wm/layouter: pointer grabbing/ungrabbing

This patch implements the following policy for applications requesting
exclusive input (relative motion): The pointer is grabbed as soon as the
user clicks inside the application window. It is forcibly ungrabbed on
any window-focus change or when tapping the KEY_SCREEN. An application
can always enable (transient) exclusive input during a key sequence,
e.g., when dragging the mouse while holding the mouse button. Transient
exclusive input is revoked when releasing the last button/key.

Fixes #5355

repos/gems/recipes/raw/motif_wm/layouter.config

@@ -15,7 +15,7 @@
 		<assign label_prefix="" target="screen_1" xpos="any" ypos="any"/>
 	</rules>
 
-	<press key="KEY_SCREEN">
+	<press key="KEY_SCREEN" action="release_grab">
 		<press key="KEY_TAB" action="next_window">
 			<release key="KEY_TAB">
 				<release key="KEY_SCREEN" action="raise_window"/>

repos/gems/run/wm.run

@@ -63,6 +63,8 @@ install_config {
 
 			<policy label_prefix="pointer" domain="pointer"/>
 			<default-policy domain="default"/>
+
+			<global-key name="KEY_SCREEN" label="wm -> wm -> decorator" />
 		</config>
 	</start>
 
@@ -154,7 +156,9 @@ set fd [open [run_dir]/genode/focus w]
 puts $fd "<focus label=\"wm -> focus\"/>"
 close $fd
 
-copy_file [genode_dir]/repos/gems/recipes/raw/motif_wm/wm.config [run_dir]/genode/
+copy_file [genode_dir]/repos/gems/recipes/raw/motif_wm/wm.config             [run_dir]/genode/
+copy_file [genode_dir]/repos/gems/recipes/raw/motif_wm/layouter.config       [run_dir]/genode/
+copy_file [genode_dir]/repos/gems/recipes/raw/motif_wm/decorator_init.config [run_dir]/genode/
 
 build { app/window_layouter app/decorator server/nitpicker server/wm test/nitpicker }
 

repos/gems/src/app/window_layouter/action.h

@@ -49,6 +49,7 @@ class Window_layouter::Action
 			PREV_TAB,
 			TOOGLE_OVERLAY,
 			SCREEN,
+			RELEASE_GRAB,
 		};
 
 	private:
@@ -64,6 +65,7 @@ class Window_layouter::Action
 			if (string == "raise_window")      return RAISE_WINDOW;
 			if (string == "toggle_fullscreen") return TOGGLE_FULLSCREEN;
 			if (string == "screen")            return SCREEN;
+			if (string == "release_grab")      return RELEASE_GRAB;
 
 			Genode::warning("cannot convert \"", string, "\" to action type");
 			return NONE;

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

@@ -196,6 +196,12 @@ struct Window_layouter::Main : Operations,
 		_gen_focus();
 	}
 
+	void release_grab() override
+	{
+		/* wm revokes exclusive input on each focus update */
+		_gen_focus();
+	}
+
 	void toggle_fullscreen(Window_id id) override
 	{
 		/* make sure that the specified window is the front-most one */

repos/gems/src/app/window_layouter/operations.h

@@ -28,6 +28,7 @@ struct Window_layouter::Operations : Interface
 	virtual void close(Window_id) = 0;
 	virtual void toggle_fullscreen(Window_id) = 0;
 	virtual void focus(Window_id) = 0;
+	virtual void release_grab() = 0;
 	virtual void to_front(Window_id) = 0;
 	virtual void drag(Window_id, Window::Element, Point clicked, Point curr) = 0;
 	virtual void finalize_drag(Window_id, Window::Element, Point clicked, Point final) = 0;

repos/gems/src/app/window_layouter/user_state.h

@@ -332,6 +332,10 @@ void Window_layouter::User_state::_handle_event(Input::Event const &e,
 				_operations.screen(action.target_name());
 				return;
 
