menu_view: basic support for styling labels

This patch allows for the customization of the text color and alpha
value of the label widget by the means of a style-definition file.
The mechanism is exemplified with the new "invisible" label style
that sets the alpha value to zero.

Issue #3629

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

@@ -0,0 +1,117 @@
+/*
+ * \brief  Helper for implementing the fading of colors
+ * \author Norman Feske
+ * \date   2020-02-19
+ */
+
+/*
+ * 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 _ANIMATED_COLOR_H_
+#define _ANIMATED_COLOR_H_
+
+/* demo includes */
+#include <util/lazy_value.h>
+#include <util/color.h>
+#include <gems/animator.h>
+
+namespace Genode { class Animated_color; }
+
+
+class Genode::Animated_color : private Animator::Item, Noncopyable
+{
+	public:
+
+		struct Steps { unsigned value; };
+
+	private:
+
+		Color _color { };
+
+		using Lazy_value = ::Lazy_value<int>;
+
+		struct Animated_channel
+		{
+			bool _initial = true;
+
+			Lazy_value _value { };
+
+			Steps _remaining { 0 };
+
+			void animate()
+			{
+				_value.animate();
+
+				if (_remaining.value > 1)
+					_remaining.value--;
+			}
+
+			bool animated() const { return _value != _value.dst(); }
+
+			void fade_to(int value, Steps steps)
+			{
+				if (_initial) {
+					_value = Lazy_value(value << 10);
+					_initial = false;
+
+				} else {
+
+					/* retarget animation while already in progress */
+					if (animated())
+						steps.value = max(_remaining.value, 1U);
+
+					_value.dst(value << 10, steps.value);
+					_remaining = steps;
+				}
+			}
+
+			int value() const { return _value >> 10; }
+		};
+
+		Animated_channel _r { }, _g { }, _b { }, _a { };
+
+	public:
+
+		Animated_color(Animator &animator) : Animator::Item(animator) { }
+
+		/**
+		 * Animator::Item interface
+		 */
+		void animate() override
+		{
+			_r.animate(); _g.animate(); _b.animate(); _a.animate();
+
+			_color = Color(_r.value(), _g.value(), _b.value(), _a.value());
+
+			/* schedule / de-schedule animation */
+			Animator::Item::animated(_r.animated() || _g.animated() ||
+			                         _b.animated() || _a.animated());
+		}
+
+		/**
+		 * Assign new target color
+		 *
+		 * The first assignment assigns the color directly without animation.
+		 * All subsequent assignments result in an animated transition to the
+		 * target color.
+		 */
+		void fade_to(Color color, Steps steps)
+		{
+			_r.fade_to(color.r, steps);
+			_g.fade_to(color.g, steps);
+			_b.fade_to(color.b, steps);
+			_a.fade_to(color.a, steps);
+
+			animate();
+		}
+
+		bool animated() const { return Animator::Item::animated(); }
+
+		Color color() const { return _color; }
+};
+
+#endif /* _ANIMATED_COLOR_H_ */

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

@@ -17,6 +17,7 @@
 /* local includes */
 #include <widget_factory.h>
 #include <text_selection.h>
+#include <animated_color.h>
 
 namespace Menu_view { struct Label_widget; }
 
@@ -29,6 +30,8 @@ struct Menu_view::Label_widget : Widget, Cursor::Glyph_position
 	typedef String<200> Text;
 	Text _text { };
 
+	Animated_color _color;
+
 	int _min_width  = 0;
 	int _min_height = 0;
 
@@ -41,6 +44,7 @@ struct Menu_view::Label_widget : Widget, Cursor::Glyph_position
 	Label_widget(Widget_factory &factory, Xml_node node, Unique_id unique_id)
 	:
 		Widget(factory, node, unique_id),
+		_color(factory.animator),
 		_cursor_update_policy(factory, *this),
 		_selection_update_policy(factory.alloc, *this)
 	{ }
@@ -58,6 +62,9 @@ struct Menu_view::Label_widget : Widget, Cursor::Glyph_position
 		_min_width  = 0;
 		_min_height = 0;
 
+		_factory.styles.with_label_style(node, [&] (Label_style style) {
+			_color.fade_to(style.color, Animated_color::Steps{80}); });
+
 		if (node.has_attribute("text")) {
 			_text       = node.attribute_value("text", _text);
 			_text       = Xml_unquoted(_text);
@@ -100,13 +107,18 @@ struct Menu_view::Label_widget : Widget, Cursor::Glyph_position
 		_selections.for_each([&] (Text_selection const &selection) {
 			selection.draw(pixel_surface, alpha_surface, at, text_size.h()); });
 
-		Text_painter::paint(pixel_surface,
-		                    Text_painter::Position(centered.x(), centered.y()),
-		                    *_font, Color(0, 0, 0), _text.string());
+		Color const color = _color.color();
+		int   const alpha = color.a;
 
-		Text_painter::paint(alpha_surface,
-		                    Text_painter::Position(centered.x(), centered.y()),
-		                    *_font, Color(255, 255, 255), _text.string());
+		if (alpha) {
+			Text_painter::paint(pixel_surface,
+			                    Text_painter::Position(centered.x(), centered.y()),
+			                    *_font, color, _text.string());
+
+			Text_painter::paint(alpha_surface,
+			                    Text_painter::Position(centered.x(), centered.y()),
+			                    *_font, Color(alpha, alpha, alpha, alpha), _text.string());
+		}
 
 		_cursors.for_each([&] (Cursor const &cursor) {
 			cursor.draw(pixel_surface, alpha_surface, at, text_size.h()); });

