MetricAffectingSpan.java revision 9066cfe9886ac131c34d59ed0e2d287b0e3c0087 
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.graphics.Paint;
20import android.text.TextPaint;
21
22/**
23 * The classes that affect character-level text formatting in a way that
24 * changes the width or height of characters extend this class.
25 */
26public abstract class MetricAffectingSpan
27extends CharacterStyle
28implements UpdateLayout {
29
30	public abstract void updateMeasureState(TextPaint p);
31
32    /**
33     * Returns "this" for most MetricAffectingSpans, but for
34     * MetricAffectingSpans that were generated by {@link #wrap},
35     * returns the underlying MetricAffectingSpan.
36     */
37    @Override
38    public MetricAffectingSpan getUnderlying() {
39        return this;
40    }
41
42    /**
43     * A Passthrough MetricAffectingSpan is one that
44     * passes {@link #updateDrawState} and {@link #updateMeasureState}
45     * calls through to the specified MetricAffectingSpan
46     * while still being a distinct object,
47     * and is therefore able to be attached to the same Spannable
48     * to which the specified MetricAffectingSpan is already attached.
49     */
50    /* package */ static class Passthrough extends MetricAffectingSpan {
51        private MetricAffectingSpan mStyle;
52
53        /**
54         * Creates a new Passthrough of the specfied MetricAffectingSpan.
55         */
56        public Passthrough(MetricAffectingSpan cs) {
57            mStyle = cs;
58        }
59
60        /**
61         * Passes updateDrawState through to the underlying MetricAffectingSpan.
62         */
63        @Override
64        public void updateDrawState(TextPaint tp) {
65            mStyle.updateDrawState(tp);
66        }
67
68        /**
69         * Passes updateMeasureState through to the underlying MetricAffectingSpan.
70         */
71        @Override
72        public void updateMeasureState(TextPaint tp) {
73            mStyle.updateMeasureState(tp);
74        }
75
76        /**
77         * Returns the MetricAffectingSpan underlying this one, or the one
78         * underlying it if it too is a Passthrough.
79         */
80        @Override
81        public MetricAffectingSpan getUnderlying() {
82            return mStyle.getUnderlying();
83        }
84    }
85}
86