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      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().DeriveFontList(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   // Temporarily apply composition underlines and selection colors.
    403   ApplyCompositionAndSelectionStyles();
    404 
    405   internal::StyleIterator style(colors(), styles());
    406   for (GSList* it = current_line_->runs; it; it = it->next) {
    407     PangoLayoutRun* run = reinterpret_cast<PangoLayoutRun*>(it->data);
    408     int glyph_count = run->glyphs->num_glyphs;
    409     // TODO(msw): Skip painting runs outside the display rect area, like Win.
    410     if (glyph_count == 0)
    411       continue;
    412 
    413     ScopedPangoFontDescription desc(
    414         pango_font_describe(run->item->analysis.font));
    415 
    416     const std::string family_name =
    417         pango_font_description_get_family(desc.get());
    418     renderer.SetTextSize(GetPangoFontSizeInPixels(desc.get()));
    419 
    420     glyphs.resize(glyph_count);
    421     pos.resize(glyph_count);
    422 
    423     // Track the current glyph and the glyph at the start of its styled range.
    424     int glyph_index = 0;
    425     int style_start_glyph_index = glyph_index;
    426 
    427     // Track the x-coordinates for each styled range (|x| marks the current).
    428     SkScalar style_start_x = x;
    429 
    430     // Track the current style and its text (not layout) index range.
    431     style.UpdatePosition(GetGlyphTextIndex(run, style_start_glyph_index));
    432     Range style_range = style.GetRange();
    433 
    434     do {
    435       const PangoGlyphInfo& glyph = run->glyphs->glyphs[glyph_index];
    436       glyphs[glyph_index] = static_cast<uint16>(glyph.glyph);
    437       // Use pango_units_to_double() rather than PANGO_PIXELS() here, so units
    438       // are not rounded to the pixel grid if subpixel positioning is enabled.
    439       pos[glyph_index].set(x + pango_units_to_double(glyph.geometry.x_offset),
    440                            y + pango_units_to_double(glyph.geometry.y_offset));
    441       x += pango_units_to_double(glyph.geometry.width);
    442 
    443       ++glyph_index;
    444       const size_t glyph_text_index = (glyph_index == glyph_count) ?
    445           style_range.end() : GetGlyphTextIndex(run, glyph_index);
    446       if (!IndexInRange(style_range, glyph_text_index)) {
    447         // TODO(asvitkine): For cases like "fi", where "fi" is a single glyph
    448         //                  but can span multiple styles, Pango splits the
    449         //                  styles evenly over the glyph. We can do this too by
    450         //                  clipping and drawing the glyph several times.
    451         renderer.SetForegroundColor(style.color());
    452         const int font_style = (style.style(BOLD) ? Font::BOLD : 0) |
    453                                (style.style(ITALIC) ? Font::ITALIC : 0);
    454         renderer.SetFontFamilyWithStyle(family_name, font_style);
    455         renderer.DrawPosText(&pos[style_start_glyph_index],
    456                              &glyphs[style_start_glyph_index],
    457                              glyph_index - style_start_glyph_index);
    458         if (style.style(UNDERLINE))
    459           SetPangoUnderlineMetrics(desc.get(), &renderer);
    460         renderer.DrawDecorations(style_start_x, y, x - style_start_x,
    461                                  style.style(UNDERLINE), style.style(STRIKE),
    462                                  style.style(DIAGONAL_STRIKE));
    463         style.UpdatePosition(glyph_text_index);
    464         style_range = style.GetRange();
    465         style_start_glyph_index = glyph_index;
    466         style_start_x = x;
    467       }
    468     } while (glyph_index < glyph_count);
    469   }
    470 
    471   // Undo the temporarily applied composition underlines and selection colors.
    472   UndoCompositionAndSelectionStyles();
    473 }
    474 
    475 GSList* RenderTextPango::GetRunContainingCaret(
    476     const SelectionModel& caret) const {
    477   size_t position = TextIndexToLayoutIndex(caret.caret_pos());
    478   LogicalCursorDirection affinity = caret.caret_affinity();
    479   GSList* run = current_line_->runs;
    480   while (run) {
    481     PangoItem* item = reinterpret_cast<PangoLayoutRun*>(run->data)->item;
    482     Range item_range(item->offset, item->offset + item->length);
    483     if (RangeContainsCaret(item_range, position, affinity))
    484       return run;
    485     run = run->next;
    486   }
    487   return NULL;
    488 }
    489 
    490 SelectionModel RenderTextPango::FirstSelectionModelInsideRun(
    491     const PangoItem* item) {
    492   size_t caret = IndexOfAdjacentGrapheme(
    493       LayoutIndexToTextIndex(item->offset), CURSOR_FORWARD);
    494   return SelectionModel(caret, CURSOR_BACKWARD);
    495 }
    496 
    497 SelectionModel RenderTextPango::LastSelectionModelInsideRun(
    498     const PangoItem* item) {
    499   size_t caret = IndexOfAdjacentGrapheme(
    500       LayoutIndexToTextIndex(item->offset + item->length), CURSOR_BACKWARD);
    501   return SelectionModel(caret, CURSOR_FORWARD);
    502 }
    503 
    504 size_t RenderTextPango::GetGlyphTextIndex(PangoLayoutRun* run,
    505                                           int glyph_index) const {
    506   return LayoutIndexToTextIndex(run->item->offset +
    507                                 run->glyphs->log_clusters[glyph_index]);
    508 }
    509 
    510 RenderText* RenderText::CreateInstance() {
    511   return new RenderTextPango;
    512 }
    513 
    514 }  // namespace gfx
    515