_title[command.title.title.capacity()];
 
@@ -793,7 +795,10 @@ class Wm::Gui::Session_component : public Rpc_object<Gui::Session>,
 					return;
 				}
 
-			case Command::OP_NOP:
+			case Command::BACK:
+			case Command::BEHIND_OF:
+			case Command::BACKGROUND:
+			case Command::NOP:
 				return;
 			}
 		}

repos/libports/src/app/pdf_view/main.cc

@@ -142,7 +142,7 @@ class Pdf_view
 
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_view, Gui::Rect(Gui::Point(), _nit_mode.area));
-			_gui.enqueue<Command::To_front>(_view, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_view);
 			_gui.execute();
 		}
 

repos/libports/src/app/usb_webcam/main.cc

@@ -70,7 +70,7 @@ class Viewer
 			using namespace Gui;
 
 			_gui.enqueue<Command::Geometry>(_view, Gui::Rect(Gui::Point(0, 0), _mode.area));
-			_gui.enqueue<Command::To_front>(_view, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_view);
 			_gui.enqueue<Command::Title>(_view, "webcam");
 			_gui.execute();
 		}

repos/libports/src/lib/qgenodeviewwidget/qgenodeviewwidget.cpp

@@ -224,7 +224,7 @@ void QGenodeViewWidget::paintEvent(QPaintEvent *event)
 	Gui::Session::View_handle const neighbor_handle =
 		gui->view_handle(platform_window->view_cap());
 
-	gui->enqueue<Command::To_front>(view_handle, neighbor_handle);
+	gui->enqueue<Command::Front_of>(view_handle, neighbor_handle);
 	gui->execute();
 
 	gui->release_view_handle(neighbor_handle);

repos/libports/src/test/mesa_demo/eglut/eglut_genode.cc

@@ -69,7 +69,7 @@ struct Window : Genode_egl_window
 		mode_change();
 
 		gui.enqueue<Command::Title>(view, "eglut");
-		gui.enqueue<Command::To_front>(view, View_handle());
+		gui.enqueue<Command::Front>(view);
 		gui.execute();
 	}
 

repos/os/include/gui_session/gui_session.h

@@ -63,52 +63,29 @@ struct Gui::Session : Genode::Session
 
 	struct Command
 	{
-		enum Opcode { OP_GEOMETRY, OP_OFFSET,
+		enum Opcode { GEOMETRY, OFFSET, FRONT, BACK, FRONT_OF, BEHIND_OF,
-		              OP_TO_FRONT, OP_TO_BACK, OP_BACKGROUND,
+		              BACKGROUND, TITLE, NOP };
-		              OP_TITLE, OP_NOP };
 
-		struct Nop { static Opcode opcode() { return OP_NOP; } };
+		struct Nop { static constexpr Opcode opcode = NOP; };
 
-		struct Geometry
+		/**
+		 * Operation that takes a view as first argument
+		 */
+		template <Opcode OPCODE>
+		struct View_op
 		{
-			static Opcode opcode() { return OP_GEOMETRY; }
+			static constexpr Opcode opcode = OPCODE;
-			View_handle view;
-			Rect        rect;
-		};
-
-		struct Offset
-		{
-			static Opcode opcode() { return OP_OFFSET; }
-			View_handle view;
-			Point       offset;
-		};
-
-		struct To_front
-		{
-			static Opcode opcode() { return OP_TO_FRONT; }
-			View_handle view;
-			View_handle neighbor;
-		};
-
-		struct To_back
-		{
-			static Opcode opcode() { return OP_TO_BACK; }
-			View_handle view;
-			View_handle neighbor;
-		};
-
-		struct Background
-		{
-			static Opcode opcode() { return OP_BACKGROUND; }
 			View_handle view;
 		};
 
-		struct Title
+		struct Geometry   : View_op<GEOMETRY>   { Rect rect; };
-		{
+		struct Offset     : View_op<OFFSET>     { Point offset; };
-			static Opcode opcode() { return OP_TITLE; }
+		struct Front      : View_op<FRONT>      { };
-			View_handle view;
+		struct Back       : View_op<BACK>       { };
-			String<64> title;
+		struct Front_of   : View_op<FRONT_OF>   { View_handle neighbor; };
-		};
+		struct Behind_of  : View_op<BEHIND_OF>  { View_handle neighbor; };
+		struct Background : View_op<BACKGROUND> { };
+		struct Title      : View_op<TITLE>      { String<64> title; };
 
 		Opcode opcode;
 		union
@@ -116,16 +93,18 @@ struct Gui::Session : Genode::Session
 			Nop        nop;
 			Geometry   geometry;
 			Offset     offset;
-			To_front   to_front;
+			Front      front;
-			To_back    to_back;
+			Back       back;
+			Front_of   front_of;
+			Behind_of  behind_of;
 			Background background;
 			Title      title;
 		};
 
