chrome/browser/themes/theme_helper.h

// Copyright 2020 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_THEMES_THEME_HELPER_H_
#define CHROME_BROWSER_THEMES_THEME_HELPER_H_

#include "base/sequence_checker.h"
#include "third_party/abseil-cpp/absl/types/optional.h"
#include "third_party/skia/include/core/SkColor.h"
#include "ui/base/resource/scale_factor.h"
#include "ui/base/theme_provider.h"

class CustomThemeSupplier;

namespace theme_service_internal {
class ThemeServiceTest;
}

namespace ui {
class NativeTheme;
}

namespace gfx {
class ImageSkia;
class Image;
}  // namespace gfx

namespace color_utils {
struct HSL;
}

// Helper functions for ThemeService as part of implementing the
// ui::ThemeProvider interface with respect to a given CustomThemeSupplier and
// incognito state.
class ThemeHelper {
 public:
  // The default theme if we haven't installed a theme yet or if we've clicked
  // the "Use Classic" button.
  static const char kDefaultThemeID[];

  // Whether |theme_supplier| is installed through extensions.
  // |UsingExtensionTheme| and |UsingDefaultTheme| are not mutually exclusive as
  // default theme can be installed through extensions.
  static bool IsExtensionTheme(const CustomThemeSupplier* theme_supplier);

  // Whether we are using an autogenerated theme.
  static bool IsAutogeneratedTheme(const CustomThemeSupplier* theme_supplier);

  // Whether |theme_supplier| is a default theme.
  static bool IsDefaultTheme(const CustomThemeSupplier* theme_supplier);

  // Whether |theme_supplier| is what users would think of as a "custom theme"
  // (that is, an extension or autogenerated theme).
  static bool IsCustomTheme(const CustomThemeSupplier* theme_supplier);

  static bool HasCustomImage(int id, const CustomThemeSupplier* theme_supplier);

  static int GetDisplayProperty(int id,
                                const CustomThemeSupplier* theme_supplier);

  static base::RefCountedMemory* GetRawData(
      int id,
      const CustomThemeSupplier* theme_supplier,
      ui::ScaleFactor scale_factor);

  ThemeHelper();
  virtual ~ThemeHelper();

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

  SkColor GetColor(int id,
                   bool incognito,
                   const CustomThemeSupplier* theme_supplier,
                   bool* has_custom_color = nullptr) const;

  // Get the specified tint - |id| is one of the TINT_* enum values.
  color_utils::HSL GetTint(int id,
                           bool incognito,
                           const CustomThemeSupplier* theme_supplier) const;

  // These methods provide the implementation for ui::ThemeProvider (exposed
  // via BrowserThemeProvider).
  gfx::ImageSkia* GetImageSkiaNamed(
      int id,
      bool incognito,
      const CustomThemeSupplier* theme_supplier) const;

  // Implementation for ui::ThemeProvider.
  virtual bool ShouldUseNativeFrame(
      const CustomThemeSupplier* theme_supplier) const;

  // Decides if the IncreasedContrastThemeSupplier should be used according
  // to |native_theme|.
  virtual bool ShouldUseIncreasedContrastThemeSupplier(
      ui::NativeTheme* native_theme) const;

  void DCheckCalledOnValidSequence() const {
    DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  }

 protected:
  // Returns the color to use for |id| and |incognito| if the theme service does
  // not provide an override.
  virtual SkColor GetDefaultColor(
      int id,
      bool incognito,
      const CustomThemeSupplier* theme_supplier) const;

 private:
  friend class theme_service_internal::ThemeServiceTest;

  struct OmniboxColor {
    SkColor value;

    // True if any part of the computation of the color relied on a custom base
    // color from the theme supplier.
    bool custom;
  };

  // Computes the "toolbar top separator" color.  This color is drawn atop the
  // frame to separate it from tabs, the toolbar, and the new tab button, as
  // well as atop background tabs to separate them from other tabs or the
  // toolbar.  We use semitransparent black or white so as to darken or lighten
  // the frame, with the goal of contrasting with both the frame color and the
  // active tab (i.e. toolbar) color.  (It's too difficult to try to find colors
  // that will contrast with both of these as well as the background tab color,
  // and contrasting with the foreground tab is the most important).
  static SkColor GetSeparatorColor(SkColor tab_color, SkColor frame_color);

  // Whether the default incognito color/tint for |id| should be used, if
  // available.
  static bool UseIncognitoColor(int id,
                                const CustomThemeSupplier* theme_supplier);

  // Whether dark default colors/tints should be used, if available.
  static bool UseDarkModeColors(const CustomThemeSupplier* theme_supplier);

  // Whether the color from |theme_supplier| (if any) should be ignored for
  // the given |id| and |incognito| state.
  static bool ShouldIgnoreThemeSupplier(
      int id,
      bool incognito,
      const CustomThemeSupplier* theme_supplier);

  // Returns a cross platform image for an id.
  gfx::Image GetImageNamed(int id,
                           bool incognito,
                           const CustomThemeSupplier* theme_supplier) const;

  // Given a theme property ID |id|, returns the corresponding omnibox color
  // overridden by the system theme.  Returns absl::nullopt if the color is not
  // overridden, or if |id| does not correspond to an omnibox color.
  absl::optional<SkColor> GetOmniboxColor(
      int id,
      bool incognito,
      const CustomThemeSupplier* theme_supplier,
      bool* has_custom_color) const;

  // Helper function that contains the main implementation of GetOmniboxColor().
  absl::optional<OmniboxColor> GetOmniboxColorImpl(
      int id,
      bool incognito,
      const CustomThemeSupplier* theme_supplier) const;

  SkColor GetTabGroupColor(int id,
                           bool incognito,
                           const CustomThemeSupplier* theme_supplier) const;

  SEQUENCE_CHECKER(sequence_checker_);
};

#endif  // CHROME_BROWSER_THEMES_THEME_HELPER_H_