1 /*
2  * Copyright (C) 2006 The Android Open Source Project
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 package android.text.style;
18 
19 import android.text.TextPaint;
20 
21 /**
22  * The classes that affect character-level text formatting extend this
23  * class.  Most extend its subclass {@link MetricAffectingSpan}, but simple
24  * ones may just implement {@link UpdateAppearance}.
25  */
26 public abstract class CharacterStyle {
updateDrawState(TextPaint tp)27     public abstract void updateDrawState(TextPaint tp);
28 
29     /**
30      * A given CharacterStyle can only applied to a single region of a given
31      * Spanned.  If you need to attach the same CharacterStyle to multiple
32      * regions, you can use this method to wrap it with a new object that
33      * will have the same effect but be a distinct object so that it can
34      * also be attached without conflict.
35      */
wrap(CharacterStyle cs)36     public static CharacterStyle wrap(CharacterStyle cs) {
37         if (cs instanceof MetricAffectingSpan) {
38             return new MetricAffectingSpan.Passthrough((MetricAffectingSpan) cs);
39         } else {
40             return new Passthrough(cs);
41         }
42     }
43 
44     /**
45      * Returns "this" for most CharacterStyles, but for CharacterStyles
46      * that were generated by {@link #wrap}, returns the underlying
47      * CharacterStyle.
48      */
getUnderlying()49     public CharacterStyle getUnderlying() {
50         return this;
51     }
52 
53     /**
54      * A Passthrough CharacterStyle is one that
55      * passes {@link #updateDrawState} calls through to the
56      * specified CharacterStyle while still being a distinct object,
57      * and is therefore able to be attached to the same Spannable
58      * to which the specified CharacterStyle is already attached.
59      */
60     private static class Passthrough extends CharacterStyle {
61         private CharacterStyle mStyle;
62 
63         /**
64          * Creates a new Passthrough of the specfied CharacterStyle.
65          */
Passthrough(CharacterStyle cs)66         public Passthrough(CharacterStyle cs) {
67             mStyle = cs;
68         }
69 
70         /**
71          * Passes updateDrawState through to the underlying CharacterStyle.
72          */
73         @Override
updateDrawState(TextPaint tp)74         public void updateDrawState(TextPaint tp) {
75             mStyle.updateDrawState(tp);
76         }
77 
78         /**
79          * Returns the CharacterStyle underlying this one, or the one
80          * underlying it if it too is a Passthrough.
81          */
82         @Override
getUnderlying()83         public CharacterStyle getUnderlying() {
84             return mStyle.getUnderlying();
85         }
86     }
87 }
88