From 45b3369bc9516eab3e193be07cb73a926db7dc8a Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Thu, 10 Feb 2022 13:29:47 +0300
Subject: [PATCH] Add texture atlas implementation

---
 libs/gfx/include/psemek/gfx/texture_atlas.hpp | 75 +++++++++++++++++
 libs/util/include/psemek/util/atlas.hpp       | 81 +++++++++++++++++++
 2 files changed, 156 insertions(+)
 create mode 100644 libs/gfx/include/psemek/gfx/texture_atlas.hpp
 create mode 100644 libs/util/include/psemek/util/atlas.hpp

diff --git a/libs/gfx/include/psemek/gfx/texture_atlas.hpp b/libs/gfx/include/psemek/gfx/texture_atlas.hpp
new file mode 100644
index 00000000..afd192b0
--- /dev/null
+++ b/libs/gfx/include/psemek/gfx/texture_atlas.hpp
@@ -0,0 +1,75 @@
+#pragma once
+
+#include <psemek/util/atlas.hpp>
+#include <psemek/gfx/texture.hpp>
+#include <psemek/gfx/texture_view.hpp>
+
+namespace psemek::gfx
+{
+
+	template <typename Pixel, typename Key, typename Compare = std::less<Key>>
+	struct texture_atlas_2d
+	{
+		texture_atlas_2d(Pixel background = Pixel{}, Compare compare = Compare{});
+
+		using texture_view = texture_view_2d;
+
+		texture_2d & texture() { return texture_; }
+		texture_2d const & texture() const { return texture_; }
+
+		std::pair<texture_view, bool> insert(Key const & key, util::array<Pixel, 2> const & data);
+		texture_view find(Key const & key) const;
+		texture_view at(Key const & key) const;
+
+	private:
+		util::atlas<Pixel, 2, Key, Compare> atlas_;
+		texture_2d texture_;
+
+		void update_texture();
+
+		texture_view to_view(typename util::atlas<Pixel, 2, Key, Compare>::atlas_part const & part) const;
+	};
+
+	template <typename Pixel, typename Key, typename Compare>
+	texture_atlas_2d<Pixel, Key, Compare>::texture_atlas_2d(Pixel background, Compare compare)
+		: atlas_(std::move(background), std::move(compare))
+	{}
+
+	template <typename Pixel, typename Key, typename Compare>
+	std::pair<texture_view_2d, bool> texture_atlas_2d<Pixel, Key, Compare>::insert(Key const & key, util::array<Pixel, 2> const & data)
+	{
+		auto result = atlas_.insert(key, data);
+		if (result.second)
+			update_texture();
+
+		return {to_view(result.first), result.second};
+	}
+
+	template <typename Pixel, typename Key, typename Compare>
+	texture_view_2d texture_atlas_2d<Pixel, Key, Compare>::find(Key const & key) const
+	{
+		auto result = atlas_.find(key);
+		if (result)
+			return to_view(*result);
+		return texture_view{};
+	}
+
+	template <typename Pixel, typename Key, typename Compare>
+	texture_view_2d texture_atlas_2d<Pixel, Key, Compare>::at(Key const & key) const
+	{
+		return to_view(atlas_.at(key));
+	}
+
+	template <typename Pixel, typename Key, typename Compare>
+	void texture_atlas_2d<Pixel, Key, Compare>::update_texture()
+	{
+		texture_.load(atlas_.array());
+	}
+
+	template <typename Pixel, typename Key, typename Compare>
+	texture_view_2d texture_atlas_2d<Pixel, Key, Compare>::to_view(typename util::atlas<Pixel, 2, Key, Compare>::atlas_part const & part) const
+	{
+		return texture_view{&texture_, {{{part.begin[0], part.end[0]}, {part.begin[1], part.end[1]}}}};
+	}
+
+}
diff --git a/libs/util/include/psemek/util/atlas.hpp b/libs/util/include/psemek/util/atlas.hpp
new file mode 100644
index 00000000..3cd894eb
--- /dev/null
+++ b/libs/util/include/psemek/util/atlas.hpp
@@ -0,0 +1,81 @@
+#pragma once
+
+#include <psemek/util/array.hpp>
+
+#include <map>
+#include <optional>
+
+namespace psemek::util
+{
+
+	template <typename T, std::size_t N, typename Key, typename Compare = std::less<Key>>
+	struct atlas;
+
+	template <typename T, typename Key, typename Compare>
+	struct atlas<T, 2, Key, Compare>
+	{
+		struct atlas_part
+		{
+			std::array<std::size_t, 2> begin;
+			std::array<std::size_t, 2> end;
+		};
+
+		atlas(T default_value = T{}, Compare compare = Compare{})
+			: default_value_(std::move(default_value))
+			, data_(std::move(compare))
+		{}
+
+		util::array<T, 2> const & array() const
+		{
+			return array_;
+		}
+
+		std::pair<atlas_part, bool> insert(Key const & key, util::array<T, 2> const & data)
+		{
+			auto it = data_.find(key);
+			if (it != data_.end())
+				return {it->second, false};
+
+			atlas_part part;
+			part.begin[0] = array_.width();
+			part.end[0] = part.begin[0] + data.width();
+			part.begin[1] = 0;
+			part.end[1] = data.height();
+
+			std::size_t new_width = array_.width() + data.width();
+			std::size_t new_height = std::max(array_.height(), data.height());
+
+			array_.resize({new_width, new_height}, default_value_);
+
+			for (std::size_t y = 0; y < data.height(); ++y)
+			{
+				for (std::size_t x = 0; x < data.width(); ++x)
+				{
+					array_(part.begin[0] + x, part.begin[1] + y) = data(x, y);
+				}
+			}
+
+			data_[key] = part;
+			return {part, true};
+		}
+
+		std::optional<atlas_part> find(Key const & key) const
+		{
+			auto it = data_.find(key);
+			if (it != data_.end())
+				return it->second;
+			return std::nullopt;
+		}
+
+		atlas_part at(Key const & key) const
+		{
+			return data_.at(key);
+		}
+
+	private:
+		T default_value_;
+		std::map<Key, atlas_part, Compare> data_;
+		util::array<T, 2> array_;
+	};
+
+}