ui/gfx/render_text_linux.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_linux.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/base/text/utf16_indexing.h"
  16 #include "ui/gfx/canvas.h"
  17 #include "ui/gfx/font.h"
  18 #include "ui/gfx/font_render_params_linux.h"
  19 #include "ui/gfx/pango_util.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(ui::Range(index))| - as that would return true when
  44 // |index| == |range.end()|.
  45 bool IndexInRange(const ui::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 RenderTextLinux::RenderTextLinux()
  71     : layout_(NULL),
  72       current_line_(NULL),
  73       log_attrs_(NULL),
  74       num_log_attrs_(0),
  75       layout_text_(NULL) {
  76 }
  77
  78 RenderTextLinux::~RenderTextLinux() {
  79   ResetLayout();
  80 }
  81
  82 Size RenderTextLinux::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 int RenderTextLinux::GetBaseline() {
  95   EnsureLayout();
  96   // Keep a consistent baseline between this particular string's PangoLayout and
  97   // potentially larger text supported by the FontList.
  98   // See the example in GetStringSize().
  99   return std::max(PANGO_PIXELS(pango_layout_get_baseline(layout_)),
 100                   font_list().GetBaseline());
 101 }
 102
 103 SelectionModel RenderTextLinux::FindCursorPosition(const Point& point) {
 104   EnsureLayout();
 105
 106   if (text().empty())
 107     return SelectionModel(0, CURSOR_FORWARD);
 108
 109   Point p(ToTextPoint(point));
 110
 111   // When the point is outside of text, return HOME/END position.
 112   if (p.x() < 0)
 113     return EdgeSelectionModel(CURSOR_LEFT);
 114   if (p.x() > GetStringSize().width())
 115     return EdgeSelectionModel(CURSOR_RIGHT);
 116
 117   int caret_pos = 0, trailing = 0;
 118   pango_layout_xy_to_index(layout_, p.x() * PANGO_SCALE, p.y() * PANGO_SCALE,
 119                            &caret_pos, &trailing);
 120
 121   DCHECK_GE(trailing, 0);
 122   if (trailing > 0) {
 123     caret_pos = g_utf8_offset_to_pointer(layout_text_ + caret_pos,
 124                                          trailing) - layout_text_;
 125     DCHECK_LE(static_cast<size_t>(caret_pos), strlen(layout_text_));
 126   }
 127
 128   return SelectionModel(LayoutIndexToTextIndex(caret_pos),
 129                         (trailing > 0) ? CURSOR_BACKWARD : CURSOR_FORWARD);
 130 }
 131
 132 std::vector<RenderText::FontSpan> RenderTextLinux::GetFontSpansForTesting() {
 133   EnsureLayout();
 134
 135   std::vector<RenderText::FontSpan> spans;
 136   for (GSList* it = current_line_->runs; it; it = it->next) {
 137     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(it->data)->item;
 138     const int start = LayoutIndexToTextIndex(item->offset);
 139     const int end = LayoutIndexToTextIndex(item->offset + item->length);
 140     const ui::Range range(start, end);
 141
 142     ScopedPangoFontDescription desc(pango_font_describe(item->analysis.font));
 143     spans.push_back(RenderText::FontSpan(Font(desc.get()), range));
 144   }
 145
 146   return spans;
 147 }
 148
 149 SelectionModel RenderTextLinux::AdjacentCharSelectionModel(
 150     const SelectionModel& selection,
 151     VisualCursorDirection direction) {
 152   GSList* run = GetRunContainingCaret(selection);
 153   if (!run) {
 154     // The cursor is not in any run: we're at the visual and logical edge.
 155     SelectionModel edge = EdgeSelectionModel(direction);
 156     if (edge.caret_pos() == selection.caret_pos())
 157       return edge;
 158     else
 159       run = (direction == CURSOR_RIGHT) ?
