// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_GL_GL_CONTEXT_H_
#define UI_GL_GL_CONTEXT_H_

#include <map>
#include <memory>
#include <string>

#include "base/atomicops.h"
#include "base/cancelable_callback.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/ref_counted.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "base/synchronization/atomic_flag.h"
#include "build/build_config.h"
#include "ui/gfx/extension_set.h"
#include "ui/gl/gl_export.h"
#include "ui/gl/gl_implementation_wrapper.h"
#include "ui/gl/gl_share_group.h"
#include "ui/gl/gl_state_restorer.h"
#include "ui/gl/gpu_preference.h"

namespace gl {
class GLContextEGL;
class GLDisplayEGL;
}  // namespace gl

namespace gpu {
class GLContextVirtual;

#if BUILDFLAG(IS_APPLE)
class GL_EXPORT BackpressureMetalSharedEvent {
 public:
  virtual ~BackpressureMetalSharedEvent() = default;
  virtual bool HasCompleted() const = 0;
};
#endif  // #if BUILDFLAG(IS_APPLE)

}  // namespace gpu

namespace gl {

struct CurrentGL;
class LogGLApi;
struct DriverGL;
class GLApi;
class GLFence;
class GLSurface;
class GPUTiming;
class GPUTimingClient;
struct GLVersionInfo;
class RealGLApi;
class TraceGLApi;

// Where available, choose a GL context priority for devices that support it.
// Currently this requires the EGL_IMG_context_priority extension that is
// present on Daydream ready Android devices. Default is Medium, and the
// attribute is ignored if the extension is missing.
//
// "High" priority must only be used for special cases with strong realtime
// requirements, it is incompatible with other critical system GL work such as
// the GVR library's asynchronous reprojection for VR viewing. Please avoid
// using it for any GL contexts that may be used during VR presentation,
// see crbug.com/727800.
//
// Instead, consider using "Low" priority for possibly-slow GL work such as
// user WebGL content.
enum ContextPriority {
  ContextPriorityLow,
  ContextPriorityMedium,
  ContextPriorityHigh
};

// Angle allows selecting context virtualization group at context creation time.
// This enum is used to specify the group number to use for a given context.
// Currently all contexts which do not specify any group number are part of
// default angle context virtualization group. The below use cases in Chrome use
// become part of different virtualization groups via this enum.
enum class AngleContextVirtualizationGroup {
  kDefault = -1,
  kDrDc = 1,
  kGLImageProcessor = 2,
  kWebViewRenderThread = 3
};

struct GL_EXPORT GLContextAttribs {
  GLContextAttribs();
  GLContextAttribs(const GLContextAttribs& other);
  GLContextAttribs(GLContextAttribs&& other);
  ~GLContextAttribs();

  GLContextAttribs& operator=(const GLContextAttribs& other);
  GLContextAttribs& operator=(GLContextAttribs&& other);

  GpuPreference gpu_preference = GpuPreference::kLowPower;
  bool bind_generates_resource = true;
  bool webgl_compatibility_context = false;
  bool global_texture_share_group = false;
  bool global_semaphore_share_group = false;
  bool robust_resource_initialization = false;
  bool robust_buffer_access = false;
  int client_major_es_version = 3;
  int client_minor_es_version = 0;
  bool can_skip_validation = false;

  // Use EXT_ANGLE_create_context_passthrough_shaders if it is available to tell
  // ANGLE to not translate shaders and pass them unaltered to the driver.
  bool passthrough_shaders = false;

  // If true, and if supported (for EGL, this requires the robustness
  // extension), set the reset notification strategy to lose context on reset.
  // This setting can be changed independently of robust_buffer_access.
  // (True by default to match previous behavior.)
  bool lose_context_on_reset = true;

  // If true, EGL_ANGLE_external_context_and_surface extension will be used to
  // create ANGLE context from the current native EGL context.
  bool angle_create_from_external_context = false;

  // Allow the usage of client arrays in the created context
  bool allow_client_arrays = true;

  AngleContextVirtualizationGroup angle_context_virtualization_group_number =
      AngleContextVirtualizationGroup::kDefault;

