nitpicker: Layers and client-side mouse cursor

This patch introduces a mandatory layer attribute to domains. The layer
ordering is superimposed on the stacking order of the views. The
top-most layer can be assigned to a pointer-managing client. An example
for such a pointer is located at os/src/app/pointer. It replaces the
formerly built-in nitpicker mouse cursor.

The new layering mechanism replaces the former "stay-top" session
argument. So the Nitpicker::Connection no longer takes the stay-top flag
as the first argument.

repos/os/include/nitpicker_session/connection.h

@@ -34,7 +34,7 @@ class Nitpicker::Connection : public Genode::Connection<Session>,
 		/**
 		 * Create session and return typed session capability
 		 */
-		Session_capability _connect(bool stay_top, char const *label)
+		Session_capability _connect(char const *label)
 		{
 			enum { ARGBUF_SIZE = 128 };
 			char argbuf[ARGBUF_SIZE];
@@ -50,9 +50,6 @@ class Nitpicker::Connection : public Genode::Connection<Session>,
 			enum { SESSION_METADATA = 36*1024 };
 			Arg_string::set_arg(argbuf, sizeof(argbuf), "ram_quota", SESSION_METADATA);
 
-			if (stay_top)
-				Arg_string::set_arg(argbuf, sizeof(argbuf), "stay_top", "yes");
-
 			return session(argbuf);
 		}
 
@@ -61,10 +58,10 @@ class Nitpicker::Connection : public Genode::Connection<Session>,
 		/**
 		 * Constructor
 		 */
-		Connection(bool stay_top = false, char const *label = "")
+		Connection(char const *label = "")
 		:
 			/* establish nitpicker session */
-			Genode::Connection<Session>(_connect(stay_top, label)),
+			Genode::Connection<Session>(_connect(label)),
 			Session_client(cap()),
 
 			/* request frame-buffer and input sub sessions */

repos/os/run/demo.run

@@ -5,7 +5,8 @@
 set build_components {
 	core init
 	drivers/timer
-	server/nitpicker server/liquid_framebuffer app/launchpad app/scout
+	server/nitpicker app/pointer
+	server/liquid_framebuffer app/launchpad app/scout
 	test/nitpicker server/nitlog
 	drivers/framebuffer drivers/pci drivers/input
 }
@@ -119,8 +120,11 @@ append config {
 		<resource name="RAM" quantum="1M"/>
 		<provides><service name="Nitpicker"/></provides>
 		<config>
-			<domain name="default" color="#ffffff"/>
+			<domain name="pointer" layer="1" xray="no" origin="pointer" />
-			<policy label="" domain="default"/>
+			<domain name="default" layer="2" />
+
+			<policy label="pointer" domain="pointer"/>
+			<policy label=""        domain="default"/>
 
 			<global-key name="KEY_SCROLLLOCK" operation="xray" />
 			<global-key name="KEY_SYSRQ"      operation="kill" />
@@ -129,6 +133,9 @@ append config {
 			<global-key name="KEY_F12"        operation="xray" />
 		</config>
 	</start>
+	<start name="pointer">
+		<resource name="RAM" quantum="1M"/>
+	</start>
 	<start name="launchpad">
 		<resource name="RAM" quantum="64M" />
 		<configfile name="launchpad.config" />
@@ -163,7 +170,7 @@ close $launchpad_config_fd
 set boot_modules {
 	core init
 	timer
-	nitpicker liquid_fb launchpad scout
+	nitpicker pointer liquid_fb launchpad scout
 	testnit nitlog
 	launchpad.config
 }

