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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 in a way that
     23  * changes the width or height of characters extend this class.
     24  */
     25 public abstract class MetricAffectingSpan
     26 extends CharacterStyle
     27 implements 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