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_render_params_linux.h"
  18 #include "ui/gfx/pango_util.h"
  19 #include "ui/gfx/utf16_indexing.h"
  20
  21 namespace gfx {
  22
  23 namespace {
  24
  25 // Returns the preceding element in a GSList (O(n)).
  26 GSList* GSListPrevious(GSList* head, GSList* item) {
  27   GSList* prev = NULL;
  28   for (GSList* cur = head; cur != item; cur = cur->next) {
  29     DCHECK(cur);
  30     prev = cur;
  31   }
  32   return prev;
  33 }
  34
  35 // Returns true if the given visual cursor |direction| is logically forward
  36 // motion in the given Pango |item|.
  37 bool IsForwardMotion(VisualCursorDirection direction, const PangoItem* item) {
  38   bool rtl = item->analysis.level & 1;
  39   return rtl == (direction == CURSOR_LEFT);
  40 }
  41
  42 // Checks whether |range| contains |index|. This is not the same as calling
  43 // |range.Contains(gfx::Range(index))| - as that would return true when
  44 // |index| == |range.end()|.
  45 bool IndexInRange(const Range& range, size_t index) {
  46   return index >= range.start() && index < range.end();
  47 }
  48
  49 // Sets underline metrics on |renderer| according to Pango font |desc|.
  50 void SetPangoUnderlineMetrics(PangoFontDescription *desc,
  51                               internal::SkiaTextRenderer* renderer) {
  52   PangoFontMetrics* metrics = GetPangoFontMetrics(desc);
  53   int thickness = pango_font_metrics_get_underline_thickness(metrics);
  54   // Pango returns the position "above the baseline". Change its sign to convert
  55   // it to a vertical offset from the baseline.
  56   int position = -pango_font_metrics_get_underline_position(metrics);
  57   pango_quantize_line_geometry(&thickness, &position);
  58   // Note: pango_quantize_line_geometry() guarantees pixel boundaries, so
  59   //       PANGO_PIXELS() is safe to use.
  60   renderer->SetUnderlineMetrics(PANGO_PIXELS(thickness),
  61                                 PANGO_PIXELS(position));
  62 }
  63
  64 }  // namespace
  65
  66 // TODO(xji): index saved in upper layer is utf16 index. Pango uses utf8 index.
  67 // Since caret_pos is used internally, we could save utf8 index for caret_pos
  68 // to avoid conversion.
  69
  70 RenderTextPango::RenderTextPango()
  71     : layout_(NULL),
  72       current_line_(NULL),
  73       log_attrs_(NULL),
  74       num_log_attrs_(0),
  75       layout_text_(NULL) {
  76 }
  77
  78 RenderTextPango::~RenderTextPango() {
  79   ResetLayout();
  80 }
  81
  82 Size RenderTextPango::GetStringSize() {
  83   EnsureLayout();
  84   int width = 0, height = 0;
  85   pango_layout_get_pixel_size(layout_, &width, &height);
  86   // Keep a consistent height between this particular string's PangoLayout and
  87   // potentially larger text supported by the FontList.
  88   // For example, if a text field contains a Japanese character, which is
  89   // smaller than Latin ones, and then later a Latin one is inserted, this
  90   // ensures that the text baseline does not shift.
  91   return Size(width, std::max(height, font_list().GetHeight()));
  92 }
  93
  94 SelectionModel RenderTextPango::FindCursorPosition(const Point& point) {
  95   EnsureLayout();
  96
  97   if (text().empty())
  98     return SelectionModel(0, CURSOR_FORWARD);
  99
 100   Point p(ToTextPoint(point));
 101
 102   // When the point is outside of text, return HOME/END position.