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

@@ -0,0 +1,66 @@
+/*
+ * \brief  Minimalistic nitpicker pointer
+ * \author Norman Feske
+ * \date   2014-07-02
+ */
+
+/*
+ * Copyright (C) 2014 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+/* Genode includes */
+#include <nitpicker_session/connection.h>
+#include <os/surface.h>
+#include <os/pixel_rgb565.h>
+#include <os/attached_dataspace.h>
+#include <base/sleep.h>
+
+/* local includes */
+#include "big_mouse.h"
+
+
+template <typename PT>
+void convert_cursor_data_to_pixels(PT *pixel, Nitpicker::Area size)
+{
+	unsigned char *alpha = (unsigned char *)(pixel + size.count());
+
+	for (unsigned y = 0; y < size.h(); y++) {
+		for (unsigned x = 0; x < size.w(); x++) {
+
+			/* the source is known to be in RGB565 format */
+			Genode::Pixel_rgb565 src =
+				*(Genode::Pixel_rgb565 *)(&big_mouse.pixels[y][x]);
+
+			unsigned const i = y*size.w() + x;
+			pixel[i] = PT(src.r(), src.g(), src.b());
+			alpha[i] = src.r() ? 255 : 0;
+		}
+	}
+}
+
+
+int main(int, char **)
+{
+	static Nitpicker::Connection nitpicker;
+
+	Nitpicker::Area const cursor_size(big_mouse.w, big_mouse.h);
+
+	Framebuffer::Mode const mode(cursor_size.w(), cursor_size.h(),
+	                             Framebuffer::Mode::RGB565);
+	nitpicker.buffer(mode, true);
+
+	static Genode::Attached_dataspace ds(nitpicker.framebuffer()->dataspace());
+
+	convert_cursor_data_to_pixels(ds.local_addr<Genode::Pixel_rgb565>(), cursor_size);
+
+	Nitpicker::Session::View_handle view = nitpicker.create_view();
+	Nitpicker::Rect geometry(Nitpicker::Point(0, 0), cursor_size);
+	nitpicker.enqueue<Nitpicker::Session::Command::Geometry>(view, geometry);
+	nitpicker.enqueue<Nitpicker::Session::Command::To_front>(view);
+	nitpicker.execute();
+
+	Genode::sleep_forever();
+}

repos/os/src/app/pointer/target.mk

@@ -0,0 +1,3 @@
+TARGET = pointer
+SRC_CC = main.cc
+LIBS  += base

repos/os/src/server/nitpicker/background.h

@@ -30,8 +30,8 @@ struct Background : private Texture_base, Session, View
 	 */
 	Background(Area size)
 	:
-		Texture_base(Area(0, 0)), Session(Genode::Session_label(""), 0, false),
+		Texture_base(Area(0, 0)), Session(Genode::Session_label(""), 0),
-		View(*this, View::NOT_STAY_TOP, View::NOT_TRANSPARENT, View::BACKGROUND, 0),
+		View(*this, View::NOT_TRANSPARENT, View::BACKGROUND, 0),
 		color(25, 37, 50)
 	{
 		View::geometry(Rect(Point(0, 0), size));

repos/os/src/server/nitpicker/chunky_menubar.h

@@ -35,9 +35,8 @@ class Chunky_menubar : public Texture<PT>,
 		Chunky_menubar(PT *pixels, Area size)
 		:
 			Texture<PT>(pixels, 0, size),
-			Session(Genode::Session_label(""), 0, false),
+			Session(Genode::Session_label(""), 0),
-			View(*this, View::STAY_TOP, View::NOT_TRANSPARENT,
+			View(*this, View::NOT_TRANSPARENT, View::NOT_BACKGROUND, 0),
-			     View::NOT_BACKGROUND, 0),
 			_canvas(pixels, size)
 		{
 			View::geometry(Rect(Point(0, 0), size));

repos/os/src/server/nitpicker/domain_registry.h

@@ -44,16 +44,19 @@ class Domain_registry
 
 			private:
 
-				Name   _name;
+				Name     _name;
-				Color  _color;
+				Color    _color;
-				Xray   _xray;
+				Xray     _xray;
-				Origin _origin;
+				Origin   _origin;
+				unsigned _layer;
 
 				friend class Domain_registry;
 
