Flutter Engine
paragraph_builder.h
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1 /*
2  * Copyright 2017 Google Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef LIB_TXT_SRC_PARAGRAPH_BUILDER_H_
18 #define LIB_TXT_SRC_PARAGRAPH_BUILDER_H_
19 
20 #include <memory>
21 #include <string>
22 
23 #include "flutter/fml/macros.h"
24 #include "font_collection.h"
25 #include "paragraph.h"
26 #include "paragraph_style.h"
27 #include "placeholder_run.h"
28 #include "text_style.h"
29 
30 namespace txt {
31 
33  public:
34  static std::unique_ptr<ParagraphBuilder> CreateTxtBuilder(
35  const ParagraphStyle& style,
36  std::shared_ptr<FontCollection> font_collection);
37 
38 #if FLUTTER_ENABLE_SKSHAPER
39  static std::unique_ptr<ParagraphBuilder> CreateSkiaBuilder(
40  const ParagraphStyle& style,
41  std::shared_ptr<FontCollection> font_collection);
42 #endif
43 
44  virtual ~ParagraphBuilder() = default;
45 
46  // Push a style to the stack. The corresponding text added with AddText will
47  // use the top-most style.
48  virtual void PushStyle(const TextStyle& style) = 0;
49 
50  // Remove a style from the stack. Useful to apply different styles to chunks
51  // of text such as bolding.
52  // Example:
53  // builder.PushStyle(normal_style);
54  // builder.AddText("Hello this is normal. ");
55  //
56  // builder.PushStyle(bold_style);
57  // builder.AddText("And this is BOLD. ");
58  //
59  // builder.Pop();
60  // builder.AddText(" Back to normal again.");
61  virtual void Pop() = 0;
62 
63  // Returns the last TextStyle on the stack.
64  virtual const TextStyle& PeekStyle() = 0;
65 
66  // Adds text to the builder. Forms the proper runs to use the upper-most style
67  // on the style_stack_;
68  virtual void AddText(const std::u16string& text) = 0;
69 
70  // Pushes the information requried to leave an open space, where Flutter may
71  // draw a custom placeholder into.
72  //
73  // Internally, this method adds a single object replacement character (0xFFFC)
74  // and emplaces a new PlaceholderRun instance to the vector of inline
75  // placeholders.
76  virtual void AddPlaceholder(PlaceholderRun& span) = 0;
77 
78  // Constructs a Paragraph object that can be used to layout and paint the text
79  // to a SkCanvas.
80  virtual std::unique_ptr<Paragraph> Build() = 0;
81 
82  protected:
83  ParagraphBuilder() = default;
84 
85  private:
86  FML_DISALLOW_COPY_AND_ASSIGN(ParagraphBuilder);
87 };
88 
89 } // namespace txt
90 
91 #endif // LIB_TXT_SRC_PARAGRAPH_BUILDER_H_
virtual void AddText(const std::u16string &text)=0
virtual std::unique_ptr< Paragraph > Build()=0
virtual void AddPlaceholder(PlaceholderRun &span)=0
virtual ~ParagraphBuilder()=default
virtual void Pop()=0
virtual const TextStyle & PeekStyle()=0
virtual void PushStyle(const TextStyle &style)=0
static std::unique_ptr< ParagraphBuilder > CreateTxtBuilder(const ParagraphStyle &style, std::shared_ptr< FontCollection > font_collection)
ParagraphBuilder()=default