gpu_surface_gl_delegate.cc

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// Copyright 2013 The Flutter 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 "flutter/shell/gpu/gpu_surface_gl_delegate.h"
 
#include <cstring>
 
#include "third_party/skia/include/gpu/gl/GrGLAssembleInterface.h"
 
namespace flutter {
 
GPUSurfaceGLDelegate::~GPUSurfaceGLDelegate() = default;
 
bool GPUSurfaceGLDelegate::GLContextFBOResetAfterPresent() const {
  return false;
}
 
SurfaceFrame::FramebufferInfo GPUSurfaceGLDelegate::GLContextFramebufferInfo()
    const {
  SurfaceFrame::FramebufferInfo res;
  res.supports_readback = true;
  return res;
}
 
SkMatrix GPUSurfaceGLDelegate::GLContextSurfaceTransformation() const {
  SkMatrix matrix;
  matrix.setIdentity();
  return matrix;
}
 
GPUSurfaceGLDelegate::GLProcResolver GPUSurfaceGLDelegate::GetGLProcResolver()
    const {
  return nullptr;
}
 
static bool IsProcResolverOpenGLES(
    const GPUSurfaceGLDelegate::GLProcResolver& proc_resolver) {
  // Version string prefix that identifies an OpenGL ES implementation.
#define GPU_GL_VERSION 0x1F02
  constexpr char kGLESVersionPrefix[] = "OpenGL ES";
 
#ifdef WIN32
  using GLGetStringProc = const char*(__stdcall*)(uint32_t);
#else
  using GLGetStringProc = const char* (*)(uint32_t);
#endif
 
  GLGetStringProc gl_get_string =
      reinterpret_cast<GLGetStringProc>(proc_resolver("glGetString"));
 
  FML_CHECK(gl_get_string)
      << "The GL proc resolver could not resolve glGetString";
 
  const char* gl_version_string = gl_get_string(GPU_GL_VERSION);
 
  FML_CHECK(gl_version_string)
      << "The GL proc resolver's glGetString(GL_VERSION) failed";
 
  return strncmp(gl_version_string, kGLESVersionPrefix,
                 strlen(kGLESVersionPrefix)) == 0;
}
 
static sk_sp<const GrGLInterface> CreateGLInterface(
    const GPUSurfaceGLDelegate::GLProcResolver& proc_resolver) {
  if (proc_resolver == nullptr) {
    // If there is no custom proc resolver, ask Skia to guess the native
    // interface. This often leads to interesting results on most platforms.
    return GrGLMakeNativeInterface();
  }
 
  struct ProcResolverContext {
    GPUSurfaceGLDelegate::GLProcResolver resolver;
  };
 
  ProcResolverContext context = {proc_resolver};
 
  GrGLGetProc gl_get_proc = [](void* context,
                               const char gl_proc_name[]) -> GrGLFuncPtr {
    auto proc_resolver_context =
        reinterpret_cast<ProcResolverContext*>(context);
    return reinterpret_cast<GrGLFuncPtr>(
        proc_resolver_context->resolver(gl_proc_name));
  };
 
  // glGetString indicates an OpenGL ES interface.
  if (IsProcResolverOpenGLES(proc_resolver)) {
    return GrGLMakeAssembledGLESInterface(&context, gl_get_proc);
  }
 
  // Fallback to OpenGL.
  if (auto interface = GrGLMakeAssembledGLInterface(&context, gl_get_proc)) {
    return interface;
  }
 
  FML_LOG(ERROR) << "Could not create a valid GL interface.";
  return nullptr;
}
 
sk_sp<const GrGLInterface> GPUSurfaceGLDelegate::GetGLInterface() const {
  return CreateGLInterface(GetGLProcResolver());
}
 
sk_sp<const GrGLInterface>
GPUSurfaceGLDelegate::GetDefaultPlatformGLInterface() {
  return CreateGLInterface(nullptr);
}
 
bool GPUSurfaceGLDelegate::AllowsDrawingWhenGpuDisabled() const {
  return true;
}
 
}  // namespace flutter