From b4f116cadab5234ce96cf4b606a64046f43a8ba1 Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Fri, 15 Oct 2021 21:38:23 +0300
Subject: [PATCH] Implement scroller ui container

---
 .../psemek/ui/default_element_factory.hpp     |   1 +
 libs/ui/include/psemek/ui/element_factory.hpp |   2 +
 libs/ui/include/psemek/ui/scroller.hpp        |  51 +++++++
 libs/ui/source/default_element_factory.cpp    |   5 +
 libs/ui/source/element_factory.cpp            |   2 +
 libs/ui/source/scroller.cpp                   | 127 ++++++++++++++++++
 6 files changed, 188 insertions(+)
 create mode 100644 libs/ui/include/psemek/ui/scroller.hpp
 create mode 100644 libs/ui/source/scroller.cpp

diff --git a/libs/ui/include/psemek/ui/default_element_factory.hpp b/libs/ui/include/psemek/ui/default_element_factory.hpp
index 1717d053..55d2dc82 100644
--- a/libs/ui/include/psemek/ui/default_element_factory.hpp
+++ b/libs/ui/include/psemek/ui/default_element_factory.hpp
@@ -21,6 +21,7 @@ namespace psemek::ui
 		std::shared_ptr<slider> make_slider() override;
 		std::shared_ptr<spinbox> make_spinbox() override;
 		std::shared_ptr<button> make_arrow_button(int direction) override;
+		std::shared_ptr<scroller> make_scroller() override;
 
 	private:
 		psemek_declare_pimpl
diff --git a/libs/ui/include/psemek/ui/element_factory.hpp b/libs/ui/include/psemek/ui/element_factory.hpp
index ef79a660..dd1d4570 100644
--- a/libs/ui/include/psemek/ui/element_factory.hpp
+++ b/libs/ui/include/psemek/ui/element_factory.hpp
@@ -12,6 +12,7 @@
 #include <psemek/ui/checkbox.hpp>
 #include <psemek/ui/slider.hpp>
 #include <psemek/ui/spinbox.hpp>
+#include <psemek/ui/scroller.hpp>
 
 #include <psemek/gfx/texture.hpp>
 
@@ -39,6 +40,7 @@ namespace psemek::ui
 		// 2 - left
 		// 3 - right
 		virtual std::shared_ptr<button> make_arrow_button(int direction);
+		virtual std::shared_ptr<scroller> make_scroller();
 
 		virtual ~element_factory() {}
 	};
diff --git a/libs/ui/include/psemek/ui/scroller.hpp b/libs/ui/include/psemek/ui/scroller.hpp
new file mode 100644
index 00000000..185d055c
--- /dev/null
+++ b/libs/ui/include/psemek/ui/scroller.hpp
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <psemek/ui/element.hpp>
+#include <psemek/ui/box_shape.hpp>
+
+namespace psemek::ui
+{
+
+	struct scroller
+		: element
+	{
+		children_range children() const override { return children_; }
+
+		virtual std::shared_ptr<element> set_child(std::shared_ptr<element> c);
+
+		virtual bool set_horizontal_scroll(bool enabled);
+		virtual bool set_vertical_scroll(bool enabled);
+
+		virtual bool horizontal_scroll() const { return horizontal_; }
+		virtual bool vertical_scroll() const { return vertical_; }
+
+		virtual bool on_event(mouse_move const & e);
+		virtual bool on_event(mouse_wheel const & e);
+
+		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 update(float dt) override;
+
+		void draw(painter & p) const override;
+		void post_draw(painter & p) const override;
+
+		~scroller() override;
+
+	private:
+		box_shape shape_;
+		std::optional<geom::point<int, 2>> mouse_;
+
+		bool horizontal_ = false;
+		bool vertical_ = true;
+
+		geom::vector<float, 2> shift_{0.f, 0.f};
+		geom::vector<float, 2> shift_tgt_{0.f, 0.f};
+
+		std::shared_ptr<element> child_;
+		element * children_[1]{nullptr};
+	};
+
+}
diff --git a/libs/ui/source/default_element_factory.cpp b/libs/ui/source/default_element_factory.cpp
index 733b43e2..438b9001 100644
--- a/libs/ui/source/default_element_factory.cpp
+++ b/libs/ui/source/default_element_factory.cpp
@@ -766,4 +766,9 @@ namespace psemek::ui
 		return std::make_shared<arrow_button_impl>(direction);
 	}
 
