Add GrExternalTextureData and SkCrossContextImageData

GrExternalTextureData is an API for exporting the backend-specific
information about a texture in a type-safe way, and without pointing
into the GrTexture. The new detachBackendTexture API lets us release
ownership of a texture to the client.

SkCrossContextImageData is the public API that lets clients upload
textures on one thread/GrContext, then safely transfer ownership to
another thread and GrContext for rendering.

Only GL is implemented/supported right now. Vulkan support requires
that we add thread-safe memory pools, or otherwise transfer the
actual memory block containing the texture to the new context.

BUG=skia:

Change-Id: I784a3a74be69807df038c7d192eaed002c7e45ca
Reviewed-on: https://skia-review.googlesource.com/8529
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/include/gpu/GrExternalTextureData.h b/include/gpu/GrExternalTextureData.h
new file mode 100644
index 0000000000..9ab819ce70
--- /dev/null
+++ b/include/gpu/GrExternalTextureData.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#ifndef GrExternalTextureData_DEFINED
+#define GrExternalTextureData_DEFINED
+
+#include "GrTypes.h"
+#include "GrTypesPriv.h"
+
+class SK_API GrExternalTextureData : SkNoncopyable {
+public:
+    GrExternalTextureData(GrFence fence) : fFence(fence) {}
+    virtual ~GrExternalTextureData() {}
+    virtual GrBackend getBackend() const = 0;
+    GrFence getFence() const { return fFence; }
+
+protected:
+    virtual GrBackendObject getBackendObject() const = 0;
+
+    GrFence fFence;
+
+    friend class SkCrossContextImageData;
+};
+
+#endif