From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 15 May 2014 21:59:26 +0000 (+0300)
Subject: Generalize shader interface handling
X-Git-Url: http://git.tdb.fi/?a=commitdiff_plain;h=d542522823423f9ed2a5d412de9250ee8367334b;p=libs%2Fgl.git

Generalize shader interface handling
---

diff --git a/source/programbuilder.cpp b/source/programbuilder.cpp
index 28acc5d9..67aaf570 100644
--- a/source/programbuilder.cpp
+++ b/source/programbuilder.cpp
@@ -124,6 +124,8 @@ const ProgramBuilder::VariableDefinition ProgramBuilder::standard_variables[] =
 	{ NO_SCOPE, 0, 0, 0, 0 }
 };
 
+const char ProgramBuilder::interfaces[] = { 0, 0, 0, 'v', 0 };
+
 ProgramBuilder::ProgramBuilder(const StandardFeatures &f):
 	features(f),
 	feature_flags(features.create_flags()),
@@ -327,54 +329,43 @@ string ProgramBuilder::create_source(const list<ShaderVariable *> &variables, Va
 		if((*i)->variable->scope==UNIFORM && (*i)->is_referenced_from(scope) && !(*i)->inlined)
 			source += format("uniform %s;\n", (*i)->create_declaration());
 
-	if(scope==VERTEX)
+	/* Interface variables need to have global declarations. */
+	for(list<ShaderVariable *>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
 	{
-		const char *qualifier = (features.legacy ? "attribute" : "in");
-		for(list<ShaderVariable *>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
-			if((*i)->variable->scope==ATTRIBUTE && !(*i)->inlined)
-				source += format("%s %s;\n", qualifier, (*i)->create_declaration());
-	}
+		if(!(*i)->resolved_name.compare(0, 3, "gl_"))
+			continue;
 
-	/* Any variables defined in vertex scope but referenced from fragment scope
-	should be exported as varyings over the interface. */
-	list<ShaderVariable *> varyings;
-	for(list<ShaderVariable *>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
-		if(((*i)->variable->scope==VERTEX || (*i)->variable->scope==ATTRIBUTE) && (*i)->is_referenced_from(FRAGMENT))
+		InterfaceFlags interface = (*i)->get_interface_flags(scope);
+
+		if(interface&INPUT)
 		{
-			varyings.push_back(*i);
-			const char *qualifier;
-			if(!features.legacy)
-				qualifier = (scope==VERTEX ? "out" : "in");
-			else
-				qualifier = "varying";
-			source += format("%s %s;\n", qualifier, (*i)->create_declaration('v'));
+			const char *qualifier = (features.legacy ? scope==VERTEX ? "attribute" : "varying" : "in");
+			source += format("%s %s;\n", qualifier, (*i)->create_declaration(interfaces[scope-1]));
 		}
 
-	for(list<ShaderVariable *>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
-		if((*i)->referenced_by.empty() && (*i)->resolved_name.compare(0, 3, "gl_"))
-			source += format("out %s;\n", (*i)->create_declaration());
+		if(interface&OUTPUT)
+		{
+			const char *qualifier = (features.legacy ? "varying" : "out");
+			source += format("%s %s;\n", qualifier, (*i)->create_declaration(interfaces[scope]));
+		}
+	}
 
 	source += "void main()\n{\n";
 
 	for(list<ShaderVariable *>::const_iterator i=variables.begin(); i!=variables.end(); ++i)
+	{
+		InterfaceFlags interface = (*i)->get_interface_flags(scope);
+
 		if((*i)->variable->scope==scope && !(*i)->inlined)
 		{
-			source += '\t';
-			if((*i)->referenced_by.empty())
-				source += (*i)->resolved_name;
-			else
-				source += (*i)->create_declaration();
-			source += format(" = %s;\n", (*i)->create_expression());
+			string decl = ((interface&GOAL) ? (*i)->resolved_name : (*i)->create_declaration());
+			source += format("\t%s = %s;\n", decl, (*i)->create_expression());
 		}
 