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

@@ -111,10 +111,11 @@ struct Menu_view::Main
 
 	} _vfs_env;
 
-	Directory _root_dir  { _vfs_env };
-	Directory _fonts_dir { _root_dir, "fonts" };
+	Directory _root_dir   { _vfs_env };
+	Directory _fonts_dir  { _root_dir, "fonts" };
+	Directory _styles_dir { _root_dir, "styles" };
 
-	Style_database _styles { _env.ram(), _env.rm(), _heap, _fonts_dir };
+	Style_database _styles { _env.ram(), _env.rm(), _heap, _fonts_dir, _styles_dir };
 
 	Animator _animator { };
 

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

@@ -23,7 +23,17 @@
 /* local includes */
 #include "types.h"
 
-namespace Menu_view { struct Style_database; }
+namespace Menu_view {
+
+	struct Label_style;
+	struct Style_database;
+}
+
+
+struct Menu_view::Label_style
+{
+	Color color;
+};
 
 
 class Menu_view::Style_database
@@ -36,6 +46,35 @@ class Menu_view::Style_database
 
 		typedef ::File::Reading_failed Reading_failed;
 
+		struct Label_style_entry : List<Label_style_entry>::Element, Noncopyable
+		{
+			Path        const path;  /* needed for lookup */
+			Label_style const style;
+
+			static Label_style _init_style(Allocator &alloc,
+			                               Directory const &styles_dir,
+			                               Path const &path)
+			{
+				Label_style result { .color = Color(0, 0, 0) };
+
+				try {
+					File_content const content(alloc, styles_dir, path,
+					                           File_content::Limit{1024});
+					content.xml([&] (Xml_node node) {
+						result.color = node.attribute_value("color", result.color);
+					});
+				} catch (...) { }
+
+				return result;
+			}
+
+			Label_style_entry(Allocator &alloc, Directory const &styles_dir,
+			                  Path const &path)
+			:
+				path(path), style(_init_style(alloc, styles_dir, path))
+			{ }
+		};
+
 		struct Texture_entry : List<Texture_entry>::Element
 		{
 			Path             const path;
@@ -86,13 +125,15 @@ class Menu_view::Style_database
 		Region_map      &_rm;
 		Allocator       &_alloc;
 		Directory const &_fonts_dir;
+		Directory const &_styles_dir;
 
 		/*
-		 * The list is mutable because it is populated as a side effect of
-		 * calling the const lookup function.
+		 * The lists are mutable because they are populated as a side effect of
+		 * calling the const lookup functions.
 		 */
-		List<Texture_entry> mutable _textures { };
-		List<Font_entry>    mutable _fonts    { };
+		List<Texture_entry>     mutable _textures     { };
+		List<Font_entry>        mutable _fonts        { };
+		List<Label_style_entry> mutable _label_styles { };
 
 		template <typename T>
 		T const *_lookup(List<T> &list, char const *path) const
@@ -105,28 +146,56 @@ class Menu_view::Style_database
 		}
 
 		/*
-		 * Assemble path name 'styles/<widget>/<style>/<name>.<extension>'
+		 * Assemble path name 'styles/<widget>/<style>/<name>.png'
 		 */
-		static Path _construct_path(Xml_node node, char const *name,
-		                            char const *extension)
+		static Path _construct_png_path(Xml_node node, char const *name)
 		{
 			typedef String<64> Style;
 			Style const style = node.attribute_value("style", Style("default"));
 
-			return Path("/styles/", node.type(), "/", style, "/", name, ".", extension);
+			return Path("/styles/", node.type(), "/", style, "/", name, ".png");
+		}
+
+		/*
+		 * Assemble path of style file relative to the styles directory
+		 */
+		static Path _widget_style_path(Xml_node const &node)
+		{
+			typedef String<64> Style;
+			Style const style = node.attribute_value("style", Style("default"));
+
+			return Path(node.type(), "/", style, "/", "style");
+		}
+
+		Label_style const &_label_style(Xml_node node) const
+		{
+			Path const path = _widget_style_path(node);
+
+			if (Label_style_entry const *e = _lookup(_label_styles, path.string()))
+				return e->style;
+
+			/*
+			 * Load and remember style
+			 */
+			Label_style_entry &e = *new (_alloc)
+				Label_style_entry(_alloc, _styles_dir, path);
+
+			_label_styles.insert(&e);
+			return e.style;
 		}
 
 	public:
 
 		Style_database(Ram_allocator &ram, Region_map &rm, Allocator &alloc,
-		               Directory const &fonts_dir)
+		               Directory const &fonts_dir, Directory const &styles_dir)
 		:
-			_ram(ram), _rm(rm), _alloc(alloc), _fonts_dir(fonts_dir)
+			_ram(ram), _rm(rm), _alloc(alloc),
+			_fonts_dir(fonts_dir), _styles_dir(styles_dir)
 		{ }
 
 		Texture<Pixel_rgb888> const *texture(Xml_node node, char const *png_name) const
 		{
-			Path const path = _construct_path(node, png_name, "png");
+			Path const path = _construct_png_path(node, png_name);
 
 			if (Texture_entry const *e = _lookup(_textures, path.string()))
 				return &e->texture;
@@ -173,6 +242,12 @@ class Menu_view::Style_database
 
 			return nullptr;
 		}
+
+		template <typename FN>
+		void with_label_style(Xml_node node, FN const &fn) const
+		{
+			fn(_label_style(node));
+		}
 };
 
 #endif /* _STYLE_DATABASE_H_ */

repos/gems/src/app/menu_view/styles/label/invisible/style

@@ -0,0 +1 @@
+<style color="#00000000"/>