components/exo/wayland/zcr_alpha_compositing.cc

// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/exo/wayland/zcr_alpha_compositing.h"

#include <alpha-compositing-unstable-v1-server-protocol.h>

#include "base/memory/raw_ptr.h"
#include "components/exo/surface.h"
#include "components/exo/surface_observer.h"
#include "components/exo/wayland/server_util.h"

namespace exo {
namespace wayland {
namespace {

// A property key containing a boolean set to true if a blending object is
// associated with surface object.
DEFINE_UI_CLASS_PROPERTY_KEY(bool, kSurfaceHasBlendingKey, false)

////////////////////////////////////////////////////////////////////////////////
// blending_interface:

// Implements the blending interface to a Surface. The "blend mode" and
// "alpha"-state is set to SrcOver and 1 upon destruction. A window property
// will be set during the lifetime of this class to prevent multiple instances
// from being created for the same Surface.
class Blending : public SurfaceObserver {
 public:
  explicit Blending(Surface* surface) : surface_(surface) {
    surface_->AddSurfaceObserver(this);
    surface_->SetProperty(kSurfaceHasBlendingKey, true);
  }

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

  ~Blending() override {
    if (surface_) {
      surface_->RemoveSurfaceObserver(this);
      surface_->SetBlendMode(SkBlendMode::kSrcOver);
      surface_->SetAlpha(1.0f);
      surface_->SetProperty(kSurfaceHasBlendingKey, false);
    }
  }

  void SetBlendMode(SkBlendMode blend_mode) {
    if (surface_)
      surface_->SetBlendMode(blend_mode);
  }

  void SetAlpha(float value) {
    if (surface_)
      surface_->SetAlpha(value);
  }

  // Overridden from SurfaceObserver:
  void OnSurfaceDestroying(Surface* surface) override {
    surface->RemoveSurfaceObserver(this);
    surface_ = nullptr;
  }

 private:
  raw_ptr<Surface> surface_;
};

void blending_destroy(wl_client* client, wl_resource* resource) {
  wl_resource_destroy(resource);
}

void blending_set_blending(wl_client* client,
                           wl_resource* resource,
                           uint32_t equation) {
  switch (equation) {
    case ZCR_BLENDING_V1_BLENDING_EQUATION_NONE:
      GetUserDataAs<Blending>(resource)->SetBlendMode(SkBlendMode::kSrc);
      break;
    case ZCR_BLENDING_V1_BLENDING_EQUATION_PREMULT:
      GetUserDataAs<Blending>(resource)->SetBlendMode(SkBlendMode::kSrcOver);
      break;
    case ZCR_BLENDING_V1_BLENDING_EQUATION_COVERAGE:
      NOTIMPLEMENTED();
      break;
    default:
      DLOG(WARNING) << "Unsupported blending equation: " << equation;
      break;
  }
}

void blending_set_alpha(wl_client* client,
                        wl_resource* resource,
                        wl_fixed_t alpha) {
  GetUserDataAs<Blending>(resource)->SetAlpha(wl_fixed_to_double(alpha));
}

const struct zcr_blending_v1_interface blending_implementation = {
    blending_destroy, blending_set_blending, blending_set_alpha};

////////////////////////////////////////////////////////////////////////////////
// alpha_compositing_interface:

void alpha_compositing_destroy(wl_client* client, wl_resource* resource) {
  wl_resource_destroy(resource);
}

void alpha_compositing_get_blending(wl_client* client,
                                    wl_resource* resource,
                                    uint32_t id,
                                    wl_resource* surface_resource) {
  Surface* surface = GetUserDataAs<Surface>(surface_resource);
  if (surface->GetProperty(kSurfaceHasBlendingKey)) {
    wl_resource_post_error(resource,
                           ZCR_ALPHA_COMPOSITING_V1_ERROR_BLENDING_EXISTS,
                           "a blending object for that surface already exists");
    return;
  }

  wl_resource* blending_resource =
      wl_resource_create(client, &zcr_blending_v1_interface, 1, id);

  SetImplementation(blending_resource, &blending_implementation,
                    std::make_unique<Blending>(surface));
}

const struct zcr_alpha_compositing_v1_interface
    alpha_compositing_implementation = {alpha_compositing_destroy,
                                        alpha_compositing_get_blending};

}  // namespace

void bind_alpha_compositing(wl_client* client,
                            void* data,
                            uint32_t version,
                            uint32_t id) {
  wl_resource* resource =
      wl_resource_create(client, &zcr_alpha_compositing_v1_interface, 1, id);

  wl_resource_set_implementation(resource, &alpha_compositing_implementation,
                                 data, nullptr);
}

}  // namespace wayland
}  // namespace exo