Support gpu buffer texture

shell/platform/common/client_wrapper/core_implementations.cc

@@ -169,6 +169,26 @@ int64_t TextureRegistrarImpl::RegisterTexture(TextureVariant* texture) {
       return buffer;
     };
 
+    int64_t texture_id = FlutterDesktopTextureRegistrarRegisterExternalTexture(
+        texture_registrar_ref_, &info);
+    return texture_id;
+  } else if (auto gpu_buffer_texture = std::get_if<GpuBufferTexture>(texture)) {
+    FlutterDesktopTextureInfo info = {};
+    info.type = kFlutterDesktopGpuBufferTexture;
+    info.gpu_buffer_config.user_data = gpu_buffer_texture;
+    info.gpu_buffer_config.callback =
+        [](size_t width, size_t height,
+           void* user_data) -> const FlutterDesktopGpuBuffer* {
+      auto texture = static_cast<GpuBufferTexture*>(user_data);
+      auto buffer = texture->ObtainGpuBuffer(width, height);
+      return buffer;
+    };
+
+    info.gpu_buffer_config.destruction_callback = [](void* user_data) -> void {
+      auto texture = static_cast<GpuBufferTexture*>(user_data);
+      texture->Destruct();
+    };
+
     int64_t texture_id = FlutterDesktopTextureRegistrarRegisterExternalTexture(
         texture_registrar_ref_, &info);
     return texture_id;

shell/platform/common/client_wrapper/include/flutter/texture_registrar.h

@@ -42,10 +42,50 @@ class PixelBufferTexture {
   const CopyBufferCallback copy_buffer_callback_;
 };
 
+// A gpu buffer texture.
+class GpuBufferTexture {
+ public:
+  // A callback used for retrieving gpu buffers.
+  typedef std::function<const FlutterDesktopGpuBuffer*(size_t width,
+                                                       size_t height)>
+      ObtainGpuBufferCallback;
+
+  typedef std::function<void(void* buffer)> DestructGpuBufferCallback;
+
+  // Creates a gpu buffer texture that uses the provided |obtain_buffer_cb| to
+  // retrieve the buffer.
+  // As the callback is usually invoked from the render thread, the callee must
+  // take care of proper synchronization. It also needs to be ensured that the
+  // returned buffer isn't released prior to unregistering this texture.
+  GpuBufferTexture(ObtainGpuBufferCallback obtain_buffer_callback,
+                   DestructGpuBufferCallback destruction_callback)
+      : obtain_gpu_buffer_callback_(obtain_buffer_callback),
+        destruct_gpu_buffer_callback_(destruction_callback),
+        buffer_(nullptr) {}
+
+  // Returns the callback-provided FlutterDesktopGpuBuffer that contains the
+  // actual gpu buffer pointer. The intended surface size is specified by
+  // |width| and |height|.
+  const FlutterDesktopGpuBuffer* ObtainGpuBuffer(size_t width, size_t height) {
+    const FlutterDesktopGpuBuffer* flutter_buffer =
+        obtain_gpu_buffer_callback_(width, height);
+    if (flutter_buffer) {
+      buffer_ = const_cast<void*>(flutter_buffer->buffer);
+    }
+    return flutter_buffer;
+  }
+
+  void Destruct() { destruct_gpu_buffer_callback_(buffer_); }
+
+ private:
+  const ObtainGpuBufferCallback obtain_gpu_buffer_callback_;
+  const DestructGpuBufferCallback destruct_gpu_buffer_callback_;
+  void* buffer_;
+};
+
 // The available texture variants.
-// Only PixelBufferTexture is currently implemented.
-// Other variants are expected to be added in the future.
-typedef std::variant<PixelBufferTexture> TextureVariant;
+// Only PixelBufferTexture and GpuBufferTexture are currently implemented.
+typedef std::variant<PixelBufferTexture, GpuBufferTexture> TextureVariant;
 
 // An object keeping track of external textures.
 //

shell/platform/common/public/flutter_texture_registrar.h

@@ -23,7 +23,9 @@ typedef struct FlutterDesktopTextureRegistrar*
 // Additional types may be added in the future.
 typedef enum {
   // A Pixel buffer-based texture.
-  kFlutterDesktopPixelBufferTexture
+  kFlutterDesktopPixelBufferTexture,
+  // A Gpu buffer-based texture.
+  kFlutterDesktopGpuBufferTexture
 } FlutterDesktopTextureType;
 
 // An image buffer object.
@@ -36,6 +38,16 @@ typedef struct {
   size_t height;
 } FlutterDesktopPixelBuffer;
 
+// An image buffer object.
+typedef struct {
+  // The gpu data buffer.
+  const void* buffer;
+  // Width of the gpu buffer.
+  size_t width;
+  // Height of the gpu buffer.
+  size_t height;
+} FlutterDesktopGpuBuffer;
+
 // The pixel buffer copy callback definition provided to
 // the Flutter engine to copy the texture.
 // It is invoked with the intended surface size specified by |width| and
@@ -50,6 +62,13 @@ typedef const FlutterDesktopPixelBuffer* (
                                                size_t height,
                                                void* user_data);
 
+typedef const FlutterDesktopGpuBuffer* (
+    *FlutterDesktopGpuBufferTextureCallback)(size_t width,
+                                             size_t height,
+                                             void* user_data);
+
+typedef void (*FlutterDesktopGpuBufferDestructionCallback)(void* user_data);
+
 // An object used to configure pixel buffer textures.
 typedef struct {
   // The callback used by the engine to copy the pixel buffer object.
@@ -58,10 +77,21 @@ typedef struct {
   void* user_data;
 } FlutterDesktopPixelBufferTextureConfig;
 
+// An object used to configure GPU buffer textures.
+typedef struct {
+  // The callback used by the engine to obtain the GPU buffer object.
+  FlutterDesktopGpuBufferTextureCallback callback;
+  // The callback used by the engine to destruct the GPU buffer object.
+  FlutterDesktopGpuBufferDestructionCallback destruction_callback;
+  // Opaque data that will get passed to the provided |callback|.
+  void* user_data;
+} FlutterDesktopGPUBufferTextureConfig;
+
 typedef struct {
   FlutterDesktopTextureType type;
   union {
     FlutterDesktopPixelBufferTextureConfig pixel_buffer_config;
+    FlutterDesktopGPUBufferTextureConfig gpu_buffer_config;
   };
 } FlutterDesktopTextureInfo;