From a53b32067feb02fca2391db3f99876129864dbe1 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 25 Feb 2021 09:07:39 +0300
Subject: [PATCH] UI library prototype wip

---
 examples/ui.cpp                               |  74 ++++++++++
 libs/ui/CMakeLists.txt                        |   6 +
 libs/ui/include/psemek/ui/box_shape.hpp       |  23 ++++
 libs/ui/include/psemek/ui/button.hpp          |  52 ++++++++
 libs/ui/include/psemek/ui/container.hpp       |  32 +++++
 libs/ui/include/psemek/ui/controller.hpp      |  32 +++++
 .../psemek/ui/default_element_factory.hpp     |  15 +++
 libs/ui/include/psemek/ui/element.hpp         |  53 ++++++++
 libs/ui/include/psemek/ui/event.hpp           |  35 +++++
 libs/ui/include/psemek/ui/font.hpp            |  70 ++++++++++
 libs/ui/include/psemek/ui/label.hpp           |  68 ++++++++++
 libs/ui/include/psemek/ui/monospace_font.hpp  |  36 +++++
 libs/ui/include/psemek/ui/painter.hpp         |  19 +++
 libs/ui/include/psemek/ui/painter_impl.hpp    |  30 +++++
 libs/ui/include/psemek/ui/screen.hpp          |  51 +++++++
 libs/ui/include/psemek/ui/shape.hpp           |  17 +++
 libs/ui/source/box_shape.cpp                  |  13 ++
 libs/ui/source/button.cpp                     |  74 ++++++++++
 libs/ui/source/container.cpp                  |  65 +++++++++
 libs/ui/source/controller.cpp                 | 112 ++++++++++++++++
 libs/ui/source/default_element_factory.cpp    |  55 ++++++++
 libs/ui/source/default_fonts.cpp              |  41 ++++++
 libs/ui/source/element.cpp                    |  31 +++++
 libs/ui/source/label.cpp                      |  38 ++++++
 libs/ui/source/monospace_font.cpp             |  63 +++++++++
 libs/ui/source/painter_impl.cpp               | 126 ++++++++++++++++++
 libs/ui/source/screen.cpp                     |  95 +++++++++++++
 27 files changed, 1326 insertions(+)
 create mode 100644 examples/ui.cpp
 create mode 100644 libs/ui/CMakeLists.txt
 create mode 100644 libs/ui/include/psemek/ui/box_shape.hpp
 create mode 100644 libs/ui/include/psemek/ui/button.hpp
 create mode 100644 libs/ui/include/psemek/ui/container.hpp
 create mode 100644 libs/ui/include/psemek/ui/controller.hpp
 create mode 100644 libs/ui/include/psemek/ui/default_element_factory.hpp
 create mode 100644 libs/ui/include/psemek/ui/element.hpp
 create mode 100644 libs/ui/include/psemek/ui/event.hpp
 create mode 100644 libs/ui/include/psemek/ui/font.hpp
 create mode 100644 libs/ui/include/psemek/ui/label.hpp
 create mode 100644 libs/ui/include/psemek/ui/monospace_font.hpp
 create mode 100644 libs/ui/include/psemek/ui/painter.hpp
 create mode 100644 libs/ui/include/psemek/ui/painter_impl.hpp
 create mode 100644 libs/ui/include/psemek/ui/screen.hpp
 create mode 100644 libs/ui/include/psemek/ui/shape.hpp
 create mode 100644 libs/ui/source/box_shape.cpp
 create mode 100644 libs/ui/source/button.cpp
 create mode 100644 libs/ui/source/container.cpp
 create mode 100644 libs/ui/source/controller.cpp
 create mode 100644 libs/ui/source/default_element_factory.cpp
 create mode 100644 libs/ui/source/default_fonts.cpp
 create mode 100644 libs/ui/source/element.cpp
 create mode 100644 libs/ui/source/label.cpp
 create mode 100644 libs/ui/source/monospace_font.cpp
 create mode 100644 libs/ui/source/painter_impl.cpp
 create mode 100644 libs/ui/source/screen.cpp

diff --git a/examples/ui.cpp b/examples/ui.cpp
new file mode 100644
index 00000000..2a885944
--- /dev/null
+++ b/examples/ui.cpp
@@ -0,0 +1,74 @@
+#include <psemek/app/app.hpp>
+#include <psemek/app/main.hpp>
+
+#include <psemek/gfx/gl.hpp>
+
+#include <psemek/ui/controller.hpp>
+#include <psemek/ui/default_element_factory.hpp>
+#include <psemek/ui/font.hpp>
+
+#include <psemek/geom/camera.hpp>
+
+using namespace psemek;
+
+struct ui_example
+	: app::app
+{
+	ui_example()
+		: app("UI example", 1)
+	{
+		ui_controller.set_font(ui::make_default_9x12_font());
+
+		auto screen = element_factory.make_screen();
+		screen->add(element_factory.make_button(), ui::screen::x_policy::center, ui::screen::y_policy::center);
+
+		ui_controller.set_root(std::move(screen));
+	}
+
+	void on_resize(int width, int height) override
+	{
+		app::on_resize(width, height);
+		ui_controller.reshape({{{0, width}, {0, height}}});
+	}
+
+	void on_mouse_move(int x, int y, int dx, int dy) override
+	{
+		app::on_mouse_move(x, y, dx, dy);
+		ui_controller.event(ui::mouse_move{{x, y}});
+	}
+
+	void on_left_button_down() override
+	{
+		app::on_left_button_down();
+		ui_controller.event(ui::mouse_click{ui::mouse_button::left, true});
+	}
+
+	void on_left_button_up() override
+	{
+		app::on_left_button_up();
+		ui_controller.event(ui::mouse_click{ui::mouse_button::left, false});
+	}
+
+	void present() override;
+
