[Favicon] Add new fallback icon rendering flow.

components/favicon_base/fallback_icon_specs_builder.cc

Index: components/favicon_base/fallback_icon_specs_builder.cc
diff --git a/components/favicon_base/fallback_icon_specs_builder.cc b/components/favicon_base/fallback_icon_specs_builder.cc
new file mode 100644
index 0000000000000000000000000000000000000000..bea69a86878a6ab819dd0c39b2188588da02b061
--- /dev/null
+++ b/components/favicon_base/fallback_icon_specs_builder.cc
@@ -0,0 +1,163 @@
+// Copyright 2015 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.
+
+#include "components/favicon_base/fallback_icon_specs_builder.h"
+
+#include <string>
+#include <vector>
+
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "ui/gfx/color_utils.h"
+
+namespace favicon_base {
+
+namespace {
+
+double kMaxFontSizeRatio = 1.0;
+double kMaxCornerRadiusRatio = 0.5;
+
+// Luminance threshold for background color determine whether to use dark or
+// light text color.
+int kDarkTextLuminanceThreshold = 190;
+
+// Default values.
+SkColor kDefaultBackgroundColor = SkColorSetRGB(0x80, 0x80, 0x80);
+SkColor kDefaultTextColorDark = SK_ColorBLACK;
+SkColor kDefaultTextColorLight = SK_ColorWHITE;
+double kDefaultFontSizeRatio = 0.8;
+double kDefaultCornerRadiusRatio = 0.0625;  // 1 / 16.
+
+}  // namespace
+
+FallbackIconSpecsBuilder::FallbackIconSpecsBuilder()
+    : is_init_(0U) {
+}
+
+FallbackIconSpecsBuilder::~FallbackIconSpecsBuilder() {
+}
+
+bool FallbackIconSpecsBuilder::Reset() {
+  is_init_ = 0U;
+  specs_ = FallbackIconSpecs();
+  return false;  // This is to simplify Parse().
+}
+
+bool FallbackIconSpecsBuilder::Has(DataMember mask) const {
+  return (is_init_ & mask) != 0;
+}
+
+// Setters, which does not validate |value|.
+void FallbackIconSpecsBuilder::SetBackgroundColor(SkColor value) {
+  is_init_ |= BACKGROUND_COLOR;
+  specs_.background_color = value;
+}
+
+void FallbackIconSpecsBuilder::SetTextColor(SkColor value) {
+  is_init_ |= TEXT_COLOR;
+  specs_.text_color = value;
+}
+
+void FallbackIconSpecsBuilder::SetFontSizeRatio(double value) {
+  is_init_ |= FONT_SIZE_RATIO;
+  specs_.font_size_ratio = value;
+}
+
+void FallbackIconSpecsBuilder::SetCornerRadiusRatio(double value) {
+  is_init_ |= CORNER_RADIUS_RATIO;
+  specs_.corner_radius_ratio = value;
+}
+
+// static
+bool FallbackIconSpecsBuilder::ParseColor(const std::string& str,
+                                          SkColor* color) {
+  size_t len = str.length();
+  if (len != 3 && len != 6 && len != 8)
+    return false;
+  // Translate and validate each digits.
+  int d[8];
+  for (size_t i = 0; i < len; ++i) {
+    char ch = str[i];
+    if (ch >= '0' && ch <= '9')
+      d[i] = ch - '0';
+    else if (ch >= 'A' && ch <= 'F')
+      d[i] = (ch - 'A') + 10;
+    else if (ch >= 'a' && ch <= 'f')
+      d[i] = (ch - 'a') + 10;
+    else
+      return false;
+  }
+  if (len == 3) {  // RGB.
+    *color = SkColorSetRGB(d[0] * 0x11, d[1] * 0x11, d[2] * 0x11);
+  } else if (len == 6) {  // RRGGBB.
+    *color = SkColorSetRGB(
+        (d[0] << 4) | d[1], (d[2] << 4) | d[3], (d[4] << 4) | d[5]);
+  } else {  // RRGGBBAA.
+    DCHECK(len == 8);
+    *color = SkColorSetARGB((d[6] << 4) | d[7], (d[0] << 4) | d[1],
+                            (d[2] << 4) | d[3], (d[4] << 4) | d[5]);
+  }
+  return true;
+}
+
+bool FallbackIconSpecsBuilder::Parse(const std::string& specs_str) {
+  Reset();
+  std::vector<std::string> tokens;
+  base::SplitStringDontTrim(specs_str, ',', &tokens);
+  if (tokens.size() > 4)  // Too many fields.
+    return Reset();  // Returns false.
+
+  SkColor temp_color;
+  double temp_double;
+  if (tokens.size() > 0 && !tokens[0].empty()) {
+    if (!ParseColor(tokens[0], &temp_color))
+      return Reset();
+    SetBackgroundColor(temp_color);
+  }
+  if (tokens.size() > 1 && !tokens[1].empty()) {
+    if (!ParseColor(tokens[1], &temp_color))
+      return Reset();
+    SetTextColor(temp_color);
+  }
+  if (tokens.size() > 2 && !tokens[2].empty()) {
+    if (!base::StringToDouble(tokens[2], &temp_double) ||
+            temp_double < 0.0 || temp_double > kMaxFontSizeRatio) {
+      return Reset();
+    }
+    SetFontSizeRatio(temp_double);
+  }
+  if (tokens.size() > 3 && !tokens[3].empty()) {
+    if (!base::StringToDouble(tokens[3], &temp_double) ||
+            temp_double < 0.0 || temp_double > kMaxCornerRadiusRatio) {
+      return Reset();
+    }
+    SetCornerRadiusRatio(temp_double);
+  }
+  return true;
+}
+
+void FallbackIconSpecsBuilder::AssignDefaults() {
+  if (!Has(BACKGROUND_COLOR))
+    SetBackgroundColor(kDefaultBackgroundColor);
+
+  // Uses dark/light text for background with high/low luminance.
+  if (!Has(TEXT_COLOR)) {
+    int luminance = color_utils::GetLuminanceForColor(specs_.background_color);
+    SetTextColor(luminance >= kDarkTextLuminanceThreshold ?
+        kDefaultTextColorDark : kDefaultTextColorLight);
+  }
+
+  if (!Has(FONT_SIZE_RATIO))
+    SetFontSizeRatio(kDefaultFontSizeRatio);
+
+  if (!Has(CORNER_RADIUS_RATIO))
+    SetCornerRadiusRatio(kDefaultCornerRadiusRatio);
+}
+
+const FallbackIconSpecs& FallbackIconSpecsBuilder::Build() {
+  AssignDefaults();
+  return specs_;
+}
+
+}  // namespace favicon_base