+			case Action::RELEASE_GRAB:
+				_operations.release_grab();
+				return;
+
 			default:
 				warning("action ", (int)action.type(), " unhanded");
 			}

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

@@ -560,10 +560,35 @@ class Wm::Gui::Session_component : public Session_object<Gui::Session>,
 		Input::Session_component _input_session {
 			_env.ep(), _ram, _env.rm(), *this };
 
+		bool _exclusive_input_requested = false,
+		     _exclusive_input_granted   = false;
+
+		/* used for hiding the click-to-grab event from the client */
+		bool _consume_one_btn_left_release = false;
+
 		/**
 		 * Input::Session_component::Action interface
 		 */
-		void exclusive_input_requested(bool) override { }
+		void exclusive_input_requested(bool const requested) override
+		{
+			if (requested == _exclusive_input_requested)
+				return;
+
+			/*
+			 * Allow immediate changes when
+			 *
+			 * 1. Exclusive input is already granted by the user having clicked
+			 *    into the window, or
+			 * 2. The client yields the exclusivity, or
+			 * 3. Transient exclusive input is requested while a button is held.
+			 *    In this case, exclusive input will be revoked as soon as the
+			 *    last button/key is released.
+			 */
+			if (_exclusive_input_granted || _key_cnt || !requested)
+				_gui_input.exclusive(requested);
+
+			_exclusive_input_requested = requested;
+		}
 
 		Click_handler &_click_handler;
 
@@ -734,6 +759,31 @@ class Wm::Gui::Session_component : public Session_object<Gui::Session>,
 					if (propagate_to_pointer_state)
 						_pointer_state.apply_event(ev);
 
+					/*
+					 * Handle pointer grabbing/ungrabbing
+					 */
+
+					/* revoke transient exclusive input (while clicked) */
+					if (ev.release() && _key_cnt == 0)
+						if (_exclusive_input_requested && !_exclusive_input_granted)
+							_gui_input.exclusive(false);
+
+					/* grant exclusive input when clicking into window */
+					if (ev.key_press(Input::BTN_LEFT) && _key_cnt == 1) {
+						if (_exclusive_input_requested && !_exclusive_input_granted) {
+							_gui_input.exclusive(true);
+							_exclusive_input_granted = true;
+							_consume_one_btn_left_release = true;
+							continue;
+						}
+					}
+					if (ev.key_release(Input::BTN_LEFT)) {
+						if (_consume_one_btn_left_release) {
+							_consume_one_btn_left_release = false;
+							continue;
+						}
+					}
+
 					/* submit event to the client */
 					_input_session.submit(_translate_event(ev, input_origin));
 				}
@@ -1014,6 +1064,14 @@ class Wm::Gui::Session_component : public Session_object<Gui::Session>,
 				_info_rom->trigger_update();
 		}
 
+		void revoke_exclusive_input()
+		{
+			if (_exclusive_input_granted) {
+				_gui_input.exclusive(false);
+				_exclusive_input_granted = false;
+			}
+		}
+
 
 		/***************************
 		 ** GUI session interface **
@@ -1650,6 +1708,12 @@ class Wm::Gui::Root : public  Rpc_object<Typed_root<Gui::Session> >,
 			for (Session_component *s = _sessions.first(); s; s = s->next())
 				s->propagate_mode_change();
 		}
+
+		void revoke_exclusive_input()
+		{
+			for (Session_component *s = _sessions.first(); s; s = s->next())
+				s->revoke_exclusive_input();
+		}
 };
 
 #endif /* _GUI_H_ */

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

@@ -77,6 +77,7 @@ struct Wm::Main : Pointer::Tracker, Gui::Session_component::Action
 
 	void _handle_focus_update()
 	{
+		_gui_root.revoke_exclusive_input();
 		_focus_rom.update();
 		_focus_rom.xml().with_optional_sub_node("window", [&] (Xml_node const &window) {
 			_with_win_id_from_xml(window, [&] (Window_registry::Id id) {