 103   if (p.x() < 0)
 104     return EdgeSelectionModel(CURSOR_LEFT);
 105   if (p.x() > GetStringSize().width())
 106     return EdgeSelectionModel(CURSOR_RIGHT);
 107
 108   int caret_pos = 0, trailing = 0;
 109   pango_layout_xy_to_index(layout_, p.x() * PANGO_SCALE, p.y() * PANGO_SCALE,
 110                            &caret_pos, &trailing);
 111
 112   DCHECK_GE(trailing, 0);
 113   if (trailing > 0) {
 114     caret_pos = g_utf8_offset_to_pointer(layout_text_ + caret_pos,
 115                                          trailing) - layout_text_;
 116     DCHECK_LE(static_cast<size_t>(caret_pos), strlen(layout_text_));
 117   }
 118
 119   return SelectionModel(LayoutIndexToTextIndex(caret_pos),
 120                         (trailing > 0) ? CURSOR_BACKWARD : CURSOR_FORWARD);
 121 }
 122
 123 std::vector<RenderText::FontSpan> RenderTextPango::GetFontSpansForTesting() {
 124   EnsureLayout();
 125
 126   std::vector<RenderText::FontSpan> spans;
 127   for (GSList* it = current_line_->runs; it; it = it->next) {
 128     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(it->data)->item;
 129     const int start = LayoutIndexToTextIndex(item->offset);
 130     const int end = LayoutIndexToTextIndex(item->offset + item->length);
 131     const Range range(start, end);
 132
 133     ScopedPangoFontDescription desc(pango_font_describe(item->analysis.font));
 134     spans.push_back(RenderText::FontSpan(Font(desc.get()), range));
 135   }
 136
 137   return spans;
 138 }
 139
 140 int RenderTextPango::GetLayoutTextBaseline() {
 141   EnsureLayout();
 142   return PANGO_PIXELS(pango_layout_get_baseline(layout_));
 143 }
 144
 145 SelectionModel RenderTextPango::AdjacentCharSelectionModel(
 146     const SelectionModel& selection,
 147     VisualCursorDirection direction) {
 148   GSList* run = GetRunContainingCaret(selection);
 149   if (!run) {
 150     // The cursor is not in any run: we're at the visual and logical edge.
 151     SelectionModel edge = EdgeSelectionModel(direction);
 152     if (edge.caret_pos() == selection.caret_pos())
 153       return edge;
 154     else
 155       run = (direction == CURSOR_RIGHT) ?
 156           current_line_->runs : g_slist_last(current_line_->runs);
 157   } else {
 158     // If the cursor is moving within the current run, just move it by one
 159     // grapheme in the appropriate direction.
 160     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 161     size_t caret = selection.caret_pos();
 162     if (IsForwardMotion(direction, item)) {
 163       if (caret < LayoutIndexToTextIndex(item->offset + item->length)) {
 164         caret = IndexOfAdjacentGrapheme(caret, CURSOR_FORWARD);
 165         return SelectionModel(caret, CURSOR_BACKWARD);
 166       }
 167     } else {
 168       if (caret > LayoutIndexToTextIndex(item->offset)) {
 169         caret = IndexOfAdjacentGrapheme(caret, CURSOR_BACKWARD);
 170         return SelectionModel(caret, CURSOR_FORWARD);
 171       }
 172     }
 173     // The cursor is at the edge of a run; move to the visually adjacent run.
 174     // TODO(xji): Keep a vector of runs to avoid using a singly-linked list.
 175     run = (direction == CURSOR_RIGHT) ?
 176         run->next : GSListPrevious(current_line_->runs, run);
 177     if (!run)
 178       return EdgeSelectionModel(direction);
 179   }
 180   PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 181   return IsForwardMotion(direction, item) ?
 182       FirstSelectionModelInsideRun(item) : LastSelectionModelInsideRun(item);
 183 }
 184
 185 SelectionModel RenderTextPango::AdjacentWordSelectionModel(
 186     const SelectionModel& selection,
 187     VisualCursorDirection direction) {
 188   if (obscured())
 189     return EdgeSelectionModel(direction);
 190
 191   base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
 192   bool success = iter.Init();
 193   DCHECK(success);
 194   if (!success)
 195     return selection;
 196
 197   SelectionModel cur(selection);
 198   for (;;) {
 199     cur = AdjacentCharSelectionModel(cur, direction);
 200     GSList* run = GetRunContainingCaret(cur);
 201     if (!run)
 202       break;
 203     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 204     size_t cursor = cur.caret_pos();
 205     if (IsForwardMotion(direction, item) ?
