Introduce VULKAN_HPP_NO_STRUCT_CONSTRUCTORS so support designated initializers.

You have to define VULKAN_HPP_NO_STRUCT_CONSTRUCTORS to remove all the struct constructors from vulkan.hpp, so that you can use designated initializers on them.
Of course, makes only sense with C++20.

tests/DesignatedInitializers/CMakeLists.txt

@@ -0,0 +1,39 @@
+# Copyright(c) 2020, NVIDIA CORPORATION. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+cmake_minimum_required(VERSION 3.2)
+
+if (NOT TESTS_BUILD_ONLY_DYNAMIC)
+	project(DesignatedInitializers)
+
+    set(CMAKE_CXX_STANDARD 20)
+
+	set(HEADERS
+	)
+
+	set(SOURCES
+	  DesignatedInitializers.cpp
+	)
+
+	source_group(headers FILES ${HEADERS})
+	source_group(sources FILES ${SOURCES})
+
+	add_executable(DesignatedInitializers
+	  ${HEADERS}
+	  ${SOURCES}
+	)
+
+	set_target_properties(DesignatedInitializers PROPERTIES FOLDER "Tests")
+	target_link_libraries(DesignatedInitializers "${Vulkan_LIBRARIES}")
+endif()

tests/DesignatedInitializers/DesignatedInitializers.cpp

@@ -0,0 +1,70 @@
+// Copyright(c) 2020, NVIDIA CORPORATION. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// VulkanHpp Tests : DesignatedInitializers
+//                   Compile test on using designated initializers
+
+#define VULKAN_HPP_NO_STRUCT_CONSTRUCTORS
+
+#include "vulkan/vulkan.hpp"
+
+#include <iostream>
+
+int main( int /*argc*/, char ** /*argv*/ )
+{
+  char const * appName       = "DesignatedInitializers";
+  uint32_t     appVersion    = 1;
+  char const * engineName    = "Vulkan.hpp";
+  uint32_t     engineVersion = 1;
+
+  // default initialization is available in any case
+  vk::ApplicationInfo ai0;
+
+#if !defined( VULKAN_HPP_NO_STRUCT_CONSTRUCTORS )
+  // due to default initializers, any number of members can be initialized
+  // most IDEs will probably help with the order of the members !
+  vk::ApplicationInfo ai1( appName );
+  vk::ApplicationInfo ai2( appName, appVersion );
+  vk::ApplicationInfo ai3( appName, appVersion, engineName );
+  vk::ApplicationInfo ai4( appName, appVersion, engineName, engineVersion );
+  vk::ApplicationInfo ai5( appName, appVersion, engineName, engineVersion, VK_API_VERSION_1_2 );
+
+  // a structure in namespace vk:: can be copied from the corresponding vulkan C-struct
+  VkApplicationInfo   vai;
+  vk::ApplicationInfo ai6( vai );
+
+#else
+
+  // aggregate initialization: need to explicitly specify sType and pNext, as well as all the other members !
+  vk::ApplicationInfo ai1{
+    vk::StructureType::eApplicationInfo, nullptr, appName, appVersion, engineName, engineVersion, VK_API_VERSION_1_2
+  };
+
+#  if ( 20 <= VULKAN_HPP_CPP_VERSION )
+  // designated initializers are available with C++20
+
+  // it's allowed, but not recommended to explicitly specify sType
+  vk::ApplicationInfo ai2 = { .sType = vk::StructureType::eApplicationInfo };
+
+  // any number of the members can be specified; the order has to be respected
+  vk::ApplicationInfo ai3 = { .pApplicationName = appName };
+  vk::ApplicationInfo ai4 = { .applicationVersion = 1, .engineVersion = 2 };
+
+  vk::ApplicationInfo ai5{ .pEngineName = engineName };
+  vk::ApplicationInfo ai6{ .pApplicationName = appName, .apiVersion = VK_API_VERSION_1_2 };
+#  endif
+#endif
+
+  return 0;
+}