 160           current_line_->runs : g_slist_last(current_line_->runs);
 161   } else {
 162     // If the cursor is moving within the current run, just move it by one
 163     // grapheme in the appropriate direction.
 164     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 165     size_t caret = selection.caret_pos();
 166     if (IsForwardMotion(direction, item)) {
 167       if (caret < LayoutIndexToTextIndex(item->offset + item->length)) {
 168         caret = IndexOfAdjacentGrapheme(caret, CURSOR_FORWARD);
 169         return SelectionModel(caret, CURSOR_BACKWARD);
 170       }
 171     } else {
 172       if (caret > LayoutIndexToTextIndex(item->offset)) {
 173         caret = IndexOfAdjacentGrapheme(caret, CURSOR_BACKWARD);
 174         return SelectionModel(caret, CURSOR_FORWARD);
 175       }
 176     }
 177     // The cursor is at the edge of a run; move to the visually adjacent run.
 178     // TODO(xji): Keep a vector of runs to avoid using a singly-linked list.
 179     run = (direction == CURSOR_RIGHT) ?
 180         run->next : GSListPrevious(current_line_->runs, run);
 181     if (!run)
 182       return EdgeSelectionModel(direction);
 183   }
 184   PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 185   return IsForwardMotion(direction, item) ?
 186       FirstSelectionModelInsideRun(item) : LastSelectionModelInsideRun(item);
 187 }
 188
 189 SelectionModel RenderTextLinux::AdjacentWordSelectionModel(
 190     const SelectionModel& selection,
 191     VisualCursorDirection direction) {
 192   if (obscured())
 193     return EdgeSelectionModel(direction);
 194
 195   base::i18n::BreakIterator iter(text(), base::i18n::BreakIterator::BREAK_WORD);
 196   bool success = iter.Init();
 197   DCHECK(success);
 198   if (!success)
 199     return selection;
 200
 201   SelectionModel cur(selection);
 202   for (;;) {
 203     cur = AdjacentCharSelectionModel(cur, direction);
 204     GSList* run = GetRunContainingCaret(cur);
 205     if (!run)
 206       break;
 207     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 208     size_t cursor = cur.caret_pos();
 209     if (IsForwardMotion(direction, item) ?
 210         iter.IsEndOfWord(cursor) : iter.IsStartOfWord(cursor))
 211       break;
 212   }
 213
 214   return cur;
 215 }
 216
 217 ui::Range RenderTextLinux::GetGlyphBounds(size_t index) {
 218   PangoRectangle pos;
 219   pango_layout_index_to_pos(layout_, TextIndexToLayoutIndex(index), &pos);
 220   // TODO(derat): Support fractional ranges for subpixel positioning?
 221   return ui::Range(PANGO_PIXELS(pos.x), PANGO_PIXELS(pos.x + pos.width));
 222 }
 223
 224 std::vector<Rect> RenderTextLinux::GetSubstringBounds(const ui::Range& range) {
 225   DCHECK_LE(range.GetMax(), text().length());
 226   if (range.is_empty())
 227     return std::vector<Rect>();
 228
 229   EnsureLayout();
 230   int* ranges = NULL;
 231   int n_ranges = 0;
 232   pango_layout_line_get_x_ranges(current_line_,
 233                                  TextIndexToLayoutIndex(range.GetMin()),
 234                                  TextIndexToLayoutIndex(range.GetMax()),
 235                                  &ranges,
 236                                  &n_ranges);
 237
 238   const int height = GetStringSize().height();
 239
 240   std::vector<Rect> bounds;
 241   for (int i = 0; i < n_ranges; ++i) {
 242     // TODO(derat): Support fractional bounds for subpixel positioning?