 206         iter.IsEndOfWord(cursor) : iter.IsStartOfWord(cursor))
 207       break;
 208   }
 209
 210   return cur;
 211 }
 212
 213 Range RenderTextPango::GetGlyphBounds(size_t index) {
 214   PangoRectangle pos;
 215   pango_layout_index_to_pos(layout_, TextIndexToLayoutIndex(index), &pos);
 216   // TODO(derat): Support fractional ranges for subpixel positioning?
 217   return Range(PANGO_PIXELS(pos.x), PANGO_PIXELS(pos.x + pos.width));
 218 }
 219
 220 std::vector<Rect> RenderTextPango::GetSubstringBounds(const Range& range) {
 221   DCHECK_LE(range.GetMax(), text().length());
 222   if (range.is_empty())
 223     return std::vector<Rect>();
 224
 225   EnsureLayout();
 226   int* ranges = NULL;
 227   int n_ranges = 0;
 228   pango_layout_line_get_x_ranges(current_line_,
 229                                  TextIndexToLayoutIndex(range.GetMin()),
 230                                  TextIndexToLayoutIndex(range.GetMax()),
 231                                  &ranges,
 232                                  &n_ranges);
 233
 234   const int height = GetStringSize().height();
 235
 236   std::vector<Rect> bounds;
 237   for (int i = 0; i < n_ranges; ++i) {
 238     // TODO(derat): Support fractional bounds for subpixel positioning?
 239     int x = PANGO_PIXELS(ranges[2 * i]);
 240     int width = PANGO_PIXELS(ranges[2 * i + 1]) - x;
 241     Rect rect(x, 0, width, height);
 242     rect.set_origin(ToViewPoint(rect.origin()));
 243     bounds.push_back(rect);
 244   }
 245   g_free(ranges);
 246   return bounds;
 247 }
 248
 249 size_t RenderTextPango::TextIndexToLayoutIndex(size_t index) const {
 250   DCHECK(layout_);
 251   ptrdiff_t offset = gfx::UTF16IndexToOffset(text(), 0, index);
 252   // Clamp layout indices to the length of the text actually used for layout.
 253   offset = std::min<size_t>(offset, g_utf8_strlen(layout_text_, -1));
 254   const char* layout_pointer = g_utf8_offset_to_pointer(layout_text_, offset);
 255   return (layout_pointer - layout_text_);
 256 }
 257
 258 size_t RenderTextPango::LayoutIndexToTextIndex(size_t index) const {
 259   DCHECK(layout_);
 260   const char* layout_pointer = layout_text_ + index;
 261   const long offset = g_utf8_pointer_to_offset(layout_text_, layout_pointer);
 262   return gfx::UTF16OffsetToIndex(text(), 0, offset);
 263 }
 264
 265 bool RenderTextPango::IsCursorablePosition(size_t position) {
 266   if (position == 0 && text().empty())
 267     return true;
 268   if (position >= text().length())
 269     return position == text().length();
 270   if (!gfx::IsValidCodePointIndex(text(), position))
 271     return false;
 272
 273   EnsureLayout();
 274   ptrdiff_t offset = gfx::UTF16IndexToOffset(text(), 0, position);
 275   // Check that the index corresponds with a valid text code point, that it is
 276   // marked as a legitimate cursor position by Pango, and that it is not
 277   // truncated from layout text (its glyph is shown on screen).
 278   return (offset < num_log_attrs_ && log_attrs_[offset].is_cursor_position &&
 279           offset < g_utf8_strlen(layout_text_, -1));
 280 }
 281
 282 void RenderTextPango::ResetLayout() {
 283   // set_cached_bounds_and_offset_valid(false) is done in RenderText for every
 284   // operation that triggers ResetLayout().
