Make cross-process CALayers work on Mac

content/common/gpu/surface_handle_types_mac.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "content/common/gpu/surface_handle_types_mac.h"
+
+#include "base/logging.h"
+
+namespace content {
+namespace {
+
+// The type of the handle is stored in the upper 64 bits.
+const uint64 kTypeMask = 0xFFFFFFFFull << 32;
+
+const uint64 kTypeIOSurface = 0x01010101ull << 32;
+const uint64 kTypeCAContext = 0x02020202ull << 32;
+
+// To make it a bit less likely that we'll just cast off the top bits of the
+// handle to get the ID, XOR lower bits with a type-specific mask.
+const uint32 kXORMaskIOSurface = 0x01010101;
+const uint32 kXORMaskCAContext = 0x02020202;
+
+}  // namespace
+
+SurfaceHandleType GetSurfaceHandleType(uint64 surface_handle) {
+  switch(surface_handle & kTypeMask) {
+    case kTypeIOSurface:
+      return kSurfaceHandleTypeIOSurface;
+    case kTypeCAContext:
+      return kSurfaceHandleTypeCAContext;
+  }
+  return kSurfaceHandleTypeInvalid;
+}
+
+IOSurfaceID IOSurfaceIDFromSurfaceHandle(uint64 surface_handle) {
+  DCHECK_EQ(kSurfaceHandleTypeIOSurface, GetSurfaceHandleType(surface_handle));
+  return static_cast<uint32>(surface_handle) ^ kXORMaskIOSurface;
+}
+
+CAContextID CAContextIDFromSurfaceHandle(uint64 surface_handle) {
+  DCHECK_EQ(kSurfaceHandleTypeCAContext, GetSurfaceHandleType(surface_handle));
+  return static_cast<uint32>(surface_handle) ^ kXORMaskCAContext;
+}
+
+uint64 SurfaceHandleFromIOSurfaceID(IOSurfaceID io_surface_id) {
+  return kTypeIOSurface | (io_surface_id ^ kXORMaskIOSurface);
+}
+
+uint64 SurfaceHandleFromCAContextID(CAContextID ca_context_id) {

[piman, 2014/06/19 21:51:02]

How about making a struct { type, id } instead of a uint64? Seems a little
cleaner than this xor magic...

[ccameron, 2014/06/19 23:56:41]

The thing that bugs we is that both id types are typedefs of uint32s, so we have
no safety between them -- I wanted the XOR so that people would be punished for
just reading the id field without checking the type (either via a cast or by
accessing as a member of a struct).

+  return kTypeCAContext | (ca_context_id ^ kXORMaskCAContext);
+}
+
+}  //  namespace content