Add a function to scroll a platform canvas. This uses the platform scroll...

gfx/blit_unittest.cc

+// Copyright (c) 2010 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 "base/basictypes.h"
+#include "gfx/blit.h"
+#include "skia/ext/platform_canvas.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace {
+
+// Fills the given canvas with the values by duplicating the values into each
+// color channel for the corresponding pixel.
+//
+// Example values = {{0x0, 0x01}, {0x12, 0xFF}} would give a canvas with:
+//   0x00000000 0x01010101
+//   0x12121212 0xFFFFFFFF
+template<int w, int h>
+void SetToCanvas(skia::PlatformCanvas* canvas, uint8 values[h][w]) {
+  SkBitmap& bitmap = const_cast<SkBitmap&>(
+      canvas->getTopPlatformDevice().accessBitmap(true));
+  SkAutoLockPixels lock(bitmap);
+  ASSERT_EQ(w, bitmap.width());
+  ASSERT_EQ(h, bitmap.height());
+
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      uint8 value = values[y][x];
+      *bitmap.getAddr32(x, y) =
+          (value << 24) | (value << 16) | (value << 8) | value;
+    }
+  }
+}
+
+// Checks each pixel in the given canvas and see if it is made up of the given
+// values, where each value has been duplicated into each channel of the given
+// bitmap (see SetToCanvas above).
+template<int w, int h>
+void VerifyCanvasValues(skia::PlatformCanvas* canvas, uint8 values[h][w]) {
+  SkBitmap& bitmap = const_cast<SkBitmap&>(
+      canvas->getTopPlatformDevice().accessBitmap(true));
+  SkAutoLockPixels lock(bitmap);
+  ASSERT_EQ(w, bitmap.width());
+  ASSERT_EQ(h, bitmap.height());
+
+  for (int y = 0; y < h; y++) {
+    for (int x = 0; x < w; x++) {
+      uint8 value = values[y][x];
+      uint32 expected =
+          (value << 24) | (value << 16) | (value << 8) | value;
+      ASSERT_EQ(expected, *bitmap.getAddr32(x, y));
+    }
+  }
+}
+
+}  // namespace
+
+TEST(Blit, ScrollBasic) {
+  static const int kCanvasWidth = 5;
+  static const int kCanvasHeight = 5;
+  skia::PlatformCanvas canvas(kCanvasWidth, kCanvasHeight, true);
+  uint8 initial_values[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x11, 0x12, 0x13, 0x14 },
+      { 0x20, 0x21, 0x22, 0x23, 0x24 },
+      { 0x30, 0x31, 0x32, 0x33, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  SetToCanvas<5, 5>(&canvas, initial_values);
+
+  // Sanity check on input.
+  VerifyCanvasValues<5, 5>(&canvas, initial_values);
+
+  // Scroll none and make sure it's a NOP.
+  gfx::ScrollCanvas(&canvas,
+                    gfx::Rect(0, 0, kCanvasWidth, kCanvasHeight),
+                    gfx::Point(0, 0));
+
+  // Scroll the center 3 pixels up one.
+  gfx::Rect center_three(1, 1, 3, 3);
+  gfx::ScrollCanvas(&canvas, center_three, gfx::Point(0, -1));
+  uint8 scroll_up_expected[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x21, 0x22, 0x23, 0x14 },
+      { 0x20, 0x31, 0x32, 0x33, 0x24 },
+      { 0x30, 0x31, 0x32, 0x33, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  VerifyCanvasValues<5, 5>(&canvas, scroll_up_expected);
+
+  // Reset and scroll the center 3 pixels down one.
+  SetToCanvas<5, 5>(&canvas, initial_values);
+  gfx::ScrollCanvas(&canvas, center_three, gfx::Point(0, 1));
+  uint8 scroll_down_expected[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x11, 0x12, 0x13, 0x14 },
+      { 0x20, 0x11, 0x12, 0x13, 0x24 },
+      { 0x30, 0x21, 0x22, 0x23, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  VerifyCanvasValues<5, 5>(&canvas, scroll_down_expected);
+
+  // Reset and scroll the center 3 pixels right one.
+  SetToCanvas<5, 5>(&canvas, initial_values);
+  gfx::ScrollCanvas(&canvas, center_three, gfx::Point(1, 0));
+  uint8 scroll_right_expected[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x11, 0x11, 0x12, 0x14 },
+      { 0x20, 0x21, 0x21, 0x22, 0x24 },
+      { 0x30, 0x31, 0x31, 0x32, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  VerifyCanvasValues<5, 5>(&canvas, scroll_right_expected);
+
+  // Reset and scroll the center 3 pixels left one.
+  SetToCanvas<5, 5>(&canvas, initial_values);
+  gfx::ScrollCanvas(&canvas, center_three, gfx::Point(-1, 0));
+  uint8 scroll_left_expected[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x12, 0x13, 0x13, 0x14 },
+      { 0x20, 0x22, 0x23, 0x23, 0x24 },
+      { 0x30, 0x32, 0x33, 0x33, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  VerifyCanvasValues<5, 5>(&canvas, scroll_left_expected);
+
+  // Diagonal scroll.
+  SetToCanvas<5, 5>(&canvas, initial_values);
+  gfx::ScrollCanvas(&canvas, center_three, gfx::Point(2, 2));
+  uint8 scroll_diagonal_expected[kCanvasHeight][kCanvasWidth] = {
+      { 0x00, 0x01, 0x02, 0x03, 0x04 },
+      { 0x10, 0x11, 0x12, 0x13, 0x14 },
+      { 0x20, 0x21, 0x22, 0x23, 0x24 },
+      { 0x30, 0x31, 0x32, 0x11, 0x34 },
+      { 0x40, 0x41, 0x42, 0x43, 0x44 }};
+  VerifyCanvasValues<5, 5>(&canvas, scroll_diagonal_expected);
+}