Add chrome to the repository.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@15 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 126 insertions, 0 deletions

diff --git a/chrome/common/thumbnail_score.cc b/chrome/common/thumbnail_score.cc
new file mode 100644
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+++ b/chrome/common/thumbnail_score.cc
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+// Copyright 2008, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "chrome/common/thumbnail_score.h"
+
+#include "base/logging.h"
+
+const TimeDelta ThumbnailScore::kUpdateThumbnailTime = TimeDelta::FromDays(1);
+const double ThumbnailScore::kThumbnailMaximumBoringness = 0.94;
+const double ThumbnailScore::kThumbnailDegradePerHour = 0.01;
+
+// Calculates a numeric score from traits about where a snapshot was
+// taken. We store the raw components in the database because I'm sure
+// this will evolve and I don't want to break databases.
+static int GetThumbnailType(bool good_clipping, bool at_top) {
+  if (good_clipping && at_top) {
+    return 0;
+  } else if (good_clipping && !at_top) {
+    return 1;
+  } else if (!good_clipping && at_top) {
+    return 2;
+  } else if (!good_clipping && !at_top) {
+    return 3;
+  } else {
+    NOTREACHED();
+    return -1;
+  }
+}
+
+ThumbnailScore::ThumbnailScore()
+    : boring_score(1.0),
+      good_clipping(false),
+      at_top(false),
+      time_at_snapshot(Time::Now()) {
+}
+
+ThumbnailScore::ThumbnailScore(double score, bool clipping, bool top)
+    : boring_score(score),
+      good_clipping(clipping),
+      at_top(top),
+      time_at_snapshot(Time::Now()) {
+}
+
+ThumbnailScore::ThumbnailScore(double score, bool clipping, bool top,
+                               const Time& time)
+    : boring_score(score),
+      good_clipping(clipping),
+      at_top(top),
+      time_at_snapshot(time) {
+}
+
+ThumbnailScore::~ThumbnailScore() {
+}
+
+bool ThumbnailScore::Equals(const ThumbnailScore& rhs) const {
+  // When testing equality we use ToTimeT() because that's the value
+  // stuck in the SQL database, so we need to test equivalence with
+  // that lower resolution.
+  return boring_score == rhs.boring_score &&
+      good_clipping == rhs.good_clipping &&
+      at_top == rhs.at_top &&
+      time_at_snapshot.ToTimeT() == rhs.time_at_snapshot.ToTimeT();
+}
+
+bool ShouldReplaceThumbnailWith(const ThumbnailScore& current,
+                                const ThumbnailScore& replacement) {
+  int current_type = GetThumbnailType(current.good_clipping, current.at_top);
+  int replacement_type = GetThumbnailType(replacement.good_clipping,
+                                          replacement.at_top);
+  if (replacement_type < current_type) {
+    // If we have a better class of thumbnail, add it if it meets
+    // certain minimum boringness.
+    return replacement.boring_score <
+        ThumbnailScore::kThumbnailMaximumBoringness;
+  } else if (replacement_type == current_type) {
+    if (replacement.boring_score < current.boring_score) {
+      // If we have a thumbnail that's straight up less boring, use it.
+      return true;
+    }
+
+    // Slowly degrade the boring score of the current thumbnail
+    // so we take thumbnails which are slightly less good:
+    TimeDelta since_last_thumbnail =
+        replacement.time_at_snapshot - current.time_at_snapshot;
+    double degraded_boring_score = current.boring_score +
+        (since_last_thumbnail.InHours() *
+         ThumbnailScore::kThumbnailDegradePerHour);
+
+    if (degraded_boring_score > ThumbnailScore::kThumbnailMaximumBoringness)
+      degraded_boring_score = ThumbnailScore::kThumbnailMaximumBoringness;
+    if (replacement.boring_score < degraded_boring_score)
+      return true;
+  }
+
+  // If the current thumbnail doesn't meet basic boringness
+  // requirements, but the replacement does, always replace the
+  // current one even if we're using a worse thumbnail type.
+  return current.boring_score >= ThumbnailScore::kThumbnailMaximumBoringness &&
+      replacement.boring_score < ThumbnailScore::kThumbnailMaximumBoringness;
+}