Fix bug where custom cursors would dissappear when screen was rotated

ui/base/cursor/cursor_util.cc

 // Copyright 2014 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/base/cursor/cursor_util.h"
 
 #include "base/logging.h"
 #include "skia/ext/image_operations.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/geometry/point_conversions.h"
 #include "ui/gfx/geometry/size_conversions.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/skbitmap_operations.h"
 #include "ui/gfx/skia_util.h"
 
 namespace ui {
 
+namespace {
+
+// Converts the SkBitmap to use a different alpha type. Returns true if bitmap
+// was modified, otherwise returns false.
+bool ConvertSkBitmapAlphaType(SkBitmap* bitmap, SkAlphaType alphaType) {

[sadrul, 2015/12/18 18:00:09]

alpha_type (see
https://google.github.io/styleguide/cppguide.html#Variable_Names)

[kylechar, 2015/12/18 18:10:31]

Whoops. Spend the last two years writing mostly Java... Fixed.

+  if (bitmap->info().alphaType() == alphaType) {
+    return false;
+  }
+
+  // Copy the bitmap into a temporary buffer. This will convert alpha type.
+  SkImageInfo image_info =
+      SkImageInfo::MakeN32(bitmap->width(), bitmap->height(), alphaType);
+  std::vector<char> buffer(bitmap->getSize());
+  bitmap->readPixels(image_info, &buffer[0], image_info.minRowBytes(), 0, 0);
+  // Read the temporary buffer back into the original bitmap.
+  bitmap->reset();
+  bitmap->allocPixels(image_info);
+  memcpy(bitmap->getPixels(), &buffer[0], buffer.size());
+
+  return true;
+}
+
+} // namespace
+
 void ScaleAndRotateCursorBitmapAndHotpoint(float scale,
                                            gfx::Display::Rotation rotation,
                                            SkBitmap* bitmap,
                                            gfx::Point* hotpoint) {
+  // SkBitmapOperations::Rotate() needs the bitmap to have premultiplied alpha,
+  // so convert bitmap alpha type if we are going to rotate.
+  bool was_converted = false;
+  if (rotation != gfx::Display::ROTATE_0 &&
+      bitmap->info().alphaType() == kUnpremul_SkAlphaType) {
+    ConvertSkBitmapAlphaType(bitmap, kPremul_SkAlphaType);
+    was_converted = true;
+  }
+
   switch (rotation) {
     case gfx::Display::ROTATE_0:
       break;
     case gfx::Display::ROTATE_90:
       hotpoint->SetPoint(bitmap->height() - hotpoint->y(), hotpoint->x());
       *bitmap = SkBitmapOperations::Rotate(
           *bitmap, SkBitmapOperations::ROTATION_90_CW);
       break;
     case gfx::Display::ROTATE_180:
       hotpoint->SetPoint(
           bitmap->width() - hotpoint->x(), bitmap->height() - hotpoint->y());
       *bitmap = SkBitmapOperations::Rotate(
           *bitmap, SkBitmapOperations::ROTATION_180_CW);
       break;
     case gfx::Display::ROTATE_270:
       hotpoint->SetPoint(hotpoint->y(), bitmap->width() - hotpoint->x());
       *bitmap = SkBitmapOperations::Rotate(
           *bitmap, SkBitmapOperations::ROTATION_270_CW);
       break;
   }
 
+  if (was_converted) {
+    ConvertSkBitmapAlphaType(bitmap, kUnpremul_SkAlphaType);
+  }
+
   if (scale < FLT_EPSILON) {
     NOTREACHED() << "Scale must be larger than 0.";
     scale = 1.0f;
   }
 
   if (scale == 1.0f)
     return;
 
   gfx::Size scaled_size = gfx::ScaleToFlooredSize(
       gfx::Size(bitmap->width(), bitmap->height()), scale);
@@ skipping 48 matching lines @@
     SkBitmap cropped = SkBitmapOperations::CreateTiledBitmap(
         bitmap, x_offset, 0, frame_width, frame_height);
     DCHECK_EQ(frame_width, cropped.width());
     DCHECK_EQ(frame_height, cropped.height());
 
     (*bitmaps)[frame] = cropped;
   }
 }
 
 }  // namespace ui