+	ui::controller ui_controller;
+	ui::default_element_factory element_factory;
+};
+
+void ui_example::present()
+{
+	gl::ClearColor(0.8f, 0.8f, 0.8f, 1.f);
+	gl::Clear(gl::COLOR_BUFFER_BIT);
+
+	gfx::render_target rt;
+	rt.framebuffer = &gfx::framebuffer::null();
+	rt.draw_buffer = gl::BACK_LEFT;
+	rt.viewport = {{{0, width()}, {0, height()}}};
+
+	ui_controller.render(rt);
+}
+
+int main()
+{
+	return app::main<ui_example>();
+}
diff --git a/libs/ui/CMakeLists.txt b/libs/ui/CMakeLists.txt
new file mode 100644
index 00000000..85a5ea66
--- /dev/null
+++ b/libs/ui/CMakeLists.txt
@@ -0,0 +1,6 @@
+file(GLOB_RECURSE PSEMEK_UI_HEADERS RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "include/*.hpp")
+file(GLOB_RECURSE PSEMEK_UI_SOURCES RELATIVE "${CMAKE_CURRENT_SOURCE_DIR}" "source/*.cpp")
+
+psemek_add_library(psemek-ui ${PSEMEK_UI_HEADERS} ${PSEMEK_UI_SOURCES})
+target_include_directories(psemek-ui PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/include")
+target_link_libraries(psemek-ui PUBLIC psemek-util psemek-log psemek-geom psemek-cg psemek-gfx psemek-async)
diff --git a/libs/ui/include/psemek/ui/box_shape.hpp b/libs/ui/include/psemek/ui/box_shape.hpp
new file mode 100644
index 00000000..1d4f3332
--- /dev/null
+++ b/libs/ui/include/psemek/ui/box_shape.hpp
@@ -0,0 +1,23 @@
+#pragma once
+
+#include <psemek/ui/shape.hpp>
+
+namespace psemek::ui
+{
+
+	struct box_shape
+		: shape
+	{
+		geom::box<float, 2> box;
+
+		box_shape() = default;
+
+		box_shape(geom::box<float, 2> box)
+			: box{box}
+		{}
+
+		bool contains(geom::point<float, 2> const & point) const override;
+		geom::box<float, 2> bbox() const override { return box; }
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/button.hpp b/libs/ui/include/psemek/ui/button.hpp
new file mode 100644
index 00000000..4bcee76a
--- /dev/null
+++ b/libs/ui/include/psemek/ui/button.hpp
@@ -0,0 +1,52 @@
+#pragma once
+
+#include <psemek/ui/element.hpp>
+#include <psemek/ui/label.hpp>
+
+#include <functional>
+
+namespace psemek::ui
+{
+
+	struct button
+		: element
+	{
+		struct label * label() { return label_.get(); }
+		struct label const * label() const { return label_.get(); }
+
+		children_range children() const override;
+
+		bool on_event(mouse_move const & e) override;
+		bool on_event(mouse_click const & e) override;
+
+		using on_click_callback = std::function<void()>;
+
+		void on_click(on_click_callback callback)
+		{
+			callback_ = std::move(callback);
+		}
+
+	protected:
+		enum class state_t
+		{
+			normal,
+			mouseover,
+			mousedown,
+		};
+
+		virtual state_t state() const { return state_; }
+
+		virtual void on_state_changed() {}
+
+		void set_label(std::unique_ptr<struct label> label);
+
+	private:
+		state_t state_ = state_t::normal;
+
+		on_click_callback callback_;
+
+		std::unique_ptr<struct label> label_;
+		element * children_[1]{nullptr};
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/container.hpp b/libs/ui/include/psemek/ui/container.hpp
new file mode 100644
index 00000000..a25f01de
--- /dev/null
+++ b/libs/ui/include/psemek/ui/container.hpp
@@ -0,0 +1,32 @@
+#pragma once
+
+#include <psemek/ui/element.hpp>
+
+#include <vector>
+
+namespace psemek::ui
+{
+
+	struct container
+		: element
+	{
+		children_range children() const override;
+
+	protected:
+		std::size_t children_count() const { return children_.size(); }
+
+		std::size_t add(std::unique_ptr<element> c);
+		void add(std::unique_ptr<element> c, std::size_t index);
+
+		element * get(std::size_t index);
+		std::optional<std::size_t> find(element * c);
+
+		std::unique_ptr<element> remove(element * c);
+		std::unique_ptr<element> remove(std::size_t index);
+
+	private:
+		std::vector<std::unique_ptr<element>> children_;
+		std::vector<element *> children_range_;
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/controller.hpp b/libs/ui/include/psemek/ui/controller.hpp
new file mode 100644
index 00000000..9c360b9b
--- /dev/null
+++ b/libs/ui/include/psemek/ui/controller.hpp
@@ -0,0 +1,32 @@
+#pragma once
+
+#include <psemek/ui/element.hpp>
+#include <psemek/ui/font.hpp>
+#include <psemek/gfx/render_target.hpp>
+#include <psemek/util/pimpl.hpp>
+
+namespace psemek::ui
+{
+
+	struct controller
+	{
+		controller();
+		~controller();
+
+		std::unique_ptr<element> set_root(std::unique_ptr<element> r);
+		element * root();
+
+		void set_font(std::shared_ptr<font> f);
+		void reshape(geom::box<float, 2> const & shape);
+
+		bool event(mouse_move const & e);
+		bool event(mouse_click const & e);
+		bool event(mouse_wheel const & e);
+
+		void render(gfx::render_target const & rt);
+
+	private:
+		psemek_declare_pimpl
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/default_element_factory.hpp b/libs/ui/include/psemek/ui/default_element_factory.hpp
