src/cc/base/tiling_data.cc

   1 // Copyright 2010 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "cc/base/tiling_data.h"
   6
   7 #include <algorithm>
   8
   9 #include "ui/gfx/rect.h"
  10 #include "ui/gfx/vector2d.h"
  11
  12 namespace cc {
  13
  14 static int ComputeNumTiles(int max_texture_size,
  15                            int total_size,
  16                            int border_texels) {
  17   if (max_texture_size - 2 * border_texels <= 0)
  18     return total_size > 0 && max_texture_size >= total_size ? 1 : 0;
  19
  20   int num_tiles = std::max(1,
  21                            1 + (total_size - 1 - 2 * border_texels) /
  22                            (max_texture_size - 2 * border_texels));
  23   return total_size > 0 ? num_tiles : 0;
  24 }
  25
  26 TilingData::TilingData()
  27     : border_texels_(0) {
  28   RecomputeNumTiles();
  29 }
  30
  31 TilingData::TilingData(const gfx::Size& max_texture_size,
  32                        const gfx::Rect& tiling_rect,
  33                        bool has_border_texels)
  34     : max_texture_size_(max_texture_size),
  35       tiling_rect_(tiling_rect),
  36       border_texels_(has_border_texels ? 1 : 0) {
  37   RecomputeNumTiles();
  38 }
  39
  40 TilingData::TilingData(const gfx::Size& max_texture_size,
  41                        const gfx::Rect& tiling_rect,
  42                        int border_texels)
  43     : max_texture_size_(max_texture_size),
  44       tiling_rect_(tiling_rect),
  45       border_texels_(border_texels) {
  46   RecomputeNumTiles();
  47 }
  48
  49 void TilingData::SetTilingRect(const gfx::Rect& tiling_rect) {
  50   tiling_rect_ = tiling_rect;
  51   RecomputeNumTiles();
  52 }
  53
  54 void TilingData::SetMaxTextureSize(const gfx::Size& max_texture_size) {
  55   max_texture_size_ = max_texture_size;
  56   RecomputeNumTiles();
  57 }
  58
  59 void TilingData::SetHasBorderTexels(bool has_border_texels) {
  60   border_texels_ = has_border_texels ? 1 : 0;
  61   RecomputeNumTiles();
  62 }
  63
  64 void TilingData::SetBorderTexels(int border_texels) {
  65   border_texels_ = border_texels;
  66   RecomputeNumTiles();
  67 }
  68
  69 int TilingData::TileXIndexFromSrcCoord(int src_position) const {
  70   if (num_tiles_x_ <= 1)
  71     return 0;
  72
  73   src_position -= tiling_rect_.x();
  74
  75   DCHECK_GT(max_texture_size_.width() - 2 * border_texels_, 0);
  76   int x = (src_position - border_texels_) /
  77       (max_texture_size_.width() - 2 * border_texels_);
  78   return std::min(std::max(x, 0), num_tiles_x_ - 1);
  79 }
  80
  81 int TilingData::TileYIndexFromSrcCoord(int src_position) const {
  82   if (num_tiles_y_ <= 1)
  83     return 0;
  84
  85   src_position -= tiling_rect_.y();
  86
  87   DCHECK_GT(max_texture_size_.height() - 2 * border_texels_, 0);
  88   int y = (src_position - border_texels_) /
  89       (max_texture_size_.height() - 2 * border_texels_);
  90   return std::min(std::max(y, 0), num_tiles_y_ - 1);
  91 }
  92
  93 int TilingData::FirstBorderTileXIndexFromSrcCoord(int src_position) const {
  94   if (num_tiles_x_ <= 1)
  95     return 0;
  96
  97   src_position -= tiling_rect_.x();
  98
  99   DCHECK_GT(max_texture_size_.width() - 2 * border_texels_, 0);
 100   int inner_tile_size = max_texture_size_.width() - 2 * border_texels_;
 101   int x = (src_position - 2 * border_texels_) / inner_tile_size;
 102   return std::min(std::max(x, 0), num_tiles_x_ - 1);
 103 }
 104
 105 int TilingData::FirstBorderTileYIndexFromSrcCoord(int src_position) const {