-		Command() : opcode(OP_NOP) { }
+		Command() : opcode(Opcode::NOP) { }
 
 		template <typename ARGS>
-		Command(ARGS args) : opcode(ARGS::opcode())
+		Command(ARGS args) : opcode(ARGS::opcode)
 		{
 			reinterpret_cast<ARGS &>(nop) = args;
 		}

repos/os/src/app/pointer/main.cc

@@ -357,8 +357,7 @@ Pointer::Main::Main(Genode::Env &env) : _env(env)
 		}
 	}
 
-	using View_handle = Gui::Session::View_handle;
+	_gui.enqueue<Gui::Session::Command::Front>(_view);
-	_gui.enqueue<Gui::Session::Command::To_front>(_view, View_handle());
 	_gui.execute();
 
 	_update_pointer();

repos/os/src/app/status_bar/main.cc

@@ -200,8 +200,7 @@ struct Status_bar::Main
 		_gui.mode_sigh(_mode_handler);
 
 		/* schedule initial view-stacking command, needed only once */
-		using View_handle = Gui::Session::View_handle;
+		_gui.enqueue<Gui::Session::Command::Front>(_view);
-		_gui.enqueue<Gui::Session::Command::To_front>(_view, View_handle());
 
 		/* import initial state */
 		_handle_mode();

repos/os/src/server/gui_fb/main.cc

@@ -304,7 +304,7 @@ struct Nit_fb::Main : View_updater
 	{
 		using Command = Gui::Session::Command;
 		gui.enqueue<Command::Geometry>(view, Rect(position, fb_session.size()));
-		gui.enqueue<Command::To_front>(view, View_handle());
+		gui.enqueue<Command::Front>(view);
 		gui.execute();
 	}
 

repos/os/src/server/nitpicker/gui_session.cc

@@ -62,7 +62,7 @@ void Gui_session::_execute_command(Command const &command)
 {
 	switch (command.opcode) {
 
-	case Command::OP_GEOMETRY:
+	case Command::GEOMETRY:
 		{
 			Command::Geometry const &cmd = command.geometry;
 			Locked_ptr<View> view(_view_handle_registry.lookup(cmd.view));
@@ -81,7 +81,7 @@ void Gui_session::_execute_command(Command const &command)
 			return;
 		}
 
-	case Command::OP_OFFSET:
+	case Command::OFFSET:
 		{
 			Command::Offset const &cmd = command.offset;
 			Locked_ptr<View> view(_view_handle_registry.lookup(cmd.view));
@@ -92,9 +92,29 @@ void Gui_session::_execute_command(Command const &command)
 			return;
 		}
 
-	case Command::OP_TO_FRONT:
+	case Command::FRONT:
 		{
-			Command::To_front const &cmd = command.to_front;
+			Command::Front const &cmd = command.front;
+
+			Locked_ptr<View> view(_view_handle_registry.lookup(cmd.view));
+			if (view.valid())
+				_view_stack.stack(*view, nullptr, true);
+			return;
+		}
+
+	case Command::BACK:
+		{
+			Command::Back const &cmd = command.back;
+
+			Locked_ptr<View> view(_view_handle_registry.lookup(cmd.view));
+			if (view.valid())
+				_view_stack.stack(*view, nullptr, false);
+			return;
+		}
+
+	case Command::FRONT_OF:
+		{
+			Command::Front_of const &cmd = command.front_of;
 			if (_views_are_equal(cmd.view, cmd.neighbor))
 				return;
 
@@ -102,23 +122,16 @@ void Gui_session::_execute_command(Command const &command)
 			if (!view.valid())
 				return;
 
-			/* bring to front if no neighbor is specified */
-			if (!cmd.neighbor.valid()) {
-				_view_stack.stack(*view, nullptr, true);
-				return;
-			}
-
 			/* stack view relative to neighbor */
 			Locked_ptr<View> neighbor(_view_handle_registry.lookup(cmd.neighbor));
 			if (neighbor.valid())
 				_view_stack.stack(*view, &(*neighbor), false);
-
 			return;
 		}
 
-	case Command::OP_TO_BACK:
+	case Command::BEHIND_OF:
 		{
-			Command::To_back const &cmd = command.to_back;
+			Command::Behind_of const &cmd = command.behind_of;
 			if (_views_are_equal(cmd.view, cmd.neighbor))
 				return;
 
@@ -126,21 +139,14 @@ void Gui_session::_execute_command(Command const &command)
 			if (!view.valid())
 				return;
 