new file mode 100644
index 00000000..8f3d53a1
--- /dev/null
+++ b/libs/ui/include/psemek/ui/default_element_factory.hpp
@@ -0,0 +1,15 @@
+#pragma once
+
+#include <psemek/ui/button.hpp>
+#include <psemek/ui/screen.hpp>
+
+namespace psemek::ui
+{
+
+	struct default_element_factory
+	{
+		std::unique_ptr<button> make_button();
+		std::unique_ptr<screen> make_screen();
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/element.hpp b/libs/ui/include/psemek/ui/element.hpp
new file mode 100644
index 00000000..75a95ac5
--- /dev/null
+++ b/libs/ui/include/psemek/ui/element.hpp
@@ -0,0 +1,53 @@
+#pragma once
+
+#include <psemek/ui/shape.hpp>
+#include <psemek/ui/event.hpp>
+#include <psemek/ui/painter.hpp>
+
+#include <psemek/async/executor.hpp>
+
+#include <psemek/util/span.hpp>
+
+namespace psemek::ui
+{
+
+	struct element
+	{
+		virtual element * parent() const { return parent_; }
+		virtual void set_parent(element * parent) { parent_ = parent; }
+
+		using children_range = util::span<element * const>;
+
+		virtual children_range children() const { return {}; }
+
+		virtual element * root();
+		virtual element const * root() const;
+		virtual async::executor * loop() const { return loop_; }
+		virtual void set_loop(async::executor * loop) { loop_ = loop; }
+
+		virtual bool on_event(mouse_move  const &) { return false; }
+		virtual bool on_event(mouse_click const &) { return false; }
+		virtual bool on_event(mouse_wheel const &) { return false; }
+
+		virtual struct shape const & shape() const = 0;
+		virtual void reshape(geom::box<float, 2> const & bbox) = 0;
+		virtual void reshape();
+
+		virtual geom::box<float, 2> size_constraints() const;
+
+		virtual bool enabled() const { return enabled_; }
+		virtual void set_enabled(bool value) { enabled_ = value; }
+		virtual void enable() { set_enabled(true); }
+		virtual void disable() { set_enabled(false); }
+
+		virtual void draw(painter & p) const = 0;
+
+		virtual ~element() {}
+
+	private:
+		element * parent_ = nullptr;
+		async::executor * loop_ = nullptr;
+		bool enabled_ = true;
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/event.hpp b/libs/ui/include/psemek/ui/event.hpp
new file mode 100644
index 00000000..722b74f7
--- /dev/null
+++ b/libs/ui/include/psemek/ui/event.hpp
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <psemek/geom/point.hpp>
+
+#include <tuple>
+
+namespace psemek::ui
+{
+
+	struct mouse_move
+	{
+		geom::point<int, 2> position;
+	};
+
+	enum class mouse_button
+	{
+		left,
+		middle,
+		right,
+	};
+
+	struct mouse_click
+	{
+		mouse_button button;
+		bool down;
+	};
+
+	struct mouse_wheel
+	{
+		int delta;
+	};
+
+	using event_type_list = std::tuple<mouse_move, mouse_click, mouse_wheel>;
+
+}
diff --git a/libs/ui/include/psemek/ui/font.hpp b/libs/ui/include/psemek/ui/font.hpp
new file mode 100644
index 00000000..1813e422
--- /dev/null
+++ b/libs/ui/include/psemek/ui/font.hpp
@@ -0,0 +1,70 @@
+#pragma once
+
+#include <psemek/geom/vector.hpp>
+#include <psemek/geom/box.hpp>
+
+#include <psemek/gfx/texture.hpp>
+
+#include <string_view>
+#include <vector>
+#include <memory>
+
+namespace psemek::ui
+{
+
+	enum class font_type
+	{
+		bitmap,
+		sdf,
+	};
+
+	struct character_range
+	{
+		char32_t begin;
+		char32_t end;
+	};
+
+	struct glyph
+	{
+		geom::box<float, 2> position;
+		char32_t character;
+	};
+
+	struct shape_options
+	{
+		enum direction_t
+		{
+			left_to_right,
+			right_to_left,
+			top_to_bottom,
+			bottom_to_top,
+		} direction = left_to_right;
+
+		char32_t unknown_character = '?';
+
+		float scale = 1.f;
+	};
+
+	struct font
+	{
+		virtual font_type type() const = 0;
+
+		virtual std::string_view name() const = 0;
+
+		virtual geom::vector<int, 2> size() const = 0;
+
+		virtual bool supports_character(char32_t c) const = 0;
+		virtual std::vector<character_range> supported_characters() const = 0;
+
+		virtual std::vector<glyph> shape(std::string_view str, shape_options const & options) const = 0;
+
+		virtual gfx::texture_2d const & atlas() const = 0;
+
+		virtual std::optional<geom::box<float, 2>> texcoords(char32_t character) const = 0;
+
+		virtual ~font() {}
+	};
+
+	std::unique_ptr<font> make_default_9x12_font();
+
+}
diff --git a/libs/ui/include/psemek/ui/label.hpp b/libs/ui/include/psemek/ui/label.hpp
new file mode 100644
index 00000000..daa65415
--- /dev/null
+++ b/libs/ui/include/psemek/ui/label.hpp
@@ -0,0 +1,68 @@
+#pragma once
+
+#include <psemek/ui/element.hpp>
+
+#include <string>
+#include <string_view>
+
+namespace psemek::ui
+{
+
+	struct label
+		: element
+	{
+		enum class halignment
+		{
+			left,
+			center,
+			right,
+		};
+
+		enum class valignment
+		{
+			top,
+			center,
+			bottom,
+		};