 106   if (num_tiles_y_ <= 1)
 107     return 0;
 108
 109   src_position -= tiling_rect_.y();
 110
 111   DCHECK_GT(max_texture_size_.height() - 2 * border_texels_, 0);
 112   int inner_tile_size = max_texture_size_.height() - 2 * border_texels_;
 113   int y = (src_position - 2 * border_texels_) / inner_tile_size;
 114   return std::min(std::max(y, 0), num_tiles_y_ - 1);
 115 }
 116
 117 int TilingData::LastBorderTileXIndexFromSrcCoord(int src_position) const {
 118   if (num_tiles_x_ <= 1)
 119     return 0;
 120
 121   src_position -= tiling_rect_.x();
 122
 123   DCHECK_GT(max_texture_size_.width() - 2 * border_texels_, 0);
 124   int inner_tile_size = max_texture_size_.width() - 2 * border_texels_;
 125   int x = src_position / inner_tile_size;
 126   return std::min(std::max(x, 0), num_tiles_x_ - 1);
 127 }
 128
 129 int TilingData::LastBorderTileYIndexFromSrcCoord(int src_position) const {
 130   if (num_tiles_y_ <= 1)
 131     return 0;
 132
 133   src_position -= tiling_rect_.y();
 134
 135   DCHECK_GT(max_texture_size_.height() - 2 * border_texels_, 0);
 136   int inner_tile_size = max_texture_size_.height() - 2 * border_texels_;
 137   int y = src_position / inner_tile_size;
 138   return std::min(std::max(y, 0), num_tiles_y_ - 1);
 139 }
 140
 141 gfx::Rect TilingData::ExpandRectToTileBoundsWithBorders(
 142     const gfx::Rect rect) const {
 143   if (!rect.Intersects(tiling_rect_) || has_empty_bounds())
 144     return gfx::Rect();
 145   int index_x = FirstBorderTileXIndexFromSrcCoord(rect.x());
 146   int index_y = FirstBorderTileYIndexFromSrcCoord(rect.y());
 147   int index_right = LastBorderTileXIndexFromSrcCoord(rect.right());
 148   int index_bottom = LastBorderTileYIndexFromSrcCoord(rect.bottom());
 149
 150   gfx::Rect rect_top_left(TileBoundsWithBorder(index_x, index_y));
 151   gfx::Rect rect_bottom_right(TileBoundsWithBorder(index_right, index_bottom));
 152
 153   gfx::Rect expanded(rect_top_left);
 154   expanded.Union(rect_bottom_right);
 155   return expanded;
 156 }
 157
 158 gfx::Rect TilingData::TileBounds(int i, int j) const {
 159   AssertTile(i, j);
 160   int max_texture_size_x = max_texture_size_.width() - 2 * border_texels_;
 161   int max_texture_size_y = max_texture_size_.height() - 2 * border_texels_;
 162
 163   int lo_x = tiling_rect_.x() + max_texture_size_x * i;
 164   if (i != 0)
 165     lo_x += border_texels_;
 166
 167   int lo_y = tiling_rect_.y() + max_texture_size_y * j;
 168   if (j != 0)
 169     lo_y += border_texels_;
 170
 171   int hi_x = tiling_rect_.x() + max_texture_size_x * (i + 1) + border_texels_;
 172   if (i + 1 == num_tiles_x_)
 173     hi_x += border_texels_;
 174
 175   int hi_y = tiling_rect_.y() + max_texture_size_y * (j + 1) + border_texels_;
 176   if (j + 1 == num_tiles_y_)
 177     hi_y += border_texels_;
 178
 179   hi_x = std::min(hi_x, tiling_rect_.right());
 180   hi_y = std::min(hi_y, tiling_rect_.bottom());
 181
 182   int x = lo_x;
 183   int y = lo_y;
 184   int width = hi_x - lo_x;
 185   int height = hi_y - lo_y;
 186   DCHECK_GE(x, tiling_rect_.x());
 187   DCHECK_GE(y, tiling_rect_.y());
 188   DCHECK_GE(width, 0);
 189   DCHECK_GE(height, 0);
 190   DCHECK_LE(x, tiling_rect_.right());
 191   DCHECK_LE(y, tiling_rect_.bottom());
 192   return gfx::Rect(x, y, width, height);
 193 }
 194
 195 gfx::Rect TilingData::TileBoundsWithBorder(int i, int j) const {
 196   AssertTile(i, j);
 197   int max_texture_size_x = max_texture_size_.width() - 2 * border_texels_;