 285   if (layout_) {
 286     // TODO(msw): Keep |layout_| across text changes, etc.; it can be re-used.
 287     g_object_unref(layout_);
 288     layout_ = NULL;
 289   }
 290   if (current_line_) {
 291     pango_layout_line_unref(current_line_);
 292     current_line_ = NULL;
 293   }
 294   if (log_attrs_) {
 295     g_free(log_attrs_);
 296     log_attrs_ = NULL;
 297     num_log_attrs_ = 0;
 298   }
 299   layout_text_ = NULL;
 300 }
 301
 302 void RenderTextPango::EnsureLayout() {
 303   if (layout_ == NULL) {
 304     cairo_surface_t* surface =
 305         cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 0, 0);
 306     CHECK_EQ(CAIRO_STATUS_SUCCESS, cairo_surface_status(surface));
 307     cairo_t* cr = cairo_create(surface);
 308     CHECK_EQ(CAIRO_STATUS_SUCCESS, cairo_status(cr));
 309
 310     layout_ = pango_cairo_create_layout(cr);
 311     CHECK_NE(static_cast<PangoLayout*>(NULL), layout_);
 312     cairo_destroy(cr);
 313     cairo_surface_destroy(surface);
 314
 315     SetupPangoLayoutWithFontDescription(layout_,
 316                                         GetLayoutText(),
 317                                         font_list().GetFontDescriptionString(),
 318                                         0,
 319                                         GetTextDirection(),
 320                                         Canvas::DefaultCanvasTextAlignment());
 321
 322     // No width set so that the x-axis position is relative to the start of the
 323     // text. ToViewPoint and ToTextPoint take care of the position conversion
 324     // between text space and view spaces.
 325     pango_layout_set_width(layout_, -1);
 326     // TODO(xji): If RenderText will be used for displaying purpose, such as
 327     // label, we will need to remove the single-line-mode setting.
 328     pango_layout_set_single_paragraph_mode(layout_, true);
 329
 330     layout_text_ = pango_layout_get_text(layout_);
 331     SetupPangoAttributes(layout_);
 332
 333     current_line_ = pango_layout_get_line_readonly(layout_, 0);
 334     CHECK_NE(static_cast<PangoLayoutLine*>(NULL), current_line_);
 335     pango_layout_line_ref(current_line_);
 336
 337     pango_layout_get_log_attrs(layout_, &log_attrs_, &num_log_attrs_);
 338   }
 339 }
 340
 341 void RenderTextPango::SetupPangoAttributes(PangoLayout* layout) {
 342   PangoAttrList* attrs = pango_attr_list_new();
 343
 344   // Splitting text runs to accommodate styling can break Arabic glyph shaping.
 345   // Only split text runs as needed for bold and italic font styles changes.
 346   BreakList<bool>::const_iterator bold = styles()[BOLD].breaks().begin();
 347   BreakList<bool>::const_iterator italic = styles()[ITALIC].breaks().begin();
 348   while (bold != styles()[BOLD].breaks().end() &&
 349          italic != styles()[ITALIC].breaks().end()) {
 350     const int style = (bold->second ? Font::BOLD : 0) |
 351                       (italic->second ? Font::ITALIC : 0);
 352     const size_t bold_end = styles()[BOLD].GetRange(bold).end();
 353     const size_t italic_end = styles()[ITALIC].GetRange(italic).end();
 354     const size_t style_end = std::min(bold_end, italic_end);
 355     if (style != font_list().GetFontStyle()) {
 356       FontList derived_font_list = font_list().DeriveWithStyle(style);
 357       ScopedPangoFontDescription desc(pango_font_description_from_string(
 358           derived_font_list.GetFontDescriptionString().c_str()));
 359
 360       PangoAttribute* pango_attr = pango_attr_font_desc_new(desc.get());
 361       pango_attr->start_index =
 362           TextIndexToLayoutIndex(std::max(bold->first, italic->first));
 363       pango_attr->end_index = TextIndexToLayoutIndex(style_end);
 364       pango_attr_list_insert(attrs, pango_attr);
 365     }
 366     bold += bold_end == style_end ? 1 : 0;
 367     italic += italic_end == style_end ? 1 : 0;
 368   }
 369   DCHECK(bold == styles()[BOLD].breaks().end());
 370   DCHECK(italic == styles()[ITALIC].breaks().end());
 371
 372   pango_layout_set_attributes(layout, attrs);
 373   pango_attr_list_unref(attrs);
 374 }
 375
 376 void RenderTextPango::DrawVisualText(Canvas* canvas) {
 377   DCHECK(layout_);
 378
 379   // Skia will draw glyphs with respect to the baseline.
