Loading/Creating images for mutiple scale factors on the fly

ui/gfx/image/image_skia_unittest.cc

+// 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.
+
+#include "ui/gfx/image/image_skia.h"
+
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/image/image_skia_rep.h"
+#include "ui/gfx/image/image_skia_source.h"
+#include "ui/gfx/size.h"
+#include "ui/base/layout.h"
+
+namespace gfx {
+
+namespace {
+
+ImageSkiaRep CreateImage(const gfx::Size& size, ui::ScaleFactor scale_factor) {
+  SkBitmap bitmap;
+  gfx::Size pixel_size = size.Scale(ui::GetScaleFactorScale(scale_factor));
+  bitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                   pixel_size.width(), pixel_size.height());
+  bitmap.allocPixels();
+  return ImageSkiaRep(bitmap, scale_factor);
+}
+
+class FixedSource : public ImageSkiaSource {
+ public:
+  FixedSource(const ImageSkiaRep& image) : image_(image) {}
+
+  virtual ImageSkiaRep GetImageForScale(ui::ScaleFactor scale_factor) OVERRIDE {
+    return image_;
+  }
+
+ private:
+  ImageSkiaRep image_;
+
+  DISALLOW_COPY_AND_ASSIGN(FixedSource);
+};
+
+class DynamicSource : public ImageSkiaSource {
+ public:
+  DynamicSource(const gfx::Size& size) : size_(size) {}
+
+  virtual ImageSkiaRep GetImageForScale(ui::ScaleFactor scale_factor) OVERRIDE {
+    return CreateImage(size_, scale_factor);
+  }
+
+ private:
+  gfx::Size size_;
+
+  DISALLOW_COPY_AND_ASSIGN(DynamicSource);
+};
+
+}  // namespace;
+
+typedef testing::Test ImageSkiaTest;
+
+TEST(ImageSkiaTest, NoSource) {
+  ImageSkia image_skia(NULL, Size(100, 200));
+  EXPECT_FALSE(image_skia.empty());
+  EXPECT_FALSE(image_skia.isNull());  // Is this expected?

[oshima, 2012/07/01 19:01:57]

peter, is this correct?

[pkotwicz, 2012/07/01 22:22:23]

This is correct. When an ImageSkia has an ImageSkiaSource, there is no way for
the ImageSkia to know if the ImageSkiaSource is capable of generating image
reps, other than trying to upon a call to isNull() or empty() which is
suboptimal. Thus, an ImageSkia with an ImageSkiaSource MUST be able to generate
a bitmap for at least one scale factor.
You will have to change GetRepresentation accordingly in order to guarantee this

[oshima, 2012/07/02 16:43:34]

Actually, the soruce should never be NULL (there is no use case to pass NULL),
so I removed this test. Please disregard this question.

[pkotwicz, 2012/07/02 17:13:53]

You are correct that the source should never be NULL. Sorry I didn't read the
test well enough.
But I think you are still missing handling for code which does something like
this.
ImageSkia image_skia(new FixedSource(...));
if (image_skia.isNull())
   SetImage(... some default image ...)
else
   SetImage(image_skia)

[oshima, 2012/07/02 17:26:47]

Do you have real example you want to do this? That is, you set source, but it
may return
null?

[oshima, 2012/07/02 17:48:43]

By the way, I'm thinking of introducing "primary scale factor" so that in case
you want to compute the layout from image's size, we can load it immediately.
I'll add it when I found good example that needs this.

[pkotwicz, 2012/07/02 18:05:12]

I don't know of any case where you would want a source which is unable of
generating bitmaps for any scale.

+  EXPECT_EQ(100, image_skia.width());
+  EXPECT_EQ(200, image_skia.height());
+}
+
+TEST(ImageSkiaTest, FixedSource) {
+  ImageSkiaRep image(CreateImage(Size(100, 200), ui::SCALE_FACTOR_100P));
+  ImageSkia image_skia(new FixedSource(image), Size(100, 200));
+  EXPECT_EQ(0U, image_skia.image_reps().size());
+
+  const ImageSkiaRep& result_100p =
+      image_skia.GetRepresentation(ui::SCALE_FACTOR_100P);
+  EXPECT_EQ(100, result_100p.GetWidth());
+  EXPECT_EQ(200, result_100p.GetHeight());
+  EXPECT_EQ(ui::SCALE_FACTOR_100P, result_100p.scale_factor());
+  EXPECT_EQ(1U, image_skia.image_reps().size());
+
+  const ImageSkiaRep& result_200p =
+      image_skia.GetRepresentation(ui::SCALE_FACTOR_200P);
+
+  EXPECT_EQ(100, result_200p.GetWidth());
+  EXPECT_EQ(200, result_200p.GetHeight());
+  EXPECT_EQ(100, result_200p.pixel_width());
+  EXPECT_EQ(200, result_200p.pixel_height());
+  EXPECT_EQ(ui::SCALE_FACTOR_100P, result_200p.scale_factor());
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+
+  image_skia.GetRepresentation(ui::SCALE_FACTOR_100P);
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+
+  image_skia.GetRepresentation(ui::SCALE_FACTOR_200P);
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+}
+
+TEST(ImageSkiaTest, DynamicSource) {
+  ImageSkia image_skia(new DynamicSource(Size(100, 200)), Size(100, 200));
+  EXPECT_EQ(0U, image_skia.image_reps().size());
+  const ImageSkiaRep& result_100p =
+      image_skia.GetRepresentation(ui::SCALE_FACTOR_100P);
+  EXPECT_EQ(100, result_100p.GetWidth());
+  EXPECT_EQ(200, result_100p.GetHeight());
+  EXPECT_EQ(ui::SCALE_FACTOR_100P, result_100p.scale_factor());
+  EXPECT_EQ(1U, image_skia.image_reps().size());
+
+  const ImageSkiaRep& result_200p =
+      image_skia.GetRepresentation(ui::SCALE_FACTOR_200P);
+  EXPECT_EQ(100, result_200p.GetWidth());
+  EXPECT_EQ(200, result_200p.GetHeight());
+  EXPECT_EQ(200, result_200p.pixel_width());
+  EXPECT_EQ(400, result_200p.pixel_height());
+  EXPECT_EQ(ui::SCALE_FACTOR_200P, result_200p.scale_factor());
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+
+  // Get the representation again and make sure they
+  // retuns the sam
+  image_skia.GetRepresentation(ui::SCALE_FACTOR_100P);
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+  image_skia.GetRepresentation(ui::SCALE_FACTOR_200P);
+  EXPECT_EQ(2U, image_skia.image_reps().size());
+}
+
+}  // namespace gfx