Add a default constructor for gfx::Image.

BUG=None
TEST=None

Review URL: http://codereview.chromium.org/7101005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123103 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 48 insertions, 3 deletions

diff --git a/ui/gfx/image/image.cc b/ui/gfx/image/image.cc
index d31e2d8..61a84e7 100644
--- a/ui/gfx/image/image.cc
+++ b/ui/gfx/image/image.cc
@@ -100,6 +100,7 @@ class ImageRepSkia : public ImageRep {
   explicit ImageRepSkia(const SkBitmap* bitmap)
       : ImageRep(Image::kImageRepSkia) {
     CHECK(bitmap);
+    // TODO(rohitrao): Add a CHECK to ensure that !bitmap->isNull().
     bitmaps_.push_back(bitmap);
   }
 
@@ -107,6 +108,8 @@ class ImageRepSkia : public ImageRep {
       : ImageRep(Image::kImageRepSkia),
         bitmaps_(bitmaps) {
     CHECK(!bitmaps_.empty());
+    // TODO(rohitrao): Add a CHECK to ensure that !bitmap->isNull() for each
+    // vector element.
   }
 
   virtual ~ImageRepSkia() {
@@ -230,6 +233,10 @@ class ImageStorage : public base::RefCounted<ImageStorage> {
 
 }  // namespace internal
 
+Image::Image() {
+  // |storage_| is NULL for empty Images.
+}
+
 Image::Image(const SkBitmap* bitmap)
     : storage_(new internal::ImageStorage(Image::kImageRepSkia)) {
   internal::ImageRepSkia* rep = new internal::ImageRepSkia(bitmap);
@@ -334,18 +341,26 @@ Image::operator NSImage*() const {
 #endif
 
 bool Image::HasRepresentation(RepresentationType type) const {
-  return storage_->representations().count(type) != 0;
+  return storage_.get() && storage_->representations().count(type) != 0;
 }
 
 size_t Image::RepresentationCount() const {
+  if (!storage_.get())
+    return 0;
+
   return storage_->representations().size();
 }
 
+bool Image::IsEmpty() const {
+  return RepresentationCount() == 0;
+}
+
 void Image::SwapRepresentations(gfx::Image* other) {
   storage_.swap(other->storage_);
 }
 
 internal::ImageRep* Image::DefaultRepresentation() const {
+  CHECK(storage_.get());
   RepresentationMap& representations = storage_->representations();
   RepresentationMap::iterator it =
       representations.find(storage_->default_representation_type());
@@ -355,6 +370,7 @@ internal::ImageRep* Image::DefaultRepresentation() const {
 
 internal::ImageRep* Image::GetRepresentation(
     RepresentationType rep_type) const {
+  CHECK(storage_.get());
   // If the requested rep is the default, return it.
   internal::ImageRep* default_rep = DefaultRepresentation();
   if (rep_type == storage_->default_representation_type())
@@ -435,6 +451,7 @@ internal::ImageRep* Image::GetRepresentation(
 }
 
 void Image::AddRepresentation(internal::ImageRep* rep) const {
+  CHECK(storage_.get());
   storage_->representations().insert(std::make_pair(rep->type(), rep));
 }
 
diff --git a/ui/gfx/image/image.h b/ui/gfx/image/image.h
index dd4b8ec..d5e630b 100644
--- a/ui/gfx/image/image.h
+++ b/ui/gfx/image/image.h
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -12,6 +12,9 @@
 // cheaply passed around by value, the actual image data is stored in a ref-
 // counted member. When all Images referencing this storage are deleted, the
 // actual representations are deleted, too.
+//
+// Images can be empty, in which case they have no backing representation.
+// Attempting to use an empty Image will result in a crash.
 
 #ifndef UI_GFX_IMAGE_IMAGE_H_
 #define UI_GFX_IMAGE_IMAGE_H_
@@ -55,6 +58,9 @@ class UI_EXPORT Image {
 
   typedef std::map<RepresentationType, internal::ImageRep*> RepresentationMap;
 
+  // Creates an empty image with no representations.
+  Image();
+
   // Creates a new image with the default representation. The object will take
   // ownership of the image.
   explicit Image(const SkBitmap* bitmap);
@@ -134,6 +140,9 @@ class UI_EXPORT Image {
   // Returns the number of representations.
   size_t RepresentationCount() const;
 
+  // Returns true if this Image has no representations.
+  bool IsEmpty() const;
+
   // Swaps this image's internal representations with |other|.
   void SwapRepresentations(gfx::Image* other);
 
diff --git a/ui/gfx/image/image_unittest.cc b/ui/gfx/image/image_unittest.cc
index 2c82700..6cc622a 100644
--- a/ui/gfx/image/image_unittest.cc
+++ b/ui/gfx/image/image_unittest.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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.
 
@@ -29,6 +29,25 @@ class ImageTest : public testing::Test {
 
 namespace gt = gfx::test;
 
+TEST_F(ImageTest, EmptyImage) {
+  // Test the default constructor.
+  gfx::Image image;
+  EXPECT_EQ(0U, image.RepresentationCount());
+  EXPECT_TRUE(image.IsEmpty());
+
+  // Test the copy constructor.
+  gfx::Image imageCopy(image);
+  EXPECT_TRUE(imageCopy.IsEmpty());
+
+  // Test calling SwapRepresentations() with an empty image.
+  gfx::Image image2(gt::CreateBitmap(25, 25));
+  EXPECT_FALSE(image2.IsEmpty());
+
+  image.SwapRepresentations(&image2);
+  EXPECT_FALSE(image.IsEmpty());
+  EXPECT_TRUE(image2.IsEmpty());
+}
+
 TEST_F(ImageTest, SkiaToSkia) {
   gfx::Image image(gt::CreateBitmap(25, 25));
   const SkBitmap* bitmap = image.ToSkBitmap();