-				Entry(Name const &name, Color color, Xray xray, Origin origin)
+				Entry(Name const &name, Color color, Xray xray, Origin origin,
+				      unsigned layer)
 				:
-					_name(name), _color(color), _xray(xray), _origin(origin)
+					_name(name), _color(color), _xray(xray), _origin(origin),
+					_layer(layer)
 				{ }
 
 			public:
@@ -62,6 +65,8 @@ class Domain_registry
 
 				Color color() const { return _color; }
 
+				unsigned layer() const { return _layer; }
+
 				bool xray_opaque()    const { return _xray == XRAY_OPAQUE; }
 				bool xray_no()        const { return _xray == XRAY_NO; }
 				bool origin_pointer() const { return _origin == ORIGIN_POINTER; }
@@ -126,10 +131,17 @@ class Domain_registry
 				return;
 			}
 
+			if (!domain.has_attribute("layer")) {
+				PERR("no layer specified for domain \"%s\"", name.string());
+				return;
+			}
+
+			unsigned const layer = domain.attribute_value("layer", ~0UL);
+
 			Entry::Color const color = domain.attribute_value("color", WHITE);
 
 			_entries.insert(new (_alloc) Entry(name, color, _xray(domain),
-			                                   _origin(domain)));
+			                                   _origin(domain), layer));
 		}
 
 	private:

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

@@ -34,10 +34,9 @@
 
 /* local includes */
 #include "input.h"
-#include "big_mouse.h"
 #include "background.h"
 #include "clip_guard.h"
-#include "mouse_cursor.h"
+#include "pointer_origin.h"
 #include "chunky_menubar.h"
 #include "domain_registry.h"
 
@@ -638,11 +637,10 @@ class Nitpicker::Session_component : public Genode::Rpc_object<Session>,
 		                  Framebuffer::Session &framebuffer,
 		                  int                   v_offset,
 		                  bool                  provides_default_bg,
-		                  bool                  stay_top,
 		                  Allocator            &session_alloc,
 		                  size_t                ram_quota)
 		:
-			::Session(label, v_offset, stay_top),
+			::Session(label, v_offset),
 			_session_alloc(&session_alloc, ram_quota),
 			_framebuffer(framebuffer),
 			_framebuffer_session_component(view_stack, *this, framebuffer, *this),
@@ -729,7 +727,6 @@ class Nitpicker::Session_component : public Genode::Rpc_object<Session>,
 
 					view = new (_view_alloc)
 						View(*this,
-						     stay_top() ? View::STAY_TOP : View::NOT_STAY_TOP,
 						     View::NOT_TRANSPARENT, View::NOT_BACKGROUND,
 						     &(*parent));
 
@@ -748,7 +745,6 @@ class Nitpicker::Session_component : public Genode::Rpc_object<Session>,
 				try {
 					view = new (_view_alloc)
 						View(*this,
-						     stay_top() ? View::STAY_TOP : View::NOT_STAY_TOP,
 						     View::NOT_TRANSPARENT, View::NOT_BACKGROUND,
 						     nullptr);
 					}
@@ -921,8 +917,6 @@ class Nitpicker::Root : public Genode::Root_component<Session_component>
 
 			int const v_offset = _default_v_offset;
 
-			bool const stay_top  = Arg_string::find_arg(args, "stay_top").bool_value(false);
-
 			size_t const required_quota = Input::Session_component::ev_ds_size()
 			                            + Genode::align_addr(sizeof(Session::Command_buffer), 12);
 
@@ -940,7 +934,7 @@ class Nitpicker::Root : public Genode::Root_component<Session_component>
 			Session_component *session = new (md_alloc())
 				Session_component(Session_label(args), _view_stack, _mode,
 				                  _pointer_origin, *ep(), _framebuffer,
-				                  v_offset, provides_default_bg, stay_top,
+				                  v_offset, provides_default_bg,
 				                  *md_alloc(), unused_quota);
 
 			session->apply_session_policy(_domain_registry);
@@ -1068,9 +1062,7 @@ struct Nitpicker::Main
 	/*
 	 * Create view stack with default elements
 	 */
-	Area                   mouse_size { big_mouse.w, big_mouse.h };
+	Pointer_origin pointer_origin;
-	Mouse_cursor<PT const> mouse_cursor { (PT const *)&big_mouse.pixels[0][0],
-	                                      mouse_size, user_state };
 