 243     int x = PANGO_PIXELS(ranges[2 * i]);
 244     int width = PANGO_PIXELS(ranges[2 * i + 1]) - x;
 245     Rect rect(x, 0, width, height);
 246     rect.set_origin(ToViewPoint(rect.origin()));
 247     bounds.push_back(rect);
 248   }
 249   g_free(ranges);
 250   return bounds;
 251 }
 252
 253 size_t RenderTextLinux::TextIndexToLayoutIndex(size_t index) const {
 254   DCHECK(layout_);
 255   ptrdiff_t offset = ui::UTF16IndexToOffset(text(), 0, index);
 256   // Clamp layout indices to the length of the text actually used for layout.
 257   offset = std::min<size_t>(offset, g_utf8_strlen(layout_text_, -1));
 258   const char* layout_pointer = g_utf8_offset_to_pointer(layout_text_, offset);
 259   return (layout_pointer - layout_text_);
 260 }
 261
 262 size_t RenderTextLinux::LayoutIndexToTextIndex(size_t index) const {
 263   DCHECK(layout_);
 264   const char* layout_pointer = layout_text_ + index;
 265   const long offset = g_utf8_pointer_to_offset(layout_text_, layout_pointer);
 266   return ui::UTF16OffsetToIndex(text(), 0, offset);
 267 }
 268
 269 bool RenderTextLinux::IsCursorablePosition(size_t position) {
 270   if (position == 0 && text().empty())
 271     return true;
 272   if (position >= text().length())
 273     return position == text().length();
 274   if (!ui::IsValidCodePointIndex(text(), position))
 275     return false;
 276
 277   EnsureLayout();
 278   ptrdiff_t offset = ui::UTF16IndexToOffset(text(), 0, position);
 279   // Check that the index corresponds with a valid text code point, that it is
 280   // marked as a legitimate cursor position by Pango, and that it is not
 281   // truncated from layout text (its glyph is shown on screen).
 282   return (offset < num_log_attrs_ && log_attrs_[offset].is_cursor_position &&
 283           offset < g_utf8_strlen(layout_text_, -1));
 284 }
 285
 286 void RenderTextLinux::ResetLayout() {
 287   // set_cached_bounds_and_offset_valid(false) is done in RenderText for every
 288   // operation that triggers ResetLayout().
 289   if (layout_) {
 290     g_object_unref(layout_);
 291     layout_ = NULL;
 292   }
 293   if (current_line_) {
 294     pango_layout_line_unref(current_line_);
 295     current_line_ = NULL;
 296   }
 297   if (log_attrs_) {
 298     g_free(log_attrs_);
 299     log_attrs_ = NULL;
 300     num_log_attrs_ = 0;
 301   }
 302   layout_text_ = NULL;
 303 }
 304
 305 void RenderTextLinux::EnsureLayout() {
 306   if (layout_ == NULL) {
 307     cairo_surface_t* surface =
 308         cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 0, 0);
 309     cairo_t* cr = cairo_create(surface);
 310
 311     layout_ = pango_cairo_create_layout(cr);
 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     pango_layout_line_ref(current_line_);
 335
 336     pango_layout_get_log_attrs(layout_, &log_attrs_, &num_log_attrs_);
 337   }
 338 }
 339
 340 void RenderTextLinux::SetupPangoAttributes(PangoLayout* layout) {
 341   PangoAttrList* attrs = pango_attr_list_new();
 342
 343   // Splitting text runs to accommodate styling can break Arabic glyph shaping.
 344   // Only split text runs as needed for bold and italic font styles changes.
