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      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 {
     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