 198   int max_texture_size_y = max_texture_size_.height() - 2 * border_texels_;
 199
 200   int lo_x = tiling_rect_.x() + max_texture_size_x * i;
 201   int lo_y = tiling_rect_.y() + max_texture_size_y * j;
 202
 203   int hi_x = lo_x + max_texture_size_x + 2 * border_texels_;
 204   int hi_y = lo_y + max_texture_size_y + 2 * border_texels_;
 205
 206   hi_x = std::min(hi_x, tiling_rect_.right());
 207   hi_y = std::min(hi_y, tiling_rect_.bottom());
 208
 209   int x = lo_x;
 210   int y = lo_y;
 211   int width = hi_x - lo_x;
 212   int height = hi_y - lo_y;
 213   DCHECK_GE(x, tiling_rect_.x());
 214   DCHECK_GE(y, tiling_rect_.y());
 215   DCHECK_GE(width, 0);
 216   DCHECK_GE(height, 0);
 217   DCHECK_LE(x, tiling_rect_.right());
 218   DCHECK_LE(y, tiling_rect_.bottom());
 219   return gfx::Rect(x, y, width, height);
 220 }
 221
 222 int TilingData::TilePositionX(int x_index) const {
 223   DCHECK_GE(x_index, 0);
 224   DCHECK_LT(x_index, num_tiles_x_);
 225
 226   int pos = (max_texture_size_.width() - 2 * border_texels_) * x_index;
 227   if (x_index != 0)
 228     pos += border_texels_;
 229
 230   pos += tiling_rect_.x();
 231
 232   return pos;
 233 }
 234
 235 int TilingData::TilePositionY(int y_index) const {
 236   DCHECK_GE(y_index, 0);
 237   DCHECK_LT(y_index, num_tiles_y_);
 238
 239   int pos = (max_texture_size_.height() - 2 * border_texels_) * y_index;
 240   if (y_index != 0)
 241     pos += border_texels_;
 242
 243   pos += tiling_rect_.y();
 244
 245   return pos;
 246 }
 247
 248 int TilingData::TileSizeX(int x_index) const {
 249   DCHECK_GE(x_index, 0);
 250   DCHECK_LT(x_index, num_tiles_x_);
 251
 252   if (!x_index && num_tiles_x_ == 1)
 253     return tiling_rect_.width();
 254   if (!x_index && num_tiles_x_ > 1)
 255     return max_texture_size_.width() - border_texels_;
 256   if (x_index < num_tiles_x_ - 1)
 257     return max_texture_size_.width() - 2 * border_texels_;
 258   if (x_index == num_tiles_x_ - 1)
 259     return tiling_rect_.right() - TilePositionX(x_index);
 260
 261   NOTREACHED();
 262   return 0;
 263 }
 264
 265 int TilingData::TileSizeY(int y_index) const {
 266   DCHECK_GE(y_index, 0);
 267   DCHECK_LT(y_index, num_tiles_y_);
 268
 269   if (!y_index && num_tiles_y_ == 1)
 270     return tiling_rect_.height();
 271   if (!y_index && num_tiles_y_ > 1)
 272     return max_texture_size_.height() - border_texels_;
 273   if (y_index < num_tiles_y_ - 1)
 274     return max_texture_size_.height() - 2 * border_texels_;
 275   if (y_index == num_tiles_y_ - 1)
 276     return tiling_rect_.bottom() - TilePositionY(y_index);
 277
 278   NOTREACHED();
 279   return 0;
 280 }
 281
 282 gfx::Vector2d TilingData::TextureOffset(int x_index, int y_index) const {
 283   int left = (!x_index || num_tiles_x_ == 1) ? 0 : border_texels_;
 284   int top = (!y_index || num_tiles_y_ == 1) ? 0 : border_texels_;
 285
 286   return gfx::Vector2d(left, top);
 287 }
 288
 289 void TilingData::RecomputeNumTiles() {
 290   num_tiles_x_ = ComputeNumTiles(
 291       max_texture_size_.width(), tiling_rect_.width(), border_texels_);
 292   num_tiles_y_ = ComputeNumTiles(
 293       max_texture_size_.height(), tiling_rect_.height(), border_texels_);
 294 }
 295
 296 TilingData::BaseIterator::BaseIterator(const TilingData* tiling_data)
 297     : tiling_data_(tiling_data),
 298       index_x_(-1),
 299       index_y_(-1) {
 300 }
 301
 302 TilingData::Iterator::Iterator() : BaseIterator(NULL) { done(); }
 303
 304 TilingData::Iterator::Iterator(const TilingData* tiling_data,