+
+		enum class multiline_mode
+		{
+			none, // single-line lable
+			minimize_lines, // normal multiline text
+			minimize_area, // as square as possible
+		};
+
+		enum class overflow_mode
+		{
+			ignore,
+			drop,
+			ellipsis,
+		};
+
+		virtual void set_text(std::string text);
+		virtual std::string_view text() const { return text_; }
+
+		virtual void set_halign(halignment value);
+		virtual halignment halign() const { return halign_; }
+
+		virtual void set_valign(valignment value);
+		virtual valignment valign() const { return valign_; }
+
+		virtual void set_multiline(multiline_mode value);
+		virtual multiline_mode multiline() const { return multiline_; }
+
+		virtual void set_overflow(overflow_mode value);
+		virtual overflow_mode overflow() const { return overflow_; }
+
+	protected:
+		virtual void on_state_changed();
+
+	private:
+		std::string text_;
+		halignment halign_;
+		valignment valign_;
+		multiline_mode multiline_;
+		overflow_mode overflow_;
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/monospace_font.hpp b/libs/ui/include/psemek/ui/monospace_font.hpp
new file mode 100644
index 00000000..30a01e87
--- /dev/null
+++ b/libs/ui/include/psemek/ui/monospace_font.hpp
@@ -0,0 +1,36 @@
+#pragma once
+
+#include <psemek/ui/font.hpp>
+
+namespace psemek::ui
+{
+
+	struct monospace_font
+		: font
+	{
+		monospace_font(character_range range, std::string_view name, geom::vector<int, 2> size, gfx::texture_2d atlas, std::vector<geom::box<float, 2>> texcoords);
+
+		font_type type() const override { return font_type::bitmap; }
+
+		std::string_view name() const override { return name_; }
+
+		geom::vector<int, 2> size() const override { return size_; }
+
+		bool supports_character(char32_t c) const override { return c >= range_.begin && c < range_.end; }
+		std::vector<character_range> supported_characters() const override { return {range_}; }
+
+		std::vector<glyph> shape(std::string_view str, shape_options const & options) const override;
+
+		gfx::texture_2d const & atlas() const override { return atlas_; };
+
+		std::optional<geom::box<float, 2>> texcoords(char32_t character) const override;
+
+	private:
+		character_range range_;
+		std::string_view name_;
+		geom::vector<int, 2> size_;
+		gfx::texture_2d atlas_;
+		std::vector<geom::box<float, 2>> texcoords_;
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/painter.hpp b/libs/ui/include/psemek/ui/painter.hpp
new file mode 100644
index 00000000..46854c33
--- /dev/null
+++ b/libs/ui/include/psemek/ui/painter.hpp
@@ -0,0 +1,19 @@
+#pragma once
+
+#include <psemek/ui/font.hpp>
+#include <psemek/gfx/color.hpp>
+#include <psemek/geom/box.hpp>
+
+namespace psemek::ui
+{
+
+	struct painter
+	{
+		virtual struct font const * font() const = 0;
+
+		virtual void draw_rect(geom::box<float, 2> const & rect, gfx::color_rgba const & color) = 0;
+
+		virtual ~painter() {}
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/painter_impl.hpp b/libs/ui/include/psemek/ui/painter_impl.hpp
new file mode 100644
index 00000000..7a82443c
--- /dev/null
+++ b/libs/ui/include/psemek/ui/painter_impl.hpp
@@ -0,0 +1,30 @@
+#pragma once
+
+#include <psemek/ui/painter.hpp>
+
+#include <psemek/util/pimpl.hpp>
+
+#include <psemek/geom/matrix.hpp>
+
+namespace psemek::ui
+{
+
+	struct painter_impl
+		: painter
+	{
+		painter_impl();
+		~painter_impl();
+
+		void set_font(std::shared_ptr<struct font> font);
+
+		struct font const * font() const override;
+
+		void draw_rect(geom::box<float, 2> const & rect, gfx::color_rgba const & color) override;
+
+		void render(geom::matrix<float, 4, 4> const & transform);
+
+	private:
+		psemek_declare_pimpl
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/screen.hpp b/libs/ui/include/psemek/ui/screen.hpp
new file mode 100644
index 00000000..30152448
--- /dev/null
+++ b/libs/ui/include/psemek/ui/screen.hpp
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <psemek/ui/container.hpp>
+#include <psemek/ui/box_shape.hpp>
+
+namespace psemek::ui
+{
+
+	struct screen
+		: container
+	{
+		enum class x_policy
+		{
+			left,
+			center,
+			right,
+			floating,
+		};
+
+		enum class y_policy
+		{
+			top,
+			center,
+			bottom,
+			floating,
+		};
+
+		void add(std::unique_ptr<element> c, x_policy x, y_policy y);
+		void add(std::unique_ptr<element> c);
+		std::unique_ptr<element> remove(element * c);
+
+		struct shape const & shape() const override { return shape_; }
+		void reshape(geom::box<float, 2> const & bbox) override;
+
+		geom::box<float, 2> size_constraints() const override;
+
+		void draw(painter &) const override {}
+
+	private:
+		box_shape shape_;
+
+		struct policy
+		{
+			x_policy x;
+			y_policy y;
+		};
+
+		std::vector<policy> policies_;
+	};
+
+}
