From 48e37a09b49cd4148db390170cfd07eef92c9d02 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 19 Nov 2016 18:24:18 +0200
Subject: [PATCH] Use layout declarations to set attribute and fragment data
 locations

A fallback to glBind*Location functions is provided in case the
implementation does not support GLSL 3.30.
---
 shaderlib/singlepass.glsl  | 14 +++++------
 source/programcompiler.cpp | 50 +++++++++++++++++++++++++++++---------
 source/programsyntax.h     |  1 +
 3 files changed, 46 insertions(+), 19 deletions(-)

diff --git a/shaderlib/singlepass.glsl b/shaderlib/singlepass.glsl
index f8940f7d..67e04e6d 100644
--- a/shaderlib/singlepass.glsl
+++ b/shaderlib/singlepass.glsl
@@ -78,12 +78,12 @@ uniform Clipping
 };
 
 ////// vertex
-in vec4 vertex;
-in vec4 texcoord;
-in vec4 color;
-in vec3 normal;
-in vec3 tangent;
-in vec3 binormal;
+layout(location=0) in vec4 vertex;
+layout(location=8) in vec4 texcoord;
+layout(location=3) in vec4 color;
+layout(location=2) in vec3 normal;
+layout(location=4) in vec3 tangent;
+layout(location=5) in vec3 binormal;
 
 vec4 get_vertex_position()
 {
@@ -129,7 +129,7 @@ void main()
 }
 
 ////// fragment
-out vec4 frag_color;
+layout(location=0) out vec4 frag_color;
 
 vec4 get_diffuse_sample()
 {
diff --git a/source/programcompiler.cpp b/source/programcompiler.cpp
index ece48cf0..fd756de0 100644
--- a/source/programcompiler.cpp
+++ b/source/programcompiler.cpp
@@ -61,17 +61,20 @@ void ProgramCompiler::add_shaders(Program &program)
 	for(list<Stage>::iterator i=module->stages.begin(); i!=module->stages.end(); ++i)
 	{
 		if(i->type==VERTEX)
+		{
 			program.attach_shader_owned(new VertexShader(apply<Formatter>(*i)));
+			for(map<string, unsigned>::iterator j=i->locations.begin(); j!=i->locations.end(); ++j)
+				program.bind_attribute(j->second, j->first);
+		}
 		else if(i->type==GEOMETRY)
 			program.attach_shader_owned(new GeometryShader(apply<Formatter>(*i)));
 		else if(i->type==FRAGMENT)
+		{
 			program.attach_shader_owned(new FragmentShader(apply<Formatter>(*i)));
+			for(map<string, unsigned>::iterator j=i->locations.begin(); j!=i->locations.end(); ++j)
+				program.bind_fragment_data(j->second, j->first);
+		}
 	}
-
-	program.bind_attribute(VERTEX4, "vertex");
-	program.bind_attribute(NORMAL3, "normal");
-	program.bind_attribute(COLOR4_FLOAT, "color");
-	program.bind_attribute(TEXCOORD4, "texcoord");
 }
 
 Module *ProgramCompiler::create_builtins_module()
@@ -1294,6 +1297,7 @@ void ProgramCompiler::NodeRemover::visit(VariableDeclaration &var)
 	{
 		stage->in_variables.erase(var.name);
 		stage->out_variables.erase(var.name);
+		stage->locations.erase(var.name);
 		if(var.linked_declaration)
 			var.linked_declaration->linked_declaration = 0;
 	}
@@ -1363,19 +1367,41 @@ void ProgramCompiler::LegacyConverter::visit(FunctionCall &call)
 
 void ProgramCompiler::LegacyConverter::visit(VariableDeclaration &var)
 {
-	if(var.interface=="in" || var.interface=="out")
-		if(!check_version(Version(1, 30)))
+	if(var.layout && !check_version(Version(3, 30)))
+	{
+		vector<Layout::Qualifier>::iterator i;
+		for(i=var.layout->qualifiers.begin(); (i!=var.layout->qualifiers.end() && i->identifier!="location"); ++i) ;
+		if(i!=var.layout->qualifiers.end())
 		{
+			unsigned location = lexical_cast<unsigned>(i->value);
 			if(stage->type==VERTEX && var.interface=="in")
-				var.interface = "attribute";
-			else if((stage->type==VERTEX && var.interface=="out") || (stage->type==FRAGMENT && var.interface=="in"))
-				var.interface = "varying";
+			{
+				stage->locations[var.name] = location;
+				var.layout->qualifiers.erase(i);
+			}
 			else if(stage->type==FRAGMENT && var.interface=="out")
 			{
-				frag_out_name = var.name;
-				remove_node = true;
+				stage->locations[var.name] = location;
+				var.layout->qualifiers.erase(i);
 			}
+
+			if(var.layout->qualifiers.empty())
+				var.layout = 0;
+		}
+	}
+
+	if((var.interface=="in" || var.interface=="out") && !check_version(Version(1, 30)))
+	{
+		if(stage->type==VERTEX && var.interface=="in")
+			var.interface = "attribute";
+		else if((stage->type==VERTEX && var.interface=="out") || (stage->type==FRAGMENT && var.interface=="in"))
+			var.interface = "varying";
+		else if(stage->type==FRAGMENT && var.interface=="out")
+		{
+			frag_out_name = var.name;
+			remove_node = true;
 		}
+	}
 
 	TraversingVisitor::visit(var);
 }
diff --git a/source/programsyntax.h b/source/programsyntax.h
index 796c4b93..c502ba47 100644
--- a/source/programsyntax.h
+++ b/source/programsyntax.h
@@ -355,6 +355,7 @@ struct Stage
 	ProgramSyntax::Block content;
 	std::map<std::string, VariableDeclaration *> in_variables;
 	std::map<std::string, VariableDeclaration *> out_variables;
+	std::map<std::string, unsigned> locations;
 	Version required_version;
 
 	Stage(StageType);
-- 
2.43.0