 305                                const gfx::Rect& tiling_rect,
 306                                bool include_borders)
 307     : BaseIterator(tiling_data), left_(-1), right_(-1), bottom_(-1) {
 308   if (tiling_data_->num_tiles_x() <= 0 || tiling_data_->num_tiles_y() <= 0) {
 309     done();
 310     return;
 311   }
 312
 313   gfx::Rect rect(tiling_rect);
 314   rect.Intersect(tiling_data_->tiling_rect());
 315
 316   gfx::Rect top_left_tile;
 317   if (include_borders) {
 318     index_x_ = tiling_data_->FirstBorderTileXIndexFromSrcCoord(rect.x());
 319     index_y_ = tiling_data_->FirstBorderTileYIndexFromSrcCoord(rect.y());
 320     right_ = tiling_data_->LastBorderTileXIndexFromSrcCoord(rect.right() - 1);
 321     bottom_ = tiling_data_->LastBorderTileYIndexFromSrcCoord(rect.bottom() - 1);
 322     top_left_tile = tiling_data_->TileBoundsWithBorder(index_x_, index_y_);
 323   } else {
 324     index_x_ = tiling_data_->TileXIndexFromSrcCoord(rect.x());
 325     index_y_ = tiling_data_->TileYIndexFromSrcCoord(rect.y());
 326     right_ = tiling_data_->TileXIndexFromSrcCoord(rect.right() - 1);
 327     bottom_ = tiling_data_->TileYIndexFromSrcCoord(rect.bottom() - 1);
 328     top_left_tile = tiling_data_->TileBounds(index_x_, index_y_);
 329   }
 330   left_ = index_x_;
 331
 332   // Index functions always return valid indices, so explicitly check
 333   // for non-intersecting rects.
 334   if (!top_left_tile.Intersects(rect))
 335     done();
 336 }
 337
 338 TilingData::Iterator& TilingData::Iterator::operator++() {
 339   if (!*this)
 340     return *this;
 341
 342   index_x_++;
 343   if (index_x_ > right_) {
 344     index_x_ = left_;
 345     index_y_++;
 346     if (index_y_ > bottom_)
 347       done();
 348   }
 349
 350   return *this;
 351 }
 352
 353 TilingData::DifferenceIterator::DifferenceIterator(
 354     const TilingData* tiling_data,
 355     const gfx::Rect& consider_rect,
 356     const gfx::Rect& ignore_rect)
 357     : BaseIterator(tiling_data),
 358       consider_left_(-1),
 359       consider_top_(-1),
 360       consider_right_(-1),
 361       consider_bottom_(-1),
 362       ignore_left_(-1),
 363       ignore_top_(-1),
 364       ignore_right_(-1),
 365       ignore_bottom_(-1) {
 366   if (tiling_data_->num_tiles_x() <= 0 || tiling_data_->num_tiles_y() <= 0) {
 367     done();
 368     return;
 369   }
 370
 371   gfx::Rect consider(consider_rect);
 372   gfx::Rect ignore(ignore_rect);
 373   consider.Intersect(tiling_data_->tiling_rect());
 374   ignore.Intersect(tiling_data_->tiling_rect());
 375   if (consider.IsEmpty()) {
 376     done();
 377     return;
 378   }
 379
 380   consider_left_ =
 381       tiling_data_->FirstBorderTileXIndexFromSrcCoord(consider.x());
 382   consider_top_ =
 383       tiling_data_->FirstBorderTileYIndexFromSrcCoord(consider.y());
 384   consider_right_ =
 385       tiling_data_->LastBorderTileXIndexFromSrcCoord(consider.right() - 1);
 386   consider_bottom_ =
 387       tiling_data_->LastBorderTileYIndexFromSrcCoord(consider.bottom() - 1);
 388
 389   if (!ignore.IsEmpty()) {
 390     ignore_left_ =
 391         tiling_data_->FirstBorderTileXIndexFromSrcCoord(ignore.x());
 392     ignore_top_ =
 393         tiling_data_->FirstBorderTileYIndexFromSrcCoord(ignore.y());
 394     ignore_right_ =
 395         tiling_data_->LastBorderTileXIndexFromSrcCoord(ignore.right() - 1);
 396     ignore_bottom_ =
 397         tiling_data_->LastBorderTileYIndexFromSrcCoord(ignore.bottom() - 1);
 398
 399     // Clamp ignore indices to consider indices.
