Fix issue #34, provide null() references for structs

README.md

@@ -174,6 +174,10 @@ Here are a few code examples:
 
     // Accept std::vector as source for updateBuffer
     commandBuffer.updateBuffer(buffer, 0, {some values}); // update buffer with std::vector
+
+    // Sometimes it's necessary to pass a nullptr to a struct. For this case we've added T& null() to all structs T as replacement for nullptr.
+    device.allocateMemory(allocateInfo, vk::AllocationCallbacks::null());
+
   }
   catch (vk::Exception e)
   {

VkCppGenerator.cpp

@@ -2555,6 +2555,13 @@ void writeTypeStruct( std::ofstream & ofs, DependencyData const& dependencyData,
     }
   }
 
+  // null handle
+  ofs << "    static " << dependencyData.name << "& null()" << std::endl
+      << "    {" << std::endl
+      << "      return *((" << dependencyData.name << "*)(nullptr));" << std::endl
+      << "    }" << std::endl
+      << std::endl;
+
   // the cast-operator to the wrapped struct, and the struct itself as a private member variable
   ofs << "    operator const Vk" << dependencyData.name << "&() const" << std::endl
       << "    {" << std::endl