New uniform mapping handling

- add optional callback to handle mapping of uniform variables in linking phase
- if no resolver is provided, it uses the internal default resolver with all shifts and auto bind settings

Change-Id: Icfe38a9eabe8bfc8f8bb6d8150c06f7ed38bb762

glslang/Public/ShaderLang.h

@@ -445,7 +445,36 @@ private:
 class TReflection;
 class TIoMapper;
 
-// Make one TProgram per set of shaders that will get linked together.  Add all 
+// Allows to customize the binding layout after linking.
+// All used uniform variables will invoke at least validateBinding.
+// If validateBinding returned true then the other resolveBinding
+// and resolveSet are invoked to resolve the binding and descriptor
+// set index respectively.
+// Invocations happen in a particular order:
+// 1) var with binding and set already defined
+// 2) var with binding but no set defined
+// 3) var with set but no binding defined
+// 4) var with no binding and no set defined
+//
+// NOTE: that still limit checks are applied to bindings and sets
+// and may result in an error.
+class TIoMapResolver
+{
+public:
+  virtual ~TIoMapResolver() {}
+
+  // Should return true if the resulting/current binding would be ok.
+  // Basic idea is to do aliasing binding checks with this.
+  virtual bool validateBinding(EShLanguage stage, const char* name, const TType& type, bool is_live) = 0;
+  // Should return a value >= 0 if the current binding should be overridden.
+  // Return -1 if the current binding (including no binding) should be kept.
+  virtual int resolveBinding(EShLanguage stage, const char* name, const TType& type, bool is_live) = 0;
+  // Should return a value >= 0 if the current set should be overriden.
+  // Return -1 if the current set (including no set) should be kept.
+  virtual int resolveSet(EShLanguage stage, const char* name, const TType& type, bool is_live) = 0;
+};
+
+// Make one TProgram per set of shaders that will get linked together.  Add all
 // the shaders that are to be linked together.  After calling shader.parse()
 // for all shaders, call link().
 //
@@ -485,7 +514,9 @@ public:
     void dumpReflection();
 
     // I/O mapping: apply base offsets and map live unbound variables
-    bool mapIO();
+    // If resolver is not provided it uses the previous approach
+    // and respects auto assignment and offsets.
+    bool mapIO(TIoMapResolver* resolver = NULL);
 
 protected:
     bool linkStage(EShLanguage, EShMessages);