Shuffles the OpenGL primitives into their own collection.

Outputs/OpenGL/Primitives/Rectangle.cpp

@@ -0,0 +1,74 @@
+//
+//  Rectangle.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 11/07/2018.
+//  Copyright © 2018 Thomas Harte. All rights reserved.
+//
+
+#include "Rectangle.hpp"
+
+using namespace OpenGL;
+
+Rectangle::Rectangle(float x, float y, float width, float height):
+ 	pixel_shader_(
+		"#version 150\n"
+
+		"in vec2 position;"
+
+		"void main(void)"
+		"{"
+			"gl_Position = vec4(position, 0.0, 1.0);"
+		"}",
+
+		"#version 150\n"
+
+		"uniform vec4 colour;"
+		"out vec4 fragColour;"
+
+		"void main(void)"
+		"{"
+			"fragColour = colour;"
+		"}"
+	){
+	pixel_shader_.bind();
+
+	glGenVertexArrays(1, &drawing_vertex_array_);
+	glGenBuffers(1, &drawing_array_buffer_);
+
+	glBindVertexArray(drawing_vertex_array_);
+	glBindBuffer(GL_ARRAY_BUFFER, drawing_array_buffer_);
+
+	GLint position_attribute = pixel_shader_.get_attrib_location("position");
+	glEnableVertexAttribArray(static_cast<GLuint>(position_attribute));
+
+	glVertexAttribPointer(
+		(GLuint)position_attribute,
+		2,
+		GL_FLOAT,
+		GL_FALSE,
+		2 * sizeof(GLfloat),
+		(void *)0);
+
+	colour_uniform_ = pixel_shader_.get_uniform_location("colour");
+
+	float buffer[4*2];
+
+	// Store positions.
+	buffer[0] = x;			buffer[1] = y;
+	buffer[2] = x;			buffer[3] = y + height;
+	buffer[4] = x + width;	buffer[5] = y;
+	buffer[6] = x + width;	buffer[7] = y + height;
+
+	// Upload buffer.
+	glBindBuffer(GL_ARRAY_BUFFER, drawing_array_buffer_);
+	glBufferData(GL_ARRAY_BUFFER, sizeof(buffer), buffer, GL_STATIC_DRAW);
+}
+
+void Rectangle::draw(float red, float green, float blue) {
+	pixel_shader_.bind();
+	glUniform4f(colour_uniform_, red, green, blue, 1.0);
+
+	glBindVertexArray(drawing_vertex_array_);
+	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+}