From 1529d37d585ec38aee475519e444d2718a81fda5 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Thu, 13 Apr 2023 02:10:44 +0100
Subject: Add TextureAtlas class as an extension of Texture

---
 gfx/models/texture.cpp | 32 ++++++++++++++++++++++++++++++++
 gfx/models/texture.h   | 19 +++++++++++++++++--
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/gfx/models/texture.cpp b/gfx/models/texture.cpp
index efc76e1..a500fed 100644
--- a/gfx/models/texture.cpp
+++ b/gfx/models/texture.cpp
@@ -85,3 +85,35 @@ Texture::saveNormal(const glTexture & texture, const glm::ivec2 & size, const ch
 {
 	save(texture, GL_BGR, GL_BYTE, size, 3, path, 2);
 }
+
+TextureAtlas::TextureAtlas(GLsizei width, GLsizei height, GLuint count) : Texture(width, height, nullptr, {})
+{
+	glBindTexture(GL_TEXTURE_RECTANGLE, m_atlas);
+
+	glTexParameteri(GL_TEXTURE_RECTANGLE, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
+	glTexParameteri(GL_TEXTURE_RECTANGLE, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
+
+	glTexParameteri(GL_TEXTURE_RECTANGLE, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_RECTANGLE, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glTexImage2D(GL_TEXTURE_RECTANGLE, 0, GL_RGBA16UI, 2, static_cast<GLsizei>(count), 0, GL_RGBA_INTEGER,
+			GL_UNSIGNED_BYTE, nullptr);
+}
+
+void
+TextureAtlas::bind(GLenum unit) const
+{
+	Texture::bind(unit);
+	glActiveTexture(unit + 1);
+	glBindTexture(GL_TEXTURE_RECTANGLE, m_atlas);
+}
+
+GLuint
+TextureAtlas::add(glm::ivec2 position, glm::ivec2 size, void * data, TextureOptions)
+{
+	glTextureSubImage2D(m_texture, 0, position.x, position.y, size.x, size.y, GL_RGBA, GL_UNSIGNED_BYTE, data);
+	struct Material {
+		glm::vec<2, uint16_t> position, size, unused1 {}, unused2 {};
+	} material {position, size};
+	glTextureSubImage2D(m_atlas, 0, 0, static_cast<GLsizei>(used), 2, 1, GL_RGBA_INTEGER, GL_UNSIGNED_SHORT, &material);
+	return ++used;
+}
diff --git a/gfx/models/texture.h b/gfx/models/texture.h
index ffc9a4a..7900f17 100644
--- a/gfx/models/texture.h
+++ b/gfx/models/texture.h
@@ -16,6 +16,9 @@ struct TextureOptions {
 
 class Texture {
 public:
+	virtual ~Texture() = default;
+	DEFAULT_MOVE_NO_COPY(Texture);
+
 	explicit Texture(const std::filesystem::path & fileName, TextureOptions = {});
 	explicit Texture(const Image & image, TextureOptions = {});
 	explicit Texture(GLsizei width, GLsizei height, TextureOptions = {});
@@ -23,17 +26,29 @@ public:
 
 	static Cache<Texture, std::filesystem::path> cachedTexture;
 
-	void bind(GLenum unit = GL_TEXTURE0) const;
+	virtual void bind(GLenum unit = GL_TEXTURE0) const;
 
 	void save(const glm::ivec2 & size, const char * path) const;
 	static void save(const glTexture &, const glm::ivec2 & size, const char * path);
 	static void saveDepth(const glTexture &, const glm::ivec2 & size, const char * path);
 	static void saveNormal(const glTexture &, const glm::ivec2 & size, const char * path);
 
-private:
+protected:
 	static void save(const glTexture &, GLenum, GLenum, const glm::ivec2 & size, unsigned short channels,
 			const char * path, short tgaFormat);
 
 	glTexture m_texture;
 	GLenum type;
 };
+
+class TextureAtlas : public Texture {
+public:
+	TextureAtlas(GLsizei width, GLsizei height, GLuint count);
+
+	void bind(GLenum unit = GL_TEXTURE0) const override;
+	GLuint add(glm::ivec2 position, glm::ivec2 size, void * data, TextureOptions = {});
+
+private:
+	glTexture m_atlas;
+	GLuint used {};
+};
-- 
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