[Extensions UI] Add a placeholder icon for extensions in the toolbar

extensions/browser/extension_icon_placeholder.cc

+// 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 "extensions/browser/extension_icon_placeholder.h"
+
+#include "base/strings/string_util.h"
+#include "base/strings/utf_string_conversions.h"
+#include "extensions/grit/extensions_browser_resources.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/codec/png_codec.h"
+#include "ui/gfx/geometry/rect.h"
+#include "ui/gfx/geometry/size.h"
+#include "ui/gfx/image/canvas_image_source.h"
+#include "ui/gfx/image/image_skia.h"
+
+namespace extensions {
+
+namespace {
+
+// Returns the FontStyle to use for the given icon |size|.
+ui::ResourceBundle::FontStyle GetFontStyleForIconSize(
+    extension_misc::ExtensionIcons size) {
+  switch (size) {
+    case extension_misc::EXTENSION_ICON_INVALID:
+    case extension_misc::EXTENSION_ICON_BITTY:
+      return ui::ResourceBundle::SmallFont;
+    case extension_misc::EXTENSION_ICON_ACTION:
+    case extension_misc::EXTENSION_ICON_SMALLISH:
+    case extension_misc::EXTENSION_ICON_SMALL:
+      return ui::ResourceBundle::MediumFont;
+    case extension_misc::EXTENSION_ICON_MEDIUM:
+    case extension_misc::EXTENSION_ICON_LARGE:
+    case extension_misc::EXTENSION_ICON_EXTRA_LARGE:
+    case extension_misc::EXTENSION_ICON_GIGANTOR:
+      return ui::ResourceBundle::LargeFont;
+  }
+  NOTREACHED();
+  return ui::ResourceBundle::MediumFont;
+}
+
+// Returns the background image to use for the given icon |size|.
+gfx::Image GetBackgroundImageForIconSize(extension_misc::ExtensionIcons size) {
+  int resource_id = 0;
+  // Right now, we have resources for a 19x19 (action) and a 48x48 (extensions
+  // page icon). The implementation of the placeholder scales these correctly,
+  // so it's not a big deal to use these for other sizes, but if it's something
+  // that will be done frequently, we should probably make a devoted asset for
+  // that size.
+  switch (size) {
+    case extension_misc::EXTENSION_ICON_INVALID:
+    case extension_misc::EXTENSION_ICON_BITTY:
+    case extension_misc::EXTENSION_ICON_ACTION:
+    case extension_misc::EXTENSION_ICON_SMALLISH:
+    case extension_misc::EXTENSION_ICON_SMALL:
+      resource_id = IDR_EXTENSION_ACTION_PLAIN_BACKGROUND;
+      break;
+    case extension_misc::EXTENSION_ICON_MEDIUM:
+    case extension_misc::EXTENSION_ICON_LARGE:
+    case extension_misc::EXTENSION_ICON_EXTRA_LARGE:
+    case extension_misc::EXTENSION_ICON_GIGANTOR:
+      resource_id = IDR_EXTENSION_ICON_PLAIN_BACKGROUND;
+      break;
+  }
+  return ui::ResourceBundle::GetSharedInstance().GetImageNamed(resource_id);
+}
+
+}  // namespace
+
+ExtensionIconPlaceholder::ExtensionIconPlaceholder(
+    extension_misc::ExtensionIcons size,
+    const std::string& letter)
+    : gfx::CanvasImageSource(gfx::Size(size, size), false),
+      icon_size_(size),
+      letter_(base::UTF8ToUTF16(letter.substr(0, 1))),
+      base_image_(GetBackgroundImageForIconSize(size)) {
+}
+
+ExtensionIconPlaceholder::~ExtensionIconPlaceholder() {
+}
+
+gfx::Image ExtensionIconPlaceholder::CreateImage(
+    extension_misc::ExtensionIcons size,
+    const std::string& name) {
+  return gfx::Image(gfx::ImageSkia(new ExtensionIconPlaceholder(size, name),
+                                   gfx::Size(size, size)));
+}
+
+void ExtensionIconPlaceholder::Draw(gfx::Canvas* canvas) {
+  // Draw the background image, correctly scaled.
+  canvas->DrawImageInt(*base_image_.ToImageSkia(), 0, 0,
+                       base_image_.Size().width(), base_image_.Size().height(),
+                       0, 0, size().width(), size().height(), true);
+  gfx::Rect bounds(size().width(), size().height());
+  // Draw the letter on top.
+  canvas->DrawStringRectWithFlags(
+      letter_, ui::ResourceBundle::GetSharedInstance().GetFontList(
+                   GetFontStyleForIconSize(icon_size_)),
+      SK_ColorWHITE, bounds, gfx::Canvas::TEXT_ALIGN_CENTER);
+}
+
+}  // namespace extensions