[Feat] (MG_State/Program, DirectGLES): plumb ubo to backend

MobileGL/MG_State/GLState/ProgramState/ProgramObject.cpp

@@ -208,6 +208,9 @@ namespace MobileGL {
                     auto& ubo = m_program->getUniformBlock(i);
                     m_uniformBlockNameMaxLength = std::max(m_uniformBlockNameMaxLength, (Int)ubo.name.length());
                     m_uniformBlockIndexByName[ubo.name] = i;
+                    // if there's binding defined in shader as layout(binding = ...),
+                    // retrieve it here
+                    m_uniformBlockBinding[i] = ubo.getBinding();
                 }
             }
 

MobileGL/MG_State/GLState/ProgramState/ProgramObject.h

@@ -103,6 +103,10 @@ namespace MobileGL {
                     m_uniformBlockBinding[index] = binding;
                 }
 
+                Uint GetUniformBlockBinding(Uint index) const {
+                    return m_uniformBlockBinding[index];
+                }
+
                 Vector<Vector<unsigned>>& GetGeneratedSpirv() { return m_generatedSpirv; }
 
                 Uint GetExternalIndex() const { return m_externalIndex; }