MetricAffectingSpan.java revision 8a985d24ce9a38f40ed88fecbdcd0e75e3a68f44 
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 in a way that
23 * changes the width or height of characters extend this class.
24 */
25public abstract class MetricAffectingSpan
26extends CharacterStyle
27implements UpdateLayout {
28
29    public abstract void updateMeasureState(TextPaint p);
30
31    /**
32     * Returns "this" for most MetricAffectingSpans, but for
33     * MetricAffectingSpans that were generated by {@link #wrap},
34     * returns the underlying MetricAffectingSpan.
35     */
36    @Override
37    public MetricAffectingSpan getUnderlying() {
38        return this;
39    }
40
41    /**
42     * A Passthrough MetricAffectingSpan is one that
43     * passes {@link #updateDrawState} and {@link #updateMeasureState}
44     * calls through to the specified MetricAffectingSpan
45     * while still being a distinct object,
46     * and is therefore able to be attached to the same Spannable
47     * to which the specified MetricAffectingSpan is already attached.
48     */
49    /* package */ static class Passthrough extends MetricAffectingSpan {
50        private MetricAffectingSpan mStyle;
51
52        /**
53         * Creates a new Passthrough of the specfied MetricAffectingSpan.
54         */
55        public Passthrough(MetricAffectingSpan cs) {
56            mStyle = cs;
57        }
58
59        /**
60         * Passes updateDrawState through to the underlying MetricAffectingSpan.
61         */
62        @Override
63        public void updateDrawState(TextPaint tp) {
64            mStyle.updateDrawState(tp);
65        }
66
67        /**
68         * Passes updateMeasureState through to the underlying MetricAffectingSpan.
69         */
70        @Override
71        public void updateMeasureState(TextPaint tp) {
72            mStyle.updateMeasureState(tp);
73        }
74
75        /**
76         * Returns the MetricAffectingSpan underlying this one, or the one
77         * underlying it if it too is a Passthrough.
78         */
79        @Override
80        public MetricAffectingSpan getUnderlying() {
81            return mStyle.getUnderlying();
82        }
83    }
84}
85