 	Background background = { Area(99999, 99999) };
 
@@ -1080,7 +1072,7 @@ struct Nitpicker::Main
 	Genode::Sliced_heap sliced_heap = { env()->ram_session(), env()->rm_session() };
 
 	Root<PT> np_root = { session_list, *domain_registry, global_keys,
-	                     ep.rpc_ep(), user_state, user_state, mouse_cursor,
+	                     ep.rpc_ep(), user_state, user_state, pointer_origin,
 	                     sliced_heap, framebuffer, Framebuffer_screen::MENUBAR_HEIGHT };
 
 	Genode::Reporter pointer_reporter = { "pointer" };
@@ -1115,9 +1107,9 @@ struct Nitpicker::Main
 		fb_screen->menubar.state(Menubar_state(user_state, "", BLACK));
 
 		user_state.default_background(background);
-		user_state.stack(mouse_cursor);
+		user_state.stack(pointer_origin);
-		user_state.stack(fb_screen->menubar);
 		user_state.stack(background);
+		user_state.stack(fb_screen->menubar);
 
 		config()->sigh(config_dispatcher);
 		Signal_transmitter(config_dispatcher).submit();
@@ -1144,19 +1136,19 @@ void Nitpicker::Main::handle_input(unsigned)
 		return;
 
 	do {
-		Point const old_mouse_pos = user_state.mouse_pos();
+		Point const old_pointer_pos = user_state.pointer_pos();
 
 		/* handle batch of pending events */
 		if (input.is_pending())
 			import_input_events(ev_buf, input.flush(), user_state);
 
-		Point const new_mouse_pos  = user_state.mouse_pos();
+		Point const new_pointer_pos = user_state.pointer_pos();
-		Point const menubar_offset = Point(0, Framebuffer_screen::MENUBAR_HEIGHT);
+		Point const menubar_offset  = Point(0, Framebuffer_screen::MENUBAR_HEIGHT);
-		Point const report_pos     = new_mouse_pos - menubar_offset;
+		Point const report_pos      = new_pointer_pos - menubar_offset;
 
 		/* report mouse-position updates */
-		if (pointer_reporter.is_enabled() && old_mouse_pos != new_mouse_pos
+		if (pointer_reporter.is_enabled() && old_pointer_pos != new_pointer_pos
-		 && new_mouse_pos.y() >= 0)
+		 && new_pointer_pos.y() >= 0)
 
 			Genode::Reporter::Xml_generator xml(pointer_reporter, [&] ()
 			{
@@ -1165,8 +1157,8 @@ void Nitpicker::Main::handle_input(unsigned)
 			});
 
 		/* update mouse cursor */
-		if (old_mouse_pos != new_mouse_pos)
+		if (old_pointer_pos != new_pointer_pos)
-			user_state.geometry(mouse_cursor, Rect(new_mouse_pos, mouse_size));
+			user_state.geometry(pointer_origin, Rect(new_pointer_pos, Area()));
 
 		/* perform redraw and flush pixels to the framebuffer */
 		user_state.draw(fb_screen->screen).flush([&] (Rect const &rect) {
@@ -1226,7 +1218,13 @@ void Nitpicker::Main::handle_config(unsigned)
 	for (::Session *s = session_list.first(); s; s = s->next())
 		s->apply_session_policy(*domain_registry);
 
-	user_state.apply_origin_policy(mouse_cursor);
+	user_state.apply_origin_policy(pointer_origin);
+
+	/*
+	 * Domains may have changed their layering, resort the view stack with the
+	 * new constrains.
+	 */
+	user_state.sort_views_by_layer();
 
 	/* redraw */
 	user_state.update_all_views();
@@ -1251,7 +1249,7 @@ void Nitpicker::Main::handle_fb_mode(unsigned)
 	fb_screen->menubar.state(menubar_state);
 
 	/* re-insert menu bar behind mouse cursor */
-	user_state.stack(fb_screen->menubar, &mouse_cursor);
+	user_state.stack(fb_screen->menubar, &pointer_origin);
 
