From 4ec4cceb84ac7a25248ba17c778a08c9e4dc1203 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 1 May 2016 13:52:35 -0400
Subject: [PATCH] Made a first attempt at adding draw-as-a-quad functionality
 to texture targets.

---
 Outputs/CRT/Internals/TextureTarget.cpp | 99 ++++++++++++++++++++++++-
 Outputs/CRT/Internals/TextureTarget.hpp | 11 +++
 2 files changed, 109 insertions(+), 1 deletion(-)

diff --git a/Outputs/CRT/Internals/TextureTarget.cpp b/Outputs/CRT/Internals/TextureTarget.cpp
index f575b3d23..f63dbbbec 100644
--- a/Outputs/CRT/Internals/TextureTarget.cpp
+++ b/Outputs/CRT/Internals/TextureTarget.cpp
@@ -10,7 +10,13 @@
 
 using namespace OpenGL;
 
-TextureTarget::TextureTarget(GLsizei width, GLsizei height) : _width(width), _height(height)
+TextureTarget::TextureTarget(GLsizei width, GLsizei height) :
+	_width(width),
+	_height(height),
+	_pixel_shader(nullptr),
+	_drawing_vertex_array(0),
+	_drawing_array_buffer(0),
+	_set_aspect_ratio(0.0f)
 {
 	glGenFramebuffers(1, &_framebuffer);
 	glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer);
@@ -31,6 +37,8 @@ TextureTarget::~TextureTarget()
 {
 	glDeleteFramebuffers(1, &_framebuffer);
 	glDeleteTextures(1, &_texture);
+	if(_drawing_vertex_array) glDeleteVertexArrays(1, &_drawing_vertex_array);
+	if(_drawing_array_buffer) glDeleteBuffers(1, &_drawing_array_buffer);
 }
 
 void TextureTarget::bind_framebuffer()
@@ -43,3 +51,92 @@ void TextureTarget::bind_texture()
 {
 	glBindTexture(GL_TEXTURE_2D, _texture);
 }
+
+void TextureTarget::draw(float aspect_ratio, GLenum texture_unit)
+{
+	if(!_pixel_shader)
+	{
+		const char *vertex_shader =
+			"#version 150\n"
+
+			"in vec2 texCoord;"
+			"in vec2 position;"
+
+			"out vec2 texCoordVarying;"
+
+			"void main(void)"
+			"{"
+				"texCoordVarying = texCoord;"
+				"gl_Position = vec4(position, 0.0, 1.0);"
+			"}";
+
+		const char *fragment_shader =
+			"#version 150\n"
+
+			"in vec2 texCoordVarying;"
+			"uniform sampler2D texID;"
+			"out vec4 fragColour;"
+
+			"void main(void)"
+			"{"
+				"fragColour = texture(texID, texCoordVarying);"
+			"}";
+		_pixel_shader = std::unique_ptr<Shader>(new Shader(vertex_shader, fragment_shader, nullptr));
+
+		glGenVertexArrays(1, &_drawing_vertex_array);
+		glGenBuffers(1, &_drawing_array_buffer);
+
+		glBindVertexArray(_drawing_array_buffer);
+		glBindBuffer(GL_ARRAY_BUFFER, _drawing_vertex_array);
+
+		GLint positionAttribute			= _pixel_shader->get_attrib_location("position");
+		GLint texCoordAttribute			= _pixel_shader->get_attrib_location("texCoord");
+
+		glEnableVertexAttribArray((GLuint)positionAttribute);
+		glEnableVertexAttribArray((GLuint)texCoordAttribute);
+
+		const GLsizei vertexStride = 12;
+		glVertexAttribPointer((GLuint)positionAttribute,	2, GL_FLOAT,	GL_FALSE,	vertexStride, (void *)0);
+		glVertexAttribPointer((GLuint)texCoordAttribute,	2, GL_BYTE,		GL_FALSE,	vertexStride, (void *)(2 * sizeof(GLfloat)));
+	}
+
+	if(_set_aspect_ratio != aspect_ratio)
+	{
+		aspect_ratio = _set_aspect_ratio;
+		int8_t buffer[12*4];
+
+		// establish texture coordinates
+		buffer[8] = 0;		buffer[9] = 0;
+		buffer[20] = 0;		buffer[21] = 1;
+		buffer[32] = 1;		buffer[33] = 0;
+		buffer[44] = 1;		buffer[45] = 1;
+
+		// determine positions
+		float internal_aspect_ratio = (float)_width / (float)_height;
+		float aspect_ratio_ratio = internal_aspect_ratio / aspect_ratio;
+		float *fl_buffer = (float *)buffer;
+		if(aspect_ratio_ratio >= 1.0f)
+		{
+			// output is thinner than we are; letterbox
+			fl_buffer[0] = -1.0f;	fl_buffer[1] = 1.0f / aspect_ratio_ratio;
+			fl_buffer[3] = -1.0f;	fl_buffer[4] = -1.0f / aspect_ratio_ratio;
+			fl_buffer[6] = 1.0f;	fl_buffer[7] = 1.0f / aspect_ratio_ratio;
+			fl_buffer[9] = 1.0f;	fl_buffer[10] = -1.0f / aspect_ratio_ratio;
+		}
+		else
+		{
+			// output is wider than we are; pillarbox
+			fl_buffer[0] = -aspect_ratio_ratio;	fl_buffer[1] = 1.0f;
+			fl_buffer[3] = -aspect_ratio_ratio;	fl_buffer[4] = -1.0f;
+			fl_buffer[6] = aspect_ratio_ratio;	fl_buffer[7] = 1.0f;
+			fl_buffer[9] = aspect_ratio_ratio;	fl_buffer[10] = -1.0f;
+		}
+
+		// upload buffer
+		glBindBuffer(GL_ARRAY_BUFFER, _drawing_vertex_array);
+		glBufferData(GL_ARRAY_BUFFER, sizeof(buffer), buffer, GL_STATIC_DRAW);
+	}
+
+	glBindVertexArray(_drawing_vertex_array);
+	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+}
diff --git a/Outputs/CRT/Internals/TextureTarget.hpp b/Outputs/CRT/Internals/TextureTarget.hpp
index 471caae4b..d00d878e9 100644
--- a/Outputs/CRT/Internals/TextureTarget.hpp
+++ b/Outputs/CRT/Internals/TextureTarget.hpp
@@ -10,6 +10,8 @@
 #define TextureTarget_hpp
 
 #include "OpenGL.hpp"
+#include "Shaders/Shader.hpp"
+#include <memory>
 
 namespace OpenGL {
 
@@ -40,6 +42,11 @@ class TextureTarget {
 		*/
 		void bind_texture();
 
+		/*!
+
+		*/
+		void draw(float aspect_ratio, GLenum texture_unit);
+
 		enum {
 			ErrorFramebufferIncomplete
 		};
@@ -47,6 +54,10 @@ class TextureTarget {
 	private:
 		GLuint _framebuffer, _texture;
 		GLsizei _width, _height;
+
+		std::unique_ptr<Shader> _pixel_shader;
+		GLuint _drawing_vertex_array, _drawing_array_buffer;
+		float _set_aspect_ratio;
 };
 
 }