 400     ignore_left_ = std::max(ignore_left_, consider_left_);
 401     ignore_top_ = std::max(ignore_top_, consider_top_);
 402     ignore_right_ = std::min(ignore_right_, consider_right_);
 403     ignore_bottom_ = std::min(ignore_bottom_, consider_bottom_);
 404   }
 405
 406   if (ignore_left_ == consider_left_ && ignore_right_ == consider_right_ &&
 407       ignore_top_ == consider_top_ && ignore_bottom_ == consider_bottom_) {
 408     done();
 409     return;
 410   }
 411
 412   index_x_ = consider_left_;
 413   index_y_ = consider_top_;
 414
 415   if (in_ignore_rect())
 416     ++(*this);
 417 }
 418
 419 TilingData::DifferenceIterator& TilingData::DifferenceIterator::operator++() {
 420   if (!*this)
 421     return *this;
 422
 423   index_x_++;
 424   if (in_ignore_rect())
 425     index_x_ = ignore_right_ + 1;
 426
 427   if (index_x_ > consider_right_) {
 428     index_x_ = consider_left_;
 429     index_y_++;
 430
 431     if (in_ignore_rect()) {
 432       index_x_ = ignore_right_ + 1;
 433       // If the ignore rect spans the whole consider rect horizontally, then
 434       // ignore_right + 1 will be out of bounds.
 435       if (in_ignore_rect() || index_x_ > consider_right_) {
 436         index_y_ = ignore_bottom_ + 1;
 437         index_x_ = consider_left_;
 438       }
 439     }
 440
 441     if (index_y_ > consider_bottom_)
 442       done();
 443   }
 444
 445   return *this;
 446 }
 447
 448 TilingData::SpiralDifferenceIterator::SpiralDifferenceIterator()
 449     : BaseIterator(NULL) {
 450   done();
 451 }
 452
 453 TilingData::SpiralDifferenceIterator::SpiralDifferenceIterator(
 454     const TilingData* tiling_data,
 455     const gfx::Rect& consider_rect,
 456     const gfx::Rect& ignore_rect,
 457     const gfx::Rect& center_rect)
 458     : BaseIterator(tiling_data),
 459       consider_left_(-1),
 460       consider_top_(-1),
 461       consider_right_(-1),
 462       consider_bottom_(-1),
 463       ignore_left_(-1),
 464       ignore_top_(-1),
 465       ignore_right_(-1),
 466       ignore_bottom_(-1),
 467       direction_(RIGHT),
 468       delta_x_(1),
 469       delta_y_(0),
 470       current_step_(0),
 471       horizontal_step_count_(0),
 472       vertical_step_count_(0) {
 473   if (tiling_data_->num_tiles_x() <= 0 || tiling_data_->num_tiles_y() <= 0) {
 474     done();
 475     return;
 476   }
 477
 478   gfx::Rect consider(consider_rect);
 479   gfx::Rect ignore(ignore_rect);
 480   gfx::Rect center(center_rect);
 481   consider.Intersect(tiling_data_->tiling_rect());
 482   ignore.Intersect(tiling_data_->tiling_rect());
 483   if (consider.IsEmpty()) {
 484     done();
 485     return;
 486   }
 487
 488   consider_left_ =
 489       tiling_data_->FirstBorderTileXIndexFromSrcCoord(consider.x());
 490   consider_top_ = tiling_data_->FirstBorderTileYIndexFromSrcCoord(consider.y());
 491   consider_right_ =
 492       tiling_data_->LastBorderTileXIndexFromSrcCoord(consider.right() - 1);
 493   consider_bottom_ =
 494       tiling_data_->LastBorderTileYIndexFromSrcCoord(consider.bottom() - 1);
 495
 496   if (!ignore.IsEmpty()) {
 497     ignore_left_ = tiling_data_->FirstBorderTileXIndexFromSrcCoord(ignore.x());
 498     ignore_top_ = tiling_data_->FirstBorderTileYIndexFromSrcCoord(ignore.y());
 499     ignore_right_ =
 500         tiling_data_->LastBorderTileXIndexFromSrcCoord(ignore.right() - 1);
 501     ignore_bottom_ =
 502         tiling_data_->LastBorderTileYIndexFromSrcCoord(ignore.bottom() - 1);
 503
 504     // Clamp ignore indices to consider indices.