 	/* redraw */
 	user_state.update_all_views();

repos/os/src/server/nitpicker/mouse_cursor.h

@@ -1,81 +0,0 @@
-/*
- * \brief  Nitpicker mouse cursor
- * \author Norman Feske
- * \date   2006-08-18
- *
- * The Nitpicker mouse cursor is implemented as a transparent
- * view that stays always in front of all other views.
- */
-
-/*
- * Copyright (C) 2006-2013 Genode Labs GmbH
- *
- * This file is part of the Genode OS framework, which is distributed
- * under the terms of the GNU General Public License version 2.
- */
-
-#ifndef _MOUSE_CURSOR_H_
-#define _MOUSE_CURSOR_H_
-
-#include <nitpicker_gfx/texture_painter.h>
-
-#include "view.h"
-#include "session.h"
-
-template <typename PT>
-class Mouse_cursor : public Texture<PT>,
-                     public Session, public View
-{
-	private:
-
-		View_stack const &_view_stack;
-
-	public:
-
-		/**
-		 * Constructor
-		 */
-		Mouse_cursor(PT const *pixels, Area size, View_stack const &view_stack)
-		:
-			Texture<PT>(pixels, 0, size),
-			Session(Genode::Session_label(""), 0, false),
-			View(*this, View::STAY_TOP, View::TRANSPARENT, View::NOT_BACKGROUND, 0),
-			_view_stack(view_stack)
-		{ }
-
-
-		/***********************
-		 ** Session interface **
-		 ***********************/
-
-		void submit_input_event(Input::Event) override { }
-		void submit_sync() override { }
-
-
-		/********************
-		 ** View interface **
-		 ********************/
-
-		/*
-		 * The mouse cursor is always displayed without a surrounding frame.
-		 */
-
-		int frame_size(Mode const &mode) const override { return 0; }
-
-		void frame(Canvas_base &canvas, Mode const &mode) const override { }
-
-		void draw(Canvas_base &canvas, Mode const &mode) const override
-		{
-			Rect const view_rect = abs_geometry();
-
-			Clip_guard clip_guard(canvas, view_rect);
-
-			/* draw area behind the mouse cursor */
-			_view_stack.draw_rec(canvas, view_stack_next(), view_rect);
-
-			/* draw mouse cursor */
-			canvas.draw_texture(view_rect.p1(), *this, Texture_painter::MASKED, BLACK, true);
-		}
-};
-
-#endif

repos/os/src/server/nitpicker/pointer_origin.h

@@ -0,0 +1,46 @@
+/*
+ * \brief  View that represents the origin of the pointer coordinate system
+ * \author Norman Feske
+ * \date   2014-07-02
+ */
+
+/*
+ * Copyright (C) 2014 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU General Public License version 2.
+ */
+
+#ifndef _POINTER_ORIGIN_H_
+#define _POINTER_ORIGIN_H_
+
+#include "view.h"
+#include "session.h"
+
+struct Pointer_origin : Session, View
+{
+	Pointer_origin()
+	:
+		Session(Genode::Session_label(""), 0),
+		View(*this, View::TRANSPARENT, View::NOT_BACKGROUND, 0)
+	{ }
+
+
+	/***********************
+	 ** Session interface **
+	 ***********************/
+
+	void submit_input_event(Input::Event) override { }
+	void submit_sync() override { }
+
+
+	/********************
+	 ** View interface **
+	 ********************/
+
+	int frame_size(Mode const &) const override { return 0; }
+	void frame(Canvas_base &, Mode const &) const override { }
+	void draw(Canvas_base &, Mode const &) const override { }
+};
+
+#endif /* _POINTER_ORIGIN_H_ */

repos/os/src/server/nitpicker/session.h

@@ -42,7 +42,6 @@ class Session : public Session_list::Element
 		View                         *_background = 0;
 		int                           _v_offset;
 		unsigned char          const *_input_mask = { 0 };
-		bool                   const  _stay_top;
 
 	public:
 
