From f420ba91b26aad7701f781bf371f47662a19f452 Mon Sep 17 00:00:00 2001
From: "Steinar H. Gunderson" <sgunderson@bigfoot.com>
Date: Sat, 8 Mar 2014 18:33:17 +0100
Subject: [PATCH] Use GLSL 1.30-style attributes for the main shader.

This is in preparation for removing fixed-function use altogether,
for OpenGL 3.2+ core context support.
---
 effect_chain.cpp | 55 +++++++++++++++++++++++++++++-------------------
 vs.vert          | 12 +++++++++--
 2 files changed, 43 insertions(+), 24 deletions(-)

diff --git a/effect_chain.cpp b/effect_chain.cpp
index 9aa092b..c803c62 100644
--- a/effect_chain.cpp
+++ b/effect_chain.cpp
@@ -1446,13 +1446,6 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
 	glDepthMask(GL_FALSE);
 	check_error();
 
-	glMatrixMode(GL_PROJECTION);
-	glLoadIdentity();
-	glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0);
-
-	glMatrixMode(GL_MODELVIEW);
-	glLoadIdentity();
-
 	if (phases.size() > 1) {
 		glGenFramebuffers(1, &fbo);
 		check_error();
@@ -1476,7 +1469,8 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
 			output_textures.insert(make_pair(phases[phase], tex_num));
 		}
 
-		glUseProgram(phases[phase]->glsl_program_num);
+		const GLuint glsl_program_num = phases[phase]->glsl_program_num;
+		glUseProgram(glsl_program_num);
 		check_error();
 
 		// Set up RTT inputs for this phase.
@@ -1503,7 +1497,7 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
 			check_error();
 
 			string texture_name = string("tex_") + phases[phase]->effect_ids[input];
-			glUniform1i(glGetUniformLocation(phases[phase]->glsl_program_num, texture_name.c_str()), sampler);
+			glUniform1i(glGetUniformLocation(glsl_program_num, texture_name.c_str()), sampler);
 			check_error();
 		}
 
@@ -1536,27 +1530,44 @@ void EffectChain::render_to_fbo(GLuint dest_fbo, unsigned width, unsigned height
 		unsigned sampler_num = phases[phase]->inputs.size();
 		for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
 			Node *node = phases[phase]->effects[i];
-			node->effect->set_gl_state(phases[phase]->glsl_program_num, phases[phase]->effect_ids[node], &sampler_num);
+			node->effect->set_gl_state(glsl_program_num, phases[phase]->effect_ids[node], &sampler_num);
 			check_error();
 		}
 
 		// Now draw!
-		glBegin(GL_QUADS);
-
-		glTexCoord2f(0.0f, 0.0f);
-		glVertex2f(0.0f, 0.0f);
-
-		glTexCoord2f(1.0f, 0.0f);
-		glVertex2f(1.0f, 0.0f);
+		float vertices[] = {
+			0.0f, 0.0f,
+			1.0f, 0.0f,
+			1.0f, 1.0f,
+			0.0f, 1.0f
+		};
+
+		int position_attrib = glGetAttribLocation(glsl_program_num, "position");
+		assert(position_attrib != -1);
+		glEnableVertexAttribArray(position_attrib);
+		check_error();
+		glVertexAttribPointer(position_attrib, 2, GL_FLOAT, GL_FALSE, 0, vertices);
+		check_error();
 
-		glTexCoord2f(1.0f, 1.0f);
-		glVertex2f(1.0f, 1.0f);
+		int texcoord_attrib = glGetAttribLocation(glsl_program_num, "texcoord");
+		if (texcoord_attrib != -1) {
+			glEnableVertexAttribArray(texcoord_attrib);
+			check_error();
+			glVertexAttribPointer(texcoord_attrib, 2, GL_FLOAT, GL_FALSE, 0, vertices);  // Same as texcoords.
+			check_error();
+		}
 
-		glTexCoord2f(0.0f, 1.0f);
-		glVertex2f(0.0f, 1.0f);
+		glDrawArrays(GL_QUADS, 0, 4);
+		check_error();
 
-		glEnd();
+		glUseProgram(0);
 		check_error();
+		glDisableVertexAttribArray(position_attrib);
+		check_error();
+		if (texcoord_attrib != -1) {
+			glDisableVertexAttribArray(texcoord_attrib);
+			check_error();
+		}
 
 		for (unsigned i = 0; i < phases[phase]->effects.size(); ++i) {
 			Node *node = phases[phase]->effects[i];
diff --git a/vs.vert b/vs.vert
index 1f48069..0ba2fdc 100644
--- a/vs.vert
+++ b/vs.vert
@@ -1,7 +1,15 @@
+attribute vec2 position;
+attribute vec2 texcoord;
 varying vec2 tc;
 
 void main()
 {
-	tc = gl_MultiTexCoord0.st;
-        gl_Position = ftransform();
+	// The result of glOrtho(0.0, 1.0, 0.0, 1.0, 0.0, 1.0) is:
+	//
+	//   2.000  0.000  0.000 -1.000
+	//   0.000  2.000  0.000 -1.000
+	//   0.000  0.000 -2.000 -1.000
+	//   0.000  0.000  0.000  1.000
+	gl_Position = vec4(2.0 * position.x - 1.0, 2.0 * position.y - 1.0, -1.0, 1.0);
+	tc = texcoord;
 }
-- 
2.39.2