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