@@ -51,11 +50,10 @@ class Session : public Session_list::Element
 		 *
 		 * \param label     session label
 		 * \param v_offset  vertical screen offset of session
-		 * \param stay_top  true for views that stay always in front
 		 */
-		Session(Genode::Session_label const &label, int v_offset, bool stay_top)
+		Session(Genode::Session_label const &label, int v_offset)
 		:
-			_label(label), _v_offset(v_offset), _stay_top(stay_top)
+			_label(label), _v_offset(v_offset)
 		{ }
 
 		virtual ~Session() { }
@@ -72,6 +70,8 @@ class Session : public Session_list::Element
 
 		bool origin_pointer() const { return _domain && _domain->origin_pointer(); }
 
+		unsigned layer() const { return _domain ? _domain->layer() : ~0UL; }
+
 		Texture_base const *texture() const { return _texture; }
 
 		void texture(Texture_base const *texture, bool uses_alpha)
@@ -100,8 +100,6 @@ class Session : public Session_list::Element
 
 		void background(View *background) { _background = background; }
 
-		bool stay_top() const { return _stay_top; }
-
 		/**
 		 * Return true if session uses an alpha channel
 		 */

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

@@ -71,7 +71,7 @@ void User_state::handle_event(Input::Event ev)
 	/*
 	 * Mangle incoming events
 	 */
-	int ax = _mouse_pos.x(), ay = _mouse_pos.y();
+	int ax = _pointer_pos.x(), ay = _pointer_pos.y();
 	int rx = 0, ry = 0; /* skip info about relative motion by default */
 
 	/* transparently handle absolute and relative motion events */
@@ -94,13 +94,13 @@ void User_state::handle_event(Input::Event ev)
 	/* create the mangled event */
 	ev = Input::Event(type, keycode, ax, ay, rx, ry);
 
-	_mouse_pos = Point(ax, ay);
+	_pointer_pos = Point(ax, ay);
 
 	/* count keys */
 	if (type == Event::PRESS)                   Mode::inc_key_cnt();
 	if (type == Event::RELEASE && Mode::drag()) Mode::dec_key_cnt();
 
-	View const * const pointed_view    = find_view(_mouse_pos);
+	View const * const pointed_view    = find_view(_pointer_pos);
 	::Session  * const pointed_session = pointed_view ? &pointed_view->session() : 0;
 
 	/*
@@ -268,7 +268,7 @@ void User_state::forget(::Session const &session)
 	Mode::forget(session);
 
 	if (_pointed_session == &session) {
-		View * const pointed_view = find_view(_mouse_pos);
+		View * const pointed_view = find_view(_pointer_pos);
 		_pointed_session = pointed_view ? &pointed_view->session() : nullptr;
 	}
 

repos/os/src/server/nitpicker/user_state.h

@@ -40,9 +40,9 @@ class User_state : public Mode, public View_stack
 		Menubar &_menubar;
 
 		/*
-		 * Current mouse cursor position
+		 * Current pointer position
 		 */
-		Point _mouse_pos;
+		Point _pointer_pos;
 
 		/*
 		 * Currently pointed-at session
@@ -80,7 +80,7 @@ class User_state : public Mode, public View_stack
 		/**
 		 * Accessors
 		 */
-		Point mouse_pos() { return _mouse_pos; }
+		Point pointer_pos() { return _pointer_pos; }
 
 		/**
 		 * (Re-)apply origin policy to all views

repos/os/src/server/nitpicker/view.h

@@ -76,13 +76,11 @@ class View : public Same_buffer_list_elem,
 
 		enum { TITLE_LEN = 32 };   /* max.characters of a title */
 
-		enum Stay_top    { NOT_STAY_TOP    = 0, STAY_TOP    = 1 };
 		enum Transparent { NOT_TRANSPARENT = 0, TRANSPARENT = 1 };
 		enum Background  { NOT_BACKGROUND  = 0, BACKGROUND  = 1 };
 
 	private:
 
-		Stay_top    const _stay_top;      /* keep view always on top      */
 		Transparent const _transparent;   /* background is partly visible */
 		Background        _background;    /* view is a background view    */
 
