menu_view: text cursor support

This patch equips the label widget with the ability to display a text
cursor, as illustrated by the following example:

  <label text="...">
    <cursor at="10"/>
  </label>

Issue #3607
Issue #3629

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

@@ -0,0 +1,146 @@
+/*
+ * \brief  Text cursor
+ * \author Norman Feske
+ * \date   2020-01-14
+ */
+
+/*
+ * Copyright (C) 2020 Genode Labs GmbH
+ *
+ * This file is part of the Genode OS framework, which is distributed
+ * under the terms of the GNU Affero General Public License version 3.
+ */
+
+#ifndef _CURSOR_H_
+#define _CURSOR_H_
+
+/* Genode includes */
+#include <util/xml_generator.h>
+#include <util/list_model.h>
+#include <gems/animated_geometry.h>
+
+/* local includes */
+#include <types.h>
+#include <widget_factory.h>
+
+namespace Menu_view { struct Cursor; }
+
+class Menu_view::Cursor : List_model<Cursor>::Element
+{
+	public:
+
+		/**
+		 * Interface for requesting the pixel position for a given char index
+		 */
+		struct Glyph_position : Interface, Noncopyable
+		{
+			virtual int xpos_of_glyph(unsigned at) const = 0;
+		};
+
+	private:
+
+		friend class List_model<Cursor>;
+		friend class List<Cursor>;
+
+		using Steps = Animated_rect::Steps;
+
+		Texture<Pixel_rgb888> const * const _texture;
+
+		Glyph_position &_glyph_position;
+
+		enum { NAME_MAX_LEN = 32 };
+		typedef String<NAME_MAX_LEN> Name;
+
+		Name const _name;
+
+		/* cursor position in pixels, only p1.x is used */
+		Animated_rect _position;
+
+		int _xpos() const { return _position.p1().x(); }
+
+		static Name _node_name(Xml_node node)
+		{
+			return node.attribute_value("name", Name(node.type()));
+		}
+
+		int _position_from_xml_node(Xml_node node)
+		{
+			return _glyph_position.xpos_of_glyph(node.attribute_value("at", 0U));
+		}
+
+		void _move_to(int position, Steps steps)
+		{
+			_position.move_to(Rect(Point(position, 0), Point()), steps);
+		}
+
+		/*
+		 * Noncopyable
+		 */
+		Cursor(Cursor const &);
+		void operator = (Cursor const &);
+
+	public:
+
+		Cursor(Xml_node node, Animator &animator, Glyph_position &glyph_position,
+		       Style_database &styles)
+		:
+			_texture(styles.texture(node, "cursor")),
+			_glyph_position(glyph_position),
+			_name(_node_name(node)),
+			_position(animator)
+		{
+			_move_to(_position_from_xml_node(node), Steps{0});
+		}
+
+
+		void draw(Surface<Pixel_rgb888> &pixel_surface,
+		          Surface<Pixel_alpha8> &alpha_surface,
+		          Point at, unsigned height) const
+		{
+			if (_texture == nullptr) {
+				Box_painter::paint(pixel_surface,
+				                   Rect(at + Point(_xpos(), 0), Area(1, height)),
+				                   Color(0, 0, 0, 255));
+			} else {
+				unsigned const w = _texture->size().w();
+				Rect const rect(Point(_xpos() + at.x() - w/2 + 1, at.y()),
+				                Area(w, height));
+
+				Icon_painter::paint(pixel_surface, rect, *_texture, 255);
+				Icon_painter::paint(alpha_surface, rect, *_texture, 255);
+			}
+		}
+
+		struct Model_update_policy : List_model<Cursor>::Update_policy
+		{
+			Widget_factory &_factory;
+			Glyph_position &_glyph_position;
+
+			Model_update_policy(Widget_factory &factory, Glyph_position &glyph_position)
+			:
+				_factory(factory), _glyph_position(glyph_position)
+			{ }
+
+			void destroy_element(Cursor &c) { destroy(_factory.alloc, &c); }
+
+			Cursor &create_element(Xml_node node)
+			{
+				return *new (_factory.alloc)
+					Cursor(node, _factory.animator, _glyph_position, _factory.styles);
+			}
+
+			void update_element(Cursor &c, Xml_node node)
+			{
+				c._move_to(c._position_from_xml_node(node), Steps{12});
+			}
+
+			static bool element_matches_xml_node(Cursor const &c, Xml_node node)
+			{
+				return node.has_type("cursor") && _node_name(node) == c._name;
+			}
+
+			static bool node_is_element(Xml_node node) { return node.has_type("cursor"); }
+		};
+};
+
+#endif /* _CURSOR_H_ */

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

@@ -16,43 +16,55 @@
 
 /* local includes */
 #include <widget_factory.h>
+#include <cursor.h>
 
 namespace Menu_view { struct Label_widget; }
 
-struct Menu_view::Label_widget : Widget
+struct Menu_view::Label_widget : Widget, Cursor::Glyph_position
 {
-	Text_painter::Font const *font = nullptr;
+	Text_painter::Font const *_font = nullptr;
 
 	enum { LABEL_MAX_LEN = 256 };
 
 	typedef String<200> Text;
-	Text text { };
+	Text _text { };
+
+	Cursor::Model_update_policy _cursor_update_policy;
+
+	List_model<Cursor> _cursors { };
 
 	Label_widget(Widget_factory &factory, Xml_node node, Unique_id unique_id)
 	:
-		Widget(factory, node, unique_id)
+		Widget(factory, node, unique_id), _cursor_update_policy(factory, *this)
 	{ }
 
+	~Label_widget()
+	{
+		_cursors.destroy_all_elements(_cursor_update_policy);
+	}
+
 	void update(Xml_node node) override
 	{
-		font = _factory.styles.font(node);
+		_font = _factory.styles.font(node);
-		text = node.attribute_value("text", Text(""));
+		_text = node.attribute_value("text", Text(""));
+
+		_cursors.update_from_xml(_cursor_update_policy, node);
 	}
 
 	Area min_size() const override
 	{
-		if (!font)
+		if (!_font)
 			return Area(0, 0);
 
-		return Area(font->string_width(text.string()).decimal(),
+		return Area(_font->string_width(_text.string()).decimal(),
-		            font->height());
+		            _font->height());
 	}
 
 	void draw(Surface<Pixel_rgb888> &pixel_surface,
 	          Surface<Pixel_alpha8> &alpha_surface,
 	          Point at) const override
 	{
-		if (!font) return;
+		if (!_font) return;
 
 		Area text_size = min_size();
 
@@ -63,13 +75,26 @@ struct Menu_view::Label_widget : Widget
 
 		Text_painter::paint(pixel_surface,
 		                    Text_painter::Position(centered.x(), centered.y()),
-		                    *font, Color(0, 0, 0), text.string());
+		                    *_font, Color(0, 0, 0), _text.string());
 
 		Text_painter::paint(alpha_surface,
 		                    Text_painter::Position(centered.x(), centered.y()),
-		                    *font, Color(255, 255, 255), text.string());
+		                    *_font, Color(255, 255, 255), _text.string());
+
+		_cursors.for_each([&] (Cursor const &cursor) {
+			cursor.draw(pixel_surface, alpha_surface, at, text_size.h()); });
 	}
 
+	/**
+	 * Cursor::Glyph_position interface
+	 */
+	 int xpos_of_glyph(unsigned at) const override
+	 {
+		Text const truncated_at(Cstring(_text.string(), at));
+
+		return _font->string_width(truncated_at.string()).decimal();
+	 }
+
 	private:
 
 		/**