chrome/browser/themes/browser_theme_pack.h

// Copyright (c) 2012 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_BROWSER_THEME_PACK_H_
#define CHROME_BROWSER_THEMES_BROWSER_THEME_PACK_H_

#include <stdint.h>

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

#include "base/macros.h"
#include "base/sequenced_task_runner_helpers.h"
#include "chrome/browser/themes/custom_theme_supplier.h"
#include "extensions/common/extension.h"
#include "third_party/skia/include/core/SkColor.h"
#include "ui/base/layout.h"
#include "ui/gfx/color_utils.h"

namespace base {
class DictionaryValue;
class FilePath;
class RefCountedMemory;
}

namespace gfx {
class Image;
}

namespace ui {
class DataPack;
}

// An optimized representation of a theme, backed by a mmapped DataPack.
//
// The idea is to pre-process all images (tinting, compositing, etc) at theme
// install time, save all the PNG-ified data into an mmappable file so we don't
// suffer multiple file system access times, therefore solving two of the
// problems with the previous implementation.
//
// A note on const-ness. All public, non-static methods are const.  We do this
// because once we've constructed a BrowserThemePack through the
// BuildFromExtension() interface, we WriteToDisk() on a thread other than the
// UI thread that consumes a BrowserThemePack. There is no locking; thread
// safety between the writing thread and the UI thread is ensured by having the
// data be immutable.
//
// BrowserThemePacks are always deleted on a sequence with I/O allowed because
// in the common case, they are backed by mmapped data and the unmmapping
// operation will trip our IO on the UI thread detector.
// See CustomThemeSupplier constructor more more details.
class BrowserThemePack : public CustomThemeSupplier {
 public:
  // Builds the theme from |extension| into |pack|. This may be done on a
  // separate thread as it takes so long. This can fail in the case where the
  // theme has invalid data, in which case |pack->is_valid()| will be false.
  static void BuildFromExtension(const extensions::Extension* extension,
                                 scoped_refptr<BrowserThemePack> pack);

  // Builds the theme pack from a previously performed WriteToDisk(). This
  // operation should be relatively fast, as it should be an mmap() and some
  // pointer swizzling. Returns NULL on any error attempting to read |path|.
  static scoped_refptr<BrowserThemePack> BuildFromDataPack(
      const base::FilePath& path, const std::string& expected_id);

  // Returns whether the specified identifier is one of the images we persist
  // in the data pack.
  static bool IsPersistentImageID(int id);

  // Default. Everything is empty.
  BrowserThemePack();

  bool is_valid() const { return is_valid_; }

  // Builds a data pack on disk at |path| for future quick loading by
  // BuildFromDataPack(). Often (but not always) called from the file thread;
  // implementation should be threadsafe because neither thread will write to
  // |image_memory_| and the worker thread will keep a reference to prevent
  // destruction.
  bool WriteToDisk(const base::FilePath& path) const;

  // Overridden from CustomThemeSupplier:
  bool GetTint(int id, color_utils::HSL* hsl) const override;
  bool GetColor(int id, SkColor* color) const override;
  bool GetDisplayProperty(int id, int* result) const override;
  gfx::Image GetImageNamed(int id) override;
  base::RefCountedMemory* GetRawData(int id, ui::ScaleFactor scale_factor)
      const override;
  bool HasCustomImage(int id) const override;

 private:
  friend class BrowserThemePackTest;

  // Cached images.
  typedef std::map<int, gfx::Image> ImageCache;

  // The raw PNG memory associated with a certain id.
  typedef std::map<int, scoped_refptr<base::RefCountedMemory> > RawImages;

  // The type passed to ui::DataPack::WritePack.
  typedef std::map<uint16_t, base::StringPiece> RawDataForWriting;

  // Maps scale factors (enum values) to file paths.
  typedef std::map<ui::ScaleFactor, base::FilePath> ScaleFactorToFileMap;

  // Maps image ids to maps of scale factors to file paths.
  typedef std::map<int, ScaleFactorToFileMap> FilePathMap;

  ~BrowserThemePack() override;

  // Modifies |colors_| to set the entry with identifier |id| to |color|.  Only
  // valid to call after BuildColorsFromJSON(), which creates |colors_|.
  void SetColor(int id, SkColor color);

  // If |colors_| does not already contain an entry with identifier |id|, sets
  // it to the dominant color of the top |height| rows of |image|.
  void ComputeColorFromImage(int id, int height, const gfx::Image& image);

  // Builds a header ready to write to disk.
  void BuildHeader(const extensions::Extension* extension);

  // Transforms the JSON tint values into their final versions in the |tints_|
  // array.
  void BuildTintsFromJSON(const base::DictionaryValue* tints_value);

  // Transforms the JSON color values into their final versions in the
  // |colors_| array and also fills in unspecified colors based on tint values.
  void BuildColorsFromJSON(const base::DictionaryValue* color_value);

  // Implementation details of BuildColorsFromJSON().
  void ReadColorsFromJSON(const base::DictionaryValue* colors_value,
                          std::map<int, SkColor>* temp_colors);

  // Transforms the JSON display properties into |display_properties_|.
  void BuildDisplayPropertiesFromJSON(
      const base::DictionaryValue* display_value);

  // Parses the image names out of an extension.
  void ParseImageNamesFromJSON(const base::DictionaryValue* images_value,
                               const base::FilePath& images_path,
                               FilePathMap* file_paths) const;

  // Helper function to populate the FilePathMap.
  void AddFileAtScaleToMap(const std::string& image_name,
                           ui::ScaleFactor scale_factor,
                           const base::FilePath& image_path,
                           FilePathMap* file_paths) const;