diff --git a/libs/ui/include/psemek/ui/shape.hpp b/libs/ui/include/psemek/ui/shape.hpp
new file mode 100644
index 00000000..69a0f853
--- /dev/null
+++ b/libs/ui/include/psemek/ui/shape.hpp
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <psemek/geom/point.hpp>
+#include <psemek/geom/box.hpp>
+
+namespace psemek::ui
+{
+
+	struct shape
+	{
+		virtual bool contains(geom::point<float, 2> const & point) const = 0;
+		virtual geom::box<float, 2> bbox() const = 0;
+
+		virtual ~shape() {}
+	};
+
+}
diff --git a/libs/ui/source/box_shape.cpp b/libs/ui/source/box_shape.cpp
new file mode 100644
index 00000000..e0815683
--- /dev/null
+++ b/libs/ui/source/box_shape.cpp
@@ -0,0 +1,13 @@
+#include <psemek/ui/box_shape.hpp>
+
+#include <psemek/geom/contains.hpp>
+
+namespace psemek::ui
+{
+
+	bool box_shape::contains(geom::point<float, 2> const & point) const
+	{
+		return geom::contains(box, point);
+	}
+
+}
diff --git a/libs/ui/source/button.cpp b/libs/ui/source/button.cpp
new file mode 100644
index 00000000..7c4edc17
--- /dev/null
+++ b/libs/ui/source/button.cpp
@@ -0,0 +1,74 @@
+#include <psemek/ui/button.hpp>
+
+namespace psemek::ui
+{
+
+	element::children_range button::children() const
+	{
+		if (!label_)
+			return {};
+		return children_range{children_};
+	}
+
+	bool button::on_event(mouse_move const & e)
+	{
+		bool const over = shape().contains(geom::cast<float>(e.position));
+
+		switch (state_) {
+		case state_t::normal:
+			if (over)
+			{
+				state_ = state_t::mouseover;
+				on_state_changed();
+			}
+			break;
+		case state_t::mouseover:
+		case state_t::mousedown:
+			if (!over)
+			{
+				state_ = state_t::normal;
+				on_state_changed();
+			}
+			break;
+		}
+
+		return false;
+	}
+
+	bool button::on_event(mouse_click const & e)
+	{
+		if (e.button != mouse_button::left) return false;
+
+		switch (state_) {
+		case state_t::normal:
+			break;
+		case state_t::mouseover:
+			if (e.down)
+			{
+				state_ = state_t::mousedown;
+				if (callback_)
+					root()->loop()->post(callback_);
+				on_state_changed();
+				return true;
+			}
+			break;
+		case state_t::mousedown:
+			if (!e.down)
+			{
+				state_ = state_t::mouseover;
+				on_state_changed();
+				return true;
+			}
+			break;
+		}
+
+		return false;
+	}
+
+	void button::set_label(std::unique_ptr<struct label> label)
+	{
+		label_ = std::move(label);
+		children_[0] = label_.get();
+	}
+
+}
diff --git a/libs/ui/source/container.cpp b/libs/ui/source/container.cpp
new file mode 100644
index 00000000..2f30f338
--- /dev/null
+++ b/libs/ui/source/container.cpp
@@ -0,0 +1,65 @@
+#include <psemek/ui/container.hpp>
+
+namespace psemek::ui
+{
+
+	element::children_range container::children() const
+	{
+		return children_range{children_range_.data(), children_range_.data() + children_range_.size()};
+	}
+
+	std::size_t container::add(std::unique_ptr<element> c)
+	{
+		std::size_t index = 0;
+		while (index < children_.size() && children_[index]) ++index;
+		add(std::move(c), index);
+		return index;
+	}
+
+	void container::add(std::unique_ptr<element> c, std::size_t index)
+	{
+		if (index >= children_.size())
+		{
+			children_.resize(index + 1);
+			children_range_.resize(index + 1);
+		}
+
+		children_[index] = std::move(c);
+		children_range_[index] = children_[index].get();
+	}
+
+	element * container::get(std::size_t index)
+	{
+		if (index < children_.size())
+			return children_[index].get();
+		return nullptr;
+	}
+
+	std::optional<std::size_t> container::find(element * c)
+	{
+		for (std::size_t i = 0; i < children_.size(); ++i)
+		{
+			if (children_[i].get() == c)
+				return i;
+		}
+		return std::nullopt;
+	}
+
+	std::unique_ptr<element> container::remove(element * c)
+	{
+		if (auto i = find(c))
+			return remove(*i);
+		return nullptr;
+	}
+
+	std::unique_ptr<element> container::remove(std::size_t index)
+	{
+		if (index >= children_.size())
+			return nullptr;
+
+		auto c = std::move(children_[index]);
+		children_range_[index] = nullptr;
+		return c;
+	}
+
+}
diff --git a/libs/ui/source/controller.cpp b/libs/ui/source/controller.cpp
new file mode 100644
index 00000000..97d2bb6a
--- /dev/null
+++ b/libs/ui/source/controller.cpp
@@ -0,0 +1,112 @@
+#include <psemek/ui/controller.hpp>
+
+#include <psemek/ui/painter_impl.hpp>
+#include <psemek/async/event_loop.hpp>
+#include <psemek/gfx/gl.hpp>
+#include <psemek/util/recursive.hpp>
+#include <psemek/geom/camera.hpp>
+
+namespace psemek::ui
+{
+
+	struct controller::impl
+	{
+		painter_impl painter;
+		std::unique_ptr<element> root;
+		async::event_loop loop;
+		geom::box<float, 2> shape{{{0.f, 0.f}, {0.f, 0.f}}};
+
+		template <typename E>
+		bool event(E const & e);
+	};
+
+	template <typename E>
+	bool controller::impl::event(E const & e)
