From 85ad4900890d13e30d755c7fe08799f28979181b Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomasharte@google.com>
Date: Fri, 25 Jan 2019 21:56:55 -0500
Subject: [PATCH] Offers a less error-prone route to attribute binding.

---
 Outputs/OpenGL/Primitives/Shader.cpp       | 14 +++++++++++
 Outputs/OpenGL/Primitives/Shader.hpp       | 10 ++++++++
 Outputs/OpenGL/ScanTargetGLSLFragments.cpp | 28 +++++++++++-----------
 3 files changed, 38 insertions(+), 14 deletions(-)

diff --git a/Outputs/OpenGL/Primitives/Shader.cpp b/Outputs/OpenGL/Primitives/Shader.cpp
index 7290cfe39..b838e3b06 100644
--- a/Outputs/OpenGL/Primitives/Shader.cpp
+++ b/Outputs/OpenGL/Primitives/Shader.cpp
@@ -46,6 +46,20 @@ GLuint Shader::compile_shader(const std::string &source, GLenum type) {
 }
 
 Shader::Shader(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<AttributeBinding> &attribute_bindings) {
+	init(vertex_shader, fragment_shader, attribute_bindings);
+}
+
+Shader::Shader(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<std::string> &binding_names) {
+	std::vector<AttributeBinding> bindings;
+	GLuint index = 0;
+	for(const auto &name: binding_names) {
+		bindings.emplace_back(name, index);
+		++index;
+	}
+	init(vertex_shader, fragment_shader, bindings);
+}
+
+void Shader::init(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<AttributeBinding> &attribute_bindings) {
 	shader_program_ = glCreateProgram();
 	const GLuint vertex = compile_shader(vertex_shader, GL_VERTEX_SHADER);
 	const GLuint fragment = compile_shader(fragment_shader, GL_FRAGMENT_SHADER);
diff --git a/Outputs/OpenGL/Primitives/Shader.hpp b/Outputs/OpenGL/Primitives/Shader.hpp
index 8610a2c7e..995bbb704 100644
--- a/Outputs/OpenGL/Primitives/Shader.hpp
+++ b/Outputs/OpenGL/Primitives/Shader.hpp
@@ -34,6 +34,7 @@ public:
 	};
 
 	struct AttributeBinding {
+		AttributeBinding(const std::string &name, GLuint index) : name(name), index(index) {}
 		const std::string name;
 		const GLuint index;
 	};
@@ -45,6 +46,13 @@ public:
 		@param attribute_bindings A vector of attribute bindings.
 	*/
 	Shader(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<AttributeBinding> &attribute_bindings = {});
+	/*!
+		Attempts to compile a shader, throwing @c VertexShaderCompilationError, @c FragmentShaderCompilationError or @c ProgramLinkageError upon failure.
+		@param vertex_shader The vertex shader source code.
+		@param fragment_shader The fragment shader source code.
+		@param binding_names A list of attributes to generate bindings for; these will be given indices 0...n-1.
+	*/
+	Shader(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<std::string> &binding_names);
 	~Shader();
 
 	/*!
@@ -109,6 +117,8 @@ public:
 	void set_uniform_matrix(const std::string &name, GLint size, GLsizei count, bool transpose, const GLfloat *values);
 
 private:
+	void init(const std::string &vertex_shader, const std::string &fragment_shader, const std::vector<AttributeBinding> &attribute_bindings);
+
 	GLuint compile_shader(const std::string &source, GLenum type);
 	GLuint shader_program_;
 
diff --git a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
index 31bd7c9e8..f9a65df07 100644
--- a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
+++ b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
@@ -179,12 +179,12 @@ std::unique_ptr<Shader> ScanTarget::composition_shader() const {
 		vertex_shader,
 		fragment_shader + "}",
 		{
-			{"startDataX", 0},
-			{"startClock", 1},
-			{"endDataX", 2},
-			{"endClock", 3},
-			{"dataY", 4},
-			{"lineY", 5},
+			"startDataX",
+			"startClock",
+			"endDataX",
+			"endClock",
+			"dataY",
+			"lineY",
 		}
 	));
 }
@@ -491,14 +491,14 @@ std::unique_ptr<Shader> ScanTarget::conversion_shader() const {
 		vertex_shader,
 		fragment_shader,
 		{
-			{"startPoint", 0},
-			{"endPoint", 1},
-			{"startClock", 2},
-			{"endClock", 3},
-			{"lineY", 4},
-			{"lineCompositeAmplitude", 5},
-			{"startCompositeAngle", 6},
-			{"endCompositeAngle", 7},
+			"startPoint",
+			"endPoint",
+			"startClock",
+			"endClock",
+			"lineY",
+			"lineCompositeAmplitude",
+			"startCompositeAngle",
+			"endCompositeAngle"
 		}
 	);