[Favicon] Add FallbackIconStyle and FallbackIconService.

Design: go/chrome-fallback-icons

This implements
- FallbackIconStyle: A struct to specify fallback data.
- FallbackIconService: Helper class to render the fallback icon as a
  filled rounded square with a single letter from the URL.
- Extra dependencies are needed to convert URL to the icon letter.

This CL is sliced off from https://codereview.chromium.org/835903005/ .

BUG=455063

Review URL: https://codereview.chromium.org/886163003

Cr-Commit-Position: refs/heads/master@{#315854}

7 files changed, 248 insertions, 3 deletions

diff --git a/components/favicon_base/BUILD.gn b/components/favicon_base/BUILD.gn
index cf060fe..57c42a4 100644
--- a/components/favicon_base/BUILD.gn
+++ b/components/favicon_base/BUILD.gn
@@ -4,6 +4,10 @@
 
 source_set("favicon_base") {
   sources = [
+    "fallback_icon_service.cc",
+    "fallback_icon_service.h",
+    "fallback_icon_style.cc",
+    "fallback_icon_style.h",
     "favicon_callback.h",
     "favicon_types.cc",
     "favicon_types.h",
diff --git a/components/favicon_base/DEPS b/components/favicon_base/DEPS
index 0265afa..dc47487 100644
--- a/components/favicon_base/DEPS
+++ b/components/favicon_base/DEPS
@@ -1,4 +1,5 @@
 include_rules = [
+  "+net/base/registry_controlled_domains/registry_controlled_domain.h",
   "+skia/ext",
   "+third_party/skia/include",
   "+ui/base",
diff --git a/components/favicon_base/fallback_icon_service.cc b/components/favicon_base/fallback_icon_service.cc
new file mode 100644
index 0000000..1642b20
--- /dev/null
+++ b/components/favicon_base/fallback_icon_service.cc
@@ -0,0 +1,98 @@
+// 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_service.h"
+
+#include <algorithm>
+
+#include "base/i18n/case_conversion.h"
+#include "base/strings/utf_string_conversions.h"
+#include "components/favicon_base/fallback_icon_style.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+#include "third_party/skia/include/core/SkPaint.h"
+#include "ui/base/l10n/l10n_util.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/font_list.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/size.h"
+#include "url/gurl.h"
+
+namespace favicon_base {
+
+namespace {
+
+// Arbitrary maximum icon size, can be reasonably increased if needed.
+const int kMaxFallbackFaviconSize = 288;
+
+// Returns a single character to represent a page URL. To do this we take the
+// first letter in a domain's name and make it upper case.
+// TODO(huangs): Handle non-ASCII ("xn--") domain names.
+base::string16 GetFallbackIconText(const GURL& url) {
+  std::string domain = net::registry_controlled_domains::GetDomainAndRegistry(
+        url, net::registry_controlled_domains::INCLUDE_PRIVATE_REGISTRIES);
+  return domain.empty() ? base::string16() :
+      base::i18n::ToUpper(base::ASCIIToUTF16(domain.substr(0, 1)));
+}
+
+}  // namespace
+
+FallbackIconService::FallbackIconService(
+    const std::vector<std::string>& font_list)
+  : font_list_(font_list) {
+}
+
+FallbackIconService::~FallbackIconService() {
+}
+
+std::vector<unsigned char> FallbackIconService::RenderFallbackIconBitmap(
+    const GURL& icon_url,
+    int size,
+    const FallbackIconStyle& style) {
+  int size_to_use = std::min(kMaxFallbackFaviconSize, size);
+  gfx::Canvas canvas(gfx::Size(size_to_use, size_to_use), 1.0f, false);
+  DrawFallbackIcon(icon_url, size_to_use, style, &canvas);
+
+  std::vector<unsigned char> bitmap_data;
+  if (!gfx::PNGCodec::EncodeBGRASkBitmap(canvas.ExtractImageRep().sk_bitmap(),