+	{
+		auto visitor = util::recursive([&](auto && self, element * elem) -> bool {
+			for (auto c : elem->children())
+				if (c && self(c)) return true;
+
+			if (elem->enabled() && elem->on_event(e)) return true;
+			return false;
+		});
+
+		if (root)
+			return visitor(root.get());
+		return false;
+	}
+
+	controller::controller()
+		: pimpl_{make_impl()}
+	{}
+
+	controller::~controller() = default;
+
+	std::unique_ptr<element> controller::set_root(std::unique_ptr<element> r)
+	{
+		auto old = std::move(impl().root);
+		impl().root = std::move(r);
+		if (old) old->set_loop(nullptr);
+		if (impl().root)
+		{
+			impl().root->set_loop(&impl().loop);
+			impl().root->reshape(impl().shape);
+		}
+		return old;
+	}
+
+	element * controller::root()
+	{
+		return impl().root.get();
+	}
+
+	void controller::set_font(std::shared_ptr<font> f)
+	{
+		impl().painter.set_font(std::move(f));
+	}
+
+	void controller::reshape(geom::box<float, 2> const & shape)
+	{
+		impl().shape = shape;
+		if (impl().root)
+			impl().root->reshape(impl().shape);
+	}
+
+	bool controller::event(mouse_move const & e)
+	{
+		return impl().event(e);
+	}
+
+	bool controller::event(mouse_click const & e)
+	{
+		return impl().event(e);
+	}
+
+	bool controller::event(mouse_wheel const & e)
+	{
+		return impl().event(e);
+	}
+
+	void controller::render(gfx::render_target const & rt)
+	{
+		rt.bind();
+
+		gl::Enable(gl::DEPTH_TEST);
+		gl::DepthFunc(gl::LEQUAL);
+
+		gl::Enable(gl::BLEND);
+		gl::BlendFunc(gl::SRC_ALPHA, gl::ONE_MINUS_SRC_ALPHA);
+
+		auto visitor = util::recursive([&](auto && self, element * elem) -> void {
+			elem->draw(impl().painter);
+			for (auto c : elem->children())
+				if (c) self(c);
+		});
+
+		if (impl().root)
+			visitor(impl().root.get());
+
+		impl().painter.render(geom::window_camera{rt.viewport[0].length(), rt.viewport[1].length()}.transform());
+	}
+
+}
diff --git a/libs/ui/source/default_element_factory.cpp b/libs/ui/source/default_element_factory.cpp
new file mode 100644
index 00000000..7cda4beb
--- /dev/null
+++ b/libs/ui/source/default_element_factory.cpp
@@ -0,0 +1,55 @@
+#include <psemek/ui/default_element_factory.hpp>
+
+#include <psemek/ui/box_shape.hpp>
+
+namespace psemek::ui
+{
+
+	namespace
+	{
+
+		struct button_impl
+			: button
+		{
+			struct shape const & shape() const override
+			{
+				return shape_;
+			}
+
+			void reshape(geom::box<float, 2> const & bbox) override
+			{
+				shape_.box = bbox;
+			}
+
+			void draw(painter & p) const override
+			{
+				gfx::color_rgba color = gfx::red;
+				if (state() == state_t::mouseover)
+					color = gfx::light(color);
+				else if (state() == state_t::mousedown)
+					color = gfx::dark(color);
+				p.draw_rect(shape_.box, color);
+			}
+
+			geom::box<float, 2> size_constraints() const override
+			{
+				return {{{100.f, 200.f}, {50.f, 100.f}}};
+			}
+
+		private:
+			box_shape shape_{{{{0.f, 0.f}, {0.f, 0.f}}}};
+		};
+
+	}
+
+	std::unique_ptr<button> default_element_factory::make_button()
+	{
+		return std::make_unique<button_impl>();
+	}
+
+	std::unique_ptr<screen> default_element_factory::make_screen()
+	{
+		return std::make_unique<screen>();
+	}
+
+}
diff --git a/libs/ui/source/default_fonts.cpp b/libs/ui/source/default_fonts.cpp
new file mode 100644
index 00000000..dd1e3dfb
--- /dev/null
+++ b/libs/ui/source/default_fonts.cpp
@@ -0,0 +1,41 @@
+#include <psemek/ui/font.hpp>
+#include <psemek/ui/monospace_font.hpp>
+
+#include <psemek/gfx/resource/font_9x12.hpp>
+
+#include <psemek/util/memory_stream.hpp>
+
+namespace psemek::ui
+{
+
+	std::unique_ptr<font> make_default_9x12_font()
+	{
+		character_range range{32, 128};
+		std::string_view name = "default_9x12";
+		geom::vector<int, 2> size{9, 12};
+
+		util::memory_istream is{gfx::resource::font_9x12};
+		gfx::texture_2d atlas = gfx::texture_2d::from_pixmap(gfx::read_pbm(is));
+		atlas.nearest_filter();
+		atlas.clamp();
+
+		std::vector<geom::box<float, 2>> texcoords(range.end - range.begin);
+
+		for (char32_t c = range.begin; c < range.end; ++c)
+		{
+			int const row = 16;
+			int x = (c - range.begin) / row;
+			int y = (c - range.begin) % row;
+
+			geom::box<float, 2> b;
+			b[0].min = x * 11 + 1;
+			b[0].max = b[0].min + 9;
+			b[1].min = y * 14 + 1;
+			b[1].max = b[1].min + 12;
+			texcoords[c - range.begin] = b;
+		}
+
+		return std::make_unique<monospace_font>(range, name, size, std::move(atlas), std::move(texcoords));
+	}
+
+}
diff --git a/libs/ui/source/element.cpp b/libs/ui/source/element.cpp
new file mode 100644
index 00000000..5f9ec969
--- /dev/null
+++ b/libs/ui/source/element.cpp
@@ -0,0 +1,31 @@
+#include <psemek/ui/element.hpp>
+
+namespace psemek::ui
+{
+
+	element * element::root()
+	{
+		element * r = this;