  ContextPriority context_priority = ContextPriorityMedium;
};

// Encapsulates an OpenGL context, hiding platform specific management.
// TODO(344606399): Consider folding GLContextEGL into this class.
class GL_EXPORT GLContext : public base::RefCounted<GLContext> {
 public:
  class GL_EXPORT GLContextObserver : public base::CheckedObserver {
   public:
    // Called for any observer when the context is marked lost.
    virtual void OnGLContextLost(GLContext* context) = 0;

    // Called for any observer when the context is about to be destroyed.
    virtual void OnGLContextWillDestroy(GLContext* context) = 0;

   protected:
    ~GLContextObserver() override = default;
  };

  explicit GLContext(GLShareGroup* share_group);

  GLContext(const GLContext&) = delete;
  GLContext& operator=(const GLContext&) = delete;

  static int32_t TotalGLContexts();

  static bool SwitchableGPUsSupported();
  // This should be called at most once at GPU process startup time.
  // By default, GPU switching is not supported unless this is called.
  static void SetSwitchableGPUsSupported();

  // Initializes the GL context to be compatible with the given surface. The GL
  // context can be made with other surface's of the same type. The compatible
  // surface is only needed for certain platforms. It should be
  // specific for all platforms though. If the compatible surface is an
  // offscreen one, it is stored by the context and can be accessed via
  // |default_surface|.
  // TODO(344606399): Consider removing the compatible_surface if it is not
  // needed for EGL.
  bool Initialize(GLSurface* compatible_surface,
                  const GLContextAttribs& attribs);

  // Makes the GL context and a surface current on the current thread.
  bool MakeCurrent(GLSurface* surface);
  // Same as above, but uses the stored offscreen surface (named as default).
  bool MakeCurrentDefault();

  // Returns a weak ptr. This ptr is invalidate in the `OnContextDestroyed`
  // call.
  base::WeakPtr<GLContext> AsWeakPtr();

  // Releases this GL context and surface as current on the current thread.
  virtual void ReleaseCurrent(GLSurface* surface) = 0;

  // Returns true if this context and surface is current. Pass a null surface
  // if the current surface is not important.
  virtual bool IsCurrent(GLSurface* surface) = 0;

  // Get the underlying platform specific GL context "handle".
  virtual void* GetHandle() = 0;

  // Creates a GPUTimingClient class which abstracts various GPU Timing exts.
  virtual scoped_refptr<GPUTimingClient> CreateGPUTimingClient() = 0;

  void SetDisabledGLExtensions(const std::string& disabled_gl_extensions);

  // Gets the GLStateRestorer for the context.
  GLStateRestorer* GetGLStateRestorer();

  // Sets the GLStateRestorer for the context (takes ownership).
  void SetGLStateRestorer(GLStateRestorer* state_restorer);

  // Returns set of extensions. The context must be current.
  virtual const gfx::ExtensionSet& GetExtensions() = 0;

  // Indicate that it is safe to force this context to switch GPUs, since
  // transitioning can cause corruption and hangs (OS X only).
  virtual void SetSafeToForceGpuSwitch();

  // Attempt to force the context to move to the GPU of its sharegroup. Return
  // false only in the event of an unexpected error on the context.
  virtual bool ForceGpuSwitchIfNeeded();

  // Indicate that the real context switches should unbind the FBO first
  // (For an Android work-around only).
  virtual void SetUnbindFboOnMakeCurrent();

  // Indicate that the context has become visible/invisible. This can be due to
  // tab-switching, window minimization, etc.
  virtual void SetVisibility(bool visibility) {}

  // Returns whether the current context supports the named extension. The
  // context must be current.
  bool HasExtension(const char* name);

  // Returns version info of the underlying GL context. The context must be
  // current.
  const GLVersionInfo* GetVersionInfo();

  GLShareGroup* share_group();

  static bool LosesAllContextsOnContextLost();

  // Returns the last GLContext made current, virtual or real.
  static GLContext* GetCurrent();

