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// Copyright (c) 2011 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_COMMON_THUMBNAIL_SCORE_H_
#define CHROME_COMMON_THUMBNAIL_SCORE_H_
#pragma once
#include <string>
#include "base/time.h"
// A set of metadata about a Thumbnail.
struct ThumbnailScore {
// Initializes the ThumbnailScore to the absolute worst possible values
// except for time, which is set to Now(), and redirect_hops_from_dest which
// is set to 0.
ThumbnailScore();
// Builds a ThumbnailScore with the passed in values, and sets the
// thumbnail generation time to Now().
ThumbnailScore(double score, bool clipping, bool top);
// Builds a ThumbnailScore with the passed in values.
ThumbnailScore(double score, bool clipping, bool top,
const base::Time& time);
~ThumbnailScore();
// Tests for equivalence between two ThumbnailScore objects.
bool Equals(const ThumbnailScore& rhs) const;
// Returns string representation of this object.
std::string ToString() const;
// How "boring" a thumbnail is. The boring score is the 0,1 ranged
// percentage of pixels that are the most common luma. Higher boring
// scores indicate that a higher percentage of a bitmap are all the
// same brightness (most likely the same color).
//
// The score should only be used for comparing two thumbnails taken from
// the same page to see which one is more boring/interesting. The
// absolute score is not suitable for judging whether the thumbnail is
// actually boring or not. For instance, www.google.com is very
// succinct, so the boring score can be as high as 0.9, depending on the
// browser window size.
double boring_score;
// Whether the thumbnail was taken with height greater then
// width. In cases where we don't have |good_clipping|, the
// thumbnails are either clipped from the horizontal center of the
// window, or are otherwise weirdly stretched.
bool good_clipping;
// Whether this thumbnail was taken while the renderer was
// displaying the top of the page. Most pages are more recognizable
// by their headers then by a set of random text half way down the
// page; i.e. most MediaWiki sites would be indistinguishable by
// thumbnails with |at_top| set to false.
bool at_top;
// Whether this thumbnail was taken after load was completed.
// Thumbnails taken while page loading may only contain partial
// contents.
bool load_completed;
// Record the time when a thumbnail was taken. This is used to make
// sure thumbnails are kept fresh.
base::Time time_at_snapshot;
// The number of hops from the final destination page that this thumbnail was
// taken at. When a thumbnail is taken, this will always be the redirect
// destination (value of 0).
//
// For the most visited view, we'll sometimes get thumbnails for URLs in the
// middle of a redirect chain. In this case, the top sites component will set
// this value so the distance from the destination can be taken into account
// by the comparison function.
//
// If "http://google.com/" redirected to "http://www.google.com/", then
// a thumbnail for the first would have a redirect hop of 1, and the second
// would have a redirect hop of 0.
int redirect_hops_from_dest;
// How bad a thumbnail needs to be before we completely ignore it.
static const double kThumbnailMaximumBoringness;
// We consider a thumbnail interesting enough if the boring score is
// lower than this.
static const double kThumbnailInterestingEnoughBoringness;
// Time before we take a worse thumbnail (subject to
// kThumbnailMaximumBoringness) over what's currently in the database
// for freshness.
static const int64 kUpdateThumbnailTimeDays;
// Penalty of how much more boring a thumbnail should be per hour.
static const double kThumbnailDegradePerHour;
// Checks whether we should consider updating a new thumbnail based on
// this score. For instance, we don't have to update a new thumbnail
// if the current thumbnail is new and interesting enough.
bool ShouldConsiderUpdating();
};
// Checks whether we should replace one thumbnail with another.
bool ShouldReplaceThumbnailWith(const ThumbnailScore& current,
const ThumbnailScore& replacement);
#endif // CHROME_COMMON_THUMBNAIL_SCORE_H_
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