-	if(scope==VERTEX)
-	{
-		for(list<ShaderVariable *>::const_iterator i=varyings.begin(); i!=varyings.end(); ++i)
+		if((interface&(OUTPUT|GOAL))==OUTPUT)
 		{
-			if((*i)->inlined)
-				source += format("\tv_%s = %s;\n", (*i)->resolved_name, (*i)->create_expression());
-			else
-				source += format("\tv_%s = %s;\n", (*i)->resolved_name, (*i)->resolved_name);
+			string expr = ((*i)->inlined ? (*i)->create_expression() : (*i)->resolved_name);
+			source += format("\t%c_%s = %s;\n", interfaces[scope], (*i)->resolved_name, expr);
 		}
 	}
 
@@ -672,6 +663,33 @@ bool ProgramBuilder::ShaderVariable::is_referenced_from(VariableScope scope) con
 	return false;
 }
 
+ProgramBuilder::InterfaceFlags ProgramBuilder::ShaderVariable::get_interface_flags(VariableScope scope) const
+{
+	/* Uniforms are available to all stages and are not passed through
+	interfaces */
+	if(variable->scope==UNIFORM)
+		return NO_INTERFACE;
+
+	int flags = NO_INTERFACE;
+
+	for(list<ShaderVariable *>::const_iterator i=referenced_by.begin(); i!=referenced_by.end(); ++i)
+	{
+		/* Variables used in a later scope than they are declared in need to go
+		through the interface */
+		if((*i)->variable->scope>scope && variable->scope<=scope)
+			flags |= OUTPUT;
+		if((*i)->variable->scope>=scope && variable->scope<scope)
+			if(!inlined || variable->scope!=ATTRIBUTE || scope!=VERTEX)
+				flags |= INPUT;
+	}
+
+	// Variables without any references are goals and also outputs.
+	if(referenced_by.empty() && variable->scope==scope)
+		flags |= OUTPUT|GOAL;
+
+	return static_cast<InterfaceFlags>(flags);
+}
+
 string ProgramBuilder::ShaderVariable::create_declaration(char interface) const
 {
 	if(variable->scope==UNIFORM)
@@ -692,8 +710,9 @@ string ProgramBuilder::ShaderVariable::create_replacement(VariableScope from_sco
 	string replacement = resolved_name;
 	if(variable)
 	{
-		if(from_scope==FRAGMENT && (variable->scope==VERTEX || variable->scope==ATTRIBUTE))
-			replacement = "v_"+replacement;
+		InterfaceFlags interface = get_interface_flags(from_scope);
+		if((interface&INPUT) && interfaces[from_scope-1])
+			replacement = format("%c_%s", interfaces[from_scope-1], replacement);
 		else if(inlined)
 		{
 			replacement = create_expression();
diff --git a/source/programbuilder.h b/source/programbuilder.h
index 821907d5..69170e02 100644
--- a/source/programbuilder.h
+++ b/source/programbuilder.h
@@ -54,6 +54,15 @@ private:
 		FRAGMENT
 	};
 
+	enum InterfaceFlags
+	{
+		NO_INTERFACE = 0,
+		INPUT = 1,
+		OUTPUT = 2,
+		PASSTHROUGH = INPUT|OUTPUT,
+		GOAL = 4
+	};
+
 	struct VariableDefinition
 	{
 		VariableScope scope;
@@ -84,6 +93,7 @@ private:
 		void update_reference(ShaderVariable &, ShaderVariable &);
 		void check_inline(bool, bool);
 		bool is_referenced_from(VariableScope) const;
+		InterfaceFlags get_interface_flags(VariableScope) const;
 		std::string create_declaration(char = 0) const;
 		std::string create_replacement(VariableScope) const;
 		std::string create_expression() const;
@@ -102,6 +112,7 @@ private:
 	bool optimize;
 
 	static const VariableDefinition standard_variables[];
+	static const char interfaces[];
 
 public:
 	ProgramBuilder(const StandardFeatures &);