-			/* bring to front if no neighbor is specified */
-			if (!cmd.neighbor.valid()) {
-				_view_stack.stack(*view, nullptr, false);
-				return;
-			}
-
 			/* stack view relative to neighbor */
 			Locked_ptr<View> neighbor(_view_handle_registry.lookup(cmd.neighbor));
 			if (neighbor.valid())
 				_view_stack.stack(*view, &(*neighbor), true);
-
 			return;
 		}
 
-	case Command::OP_BACKGROUND:
+	case Command::BACKGROUND:
 		{
 			Command::Background const &cmd = command.background;
 			if (_provides_default_bg) {
@@ -171,7 +177,7 @@ void Gui_session::_execute_command(Command const &command)
 			return;
 		}
 
-	case Command::OP_TITLE:
+	case Command::TITLE:
 		{
 			Command::Title const &cmd = command.title;
 			Locked_ptr<View> view(_view_handle_registry.lookup(cmd.view));
@@ -182,7 +188,7 @@ void Gui_session::_execute_command(Command const &command)
 			return;
 		}
 
-	case Command::OP_NOP:
+	case Command::NOP:
 		return;
 	}
 }

repos/os/src/server/vmm/virtio_gpu.h

@@ -466,7 +466,7 @@ class Vmm::Virtio_gpu_device : public Virtio_device<Virtio_gpu_queue, 2>
 
 			using Command = Gui::Session::Command;
 			_gui.enqueue<Command::Geometry>(_view, Rect(Point(0, 0), _fb_mode.area));
-			_gui.enqueue<Command::To_front>(_view, Gui::Session::View_handle());
+			_gui.enqueue<Command::Front>(_view);
 			_gui.execute();
 			return _gui.mode();
 		}

repos/os/src/test/capture/main.cc

@@ -47,7 +47,7 @@ class Test::View
 			using Command = Gui::Session::Command;
 
 			_gui.enqueue<Command::Geometry>(_handle, rect);
-			_gui.enqueue<Command::To_front>(_handle, View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/os/src/test/nitpicker/main.cc

@@ -65,7 +65,7 @@ class Test::View : private List<View>::Element, Interface
 			using namespace Gui;
 
 			_gui.enqueue<Command::Geometry>(_handle, Gui::Rect { _pos, _attr.size });
-			_gui.enqueue<Command::To_front>(_handle, View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.enqueue<Command::Title>(_handle, _attr.title);
 			_gui.execute();
 		}
@@ -77,7 +77,7 @@ class Test::View : private List<View>::Element, Interface
 
 		void top()
 		{
-			_gui.enqueue<Command::To_front>(_handle, View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/os/src/test/vfs_capture/main.cc

@@ -49,7 +49,7 @@ class Test::View
 			using Command = Gui::Session::Command;
 
 			_gui.enqueue<Command::Geometry>(_handle, rect);
-			_gui.enqueue<Command::To_front>(_handle, View_handle());
+			_gui.enqueue<Command::Front>(_handle);
 			_gui.execute();
 		}
 

repos/ports/src/virtualbox5/frontend/fb.h

@@ -76,23 +76,19 @@ class Genodefb :
 		{
 			_gui.buffer(_fb_mode, false);
 
-			typedef Gui::Session::Command Command;
-
 			Gui::Rect rect(Gui::Point(0, 0), _fb_mode.area);
 
-			_gui.enqueue<Command::Geometry>(_view, rect);
+			_gui.enqueue<Gui::Session::Command::Geometry>(_view, rect);
 			_gui.execute();
 		}
 
 		Fb_Genode::Mode _initial_setup()
 		{
-			typedef Gui::Session::Command Command;
-
 			_view = _gui.create_view();
 
 			_adjust_buffer();
 
-			_gui.enqueue<Command::To_front>(_view, View_handle());
+			_gui.enqueue<Gui::Session::Command::Front>(_view);
 			_gui.execute();
 
 			return _fb_mode;

repos/ports/src/virtualbox6/include/fb.h

@@ -74,23 +74,19 @@ class Genodefb :
 		{
 			_gui.buffer(_fb_mode, false);
 
-			using Command = Gui::Session::Command;
-
 			Gui::Rect rect(Gui::Point(0, 0), _fb_mode.area);
 
-			_gui.enqueue<Command::Geometry>(_view, rect);
+			_gui.enqueue<Gui::Session::Command::Geometry>(_view, rect);
 			_gui.execute();
 		}
 
 		Fb_Genode::Mode _initial_setup()
 		{
-			using Command = Gui::Session::Command;
-
 			_view = _gui.create_view();
 
 			_adjust_buffer();
 
-			_gui.enqueue<Command::To_front>(_view, View_handle());
+			_gui.enqueue<Gui::Session::Command::Front>(_view);
 			_gui.execute();
 
 			return _fb_mode;