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      1 // Copyright 2013 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/base/ime/composition_text_util_pango.h"
      6 
      7 #include <pango/pango-attributes.h>
      8 
      9 #include "base/basictypes.h"
     10 #include "base/i18n/char_iterator.h"
     11 #include "base/strings/string16.h"
     12 #include "base/strings/utf_string_conversions.h"
     13 #include "ui/base/ime/composition_text.h"
     14 
     15 namespace ui {
     16 
     17 void ExtractCompositionTextFromGtkPreedit(const gchar* utf8_text,
     18                                           PangoAttrList* attrs,
     19                                           int cursor_position,
     20                                           CompositionText* composition) {
     21   composition->Clear();
     22   composition->text = base::UTF8ToUTF16(utf8_text);
     23 
     24   if (composition->text.empty())
     25     return;
     26 
     27   // Gtk/Pango uses character index for cursor position and byte index for
     28   // attribute range, but we use char16 offset for them. So we need to do
     29   // conversion here.
     30   std::vector<size_t> char16_offsets;
     31   size_t length = composition->text.length();
     32   base::i18n::UTF16CharIterator char_iterator(&composition->text);
     33   do {
     34     char16_offsets.push_back(char_iterator.array_pos());
     35   } while (char_iterator.Advance());
     36 
     37   // The text length in Unicode characters.
     38   int char_length = static_cast<int>(char16_offsets.size());
     39   // Make sure we can convert the value of |char_length| as well.
     40   char16_offsets.push_back(length);
     41 
     42   size_t cursor_offset =
     43       char16_offsets[std::max(0, std::min(char_length, cursor_position))];
     44 
     45   composition->selection = gfx::Range(cursor_offset);
     46 
     47   if (attrs) {
     48     int utf8_length = strlen(utf8_text);
     49     PangoAttrIterator* iter = pango_attr_list_get_iterator(attrs);
     50 
     51     // We only care about underline and background attributes and convert
     52     // background attribute into selection if possible.
     53     do {
     54       gint start, end;
     55       pango_attr_iterator_range(iter, &start, &end);
     56 
     57       start = std::min(start, utf8_length);
     58       end = std::min(end, utf8_length);
     59       if (start >= end)
     60         continue;
     61 
     62       start = g_utf8_pointer_to_offset(utf8_text, utf8_text + start);
     63       end = g_utf8_pointer_to_offset(utf8_text, utf8_text + end);
     64 
     65       // Double check, in case |utf8_text| is not a valid utf-8 string.
     66       start = std::min(start, char_length);
     67       end = std::min(end, char_length);
     68       if (start >= end)
     69         continue;
     70 
     71       PangoAttribute* background_attr =
     72           pango_attr_iterator_get(iter, PANGO_ATTR_BACKGROUND);
     73       PangoAttribute* underline_attr =
     74           pango_attr_iterator_get(iter, PANGO_ATTR_UNDERLINE);
     75 
     76       if (background_attr || underline_attr) {
     77         // Use a black thin underline by default.
     78         CompositionUnderline underline(char16_offsets[start],
     79                                        char16_offsets[end],
     80                                        SK_ColorBLACK,
     81                                        false,
     82                                        SK_ColorTRANSPARENT);
     83 
     84         // Always use thick underline for a range with background color, which
     85         // is usually the selection range.
     86         if (background_attr) {
     87           underline.thick = true;
     88           // If the cursor is at start or end of this underline, then we treat
     89           // it as the selection range as well, but make sure to set the cursor
     90           // position to the selection end.
     91           if (underline.start_offset == cursor_offset) {
     92             composition->selection.set_start(underline.end_offset);
     93             composition->selection.set_end(cursor_offset);
     94           } else if (underline.end_offset == cursor_offset) {
     95             composition->selection.set_start(underline.start_offset);
     96             composition->selection.set_end(cursor_offset);
     97           }
     98         }
     99         if (underline_attr) {
    100           int type = reinterpret_cast<PangoAttrInt*>(underline_attr)->value;
    101           if (type == PANGO_UNDERLINE_DOUBLE)
    102             underline.thick = true;
    103           else if (type == PANGO_UNDERLINE_ERROR)
    104             underline.color = SK_ColorRED;
    105         }
    106         composition->underlines.push_back(underline);
    107       }
    108     } while (pango_attr_iterator_next(iter));
    109     pango_attr_iterator_destroy(iter);
    110   }
    111 
    112   // Use a black thin underline by default.
    113   if (composition->underlines.empty()) {
    114     composition->underlines.push_back(CompositionUnderline(
    115         0, length, SK_ColorBLACK, false, SK_ColorTRANSPARENT));
    116   }
    117 }
    118 
    119 }  // namespace ui
    120