 380   Vector2d offset(GetLineOffset(0) + Vector2d(0, GetLayoutTextBaseline()));
 381
 382   SkScalar x = SkIntToScalar(offset.x());
 383   SkScalar y = SkIntToScalar(offset.y());
 384
 385   std::vector<SkPoint> pos;
 386   std::vector<uint16> glyphs;
 387
 388   internal::SkiaTextRenderer renderer(canvas);
 389   ApplyFadeEffects(&renderer);
 390   ApplyTextShadows(&renderer);
 391
 392   // TODO(derat): Use font-specific params: http://crbug.com/125235
 393   const gfx::FontRenderParams& render_params =
 394       gfx::GetDefaultFontRenderParams();
 395   const bool use_subpixel_rendering =
 396       render_params.subpixel_rendering !=
 397           gfx::FontRenderParams::SUBPIXEL_RENDERING_NONE;
 398   renderer.SetFontSmoothingSettings(
 399       render_params.antialiasing,
 400       use_subpixel_rendering && !background_is_transparent());
 401
 402   SkPaint::Hinting skia_hinting = SkPaint::kNormal_Hinting;
 403   switch (render_params.hinting) {
 404     case gfx::FontRenderParams::HINTING_NONE:
 405       skia_hinting = SkPaint::kNo_Hinting;
 406       break;
 407     case gfx::FontRenderParams::HINTING_SLIGHT:
 408       skia_hinting = SkPaint::kSlight_Hinting;
 409       break;
 410     case gfx::FontRenderParams::HINTING_MEDIUM:
 411       skia_hinting = SkPaint::kNormal_Hinting;
 412       break;
 413     case gfx::FontRenderParams::HINTING_FULL:
 414       skia_hinting = SkPaint::kFull_Hinting;
 415       break;
 416   }
 417   renderer.SetFontHinting(skia_hinting);
 418
 419   // Temporarily apply composition underlines and selection colors.
 420   ApplyCompositionAndSelectionStyles();
 421
 422   internal::StyleIterator style(colors(), styles());
 423   for (GSList* it = current_line_->runs; it; it = it->next) {
 424     PangoLayoutRun* run = reinterpret_cast<PangoLayoutRun*>(it->data);
 425     int glyph_count = run->glyphs->num_glyphs;
 426     // TODO(msw): Skip painting runs outside the display rect area, like Win.
 427     if (glyph_count == 0)
 428       continue;
 429
 430     ScopedPangoFontDescription desc(
 431         pango_font_describe(run->item->analysis.font));
 432
 433     const std::string family_name =
 434         pango_font_description_get_family(desc.get());
 435     renderer.SetTextSize(GetPangoFontSizeInPixels(desc.get()));
 436
 437     glyphs.resize(glyph_count);
 438     pos.resize(glyph_count);
 439
 440     // Track the current glyph and the glyph at the start of its styled range.
 441     int glyph_index = 0;
 442     int style_start_glyph_index = glyph_index;
 443
 444     // Track the x-coordinates for each styled range (|x| marks the current).
 445     SkScalar style_start_x = x;
 446
 447     // Track the current style and its text (not layout) index range.