+		while (r->parent()) r = r->parent();
+		return r;
+	}
+
+	element const * element::root() const
+	{
+		element const * r = this;
+		while (r->parent()) r = r->parent();
+		return r;
+	}
+
+	void element::reshape()
+	{
+		reshape(shape().bbox());
+	}
+
+	geom::box<float, 2> element::size_constraints() const
+	{
+		static float const inf = std::numeric_limits<float>::infinity();
+		return {{{0.f, inf}, {0.f, inf}}};
+	}
+
+}
diff --git a/libs/ui/source/label.cpp b/libs/ui/source/label.cpp
new file mode 100644
index 00000000..087bca2c
--- /dev/null
+++ b/libs/ui/source/label.cpp
@@ -0,0 +1,38 @@
+#include <psemek/ui/label.hpp>
+
+namespace psemek::ui
+{
+
+	// TODO: changes should notify parent about content change
+
+	void label::set_text(std::string text)
+	{
+		text_ = std::move(text);
+		on_state_changed();
+	}
+
+	void label::set_halign(halignment value)
+	{
+		halign_ = value;
+		on_state_changed();
+	}
+
+	void label::set_valign(valignment value)
+	{
+		valign_ = value;
+		on_state_changed();
+	}
+
+	void label::set_multiline(multiline_mode value)
+	{
+		multiline_ = value;
+		on_state_changed();
+	}
+
+	void label::set_overflow(overflow_mode value)
+	{
+		overflow_ = value;
+		on_state_changed();
+	}
+
+}
diff --git a/libs/ui/source/monospace_font.cpp b/libs/ui/source/monospace_font.cpp
new file mode 100644
index 00000000..791a1954
--- /dev/null
+++ b/libs/ui/source/monospace_font.cpp
@@ -0,0 +1,63 @@
+#include <psemek/ui/monospace_font.hpp>
+
+#include <psemek/util/unicode.hpp>
+
+namespace psemek::ui
+{
+
+	monospace_font::monospace_font(character_range range, std::string_view name, geom::vector<int, 2> size, gfx::texture_2d atlas, std::vector<geom::box<float, 2>> texcoords)
+		: range_{range}
+		, name_{name}
+		, size_{size}
+		, atlas_{std::move(atlas)}
+		, texcoords_{std::move(texcoords)}
+	{
+		if (range_.end - range_.begin != texcoords_.size())
+			throw std::runtime_error("Wrong number of texture coordinates");
+
+		if (!supports_character('?'))
+			throw std::runtime_error("Monospace font must support '?' character");
+	}
+
+	static geom::vector<float, 2> advance_dir(shape_options::direction_t direction)
+	{
+		switch (direction)
+		{
+		case shape_options::left_to_right: return {1.f, 0.f};
+		case shape_options::right_to_left: return {-1.f, 0.f};
+		case shape_options::top_to_bottom: return {0.f, 1.f};
+		case shape_options::bottom_to_top: return {0.f, -1.f};
+		}
+
+		return {1.f, 0.f};
+	}
+
+	std::vector<glyph> monospace_font::shape(std::string_view str, shape_options const & options) const
+	{
+		char32_t const unknown = supports_character(options.unknown_character) ? options.unknown_character : '?';
+		geom::vector<float, 2> const size = geom::cast<float>(this->size()) * options.scale;
+		geom::vector<float, 2> const advance = geom::pointwise_mult(advance_dir(options.direction), size);
+
+		std::vector<glyph> result;
+
+		geom::vector<float, 2> pos{0.f, 0.f};
+		for (char32_t c : util::utf8_range(str))
+		{
+			glyph g;
+			g.character = supports_character(c) ? c : unknown;
+			g.position = {{{pos[0], pos[0] + size[0]}, {pos[1], pos[1] + size[1]}}};
+			result.push_back(g);
+			pos += advance;
+		}
+
+		return result;
+	}
+
+	std::optional<geom::box<float, 2>> monospace_font::texcoords(char32_t c) const
+	{
+		if (!supports_character(c)) return std::nullopt;
+
+		return texcoords_[c - range_.begin];
+	}
+
+}
diff --git a/libs/ui/source/painter_impl.cpp b/libs/ui/source/painter_impl.cpp
new file mode 100644
index 00000000..ada25aac
--- /dev/null
+++ b/libs/ui/source/painter_impl.cpp
@@ -0,0 +1,126 @@
+#include <psemek/ui/painter_impl.hpp>
+
+#include <psemek/gfx/program.hpp>
+#include <psemek/gfx/array.hpp>
+#include <psemek/gfx/buffer.hpp>
+
+namespace psemek::ui
+{
+
+	static char const colored_vs[] =
+R"(#version 330
+
+uniform mat4 u_transform;
+
+layout (location = 0) in vec2 in_position;
+layout (location = 1) in uint in_depth;
+layout (location = 2) in vec4 in_color;
+
+out vec4 color;
+
+void main()
+{
+	gl_Position = u_transform * vec4(in_position, float(in_depth) / 16777216.0 * 2.0 - 1.0, 1.0);
+	color = in_color;
+}
+)";
+
+	static char const colored_fs[] =
+R"(#version 330
+
+in vec4 color;
+
+out vec4 out_color;
+
+void main()
+{
+	out_color = color;
+}
+)";
+
+	struct colored_vertex
+	{
+		geom::point<float, 2> position;
+		std::uint32_t depth;
+		gfx::color_rgba color;
+	};
+	static_assert(sizeof(colored_vertex) == 16);
+
+	struct painter_impl::impl
+	{
+		std::shared_ptr<struct font> font;
+		std::uint32_t depth = 0;
+
+		gfx::program colored_program;
+		gfx::array colored_vao;
+		gfx::buffer colored_vbo;
+		gfx::buffer colored_ebo;
+
+		std::vector<colored_vertex> colored_vertices;
+		std::vector<std::uint32_t> colored_indices;