+	std::shared_ptr<scroller> default_element_factory::make_scroller()
+	{
+		return std::make_shared<scroller>();
+	}
+
 }
diff --git a/libs/ui/source/element_factory.cpp b/libs/ui/source/element_factory.cpp
index 8a5ce602..132cd84e 100644
--- a/libs/ui/source/element_factory.cpp
+++ b/libs/ui/source/element_factory.cpp
@@ -84,4 +84,6 @@ namespace psemek::ui
 
 	std::shared_ptr<button> element_factory::make_arrow_button(int) { return nullptr; }
 
+	std::shared_ptr<scroller> element_factory::make_scroller() { return nullptr; }
+
 }
diff --git a/libs/ui/source/scroller.cpp b/libs/ui/source/scroller.cpp
new file mode 100644
index 00000000..28ac96ea
--- /dev/null
+++ b/libs/ui/source/scroller.cpp
@@ -0,0 +1,127 @@
+#include <psemek/ui/scroller.hpp>
+
+#include <psemek/geom/contains.hpp>
+
+namespace psemek::ui
+{
+
+	std::shared_ptr<element> scroller::set_child(std::shared_ptr<element> c)
+	{
+		auto old = std::move(child_);
+		if (old) old->set_parent(nullptr);
+
+		child_ = std::move(c);
+		if (child_) child_->set_parent(this);
+		children_[0] = child_.get();
+
+		return old;
+	}
+
+	bool scroller::set_horizontal_scroll(bool enabled)
+	{
+		std::swap(horizontal_, enabled);
+		return enabled;
+	}
+
+	bool scroller::set_vertical_scroll(bool enabled)
+	{
+		std::swap(vertical_, enabled);
+		return enabled;
+	}
+
+	bool scroller::on_event(mouse_move const & e)
+	{
+		mouse_ = e.position;
+		return false;
+	}
+
+	bool scroller::on_event(mouse_wheel const & e)
+	{
+		if (mouse_ && geom::contains(shape_.box, geom::cast<float>(*mouse_)))
+		{
+			if (vertical_scroll())
+			{
+				shift_tgt_[1] += e.delta * 50.f;
+				post_reshape();
+				return true;
+			}
+			else if (horizontal_scroll())
+			{
+				shift_tgt_[0] += e.delta * 50.f;
+				post_reshape();
+				return true;
+			}
+		}
+		return false;
+	}
+
+	void scroller::reshape(geom::box<float, 2> const & bbox)
+	{
+		shape_.box = bbox;
+
+		if (child_)
+		{
+			auto child_constraints = child_->size_constraints();
+
+			auto child_bbox = bbox;
+
+			if (horizontal_scroll())
+			{
+				child_bbox[0].min += shift_[0];
+				child_bbox[0].max = child_bbox[0].min + child_constraints[0].min;
+			}
+
+			if (vertical_scroll())
+			{
+				child_bbox[1].min += shift_[1];
+				child_bbox[1].max = child_bbox[1].min + child_constraints[1].min;
+			}
+
+			child_->reshape(child_bbox);
+		}
+	}
+
+	geom::box<float, 2> scroller::size_constraints() const
+	{
+		geom::box<float, 2> result;
+		result[0] = {0.f, std::numeric_limits<float>::infinity()};
+		result[1] = {0.f, std::numeric_limits<float>::infinity()};
+
+		if (child_)
+		{
+			auto child_constraints = child_->size_constraints();
+
+			if (!horizontal_scroll())
+				result[0] = child_constraints[0];
+
+			if (!vertical_scroll())
+				result[1] = child_constraints[1];
+		}
+
+		return result;
+	}
+
+	void scroller::update(float dt)
+	{
+		shift_ += (shift_tgt_ - shift_) * std::min(10.f * dt, 1.f);
+		post_reshape();
+	}
+
+	void scroller::draw(painter & p) const
+	{
+		p.begin_stencil();
+		p.draw_rect(shape_.box, {0, 0, 0, 255});
+		p.commit_stencil();
+	}
+
+	void scroller::post_draw(painter & p) const
+	{
+		p.end_stencil();
+	}
+
+	scroller::~scroller()
+	{
+		release_children();
+	}
+
+}