 448     style.UpdatePosition(GetGlyphTextIndex(run, style_start_glyph_index));
 449     Range style_range = style.GetRange();
 450
 451     do {
 452       const PangoGlyphInfo& glyph = run->glyphs->glyphs[glyph_index];
 453       glyphs[glyph_index] = static_cast<uint16>(glyph.glyph);
 454       // Use pango_units_to_double() rather than PANGO_PIXELS() here, so units
 455       // are not rounded to the pixel grid if subpixel positioning is enabled.
 456       pos[glyph_index].set(x + pango_units_to_double(glyph.geometry.x_offset),
 457                            y + pango_units_to_double(glyph.geometry.y_offset));
 458       x += pango_units_to_double(glyph.geometry.width);
 459
 460       ++glyph_index;
 461       const size_t glyph_text_index = (glyph_index == glyph_count) ?
 462           style_range.end() : GetGlyphTextIndex(run, glyph_index);
 463       if (!IndexInRange(style_range, glyph_text_index)) {
 464         // TODO(asvitkine): For cases like "fi", where "fi" is a single glyph
 465         //                  but can span multiple styles, Pango splits the
 466         //                  styles evenly over the glyph. We can do this too by
 467         //                  clipping and drawing the glyph several times.
 468         renderer.SetForegroundColor(style.color());
 469         const int font_style = (style.style(BOLD) ? Font::BOLD : 0) |
 470                                (style.style(ITALIC) ? Font::ITALIC : 0);
 471         renderer.SetFontFamilyWithStyle(family_name, font_style);
 472         renderer.DrawPosText(&pos[style_start_glyph_index],
 473                              &glyphs[style_start_glyph_index],
 474                              glyph_index - style_start_glyph_index);
 475         if (style.style(UNDERLINE))
 476           SetPangoUnderlineMetrics(desc.get(), &renderer);
 477         renderer.DrawDecorations(style_start_x, y, x - style_start_x,
 478                                  style.style(UNDERLINE), style.style(STRIKE),
 479                                  style.style(DIAGONAL_STRIKE));
 480         style.UpdatePosition(glyph_text_index);
 481         style_range = style.GetRange();
 482         style_start_glyph_index = glyph_index;
 483         style_start_x = x;
 484       }
 485     } while (glyph_index < glyph_count);
 486   }
 487
 488   // Undo the temporarily applied composition underlines and selection colors.
 489   UndoCompositionAndSelectionStyles();
 490 }
 491
 492 GSList* RenderTextPango::GetRunContainingCaret(
 493     const SelectionModel& caret) const {
 494   size_t position = TextIndexToLayoutIndex(caret.caret_pos());
 495   LogicalCursorDirection affinity = caret.caret_affinity();
 496   GSList* run = current_line_->runs;
 497   while (run) {
 498     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 499     Range item_range(item->offset, item->offset + item->length);
 500     if (RangeContainsCaret(item_range, position, affinity))
 501       return run;
 502     run = run->next;
 503   }
 504   return NULL;
 505 }
 506
 507 SelectionModel RenderTextPango::FirstSelectionModelInsideRun(
 508     const PangoItem* item) {
 509   size_t caret = IndexOfAdjacentGrapheme(
 510       LayoutIndexToTextIndex(item->offset), CURSOR_FORWARD);
 511   return SelectionModel(caret, CURSOR_BACKWARD);
 512 }
 513
 514 SelectionModel RenderTextPango::LastSelectionModelInsideRun(
 515     const PangoItem* item) {
 516   size_t caret = IndexOfAdjacentGrapheme(
 517       LayoutIndexToTextIndex(item->offset + item->length), CURSOR_BACKWARD);
 518   return SelectionModel(caret, CURSOR_FORWARD);
 519 }
 520
 521 size_t RenderTextPango::GetGlyphTextIndex(PangoLayoutRun* run,
 522                                           int glyph_index) const {
 523   return LayoutIndexToTextIndex(run->item->offset +
 524                                 run->glyphs->log_clusters[glyph_index]);
 525 }
 526
 527 RenderText* RenderText::CreateInstance() {
 528   return new RenderTextPango;
 529 }
 530
 531 }  // namespace gfx