From e360e95dcbdc8868e50cfb515942d796619aca21 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 17 Feb 2021 01:01:55 +0000
Subject: Support multiple shader programs, set by model

---
 application/main.cpp |  2 +-
 gfx/gl/shader.cpp    | 38 +++++++++++++++++++++++++++-----------
 gfx/gl/shader.h      | 19 ++++++++++++++-----
 3 files changed, 42 insertions(+), 17 deletions(-)

diff --git a/application/main.cpp b/application/main.cpp
index 72da726..41bc15a 100644
--- a/application/main.cpp
+++ b/application/main.cpp
@@ -83,8 +83,8 @@ public:
 		Camera camera({-1250.0F, 35.0F, -1250.0F}, 70.0F, (float)DISPLAY_WIDTH / (float)DISPLAY_HEIGHT, 0.1F, 10000.0F);
 		camera.Pitch(0.24);
 		camera.RotateY(0.7854);
-		shader.Bind();
 		shader.setView(camera.GetViewProjection());
+		shader.setLight(glm::normalize(glm::vec3 {1, -1, 0}));
 
 		auto t_start = std::chrono::high_resolution_clock::now();
 		const auto framelen = std::chrono::milliseconds {1000} / 120;
diff --git a/gfx/gl/shader.cpp b/gfx/gl/shader.cpp
index 7fcdefe..979d57e 100644
--- a/gfx/gl/shader.cpp
+++ b/gfx/gl/shader.cpp
@@ -6,10 +6,12 @@
 #include <stdexcept>
 #include <string>
 
-Shader::Shader() : viewProjection_uniform {}, model_uniform {}, lightDir_uniform {}
+Shader::ProgramHandle::ProgramHandle(std::initializer_list<GLuint> srcs) :
+	viewProjection_uniform {}, model_uniform {}, lightDir_uniform {}
 {
-	glAttachShader(m_program, Source {{basicShader_vs, basicShader_vs_len}, GL_VERTEX_SHADER}.id);
-	glAttachShader(m_program, Source {{basicShader_fs, basicShader_fs_len}, GL_FRAGMENT_SHADER}.id);
+	for (const auto & srcId : srcs) {
+		glAttachShader(m_program, srcId);
+	}
 
 	glBindAttribLocation(m_program, 0, "position");
 	glBindAttribLocation(m_program, 1, "texCoord");
@@ -26,24 +28,38 @@ Shader::Shader() : viewProjection_uniform {}, model_uniform {}, lightDir_uniform
 	lightDir_uniform = glGetUniformLocation(m_program, "lightDirection");
 }
 
-void
-Shader::Bind() const
+Shader::Shader() :
+	programs {{{
+			Source {{basicShader_vs, basicShader_vs_len}, GL_VERTEX_SHADER}.id,
+			Source {{basicShader_fs, basicShader_fs_len}, GL_FRAGMENT_SHADER}.id,
+	}}}
 {
-	glUseProgram(m_program);
 }
 
 void
 Shader::setView(glm::mat4 proj) const
 {
-	glUniformMatrix4fv(viewProjection_uniform, 1, GL_FALSE, &proj[0][0]);
-	const glm::vec3 lightDir = glm::normalize(glm::vec3 {1, -1, 0});
-	glUniform3fv(lightDir_uniform, 1, &lightDir[0]);
+	for (const auto & prog : programs) {
+		glUseProgram(prog.m_program);
+		glUniformMatrix4fv(prog.viewProjection_uniform, 1, GL_FALSE, &proj[0][0]);
+	}
+}
+
+void
+Shader::setLight(glm::vec3 lightDir) const
+{
+	for (const auto & prog : programs) {
+		glUseProgram(prog.m_program);
+		glUniform3fv(prog.lightDir_uniform, 1, &lightDir[0]);
+	}
 }
 
 void
-Shader::setModel(glm::mat4 model) const
+Shader::setModel(glm::mat4 model, Program pid) const
 {
-	glUniformMatrix4fv(model_uniform, 1, GL_FALSE, &model[0][0]);
+	auto & prog = programs[(int)pid];
+	glUseProgram(prog.m_program);
+	glUniformMatrix4fv(prog.model_uniform, 1, GL_FALSE, &model[0][0]);
 }
 
 void
diff --git a/gfx/gl/shader.h b/gfx/gl/shader.h
index a839b9b..98e0348 100644
--- a/gfx/gl/shader.h
+++ b/gfx/gl/shader.h
@@ -2,17 +2,20 @@
 #define SHADER_INCLUDED_H
 
 #include <GL/glew.h>
+#include <array>
 #include <glRef.hpp>
 #include <glm/glm.hpp>
 #include <string_view>
 
 class Shader {
 public:
+	enum class Program { Basic = 0 };
+
 	Shader();
 
-	void Bind() const;
 	void setView(glm::mat4 view) const;
-	void setModel(glm::mat4 model) const;
+	void setModel(glm::mat4 model, Program = Program::Basic) const;
+	void setLight(glm::vec3 dir) const;
 
 private:
 	class Source {
@@ -27,10 +30,16 @@ private:
 
 	static void CheckShaderError(GLuint shader, GLuint flag, bool isProgram, std::string_view errorMessage);
 
-	using ProgramRef = glRef<GLuint, __glewCreateProgram, __glewDeleteProgram>;
+	class ProgramHandle {
+	public:
+		ProgramHandle(std::initializer_list<GLuint>);
+		using ProgramRef = glRef<GLuint, __glewCreateProgram, __glewDeleteProgram>;
+
+		ProgramRef m_program;
+		GLint viewProjection_uniform, model_uniform, lightDir_uniform;
+	};
 
-	ProgramRef m_program;
-	GLint viewProjection_uniform, model_uniform, lightDir_uniform;
+	std::array<ProgramHandle, 1> programs;
 };
 
 #endif
-- 
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