 345   BreakList<bool>::const_iterator bold = styles()[BOLD].breaks().begin();
 346   BreakList<bool>::const_iterator italic = styles()[ITALIC].breaks().begin();
 347   while (bold != styles()[BOLD].breaks().end() &&
 348          italic != styles()[ITALIC].breaks().end()) {
 349     const int style = (bold->second ? Font::BOLD : 0) |
 350                       (italic->second ? Font::ITALIC : 0);
 351     const size_t bold_end = styles()[BOLD].GetRange(bold).end();
 352     const size_t italic_end = styles()[ITALIC].GetRange(italic).end();
 353     const size_t style_end = std::min(bold_end, italic_end);
 354     if (style != font_list().GetFontStyle()) {
 355       FontList derived_font_list = font_list().DeriveFontList(style);
 356       ScopedPangoFontDescription desc(pango_font_description_from_string(
 357           derived_font_list.GetFontDescriptionString().c_str()));
 358
 359       PangoAttribute* pango_attr = pango_attr_font_desc_new(desc.get());
 360       pango_attr->start_index =
 361           TextIndexToLayoutIndex(std::max(bold->first, italic->first));
 362       pango_attr->end_index = TextIndexToLayoutIndex(style_end);
 363       pango_attr_list_insert(attrs, pango_attr);
 364     }
 365     bold += bold_end == style_end ? 1 : 0;
 366     italic += italic_end == style_end ? 1 : 0;
 367   }
 368   DCHECK(bold == styles()[BOLD].breaks().end());
 369   DCHECK(italic == styles()[ITALIC].breaks().end());
 370
 371   pango_layout_set_attributes(layout, attrs);
 372   pango_attr_list_unref(attrs);
 373 }
 374
 375 void RenderTextLinux::DrawVisualText(Canvas* canvas) {
 376   DCHECK(layout_);
 377
 378   // Skia will draw glyphs with respect to the baseline.
 379   Vector2d offset(GetTextOffset() + Vector2d(0, GetBaseline()));
 380
 381   SkScalar x = SkIntToScalar(offset.x());
 382   SkScalar y = SkIntToScalar(offset.y());
 383
 384   std::vector<SkPoint> pos;
 385   std::vector<uint16> glyphs;
 386
 387   internal::SkiaTextRenderer renderer(canvas);
 388   ApplyFadeEffects(&renderer);
 389   ApplyTextShadows(&renderer);
 390
 391   // TODO(derat): Use font-specific params: http://crbug.com/125235
 392   const gfx::FontRenderParams& render_params =
 393       gfx::GetDefaultFontRenderParams();
 394   const bool use_subpixel_rendering =
 395       render_params.subpixel_rendering !=
 396           gfx::FontRenderParams::SUBPIXEL_RENDERING_NONE;
 397   renderer.SetFontSmoothingSettings(
 398       render_params.antialiasing,
 399       use_subpixel_rendering && !background_is_transparent());
 400
 401   // Temporarily apply composition underlines and selection colors.
 402   ApplyCompositionAndSelectionStyles();
 403
 404   internal::StyleIterator style(colors(), styles());
 405   for (GSList* it = current_line_->runs; it; it = it->next) {
 406     PangoLayoutRun* run = reinterpret_cast<PangoLayoutRun*>(it->data);
 407     int glyph_count = run->glyphs->num_glyphs;
 408     // TODO(msw): Skip painting runs outside the display rect area, like Win.
 409     if (glyph_count == 0)
 410       continue;
 411
 412     ScopedPangoFontDescription desc(
 413         pango_font_describe(run->item->analysis.font));
 414
 415     const std::string family_name =
 416         pango_font_description_get_family(desc.get());
 417     renderer.SetTextSize(GetPangoFontSizeInPixels(desc.get()));
 418
 419     glyphs.resize(glyph_count);
 420     pos.resize(glyph_count);
 421
 422     // Track the current glyph and the glyph at the start of its styled range.
 423     int glyph_index = 0;
 424     int style_start_glyph_index = glyph_index;
 425
 426     // Track the x-coordinates for each styled range (|x| marks the current).
 427     SkScalar style_start_x = x;
 428
 429     // Track the current style and its text (not layout) index range.
 430     style.UpdatePosition(GetGlyphTextIndex(run, style_start_glyph_index));
 431     ui::Range style_range = style.GetRange();
 432
 433     do {
 434       const PangoGlyphInfo& glyph = run->glyphs->glyphs[glyph_index];
 435       glyphs[glyph_index] = static_cast<uint16>(glyph.glyph);
 436       // Use pango_units_to_double() rather than PANGO_PIXELS() here, so units
 437       // are not rounded to the pixel grid if subpixel positioning is enabled.