+
+		impl();
+	};
+
+	painter_impl::impl::impl()
+		: colored_program{colored_vs, colored_fs}
+	{
+		colored_vao.bind();
+		colored_vbo.bind();
+		gl::EnableVertexAttribArray(0);
+		gl::VertexAttribPointer(0, 2, gl::FLOAT, gl::FALSE, sizeof(colored_vertex), reinterpret_cast<void const *>(0));
+		gl::EnableVertexAttribArray(1);
+		gl::VertexAttribIPointer(1, 1, gl::UNSIGNED_INT, sizeof(colored_vertex), reinterpret_cast<void const *>(8));
+		gl::EnableVertexAttribArray(2);
+		gl::VertexAttribPointer(2, 4, gl::UNSIGNED_BYTE, gl::TRUE, sizeof(colored_vertex), reinterpret_cast<void const *>(12));
+		gl::BindBuffer(gl::ELEMENT_ARRAY_BUFFER, colored_ebo.id());
+	}
+
+	painter_impl::painter_impl()
+		: pimpl_{make_impl()}
+	{}
+
+	painter_impl::~painter_impl() = default;
+
+	void painter_impl::set_font(std::shared_ptr<struct font> font)
+	{
+		impl().font = font;
+	}
+
+	font const * painter_impl::font() const
+	{
+		return impl().font.get();
+	}
+
+	void painter_impl::draw_rect(geom::box<float, 2> const & rect, gfx::color_rgba const & color)
+	{
+		std::uint32_t const depth = impl().depth++;
+		std::uint32_t const base = impl().colored_vertices.size();
+
+		impl().colored_vertices.push_back({rect.corner(0.f, 0.f), depth, color});
+		impl().colored_vertices.push_back({rect.corner(1.f, 0.f), depth, color});
+		impl().colored_vertices.push_back({rect.corner(0.f, 1.f), depth, color});
+		impl().colored_vertices.push_back({rect.corner(1.f, 1.f), depth, color});
+
+		impl().colored_indices.insert(impl().colored_indices.end(), {base + 0, base + 1, base + 2, base + 2, base + 1, base + 3});
+	}
+
+	void painter_impl::render(geom::matrix<float, 4, 4> const & transform)
+	{
+		impl().colored_vbo.load(impl().colored_vertices);
+		impl().colored_ebo.load(impl().colored_indices);
+
+		int const colored_count = impl().colored_indices.size();
+
+		impl().colored_vertices.clear();
+		impl().colored_indices.clear();
+
+		impl().depth = 0;
+
+		impl().colored_program.bind();
+		impl().colored_program["u_transform"] = transform;
+		impl().colored_vao.bind();
+		gl::DrawElements(gl::TRIANGLES, colored_count, gl::UNSIGNED_INT, nullptr);
+	}
+
+}
diff --git a/libs/ui/source/screen.cpp b/libs/ui/source/screen.cpp
new file mode 100644
index 00000000..5fd950a9
--- /dev/null
+++ b/libs/ui/source/screen.cpp
@@ -0,0 +1,95 @@
+#include <psemek/ui/screen.hpp>
+
+namespace psemek::ui
+{
+
+	void screen::add(std::unique_ptr<element> c, x_policy x, y_policy y)
+	{
+		auto i = container::add(std::move(c));
+		if (i >= policies_.size())
+			policies_.resize(i + 1);
+		policies_[i] = {x, y};
+	}
+
+	void screen::add(std::unique_ptr<element> c)
+	{
+		add(std::move(c), x_policy::floating, y_policy::floating);
+	}
+
+	std::unique_ptr<element> screen::remove(element * c)
+	{
+		return container::remove(c);
+	}
+
+	void screen::reshape(geom::box<float, 2> const & bbox)
+	{
+		shape_.box = bbox;
+		auto cs = children();
+		for (std::size_t i = 0; i < cs.size(); ++i)
+		{
+			auto c = cs[i];
+			if (!c) continue;
+			auto sc = c->size_constraints();
+			auto size = bbox.dimensions();
+			size[0] = std::min(size[0], sc[0].min);
+			size[1] = std::min(size[1], sc[1].min);
+
+			auto m = bbox.center();
+
+			geom::box<float, 2> cbox = c->shape().bbox();
+
+			switch (policies_[i].x)
+			{
+			case x_policy::left:
+				cbox[0] = {bbox[0].min, bbox[0].min + size[0]};
+				break;
+			case x_policy::center:
+				cbox[0] = {m[0] - size[0] / 2.f, m[0] + size[0] / 2.f};
+				break;
+			case x_policy::right:
+				cbox[0] = {bbox[0].max - size[0], bbox[0].max};
+				break;
+			case x_policy::floating:
+				cbox[0] = geom::expand(cbox[0], (size[0] - cbox[0].length()) / 2.f);
+
+				if (cbox[0].min < bbox[0].min)
+					cbox[0] += (bbox[0].min - cbox[0].min);
+				else if (cbox[0].max > bbox[0].max)
+					cbox[0] -= (cbox[0].max - bbox[0].max);
+				break;
+			}
+
+			switch (policies_[i].y)
+			{
+			case y_policy::top:
+				cbox[1] = {bbox[1].min, bbox[1].min + size[1]};
+				break;
+			case y_policy::center:
+				cbox[1] = {m[1] - size[1] / 2.f, m[1] + size[1] / 2.f};
+				break;
+			case y_policy::bottom:
+				cbox[1] = {bbox[1].max - size[1], bbox[1].max};
+				break;
+			case y_policy::floating:
+				cbox[1] = geom::expand(cbox[1], (size[1] - cbox[1].length()) / 2.f);
+
+				if (cbox[1].min < bbox[1].min)
+					cbox[1] += (bbox[1].min - cbox[1].min);
+				else if (cbox[1].max > bbox[1].max)
+					cbox[1] -= (cbox[1].max - bbox[1].max);
+				break;
+			}
+
+			c->reshape(cbox);
+		}
+	}
+
+	geom::box<float, 2> screen::size_constraints() const
+	{
+		geom::box<float, 2> result = element::size_constraints();
+		for (auto c : children())
+			if (c) result &= c->size_constraints();
+		return result;
+	}
+
+}