Experiment : ShaderNetwork : Allow escaped string substitutions to work correctly

Author: danieldresser-ie

src/IECoreScene/ShaderNetwork.cpp

@@ -447,6 +447,16 @@ class ShaderNetwork::Implementation
 					h.append( 0 );
 				}
 			}
+
+			if( m_parmsNeedingSubstitution.size() && !m_neededSubstitutions.size() )
+			{
+				// If we don't rely on any attributes, but do require substitutions ( for example,
+				// because some parameters have escaped substitutions, and need the escape characters
+				// removed ), then our hash won't vary with the attributes, but we do still need to
+				// do something to the hash, so that Gaffer won't skip running substitutions on this
+				// shader.
+				h.append( true );
+			}
 		}
 
 		void applySubstitutions( const CompoundObject *attributes )