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1 // Copyright 2016 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 "core/layout/ng/ng_text_layout_algorithm.h" | |
6 | |
7 #include "core/layout/ng/ng_box_fragment.h" | |
8 #include "core/layout/ng/ng_break_token.h" | |
9 #include "core/layout/ng/ng_constraint_space.h" | |
10 #include "core/layout/ng/ng_fragment_builder.h" | |
11 #include "core/layout/ng/ng_inline_node.h" | |
12 #include "core/layout/ng/ng_layout_opportunity_iterator.h" | |
13 #include "core/layout/ng/ng_line_builder.h" | |
14 #include "core/layout/ng/ng_text_fragment.h" | |
15 #include "core/style/ComputedStyle.h" | |
16 #include "platform/text/TextBreakIterator.h" | |
17 | |
18 namespace blink { | |
19 | |
20 NGTextLayoutAlgorithm::NGTextLayoutAlgorithm( | |
21 NGInlineNode* inline_box, | |
22 NGBreakToken* break_token) | |
23 : inline_box_(inline_box), | |
24 break_token_(break_token) { | |
25 DCHECK(inline_box_); | |
26 } | |
27 | |
28 RefPtr<NGLayoutResult> NGTextLayoutAlgorithm::Layout() { | |
29 NOTREACHED(); | |
30 return nullptr; | |
31 } | |
32 | |
33 static bool IsHangable(UChar ch) { | |
34 return ch == ' '; | |
35 } | |
36 | |
37 void NGTextLayoutAlgorithm::LayoutInline(NGLineBuilder* line_builder) { | |
38 // TODO(kojii): Make this tickable. Each line is easy. Needs more thoughts | |
39 // for each fragment in a line. Bidi reordering is probably atomic. | |
40 // TODO(kojii): oof is not well-thought yet. The bottom static position may be | |
41 // in the next line, https://github.com/w3c/csswg-drafts/issues/609 | |
42 const String& text_content = inline_box_->Text(); | |
43 DCHECK(!text_content.isEmpty()); | |
44 // TODO(kojii): Give the locale to LazyLineBreakIterator. | |
45 LazyLineBreakIterator line_break_iterator(text_content); | |
46 unsigned current_offset = 0; | |
47 line_builder->SetStart(0, current_offset); | |
48 const unsigned end_offset = text_content.length(); | |
49 while (current_offset < end_offset) { | |
50 // Find the next break opportunity. | |
51 int tmp_next_breakable_offset = -1; | |
52 line_break_iterator.isBreakable(current_offset + 1, | |
53 tmp_next_breakable_offset); | |
54 current_offset = | |
55 tmp_next_breakable_offset >= 0 ? tmp_next_breakable_offset : end_offset; | |
56 DCHECK_LE(current_offset, end_offset); | |
57 | |
58 // Advance the break opportunity to the end of hangable characters; e.g., | |
59 // spaces. | |
60 // Unlike the ICU line breaker, LazyLineBreakIterator breaks before | |
61 // breakable spaces, and expect the line breaker to handle spaces | |
62 // differently. This logic computes in the ICU way; break after spaces, and | |
63 // handle spaces as hangable characters. | |
64 unsigned start_of_hangables = current_offset; | |
65 while (current_offset < end_offset && | |
66 IsHangable(text_content[current_offset])) | |
67 current_offset++; | |
68 | |
69 // Set the end to the next break opportunity. | |
70 line_builder->SetEnd(current_offset); | |
71 | |
72 // If there are more available spaces, mark the break opportunity and fetch | |
73 // more text. | |
74 // TODO(layout-ng): check if the height of the linebox can fit within | |
75 // the current opportunity. | |
76 if (line_builder->CanFitOnLine()) { | |
77 line_builder->SetBreakOpportunity(); | |
78 continue; | |
79 } | |
80 | |
81 // Compute hangable characters if exists. | |
82 if (current_offset != start_of_hangables) { | |
83 line_builder->SetStartOfHangables(start_of_hangables); | |
84 // If text before hangables can fit, include it in the current line. | |
85 if (line_builder->CanFitOnLine()) | |
86 line_builder->SetBreakOpportunity(); | |
87 } | |
88 | |
89 if (!line_builder->HasBreakOpportunity()) { | |
90 // The first word (break opportunity) did not fit on the line. | |
91 // Create a line including items that don't fit, allowing them to | |
92 // overflow. | |
93 line_builder->CreateLine(); | |
94 } else { | |
95 line_builder->CreateLineUpToLastBreakOpportunity(); | |
96 | |
97 // Items after the last break opportunity were sent to the next line. | |
98 // Set the break opportunity, or create a line if the word doesn't fit. | |
99 if (line_builder->HasItems()) { | |
100 if (!line_builder->CanFitOnLine()) | |
101 line_builder->CreateLine(); | |
102 else | |
103 line_builder->SetBreakOpportunity(); | |
104 } | |
105 } | |
106 } | |
107 | |
108 // If inline children ended with items left in the line builder, create a line | |
109 // for them. | |
110 if (line_builder->HasItems()) | |
111 line_builder->CreateLine(); | |
112 } | |
113 | |
114 } // namespace blink | |
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