Enable Vulkan extensions for Linux, Windows, Android and Fuchsia.

This CL ensures that when <vulkan/vulkan.h> is included, the
appropriate VK_USE_PLATFORM_XXX macro is defined to enable the
declaration of platform-specific types and extensions.

Note that for Linux, this requires an xlib_with_undefs.h header
to remove annoying macros that are defined by <X11/X.h> (i.e.
Success, Always, None) and which prevent compilation of other
Dawn sources that use the same symbols as enum value names.

Change-Id: I0c8d95fe8043d75ba3f74789e0fe2e3e4a477703
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/8961
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Austin Eng <enga@chromium.org>
Commit-Queue: David Turner <digit@google.com>

src/common/Platform.h

@@ -23,6 +23,9 @@
 #elif defined(__APPLE__)
 #    define DAWN_PLATFORM_APPLE 1
 #    define DAWN_PLATFORM_POSIX 1
+#elif defined(__Fuchsia__)
+#    define DAWN_PLATFORM_FUCHSIA 1
+#    define DAWN_PLATFORM_POSIX 1
 #else
 #    error "Unsupported platform."
 #endif

src/common/vulkan_platform.h

@@ -145,6 +145,20 @@ class alignas(kNativeVkHandleAlignment) VkNonDispatchableHandle {
     static_assert(sizeof(object) == sizeof(object##Native), "");           \
     static_assert(alignof(object) == kNativeVkHandleAlignment, "");
 
+// Ensure platform-specific extensions are declared appropriately.
+#if defined(DAWN_PLATFORM_LINUX)
+#    define VK_USE_PLATFORM_XLIB_KHR
+#    define VK_USE_PLATFORM_XCB_KHR
+// NOTE: For now the line below is undefined to take care of systems that don't
+//       have the Wayland headers installed on the system.
+// #    define VK_USE_PLATFORM_WAYLAND_KHR
+#elif defined(DAWN_PLATFORM_WINDOWS)
+#    define VK_USE_PLATFORM_WIN32_KHR
+#elif defined(DAWN_PLATFORM_ANDROID)
+#    define VK_USE_PLATFORM_ANDROID_KHR
+#elif defined(DAWN_PLATFORM_FUCHSIA)
+#    define VK_USE_PLATFORM_FUCHSIA
+#endif
 #    include <vulkan/vulkan.h>
 
     // VK_NULL_HANDLE is defined to 0 but we don't want our handle type to compare to arbitrary
@@ -156,5 +170,9 @@ class alignas(kNativeVkHandleAlignment) VkNonDispatchableHandle {
 #if defined(DAWN_PLATFORM_WINDOWS)
 #    include "common/windows_with_undefs.h"
 #endif
+// Remove X11/Xlib.h macros after vulkan_platform's include of it.
+#if defined(DAWN_PLATFORM_LINUX)
+#    include "common/xlib_with_undefs.h"
+#endif
 
 #endif  // COMMON_VULKANPLATFORM_H_

src/common/xlib_with_undefs.h

@@ -0,0 +1,33 @@
+// Copyright 2019 The Dawn Authors
+//
+// 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.
+
+#ifndef COMMON_XLIB_WITH_UNDEFS_H_
+#define COMMON_XLIB_WITH_UNDEFS_H_
+
+#include "common/Platform.h"
+
+#if !defined(DAWN_PLATFORM_LINUX)
+#    error "xlib_with_undefs.h included on non-Linux"
+#endif
+
+// This header includes <X11/Xlib.h> but removes all the extra defines that conflict with
+// identifiers in internal code. It should never be included in something that is part of the public
+// interface.
+#include <X11/Xlib.h>
+
+#undef Success
+#undef None
+#undef Always
+
+#endif  // COMMON_XLIB_WITH_UNDEFS_H_