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.

Re-land of https://skia-review.googlesource.com/c/8529/

BUG=skia:

Change-Id: I48ebd57d1ea0cfd3a1db10c475f2903afb821966
Reviewed-on: https://skia-review.googlesource.com/8960
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/gpu/GrTexturePriv.h b/src/gpu/GrTexturePriv.h
index 042061129d..cc0a05edfd 100644
--- a/src/gpu/GrTexturePriv.h
+++ b/src/gpu/GrTexturePriv.h
@@ -8,6 +8,7 @@
 #ifndef GrTexturePriv_DEFINED
 #define GrTexturePriv_DEFINED
 
+#include "GrExternalTextureData.h"
 #include "GrTexture.h"
 
 /** Class that adds methods to GrTexture that are only intended for use internal to Skia.
@@ -67,6 +68,15 @@ public:
     }
     SkDestinationSurfaceColorMode mipColorMode() const { return fTexture->fMipColorMode; }
 
+    /**
+     *  Return the native bookkeeping data for this texture, and detach the backend object from
+     *  this GrTexture. It's lifetime will no longer be managed by Ganesh, and this GrTexture will
+     *  no longer refer to it. Leaves this GrTexture in an orphan state.
+     */
+    std::unique_ptr<GrExternalTextureData> detachBackendTexture() {
+        return fTexture->detachBackendTexture();
+    }
+
     static void ComputeScratchKey(const GrSurfaceDesc&, GrScratchKey*);
 
 private: