ui/gfx/render_text_pango.cc

   1 // Copyright (c) 2012 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 "ui/gfx/render_text_pango.h"
   6
   7 #include <pango/pangocairo.h>
   8 #include <algorithm>
   9 #include <string>
  10 #include <vector>
  11
  12 #include "base/i18n/break_iterator.h"
  13 #include "base/logging.h"
  14 #include "third_party/skia/include/core/SkTypeface.h"
  15 #include "ui/gfx/canvas.h"
  16 #include "ui/gfx/font.h"
  17 #include "ui/gfx/font_list.h"
  18 #include "ui/gfx/font_render_params.h"
  19 #include "ui/gfx/pango_util.h"
  20 #include "ui/gfx/platform_font_pango.h"
  21 #include "ui/gfx/utf16_indexing.h"
  22
  23 namespace gfx {
  24
  25 namespace {
  26
  27 // Returns the preceding element in a GSList (O(n)).
  28 GSList* GSListPrevious(GSList* head, GSList* item) {
  29   GSList* prev = NULL;
  30   for (GSList* cur = head; cur != item; cur = cur->next) {
  31     DCHECK(cur);
  32     prev = cur;
  33   }
  34   return prev;
  35 }
  36
  37 // Returns true if the given visual cursor |direction| is logically forward
  38 // motion in the given Pango |item|.
  39 bool IsForwardMotion(VisualCursorDirection direction, const PangoItem* item) {
  40   bool rtl = item->analysis.level & 1;
  41   return rtl == (direction == CURSOR_LEFT);
  42 }
  43
  44 // Checks whether |range| contains |index|. This is not the same as calling
  45 // range.Contains(Range(index)), which returns true if |index| == |range.end()|.
  46 bool IndexInRange(const Range& range, size_t index) {
  47   return index >= range.start() && index < range.end();
  48 }
  49
  50 // Sets underline metrics on |renderer| according to Pango font |desc|.
  51 void SetPangoUnderlineMetrics(PangoFontDescription *desc,
  52                               internal::SkiaTextRenderer* renderer) {
  53   PangoFontMetrics* metrics = GetPangoFontMetrics(desc);
  54   int thickness = pango_font_metrics_get_underline_thickness(metrics);
  55   // Pango returns the position "above the baseline". Change its sign to convert
  56   // it to a vertical offset from the baseline.
  57   int position = -pango_font_metrics_get_underline_position(metrics);
  58
  59   // Note: pango_quantize_line_geometry() guarantees pixel boundaries, so
  60   //       PANGO_PIXELS() is safe to use.
  61   pango_quantize_line_geometry(&thickness, &position);
  62   int thickness_pixels = PANGO_PIXELS(thickness);
  63   int position_pixels = PANGO_PIXELS(position);
  64
  65   // Ugly hack: make sure that underlines don't get clipped. See
  66   // http://crbug.com/393117.
  67   int descent_pixels = PANGO_PIXELS(pango_font_metrics_get_descent(metrics));
  68   position_pixels = std::min(position_pixels,
  69                              descent_pixels - thickness_pixels);
  70
  71   renderer->SetUnderlineMetrics(thickness_pixels, position_pixels);
  72 }
  73
  74 }  // namespace
  75
  76 // TODO(xji): index saved in upper layer is utf16 index. Pango uses utf8 index.
  77 // Since caret_pos is used internally, we could save utf8 index for caret_pos
  78 // to avoid conversion.
  79
  80 RenderTextPango::RenderTextPango()
  81     : layout_(NULL),
  82       current_line_(NULL),
  83       log_attrs_(NULL),
  84       num_log_attrs_(0),
  85       layout_text_(NULL) {
  86 }
  87
  88 RenderTextPango::~RenderTextPango() {
  89   ResetLayout();
  90 }
  91
  92 scoped_ptr<RenderText> RenderTextPango::CreateInstanceOfSameType() const {
  93   return scoped_ptr<RenderTextPango>(new RenderTextPango);
  94 }
  95
  96 Size RenderTextPango::GetStringSize() {
  97   EnsureLayout();
  98   int width = 0, height = 0;
  99   pango_layout_get_pixel_size(layout_, &width, &height);
 100
 101   // Pango returns 0 widths for very long strings (of 0x40000 chars or more).
 102   // This is caused by an int overflow in pango_glyph_string_extents_range.
 103   // Absurdly long strings may even report non-zero garbage values for width;
 104   // while detecting that isn't worthwhile, this handles the 0 width cases.
 105   const long kAbsurdLength = 100000;
 106   if (width == 0 && g_utf8_strlen(layout_text_, -1) > kAbsurdLength)
 107     width = font_list().GetExpectedTextWidth(g_utf8_strlen(layout_text_, -1));
 108
 109   // Keep a consistent height between this particular string's PangoLayout and
 110   // potentially larger text supported by the FontList.
 111   // For example, if a text field contains a Japanese character, which is
 112   // smaller than Latin ones, and then later a Latin one is inserted, this
 113   // ensures that the text baseline does not shift.
 114   return Size(width, std::max(height, font_list().GetHeight()));
 115 }
 116
 117 SelectionModel RenderTextPango::FindCursorPosition(const Point& point) {
 118   EnsureLayout();
 119
 120   if (text().empty())
 121     return SelectionModel(0, CURSOR_FORWARD);
 122
 123   Point p(ToTextPoint(point));
 124
 125   // When the point is outside of text, return HOME/END position.
 126   if (p.x() < 0)
 127     return EdgeSelectionModel(CURSOR_LEFT);
 128   if (p.x() > GetStringSize().width())
 129     return EdgeSelectionModel(CURSOR_RIGHT);
 130
 131   int caret_pos = 0, trailing = 0;
 132   pango_layout_xy_to_index(layout_, p.x() * PANGO_SCALE, p.y() * PANGO_SCALE,
 133                            &caret_pos, &trailing);
 134
 135   DCHECK_GE(trailing, 0);
 136   if (trailing > 0) {
 137     caret_pos = g_utf8_offset_to_pointer(layout_text_ + caret_pos,
 138                                          trailing) - layout_text_;
 139     DCHECK_LE(static_cast<size_t>(caret_pos), strlen(layout_text_));
 140   }
 141
 142   return SelectionModel(LayoutIndexToTextIndex(caret_pos),
 143                         (trailing > 0) ? CURSOR_BACKWARD : CURSOR_FORWARD);
 144 }
 145
 146 std::vector<RenderText::FontSpan> RenderTextPango::GetFontSpansForTesting() {
 147   EnsureLayout();
 148
 149   std::vector<RenderText::FontSpan> spans;
 150   for (GSList* it = current_line_->runs; it; it = it->next) {
 151     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(it->data)->item;
 152     const int start = LayoutIndexToTextIndex(item->offset);
 153     const int end = LayoutIndexToTextIndex(item->offset + item->length);
 154     const Range range(start, end);
 155
 156     ScopedPangoFontDescription desc(pango_font_describe(item->analysis.font));
 157     spans.push_back(RenderText::FontSpan(Font(desc.get()), range));
 158   }
 159
 160   return spans;
 161 }
 162
 163 int RenderTextPango::GetLayoutTextBaseline() {
 164   EnsureLayout();
 165   return PANGO_PIXELS(pango_layout_get_baseline(layout_));
 166 }
 167
 168 SelectionModel RenderTextPango::AdjacentCharSelectionModel(
 169     const SelectionModel& selection,
 170     VisualCursorDirection direction) {
 171   GSList* run = GetRunContainingCaret(selection);
 172   if (!run) {
 173     // The cursor is not in any run: we're at the visual and logical edge.
 174     SelectionModel edge = EdgeSelectionModel(direction);
 175     if (edge.caret_pos() == selection.caret_pos())
 176       return edge;
 177     else
 178       run = (direction == CURSOR_RIGHT) ?
 179           current_line_->runs : g_slist_last(current_line_->runs);
 180   } else {
 181     // If the cursor is moving within the current run, just move it by one
 182     // grapheme in the appropriate direction.
 183     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 184     size_t caret = selection.caret_pos();
 185     if (IsForwardMotion(direction, item)) {
 186       if (caret < LayoutIndexToTextIndex(item->offset + item->length)) {
 187         caret = IndexOfAdjacentGrapheme(caret, CURSOR_FORWARD);
 188         return SelectionModel(caret, CURSOR_BACKWARD);
 189       }
 190     } else {
 191       if (caret > LayoutIndexToTextIndex(item->offset)) {
 192         caret = IndexOfAdjacentGrapheme(caret, CURSOR_BACKWARD);
 193         return SelectionModel(caret, CURSOR_FORWARD);
 194       }
 195     }
 196     // The cursor is at the edge of a run; move to the visually adjacent run.
 197     // TODO(xji): Keep a vector of runs to avoid using a singly-linked list.
 198     run = (direction == CURSOR_RIGHT) ?
 199         run->next : GSListPrevious(current_line_->runs, run);
 200     if (!run)
 201       return EdgeSelectionModel(direction);
 202   }
 203   PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 204   return IsForwardMotion(direction, item) ?
 205       FirstSelectionModelInsideRun(item) : LastSelectionModelInsideRun(item);
 206 }
 207
 208 SelectionModel RenderTextPango::AdjacentWordSelectionModel(
 209     const SelectionModel& selection,
 210     VisualCursorDirection direction) {
 211   if (obscured())
 212     return EdgeSelectionModel(direction);
 213
 214   base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
 215   bool success = iter.Init();
 216   DCHECK(success);
 217   if (!success)
 218     return selection;
 219
 220   SelectionModel cur(selection);
 221   for (;;) {
 222     cur = AdjacentCharSelectionModel(cur, direction);
 223     GSList* run = GetRunContainingCaret(cur);
 224     if (!run)
 225       break;
 226     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 227     size_t cursor = cur.caret_pos();
 228     if (IsForwardMotion(direction, item) ?
 229         iter.IsEndOfWord(cursor) : iter.IsStartOfWord(cursor))
 230       break;
 231   }
 232
 233   return cur;
 234 }
 235
 236 Range RenderTextPango::GetGlyphBounds(size_t index) {
 237   EnsureLayout();
 238   PangoRectangle pos;
 239   pango_layout_index_to_pos(layout_, TextIndexToLayoutIndex(index), &pos);
 240   // TODO(derat): Support fractional ranges for subpixel positioning?
 241   return Range(PANGO_PIXELS(pos.x), PANGO_PIXELS(pos.x + pos.width));
 242 }
 243
 244 std::vector<Rect> RenderTextPango::GetSubstringBounds(const Range& range) {
 245   DCHECK_LE(range.GetMax(), text().length());
 246   if (range.is_empty())
 247     return std::vector<Rect>();
 248
 249   EnsureLayout();
 250   int* ranges = NULL;
 251   int n_ranges = 0;
 252   pango_layout_line_get_x_ranges(current_line_,
 253                                  TextIndexToLayoutIndex(range.GetMin()),
 254                                  TextIndexToLayoutIndex(range.GetMax()),
 255                                  &ranges,
 256                                  &n_ranges);
 257
 258   const int height = GetStringSize().height();
 259
 260   std::vector<Rect> bounds;
 261   for (int i = 0; i < n_ranges; ++i) {
 262     // TODO(derat): Support fractional bounds for subpixel positioning?
 263     int x = PANGO_PIXELS(ranges[2 * i]);
 264     int width = PANGO_PIXELS(ranges[2 * i + 1]) - x;
 265     Rect rect(x, 0, width, height);
 266     rect.set_origin(ToViewPoint(rect.origin()));
 267     bounds.push_back(rect);
 268   }
 269   g_free(ranges);
 270   return bounds;
 271 }
 272
 273 size_t RenderTextPango::TextIndexToLayoutIndex(size_t index) const {
 274   DCHECK(layout_);
 275   ptrdiff_t offset = UTF16IndexToOffset(text(), 0, index);
 276   // Clamp layout indices to the length of the text actually used for layout.
 277   offset = std::min<size_t>(offset, g_utf8_strlen(layout_text_, -1));
 278   const char* layout_pointer = g_utf8_offset_to_pointer(layout_text_, offset);
 279   return (layout_pointer - layout_text_);
 280 }
 281
 282 size_t RenderTextPango::LayoutIndexToTextIndex(size_t index) const {
 283   DCHECK(layout_);
 284   const char* layout_pointer = layout_text_ + index;
 285   const long offset = g_utf8_pointer_to_offset(layout_text_, layout_pointer);
 286   return UTF16OffsetToIndex(text(), 0, offset);
 287 }
 288
 289 bool RenderTextPango::IsValidCursorIndex(size_t index) {
 290   if (index == 0 || index == text().length())
 291     return true;
 292   if (!IsValidLogicalIndex(index))
 293     return false;
 294
 295   EnsureLayout();
 296   ptrdiff_t offset = UTF16IndexToOffset(text(), 0, index);
 297   // Check that the index is marked as a legitimate cursor position by Pango.
 298   return offset < num_log_attrs_ && log_attrs_[offset].is_cursor_position;
 299 }
 300
 301 void RenderTextPango::ResetLayout() {
 302   // set_cached_bounds_and_offset_valid(false) is done in RenderText for every
 303   // operation that triggers ResetLayout().
 304   if (layout_) {
 305     // TODO(msw): Keep |layout_| across text changes, etc.; it can be re-used.
 306     g_object_unref(layout_);
 307     layout_ = NULL;
 308   }
 309   if (current_line_) {
 310     pango_layout_line_unref(current_line_);
 311     current_line_ = NULL;
 312   }
 313   if (log_attrs_) {
 314     g_free(log_attrs_);
 315     log_attrs_ = NULL;
 316     num_log_attrs_ = 0;
 317   }
 318   layout_text_ = NULL;
 319 }
 320
 321 void RenderTextPango::EnsureLayout() {
 322   if (layout_ == NULL) {
 323     cairo_surface_t* surface =
 324         cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 0, 0);
 325     CHECK_EQ(CAIRO_STATUS_SUCCESS, cairo_surface_status(surface));
 326     cairo_t* cr = cairo_create(surface);
 327     CHECK_EQ(CAIRO_STATUS_SUCCESS, cairo_status(cr));
 328
 329     layout_ = pango_cairo_create_layout(cr);
 330     CHECK_NE(static_cast<PangoLayout*>(NULL), layout_);
 331     cairo_destroy(cr);
 332     cairo_surface_destroy(surface);
 333
 334     SetUpPangoLayout(layout_, GetLayoutText(), font_list(), GetTextDirection(),
 335                      Canvas::DefaultCanvasTextAlignment());
 336
 337     // No width set so that the x-axis position is relative to the start of the
 338     // text. ToViewPoint and ToTextPoint take care of the position conversion
 339     // between text space and view spaces.
 340     pango_layout_set_width(layout_, -1);
 341     // TODO(xji): If RenderText will be used for displaying purpose, such as
 342     // label, we will need to remove the single-line-mode setting.
 343     pango_layout_set_single_paragraph_mode(layout_, true);
 344
 345     layout_text_ = pango_layout_get_text(layout_);
 346     SetupPangoAttributes(layout_);
 347
 348     current_line_ = pango_layout_get_line_readonly(layout_, 0);
 349     CHECK_NE(static_cast<PangoLayoutLine*>(NULL), current_line_);
 350     pango_layout_line_ref(current_line_);
 351
 352     pango_layout_get_log_attrs(layout_, &log_attrs_, &num_log_attrs_);
 353   }
 354 }
 355
 356 void RenderTextPango::SetupPangoAttributes(PangoLayout* layout) {
 357   PangoAttrList* attrs = pango_attr_list_new();
 358
 359   // Splitting text runs to accommodate styling can break Arabic glyph shaping.
 360   // Only split text runs as needed for bold and italic font styles changes.
 361   BreakList<bool>::const_iterator bold = styles()[BOLD].breaks().begin();
 362   BreakList<bool>::const_iterator italic = styles()[ITALIC].breaks().begin();
 363   while (bold != styles()[BOLD].breaks().end() &&
 364          italic != styles()[ITALIC].breaks().end()) {
 365     const int style = (bold->second ? Font::BOLD : 0) |
 366                       (italic->second ? Font::ITALIC : 0);
 367     const size_t bold_end = styles()[BOLD].GetRange(bold).end();
 368     const size_t italic_end = styles()[ITALIC].GetRange(italic).end();
 369     const size_t style_end = std::min(bold_end, italic_end);
 370     if (style != font_list().GetFontStyle()) {
 371       // TODO(derat): Don't interpret gfx::FontList font descriptions as Pango
 372       // font descriptions: http://crbug.com/393067
 373       FontList derived_font_list = font_list().DeriveWithStyle(style);
 374       ScopedPangoFontDescription desc(
 375           derived_font_list.GetFontDescriptionString());
 376
 377       PangoAttribute* pango_attr = pango_attr_font_desc_new(desc.get());
 378       pango_attr->start_index =
 379           TextIndexToLayoutIndex(std::max(bold->first, italic->first));
 380       pango_attr->end_index = TextIndexToLayoutIndex(style_end);
 381       pango_attr_list_insert(attrs, pango_attr);
 382     }
 383     bold += bold_end == style_end ? 1 : 0;
 384     italic += italic_end == style_end ? 1 : 0;
 385   }
 386   DCHECK(bold == styles()[BOLD].breaks().end());
 387   DCHECK(italic == styles()[ITALIC].breaks().end());
 388
 389   pango_layout_set_attributes(layout, attrs);
 390   pango_attr_list_unref(attrs);
 391 }
 392
 393 void RenderTextPango::DrawVisualText(Canvas* canvas) {
 394   DCHECK(layout_);
 395
 396   // Skia will draw glyphs with respect to the baseline.
 397   Vector2d offset(GetLineOffset(0) + Vector2d(0, GetLayoutTextBaseline()));
 398
 399   SkScalar x = SkIntToScalar(offset.x());
 400   SkScalar y = SkIntToScalar(offset.y());
 401
 402   std::vector<SkPoint> pos;
 403   std::vector<uint16> glyphs;
 404
 405   internal::SkiaTextRenderer renderer(canvas);
 406   ApplyFadeEffects(&renderer);
 407   ApplyTextShadows(&renderer);
 408   renderer.SetFontRenderParams(
 409       font_list().GetPrimaryFont().GetFontRenderParams(),
 410       background_is_transparent());
 411
 412   // Temporarily apply composition underlines and selection colors.
 413   ApplyCompositionAndSelectionStyles();
 414
 415   internal::StyleIterator style(colors(), styles());
 416   for (GSList* it = current_line_->runs; it; it = it->next) {
 417     // Skip painting runs outside the display area.
 418     if (SkScalarTruncToInt(x) >= display_rect().right())
 419       break;
 420
 421     PangoLayoutRun* run = reinterpret_cast<PangoLayoutRun*>(it->data);
 422     int glyph_count = run->glyphs->num_glyphs;
 423     if (glyph_count == 0)
 424       continue;
 425
 426     ScopedPangoFontDescription desc(
 427         pango_font_describe(run->item->analysis.font));
 428     const std::string family_name =
 429         pango_font_description_get_family(desc.get());
 430     renderer.SetTextSize(GetPangoFontSizeInPixels(desc.get()));
 431
 432     glyphs.resize(glyph_count);
 433     pos.resize(glyph_count);
 434
 435     // Track the current glyph and the glyph at the start of its styled range.
 436     int glyph_index = 0;
 437     int style_start_glyph_index = glyph_index;
 438
 439     // Track the x-coordinates for each styled range (|x| marks the current).
 440     SkScalar style_start_x = x;
 441
 442     // Track the current style and its text (not layout) index range.
 443     style.UpdatePosition(GetGlyphTextIndex(run, style_start_glyph_index));
 444     Range style_range = style.GetRange();
 445
 446     do {
 447       const PangoGlyphInfo& glyph = run->glyphs->glyphs[glyph_index];
 448       glyphs[glyph_index] = static_cast<uint16>(glyph.glyph);
 449       // Use pango_units_to_double() rather than PANGO_PIXELS() here, so units
 450       // are not rounded to the pixel grid if subpixel positioning is enabled.