@@ -119,10 +117,10 @@ class View : public Same_buffer_list_elem,
 
 	public:
 
-		View(Session &session, Stay_top stay_top, Transparent transparent,
+		View(Session &session, Transparent transparent,
 		     Background bg, View *parent)
 		:
-			_stay_top(stay_top), _transparent(transparent), _background(bg),
+			_transparent(transparent), _background(bg),
 			_parent(parent), _session(session)
 		{ title(""); }
 
@@ -250,7 +248,6 @@ class View : public Same_buffer_list_elem,
 		bool same_session_as(View const &other) const { return &_session == &other._session; }
 
 		bool  top_level()   const { return _parent == 0; }
-		bool  stay_top()    const { return _stay_top; }
 		bool  transparent() const { return _transparent || _session.uses_alpha(); }
 		bool  background()  const { return _background; }
 		Rect  label_rect()  const { return _label_rect; }

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

@@ -15,24 +15,6 @@
 #include "clip_guard.h"
 
 
-/***************
- ** Utilities **
- ***************/
-
-/**
- * Get last view with the stay_top attribute
- *
- * \param view  first view of the view stack
- */
-static View const *last_stay_top_view(View const *view)
-{
-	for (; view && view->view_stack_next() && view->view_stack_next()->stay_top(); )
-		view = view->view_stack_next();
-
-	return view;
-}
-
-
 /**************************
  ** View stack interface **
  **************************/
@@ -79,10 +61,9 @@ Rect View_stack::_outline(View const &view) const
 
 View const *View_stack::_target_stack_position(View const *neighbor, bool behind)
 {
-	/* find target position in view stack */
+	View const *cv = _first_view();
-	View const *cv = last_stay_top_view(_first_view());
 
-	for ( ; cv; cv = _next_view(*cv)) {
+	for (; cv; cv = _next_view(*cv)) {
 
 		/* bring view to front? */
 		if (behind && !neighbor)
@@ -101,7 +82,7 @@ View const *View_stack::_target_stack_position(View const *neighbor, bool behind
 			break;
 	}
 
-	return cv ? cv : last_stay_top_view(_first_view());
+	return cv ? cv : _first_view();
 }
 
 
@@ -296,6 +277,9 @@ void View_stack::stack(View &view, View const *neighbor, bool behind)
 	_views.remove(&view);
 	_views.insert(&view, _target_stack_position(neighbor, behind));
 
+	/* enforce stacking constrains dictated by domain layers */
+	sort_views_by_layer();
+
 	_place_labels(view.abs_geometry());
 
 	_mark_view_as_dirty(view, _outline(view));
@@ -336,3 +320,40 @@ void View_stack::remove_view(View const &view, bool redraw)
 
 	refresh(rect);
 }
+
+
+void View_stack::sort_views_by_layer()
+{
+	Genode::List<View_stack_elem> sorted;
+
+	/* last element of the sorted list */
+	View_stack_elem *at = nullptr;
+
+	while (_views.first()) {
+
+		/* find view with the lowest layer */
+		unsigned         lowest_layer = ~0UL;
+		View_stack_elem *lowest_view  = nullptr;
+		for (View_stack_elem *v = _views.first(); v; v = v->next()) {
+			unsigned const layer = static_cast<View *>(v)->session().layer();
+			if (layer < lowest_layer) {
+				lowest_layer = layer;
+				lowest_view  = v;
+			}
+		}
+
+		if (!lowest_view)
+			lowest_view = _views.first();
+
+		/*
+		 * Move lowest view from unsorted list to the end of the sorted
+		 * list.
+		 */
+		_views.remove(lowest_view);
+		sorted.insert(lowest_view, at);
+		at = lowest_view;
+	}
+
+	/* replace empty source list by newly sorted list */
+	_views = sorted;
+}

repos/os/src/server/nitpicker/view_stack.h

@@ -262,6 +262,8 @@ class View_stack
 			for (View *v = _first_view(); v; v = v->view_stack_next())
 				v->apply_origin_policy(pointer_origin);
 		}
+
+		void sort_views_by_layer();
 };
 
 #endif