 505     ignore_left_ = std::max(ignore_left_, consider_left_);
 506     ignore_top_ = std::max(ignore_top_, consider_top_);
 507     ignore_right_ = std::min(ignore_right_, consider_right_);
 508     ignore_bottom_ = std::min(ignore_bottom_, consider_bottom_);
 509   }
 510
 511   if (ignore_left_ == consider_left_ && ignore_right_ == consider_right_ &&
 512       ignore_top_ == consider_top_ && ignore_bottom_ == consider_bottom_) {
 513     done();
 514     return;
 515   }
 516
 517   // Determine around left, such that it is between -1 and num_tiles_x.
 518   int around_left = 0;
 519   if (center.x() < tiling_data->tiling_rect().x() || center.IsEmpty())
 520     around_left = -1;
 521   else if (center.x() > tiling_data->tiling_rect().right())
 522     around_left = tiling_data->num_tiles_x();
 523   else
 524     around_left = tiling_data->FirstBorderTileXIndexFromSrcCoord(center.x());
 525
 526   // Determine around top, such that it is between -1 and num_tiles_y.
 527   int around_top = 0;
 528   if (center.y() < tiling_data->tiling_rect().y() || center.IsEmpty())
 529     around_top = -1;
 530   else if (center.y() > tiling_data->tiling_rect().bottom())
 531     around_top = tiling_data->num_tiles_y();
 532   else
 533     around_top = tiling_data->FirstBorderTileYIndexFromSrcCoord(center.y());
 534
 535   // Determine around right, such that it is between -1 and num_tiles_x.
 536   int right_src_coord = center.right() - 1;
 537   int around_right = 0;
 538   if (right_src_coord < tiling_data->tiling_rect().x() || center.IsEmpty()) {
 539     around_right = -1;
 540   } else if (right_src_coord > tiling_data->tiling_rect().right()) {
 541     around_right = tiling_data->num_tiles_x();
 542   } else {
 543     around_right =
 544         tiling_data->LastBorderTileXIndexFromSrcCoord(right_src_coord);
 545   }
 546
 547   // Determine around bottom, such that it is between -1 and num_tiles_y.
 548   int bottom_src_coord = center.bottom() - 1;
 549   int around_bottom = 0;
 550   if (bottom_src_coord < tiling_data->tiling_rect().y() || center.IsEmpty()) {
 551     around_bottom = -1;
 552   } else if (bottom_src_coord > tiling_data->tiling_rect().bottom()) {
 553     around_bottom = tiling_data->num_tiles_y();
 554   } else {
 555     around_bottom =
 556         tiling_data->LastBorderTileYIndexFromSrcCoord(bottom_src_coord);
 557   }
 558
 559   vertical_step_count_ = around_bottom - around_top + 1;
 560   horizontal_step_count_ = around_right - around_left + 1;
 561   current_step_ = horizontal_step_count_ - 1;
 562
 563   index_x_ = around_right;
 564   index_y_ = around_bottom;
 565
 566   // The current index is the bottom right of the around rect, which is also
 567   // ignored. So we have to advance.