  // Returns the 'sticky' value of glGetGraphicsResetStatus, if available.
  // 'sticky' implies that if glGetGraphicsResetStatus ever returns a value
  // other than GL_NO_ERROR, that value is returned until the context is
  // destroyed.
  // The context must be current.
  unsigned int CheckStickyGraphicsResetStatus();

  // Make this context current when used for context virtualization.
  bool MakeVirtuallyCurrent(GLContext* virtual_context, GLSurface* surface);

  // Notify this context that |virtual_context|, that was using us, is
  // being released or destroyed.
  void OnReleaseVirtuallyCurrent(GLContext* virtual_context);

  // Returns the GL version string. The context must be current.
  virtual std::string GetGLVersion();

  // Returns the GL renderer string. The context must be current.
  virtual std::string GetGLRenderer();

  // Get the CurrentGL object for this context containing the driver, version
  // and API.
  CurrentGL* GetCurrentGL();

  // Reinitialize the dynamic bindings of this context.  Needed when the driver
  // may be exposing different extensions compared to when it was initialized.
  // TODO(geofflang): Try to make this call uncessessary by pre-loading all
  // extension entry points.
  void ReinitializeDynamicBindings();

  // Forces this context, which must be a virtual context, to be no
  // longer considered virtually current. The real context remains
  // current.
  virtual void ForceReleaseVirtuallyCurrent();

  // Indicates that some GL state was modified that was not tracked by virtual
  // contexts. Forces full reset from unknown state the next time a virtual
  // context is made current.
  void DirtyVirtualContextState();

  // Returns GLDisplayEGL this context belongs to if this context is a
  // GLContextEGL; returns nullptr otherwise.
  virtual GLDisplayEGL* GetGLDisplayEGL();

  virtual GLContextEGL* AsGLContextEGL();

#if BUILDFLAG(IS_APPLE)
  virtual void AddMetalSharedEventsForBackpressure(
      std::vector<std::unique_ptr<gpu::BackpressureMetalSharedEvent>> events);
  // Create a fence for all work submitted to this context so far, and return a
  // monotonically increasing handle to it. This returned handle never needs to
  // be freed. This method is used to create backpressure to throttle GL work
  // on macOS, so that we do not starve CoreAnimation.
  virtual uint64_t BackpressureFenceCreate();
  // Perform a client-side wait on a previously-created fence.
  virtual void BackpressureFenceWait(uint64_t fence);
#endif

#if BUILDFLAG(IS_MAC)
  // Flush the underlying context to avoid crashes due to driver bugs on macOS.
  // https://crbug.com/863817
  virtual void FlushForDriverCrashWorkaround();
#endif

  gl::GLSurface* default_surface() const { return default_surface_.get(); }

  void AddObserver(GLContextObserver* observer);
  void RemoveObserver(GLContextObserver* observer);

  // Returns true if |other_context| is compatible with |this| context, and a
  // client can reuse already allocated textures in |this| context when
  // |other_context| is made current.
  virtual bool CanShareTexturesWithContext(GLContext* other_context);

 protected:
  virtual ~GLContext();

  // Create the GLApi for this context using the provided driver. Creates a
  // RealGLApi by default.
  virtual GLApi* CreateGLApi(DriverGL* driver);

  // Will release the current context when going out of scope, unless canceled.
  class ScopedReleaseCurrent {
   public:
    ScopedReleaseCurrent();
    ~ScopedReleaseCurrent();

    void Cancel();

   private:
    bool canceled_;
  };

  // Sets the GL api to the real hardware API (vs the VirtualAPI)
  void BindGLApi();
  virtual void SetCurrent(GLSurface* surface);

  // Initialize function pointers to functions where the bound version depends
  // on GL version or supported extensions. Should be called immediately after
  // this context is made current.
  void InitializeDynamicBindings();

  // Returns the last real (non-virtual) GLContext made current.
  static GLContext* GetRealCurrent();

  virtual bool MakeCurrentImpl(GLSurface* surface) = 0;
  virtual unsigned int CheckStickyGraphicsResetStatusImpl();
  virtual void ResetExtensions() = 0;
  virtual bool InitializeImpl(GLSurface* compatible_surface,
                              const GLContextAttribs& attribs) = 0;