 451       pos[glyph_index].set(x + pango_units_to_double(glyph.geometry.x_offset),
 452                            y + pango_units_to_double(glyph.geometry.y_offset));
 453       x += pango_units_to_double(glyph.geometry.width);
 454
 455       ++glyph_index;
 456       // If this is the last glyph of the range or the last glyph inside the
 457       // display area (which would cause early termination of the loop), paint
 458       // the range.
 459       const size_t glyph_text_index = (glyph_index == glyph_count) ?
 460           style_range.end() : GetGlyphTextIndex(run, glyph_index);
 461       if (!IndexInRange(style_range, glyph_text_index) ||
 462           SkScalarTruncToInt(x) >= display_rect().right()) {
 463         // TODO(asvitkine): For cases like "fi", where "fi" is a single glyph
 464         //                  but can span multiple styles, Pango splits the
 465         //                  styles evenly over the glyph. We can do this too by
 466         //                  clipping and drawing the glyph several times.
 467         renderer.SetForegroundColor(style.color());
 468         const int font_style = (style.style(BOLD) ? Font::BOLD : 0) |
 469                                (style.style(ITALIC) ? Font::ITALIC : 0);
 470         renderer.SetFontFamilyWithStyle(family_name, font_style);
 471         renderer.DrawPosText(&pos[style_start_glyph_index],
 472                              &glyphs[style_start_glyph_index],
 473                              glyph_index - style_start_glyph_index);
 474         if (style.style(UNDERLINE))
 475           SetPangoUnderlineMetrics(desc.get(), &renderer);
 476         renderer.DrawDecorations(style_start_x, y, x - style_start_x,
 477                                  style.style(UNDERLINE), style.style(STRIKE),
 478                                  style.style(DIAGONAL_STRIKE));
 479         style.UpdatePosition(glyph_text_index);
 480         style_range = style.GetRange();
 481         style_start_glyph_index = glyph_index;
 482         style_start_x = x;
 483       }
 484       // Terminates loop when the end of the range has been reached or the next
 485       // glyph falls outside the display area.
 486     } while (glyph_index < glyph_count &&
 487              SkScalarTruncToInt(x) < display_rect().right());
 488   }
 489
 490   renderer.EndDiagonalStrike();
 491
 492   // Undo the temporarily applied composition underlines and selection colors.
 493   UndoCompositionAndSelectionStyles();
 494 }
 495
 496 GSList* RenderTextPango::GetRunContainingCaret(
 497     const SelectionModel& caret) const {
 498   size_t position = TextIndexToLayoutIndex(caret.caret_pos());
 499   LogicalCursorDirection affinity = caret.caret_affinity();
 500   GSList* run = current_line_->runs;
 501   while (run) {
 502     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 503     Range item_range(item->offset, item->offset + item->length);
 504     if (RangeContainsCaret(item_range, position, affinity))
 505       return run;
 506     run = run->next;
 507   }
 508   return NULL;
 509 }
 510
 511 SelectionModel RenderTextPango::FirstSelectionModelInsideRun(
 512     const PangoItem* item) {
 513   size_t caret = IndexOfAdjacentGrapheme(
 514       LayoutIndexToTextIndex(item->offset), CURSOR_FORWARD);
 515   return SelectionModel(caret, CURSOR_BACKWARD);
 516 }
 517
 518 SelectionModel RenderTextPango::LastSelectionModelInsideRun(
 519     const PangoItem* item) {
 520   size_t caret = IndexOfAdjacentGrapheme(
 521       LayoutIndexToTextIndex(item->offset + item->length), CURSOR_BACKWARD);
 522   return SelectionModel(caret, CURSOR_FORWARD);
 523 }
 524
 525 size_t RenderTextPango::GetGlyphTextIndex(PangoLayoutRun* run,
 526                                           int glyph_index) const {
 527   return LayoutIndexToTextIndex(run->item->offset +
 528                                 run->glyphs->log_clusters[glyph_index]);
 529 }
 530
 531 RenderText* RenderText::CreateNativeInstance() {
 532   return new RenderTextPango;
 533 }
 534
 535 }  // namespace gfx