chrome/browser/accessibility/page_colors.h

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_ACCESSIBILITY_PAGE_COLORS_H_
#define CHROME_BROWSER_ACCESSIBILITY_PAGE_COLORS_H_

#include "base/memory/raw_ptr.h"
#include "base/memory/weak_ptr.h"
#include "base/scoped_observation.h"
#include "build/build_config.h"
#include "components/keyed_service/core/keyed_service.h"
#include "components/prefs/pref_change_registrar.h"
#include "ui/native_theme/native_theme.h"

namespace user_prefs {
class PrefRegistrySyncable;
}

// Manages the page colors feature, which simulates forced colors mode at the
// browser level. This tracks the per-profile preference and OS preferred
// contrast state from NativeTheme to update the WebContents Page Colors state
// based on any changes.
class PageColors : public KeyedService, public ui::NativeThemeObserver {
 public:
  explicit PageColors(PrefService* profile_prefs);
  PageColors(const PageColors&) = delete;
  PageColors& operator=(const PageColors&) = delete;

  ~PageColors() override;

  static void RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry);

  void Init();

 private:
  friend class PageColorsFactory;

  // Handles when page colors preferences change.
  void OnPageColorsChanged();

  // This function makes use of different states such as the kPageColors,
  // kApplyPageColorsOnlyOnIncreasedContrast and OS increased contrast state to
  // calculate the used page colors.
  ui::NativeTheme::PageColors CalculatePageColors();

  // ui::NativeThemeObserver
  void OnPreferredContrastChanged() override;

  base::ScopedObservation<ui::NativeTheme, ui::NativeThemeObserver>
      theme_observation_{this};

  PrefChangeRegistrar pref_change_registrar_;

  raw_ptr<PrefService> profile_prefs_;

  base::WeakPtrFactory<PageColors> weak_factory_{this};
};

#endif  // CHROME_BROWSER_ACCESSIBILITY_PAGE_COLORS_H_