  GLApi* gl_api() { return gl_api_wrapper_->api(); }

#if BUILDFLAG(IS_APPLE)
  // Child classes are responsible for calling DestroyBackpressureFences during
  // their destruction while a context is current.
  bool HasBackpressureFences() const;
  void DestroyBackpressureFences();
#endif

  void OnContextWillDestroy();

 private:
  friend class base::RefCounted<GLContext>;

  // For GetRealCurrent.
  friend class gpu::GLContextVirtual;

  std::unique_ptr<GLVersionInfo> GenerateGLVersionInfo();

  void MarkContextLost();

  static base::subtle::Atomic32 total_gl_contexts_;

  static bool switchable_gpus_supported_;

  std::string disabled_gl_extensions_;

  bool static_bindings_initialized_ = false;
  bool dynamic_bindings_initialized_ = false;
  std::unique_ptr<DriverGL> driver_gl_;

  std::unique_ptr<GL_IMPL_WRAPPER_TYPE(GL)> gl_api_wrapper_;
  std::unique_ptr<CurrentGL> current_gl_;

  // Copy of the real API (if one was created) for dynamic initialization
  raw_ptr<RealGLApi> real_gl_api_ = nullptr;

  scoped_refptr<GLShareGroup> share_group_;
  raw_ptr<GLContext> current_virtual_context_ = nullptr;
  bool state_dirtied_externally_ = false;
  std::unique_ptr<GLStateRestorer> state_restorer_;
  std::unique_ptr<GLVersionInfo> version_info_;
  // This bit allows us to avoid virtual context state restoration in the case
  // where this underlying context becomes lost.  https://crbug.com/1061442
  bool context_lost_ = false;
  // The offscreen surface that has been used to initialize this context.
  scoped_refptr<gl::GLSurface> default_surface_;

#if BUILDFLAG(IS_APPLE)
  using GLFenceAndMetalSharedEvents = std::pair<
      std::unique_ptr<GLFence>,
      std::vector<std::unique_ptr<gpu::BackpressureMetalSharedEvent>>>;

  std::vector<std::unique_ptr<gpu::BackpressureMetalSharedEvent>>
      next_backpressure_events_;
  std::map<uint64_t, GLFenceAndMetalSharedEvents> backpressure_fences_;
  uint64_t next_backpressure_fence_ = 0;
#endif

  // Implementations of this must call OnContextWillDestroy so that observers
  // are notified.
  bool has_called_on_destory_ = false;

  base::ObserverList<GLContextObserver> observer_list_;
  base::WeakPtrFactory<GLContext> weak_ptr_factory_{this};
};

class GL_EXPORT GLContextReal : public GLContext {
 public:
  explicit GLContextReal(GLShareGroup* share_group);

  GLContextReal(const GLContextReal&) = delete;
  GLContextReal& operator=(const GLContextReal&) = delete;

  scoped_refptr<GPUTimingClient> CreateGPUTimingClient() override;
  const gfx::ExtensionSet& GetExtensions() override;

 protected:
  ~GLContextReal() override;

  void ResetExtensions() override;

  void SetCurrent(GLSurface* surface) override;
  void SetExtensionsFromString(std::string extensions);
  const std::string& extension_string() { return extensions_string_; }

 private:
  std::unique_ptr<GPUTiming> gpu_timing_;
  std::string extensions_string_;
  gfx::ExtensionSet extensions_;
  bool extensions_initialized_ = false;
};

// Wraps GLContext in scoped_refptr and tries to initializes it. Returns a
// scoped_refptr containing the initialized GLContext or nullptr if
// initialization fails.
GL_EXPORT scoped_refptr<GLContext> InitializeGLContext(
    scoped_refptr<GLContext> context,
    GLSurface* compatible_surface,
    const GLContextAttribs& attribs);

}  // namespace gl

#endif  // UI_GL_GL_CONTEXT_H_