 568   ++(*this);
 569 }
 570
 571 TilingData::SpiralDifferenceIterator& TilingData::SpiralDifferenceIterator::
 572 operator++() {
 573   int cannot_hit_consider_count = 0;
 574   while (cannot_hit_consider_count < 4) {
 575     if (needs_direction_switch())
 576       switch_direction();
 577
 578     index_x_ += delta_x_;
 579     index_y_ += delta_y_;
 580     ++current_step_;
 581
 582     if (in_consider_rect()) {
 583       cannot_hit_consider_count = 0;
 584
 585       if (!in_ignore_rect())
 586         break;
 587
 588       // Steps needed to reach the very edge of the ignore rect, while remaining
 589       // inside (so that the continue would take us outside).
 590       int steps_to_edge = 0;
 591       switch (direction_) {
 592         case UP:
 593           steps_to_edge = index_y_ - ignore_top_;
 594           break;
 595         case LEFT:
 596           steps_to_edge = index_x_ - ignore_left_;
 597           break;
 598         case DOWN:
 599           steps_to_edge = ignore_bottom_ - index_y_;
 600           break;
 601         case RIGHT:
 602           steps_to_edge = ignore_right_ - index_x_;
 603           break;
 604       }
 605
 606       // We need to switch directions in |max_steps|.
 607       int max_steps = current_step_count() - current_step_;
 608
 609       int steps_to_take = std::min(steps_to_edge, max_steps);
 610       DCHECK_GE(steps_to_take, 0);
 611
 612       index_x_ += steps_to_take * delta_x_;
 613       index_y_ += steps_to_take * delta_y_;
 614       current_step_ += steps_to_take;
 615     } else {
 616       int max_steps = current_step_count() - current_step_;
 617       int steps_to_take = max_steps;
 618       bool can_hit_consider_rect = false;
 619       switch (direction_) {
 620         case UP:
 621           if (valid_column() && consider_bottom_ < index_y_)
 622             steps_to_take = index_y_ - consider_bottom_ - 1;
 623           can_hit_consider_rect |= consider_right_ >= index_x_;
 624           break;
 625         case LEFT:
 626           if (valid_row() && consider_right_ < index_x_)
 627             steps_to_take = index_x_ - consider_right_ - 1;
 628           can_hit_consider_rect |= consider_top_ <= index_y_;
 629           break;
 630         case DOWN:
 631           if (valid_column() && consider_top_ > index_y_)
 632             steps_to_take = consider_top_ - index_y_ - 1;
 633           can_hit_consider_rect |= consider_left_ <= index_x_;
 634           break;
 635         case RIGHT:
 636           if (valid_row() && consider_left_ > index_x_)
 637             steps_to_take = consider_left_ - index_x_ - 1;
 638           can_hit_consider_rect |= consider_bottom_ >= index_y_;
 639           break;
 640       }
 641       steps_to_take = std::min(steps_to_take, max_steps);
 642       DCHECK_GE(steps_to_take, 0);
 643
 644       index_x_ += steps_to_take * delta_x_;
 645       index_y_ += steps_to_take * delta_y_;
 646       current_step_ += steps_to_take;
 647
 648       if (can_hit_consider_rect)
 649         cannot_hit_consider_count = 0;
 650       else
 651         ++cannot_hit_consider_count;
 652     }
 653   }
 654
 655   if (cannot_hit_consider_count >= 4)
 656     done();
 657   return *this;
 658 }
 659
 660 bool TilingData::SpiralDifferenceIterator::needs_direction_switch() const {
 661   return current_step_ >= current_step_count();
 662 }
 663
 664 void TilingData::SpiralDifferenceIterator::switch_direction() {
 665   int new_delta_x_ = delta_y_;
 666   delta_y_ = -delta_x_;
 667   delta_x_ = new_delta_x_;
 668
 669   current_step_ = 0;
 670   direction_ = static_cast<Direction>((direction_ + 1) % 4);
 671
 672   if (direction_ == RIGHT || direction_ == LEFT) {
 673     ++vertical_step_count_;
 674     ++horizontal_step_count_;
 675   }
 676 }
 677
 678 }  // namespace cc