 438       pos[glyph_index].set(x + pango_units_to_double(glyph.geometry.x_offset),
 439                            y + pango_units_to_double(glyph.geometry.y_offset));
 440       x += pango_units_to_double(glyph.geometry.width);
 441
 442       ++glyph_index;
 443       const size_t glyph_text_index = (glyph_index == glyph_count) ?
 444           style_range.end() : GetGlyphTextIndex(run, glyph_index);
 445       if (!IndexInRange(style_range, glyph_text_index)) {
 446         // TODO(asvitkine): For cases like "fi", where "fi" is a single glyph
 447         //                  but can span multiple styles, Pango splits the
 448         //                  styles evenly over the glyph. We can do this too by
 449         //                  clipping and drawing the glyph several times.
 450         renderer.SetForegroundColor(style.color());
 451         const int font_style = (style.style(BOLD) ? Font::BOLD : 0) |
 452                                (style.style(ITALIC) ? Font::ITALIC : 0);
 453         renderer.SetFontFamilyWithStyle(family_name, font_style);
 454         renderer.DrawPosText(&pos[style_start_glyph_index],
 455                              &glyphs[style_start_glyph_index],
 456                              glyph_index - style_start_glyph_index);
 457         if (style.style(UNDERLINE))
 458           SetPangoUnderlineMetrics(desc.get(), &renderer);
 459         renderer.DrawDecorations(style_start_x, y, x - style_start_x,
 460                                  style.style(UNDERLINE), style.style(STRIKE),
 461                                  style.style(DIAGONAL_STRIKE));
 462         style.UpdatePosition(glyph_text_index);
 463         style_range = style.GetRange();
 464         style_start_glyph_index = glyph_index;
 465         style_start_x = x;
 466       }
 467     } while (glyph_index < glyph_count);
 468   }
 469
 470   // Undo the temporarily applied composition underlines and selection colors.
 471   UndoCompositionAndSelectionStyles();
 472 }
 473
 474 GSList* RenderTextLinux::GetRunContainingCaret(
 475     const SelectionModel& caret) const {
 476   size_t position = TextIndexToLayoutIndex(caret.caret_pos());
 477   LogicalCursorDirection affinity = caret.caret_affinity();
 478   GSList* run = current_line_->runs;
 479   while (run) {
 480     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
 481     ui::Range item_range(item->offset, item->offset + item->length);
 482     if (RangeContainsCaret(item_range, position, affinity))
 483       return run;
 484     run = run->next;
 485   }
 486   return NULL;
 487 }
 488
 489 SelectionModel RenderTextLinux::FirstSelectionModelInsideRun(
 490     const PangoItem* item) {
 491   size_t caret = IndexOfAdjacentGrapheme(
 492       LayoutIndexToTextIndex(item->offset), CURSOR_FORWARD);
 493   return SelectionModel(caret, CURSOR_BACKWARD);
 494 }
 495
 496 SelectionModel RenderTextLinux::LastSelectionModelInsideRun(
 497     const PangoItem* item) {
 498   size_t caret = IndexOfAdjacentGrapheme(
 499       LayoutIndexToTextIndex(item->offset + item->length), CURSOR_BACKWARD);
 500   return SelectionModel(caret, CURSOR_FORWARD);
 501 }
 502
 503 size_t RenderTextLinux::GetGlyphTextIndex(PangoLayoutRun* run,
 504                                           int glyph_index) const {
 505   return LayoutIndexToTextIndex(run->item->offset +
 506                                 run->glyphs->log_clusters[glyph_index]);
 507 }
 508
 509 RenderText* RenderText::CreateInstance() {
 510   return new RenderTextLinux;
 511 }
 512
 513 }  // namespace gfx