From e9d1afd5155c12dce5f765217cc741657a231dc1 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Nov 2018 19:10:48 -0500
Subject: [PATCH] Appears to demonstrates that the line buffer is approximately
 working.

---
 Outputs/OpenGL/ScanTarget.cpp              | 22 ++++++++++++----------
 Outputs/OpenGL/ScanTarget.hpp              |  2 +-
 Outputs/OpenGL/ScanTargetGLSLFragments.cpp | 12 ++++++------
 3 files changed, 19 insertions(+), 17 deletions(-)

diff --git a/Outputs/OpenGL/ScanTarget.cpp b/Outputs/OpenGL/ScanTarget.cpp
index f7988d95e..6a1755fa4 100644
--- a/Outputs/OpenGL/ScanTarget.cpp
+++ b/Outputs/OpenGL/ScanTarget.cpp
@@ -66,38 +66,40 @@ const GLenum formatForDepth(std::size_t depth) {
 
 }
 
-template <typename T> void ScanTarget::allocate_buffer(const T &array, GLuint &buffer_name) {
+template <typename T> void ScanTarget::allocate_buffer(const T &array, GLuint &buffer_name, GLuint &vertex_array_name) {
 	const auto buffer_size = array.size() * sizeof(array[0]);
 	glGenBuffers(1, &buffer_name);
 	glBindBuffer(GL_ARRAY_BUFFER, buffer_name);
 	glBufferData(GL_ARRAY_BUFFER, GLsizeiptr(buffer_size), NULL, GL_STREAM_DRAW);
+
+	glGenVertexArrays(1, &vertex_array_name);
+	glBindVertexArray(vertex_array_name);
+	glBindBuffer(GL_ARRAY_BUFFER, buffer_name);
 }
 
 ScanTarget::ScanTarget() :
  	unprocessed_line_texture_(LineBufferWidth, LineBufferHeight, UnprocessedLineBufferTextureUnit, GL_LINEAR) {
 
 	// Allocate space for the scans and lines.
-	allocate_buffer(scan_buffer_, scan_buffer_name_);
-	allocate_buffer(line_buffer_, line_buffer_name_);
+	allocate_buffer(scan_buffer_, scan_buffer_name_, scan_vertex_array_);
+	allocate_buffer(line_buffer_, line_buffer_name_, line_vertex_array_);
 
 	// TODO: if this is OpenGL 4.4 or newer, use glBufferStorage rather than glBufferData
 	// and specify GL_MAP_PERSISTENT_BIT. Then map the buffer now, and let the client
 	// write straight into it.
 
 	glGenTextures(1, &write_area_texture_name_);
-	glGenVertexArrays(1, &scan_vertex_array_);
 
-	glBindVertexArray(scan_vertex_array_);
-	glBindBuffer(GL_ARRAY_BUFFER, scan_buffer_name_);
 	test_shader_.reset(new Shader(
-		glsl_globals(ShaderType::Scan) + glsl_default_vertex_shader(ShaderType::Scan),
+		glsl_globals(ShaderType::Line) + glsl_default_vertex_shader(ShaderType::Line),
 		"#version 150\n"
 		"out vec4 fragColour;"
 		"void main(void) {"
 			"fragColour = vec4(1.0);"
 		"}"
 	));
-	enable_vertex_attributes(ShaderType::Scan, *test_shader_);
+	glBindVertexArray(line_vertex_array_);
+	enable_vertex_attributes(ShaderType::Line, *test_shader_);
 }
 
 ScanTarget::~ScanTarget() {
@@ -354,10 +356,10 @@ void ScanTarget::draw() {
 	// the submit pointer location.
 	read_pointers_.store(submit_pointers);
 
-	// TEST: draw all scans.
+	// TEST: draw all lines.
 	glBindFramebuffer(GL_FRAMEBUFFER, 0);
 
-	glBindVertexArray(scan_vertex_array_);
+	glBindVertexArray(line_vertex_array_);
 	test_shader_->bind();
 	glDrawArraysInstanced(GL_TRIANGLE_STRIP, 0, 4, GLsizei(scan_buffer_.size()));
 }
diff --git a/Outputs/OpenGL/ScanTarget.hpp b/Outputs/OpenGL/ScanTarget.hpp
index 812db7dbb..1e64fdea3 100644
--- a/Outputs/OpenGL/ScanTarget.hpp
+++ b/Outputs/OpenGL/ScanTarget.hpp
@@ -86,7 +86,7 @@ class ScanTarget: public Outputs::Display::ScanTarget {
 		GLuint scan_buffer_name_ = 0, scan_vertex_array_ = 0;
 		GLuint line_buffer_name_ = 0, line_vertex_array_ = 0;
 
-		template <typename T> void allocate_buffer(const T &array, GLuint &buffer_name);
+		template <typename T> void allocate_buffer(const T &array, GLuint &buffer_name, GLuint &vertex_array_name);
 		template <typename T> void submit_buffer(const T &array, GLuint target, uint16_t submit_pointer, uint16_t read_pointer);
 
 		// Uses a texture to vend write areas.
diff --git a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
index 5d3464089..d8fe3c505 100644
--- a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
+++ b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
@@ -45,8 +45,8 @@ std::string ScanTarget::glsl_globals(ShaderType type) {
 }
 
 std::string ScanTarget::glsl_default_vertex_shader(ShaderType type) {
-	switch(type) {
-		case ShaderType::Scan:
+//	switch(type) {
+//		case ShaderType::Scan:
 		return
 			"void main(void) {"
 				"float lateral = float(gl_VertexID & 1);"
@@ -54,13 +54,13 @@ std::string ScanTarget::glsl_default_vertex_shader(ShaderType type) {
 
 				"vec2 centrePoint = mix(startPoint, endPoint, lateral) / scale;"
 				"vec2 height = normalize(endPoint - startPoint).yx * (longitudinal - 0.5) * rowHeight;"
-				"vec2 eyePosition = vec2(1.0) - 2.0 * (centrePoint + height);"
+				"vec2 eyePosition = vec2(-0.9, 0.9) + vec2(1.8, -1.8) * (centrePoint + height);"
 				"gl_Position = vec4(eyePosition, 0.0, 1.0);"
 			"}";
 
-		case ShaderType::Line:
-		return "";
-	}
+//		case ShaderType::Line:
+//		return "";
+//	}
 }
 
 void ScanTarget::enable_vertex_attributes(ShaderType type, Shader &target) {