  // Creates the data for |source_images_| from |file_paths|.
  void BuildSourceImagesArray(const FilePathMap& file_paths);

  // Loads the unmodified images packed in the extension to SkBitmaps. Returns
  // true if all images loaded.
  bool LoadRawBitmapsTo(const FilePathMap& file_paths,
                        ImageCache* image_cache);

  // Crops images down to a size such that most of the cropped image will be
  // displayed in the UI. Cropping is useful because images from custom themes
  // can be of any size. Source and destination is |images|.
  void CropImages(ImageCache* images) const;

  // Creates tinted and composited frame images. Source and destination is
  // |images|.  Also sets frame colors corresponding to these images if no
  // explicit color has been specified for these colors.
  void CreateFrameImagesAndColors(ImageCache* images);

  // Generates any frame colors which have not already been set.
  void GenerateFrameColors();

  // Generates background color information for the background of window control
  // buttons.  This can be used when drawing the window control/caption buttons
  // to determine what color to draw the symbol, ensuring that it contrasts
  // sufficiently with the background of the button.
  void GenerateWindowControlButtonColor(ImageCache* images);

  // Creates the semi-transparent tab background images, putting the results
  // in |images|.  Also sets colors corresponding to these images if no explicit
  // color has been specified.  Must be called after GenerateFrameImages().
  void CreateTabBackgroundImagesAndColors(ImageCache* images);

  // Generates any text colors which have not already been set.
  void GenerateMissingTextColors();

  // Generates text color for the specified id |text_color_id|, based on the
  // background color of the tab |tab_color_id|, and using the color already
  // defined for |source_color_id| as a starting point (if it exists).
  void GenerateMissingTextColorForID(int text_color_id,
                                     int tab_color_id,
                                     int frame_color_id,
                                     int source_color_id);

  // Takes all the SkBitmaps in |images|, encodes them as PNGs and places
  // them in |reencoded_images|.
  void RepackImages(const ImageCache& images,
                    RawImages* reencoded_images) const;

  // Takes all images in |source| and puts them in |destination|, freeing any
  // image already in |destination| that |source| would overwrite.
  void MergeImageCaches(const ImageCache& source,
                        ImageCache* destination) const;

  // Copies images from |source| to |destination| such that the lifetimes of
  // the images in |destination| are not affected by the lifetimes of the
  // images in |source|.
  void CopyImagesTo(const ImageCache& source, ImageCache* destination) const;

  // Changes the RefCountedMemory based |images| into StringPiece data in |out|.
  void AddRawImagesTo(const RawImages& images, RawDataForWriting* out) const;

  // Retrieves the tint OR the default tint. Unlike the public interface, we
  // always need to return a reasonable tint here, instead of partially
  // querying if the tint exists.
  color_utils::HSL GetTintInternal(int id) const;

  // Returns a unique id to use to store the raw bitmap for |prs_id| at
  // |scale_factor| in memory.
  int GetRawIDByPersistentID(int prs_id, ui::ScaleFactor scale_factor) const;

  // Returns true if the |key| specifies a valid scale (e.g. "100") and
  // the corresponding scale factor is currently in use. If true, returns
  // the scale factor in |scale_factor|.
  bool GetScaleFactorFromManifestKey(const std::string& key,
                                     ui::ScaleFactor* scale_factor) const;

  // Generates raw images for any missing scale from an available scale.
  void GenerateRawImageForAllSupportedScales(int prs_id);

  // Data pack, if we have one.
  std::unique_ptr<ui::DataPack> data_pack_;

  // All structs written to disk need to be packed; no alignment tricks here,
  // please.
#pragma pack(push,1)
  // Header that is written to disk.
  struct BrowserThemePackHeader {
    // Numeric version to make sure we're compatible in the future.
    int32_t version;

    // 1 if little_endian. 0 if big_endian. On mismatch, abort load.
    int32_t little_endian;

    // theme_id without NULL terminator.
    uint8_t theme_id[16];
  }* header_ = nullptr;

  // The remaining structs represent individual entries in an array. For the
  // following three structs, BrowserThemePack will either allocate an array or
  // will point directly to mmapped data.
  struct TintEntry {
    int32_t id;
    double h;
    double s;
    double l;
  }* tints_ = nullptr;

  struct ColorPair {
    int32_t id;
    SkColor color;
  }* colors_ = nullptr;

  struct DisplayPropertyPair {
    int32_t id;
    int32_t property;
  }* display_properties_ = nullptr;

  // A list of included source images. A pointer to a -1 terminated array of
  // our persistent IDs.
  int* source_images_ = nullptr;
#pragma pack(pop)

  // The scale factors represented by the images in the theme pack.
  std::vector<ui::ScaleFactor> scale_factors_;

  // References to raw PNG data. This map isn't touched when |data_pack_| is
  // non-NULL; |image_memory_| is only filled during BuildFromExtension(). Any
  // image data that needs to be written to the DataPack during WriteToDisk()
  // needs to be in |image_memory_|.
  RawImages image_memory_;

  // Loaded images. These are loaded from |image_memory_|, from |data_pack_|,
  // and by BuildFromExtension().
  ImageCache images_;

  // Cache of images created in BuildFromExtension(). Once the theme pack is
  // created, this cache should only be accessed on the file thread. There
  // should be no IDs in |image_memory_| that are in |images_on_file_thread_|
  // or vice versa.
  ImageCache images_on_file_thread_;

  // Whether the theme pack has been succesfully initialized and is ready to
  // use.
  bool is_valid_ = false;

  DISALLOW_COPY_AND_ASSIGN(BrowserThemePack);
};

#endif  // CHROME_BROWSER_THEMES_BROWSER_THEME_PACK_H_