+                                         false, &bitmap_data)) {
+    bitmap_data.clear();
+  }
+  return bitmap_data;
+}
+
+void FallbackIconService::DrawFallbackIcon(const GURL& icon_url,
+                                           int size,
+                                           const FallbackIconStyle& style,
+                                           gfx::Canvas* canvas) {
+  const int kOffsetX = 0;
+  const int kOffsetY = 0;
+  SkPaint paint;
+  paint.setStyle(SkPaint::kFill_Style);
+  paint.setAntiAlias(true);
+
+  // Draw a filled, colored rounded square.
+  paint.setColor(style.background_color);
+  int corner_radius = static_cast<int>(size * style.roundness * 0.5 + 0.5);
+  canvas->DrawRoundRect(
+      gfx::Rect(kOffsetX, kOffsetY, size, size), corner_radius, paint);
+
+  // Draw text.
+  base::string16 icon_text = GetFallbackIconText(icon_url);
+  if (icon_text.empty())
+    return;
+  int font_size = static_cast<int>(size * style.font_size_ratio);
+  if (font_size <= 0)
+    return;
+
+  // TODO(huangs): See how expensive gfx::FontList() is, and possibly cache.
+  canvas->DrawStringRectWithFlags(
+      icon_text,
+      gfx::FontList(font_list_, gfx::Font::NORMAL, font_size),
+      style.text_color,
+      gfx::Rect(kOffsetX, kOffsetY, size, size),
+      gfx::Canvas::TEXT_ALIGN_CENTER);
+}
+
+}  // namespace favicon_base
diff --git a/components/favicon_base/fallback_icon_service.h b/components/favicon_base/fallback_icon_service.h
new file mode 100644
index 0000000..cc98adf
--- /dev/null
+++ b/components/favicon_base/fallback_icon_service.h
@@ -0,0 +1,51 @@
+// 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.
+
+#ifndef COMPONENTS_FAVICON_BASE_FALLBACK_ICON_SERVICE_H_
+#define COMPONENTS_FAVICON_BASE_FALLBACK_ICON_SERVICE_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+
+class GURL;
+
+namespace gfx {
+class Canvas;
+}
+
+namespace favicon_base {
+
+struct FallbackIconStyle;
+
+// A service to provide methods to render fallback favicons.
+class FallbackIconService {
+ public:
+  explicit FallbackIconService(const std::vector<std::string>& font_list);
+  ~FallbackIconService();
+
+  // Renders a fallback icon synchronously and returns the bitmap. Returns an
+  // empty std::vector on failure. |size| is icon width and height in pixels.
+  std::vector<unsigned char> RenderFallbackIconBitmap(
+      const GURL& icon_url,
+      int size,
+      const FallbackIconStyle& style);
+
+ private:
+  // Renders a fallback icon on |canvas| at position (|x|, |y|). |size| is icon
+  // width and height in pixels.
+  void DrawFallbackIcon(const GURL& icon_url,
+                        int size,
+                        const FallbackIconStyle& style,
+                        gfx::Canvas* canvas);
+
+  std::vector<std::string> font_list_;
+
+  DISALLOW_COPY_AND_ASSIGN(FallbackIconService);
+};
+
+}  // namespace favicon_base
+
+#endif  // COMPONENTS_FAVICON_BASE_FALLBACK_ICON_SERVICE_H_
diff --git a/components/favicon_base/fallback_icon_style.cc b/components/favicon_base/fallback_icon_style.cc
new file mode 100644
index 0000000..e620613
--- /dev/null
+++ b/components/favicon_base/fallback_icon_style.cc
@@ -0,0 +1,48 @@
+// 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_style.h"
+
+#include "ui/gfx/color_utils.h"
+
+namespace favicon_base {
+
+namespace {
+
+// Luminance threshold for background color determine whether to use dark or
+// light text color.
+int kDarkTextLuminanceThreshold = 190;
+
+// Default values for FallbackIconStyle.
