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
17package android.text.style;
18
19import 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 */
26public abstract class CharacterStyle {
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     */
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     */
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         */
66        public Passthrough(CharacterStyle cs) {
67            mStyle = cs;
68        }
69
70        /**
71         * Passes updateDrawState through to the underlying CharacterStyle.
72         */
73        @Override
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
83        public CharacterStyle getUnderlying() {
84            return mStyle.getUnderlying();
85        }
86    }
87}
88