+SkColor kDefaultBackgroundColor = SkColorSetRGB(0x80, 0x80, 0x80);
+SkColor kDefaultTextColorDark = SK_ColorBLACK;
+SkColor kDefaultTextColorLight = SK_ColorWHITE;
+double kDefaultFontSizeRatio = 0.8;
+double kDefaultRoundness = 0.125;  // 1 / 8.
+
+}  // namespace
+
+FallbackIconStyle::FallbackIconStyle()
+    : background_color(kDefaultBackgroundColor),
+      text_color(kDefaultTextColorLight),
+      font_size_ratio(kDefaultFontSizeRatio),
+      roundness(kDefaultRoundness) {
+}
+
+FallbackIconStyle::~FallbackIconStyle() {
+}
+
+void MatchFallbackIconTextColorAgainstBackgroundColor(
+    FallbackIconStyle* style) {
+  int luminance = color_utils::GetLuminanceForColor(style->background_color);
+  style->text_color = (luminance >= kDarkTextLuminanceThreshold ?
+      kDefaultTextColorDark : kDefaultTextColorLight);
+}
+
+bool ValidateFallbackIconStyle(const FallbackIconStyle& style) {
+  return style.font_size_ratio >= 0.0 && style.font_size_ratio <= 1.0 &&
+      style.roundness >= 0.0 && style.roundness <= 1.0;
+}
+
+}  // namespace favicon_base
diff --git a/components/favicon_base/fallback_icon_style.h b/components/favicon_base/fallback_icon_style.h
new file mode 100644
index 0000000..097636b
--- /dev/null
+++ b/components/favicon_base/fallback_icon_style.h
@@ -0,0 +1,42 @@
+// 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.
+
+#ifndef COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_
+#define COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_
+
+#include "third_party/skia/include/core/SkColor.h"
+
+namespace favicon_base {
+
+// Styling specifications of a fallback icon. The icon is composed of a solid
+// rounded square containing a single letter. The specification excludes the
+// icon URL and size, which are given when the icon is rendered.
+struct FallbackIconStyle {
+  FallbackIconStyle();
+  ~FallbackIconStyle();
+
+  // If any member changes, also update FallbackIconStyleBuilder.
+
+  // Icon background fill color.
+  SkColor background_color;
+
+  // Icon text color.
+  SkColor text_color;
+
+  // Ratio in [0.0, 1.0] of the text font size (pixels) to the icon size.
+  double font_size_ratio;
+
+  // The roundness of the icon's corners. 0 => square icon, 1 => circle icon.
+  double roundness;
+};
+
+// Reassigns |style|'s |text_color| to matches well against |background_color|.
+void MatchFallbackIconTextColorAgainstBackgroundColor(FallbackIconStyle* style);
+
+// Returns whether |style| values are within bounds.
+bool ValidateFallbackIconStyle(const FallbackIconStyle& style);
+
+}  // namespace favicon_base
+
+#endif  // COMPONENTS_FAVICON_BASE_FALLBACK_ICON_STYLE_H_
diff --git a/components/favicon_base/favicon_types.cc b/components/favicon_base/favicon_types.cc
index eb0e7bc..0188f1e 100644
--- a/components/favicon_base/favicon_types.cc
+++ b/components/favicon_base/favicon_types.cc
@@ -6,14 +6,15 @@
 
 namespace favicon_base {
 
-// FaviconImageResult ---------------------------------------------------------
+// ---------------------------------------------------------
+// FaviconImageResult
 
 FaviconImageResult::FaviconImageResult() {}
 
 FaviconImageResult::~FaviconImageResult() {}
 
-// FaviconRawBitmapResult
 // --------------------------------------------------------
+// FaviconRawBitmapResult
 
 FaviconRawBitmapResult::FaviconRawBitmapResult()
     : expired(false), icon_type(INVALID_ICON) {
@@ -22,4 +23,4 @@ FaviconRawBitmapResult::FaviconRawBitmapResult()
 FaviconRawBitmapResult::~FaviconRawBitmapResult() {
 }
 
-}  // namespace chrome
+}  // namespace favicon_base