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/*
* Copyright (C) 2006 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package android.text.style;
import android.annotation.IntRange;
import android.annotation.NonNull;
import android.annotation.Px;
import android.graphics.Paint;
import android.os.Parcel;
import android.text.ParcelableSpan;
import android.text.TextPaint;
import android.text.TextUtils;
import com.android.internal.util.Preconditions;
/**
* The classes that affect the line height of paragraph should implement this interface.
*/
public interface LineHeightSpan extends ParagraphStyle, WrapTogetherSpan {
/**
* Classes that implement this should define how the height is being calculated.
*
* @param text the text
* @param start the start of the line
* @param end the end of the line
* @param spanstartv the start of the span
* @param lineHeight the line height
* @param fm font metrics of the paint, in integers
*/
public void chooseHeight(CharSequence text, int start, int end,
int spanstartv, int lineHeight,
Paint.FontMetricsInt fm);
/**
* The classes that affect the line height of paragraph with respect to density,
* should implement this interface.
*/
public interface WithDensity extends LineHeightSpan {
/**
* Classes that implement this should define how the height is being calculated.
*
* @param text the text
* @param start the start of the line
* @param end the end of the line
* @param spanstartv the start of the span
* @param lineHeight the line height
* @param paint the paint
*/
public void chooseHeight(CharSequence text, int start, int end,
int spanstartv, int lineHeight,
Paint.FontMetricsInt fm, TextPaint paint);
}
/**
* Default implementation of the {@link LineHeightSpan}, which changes the line height of the
* attached paragraph.
* <p>
* For example, a paragraph with its line height equal to 100px can be set like this:
* <pre>
* SpannableString string = new SpannableString("This is a multiline paragraph. This is a multiline paragraph.");
* string.setSpan(new LineHeightSpan.Standard(100), 0, string.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);
* </pre>
* <img src="{@docRoot}reference/android/images/text/style/lineheightspan.png" />
* <figcaption>Text with line height set to 100 pixels.</figcaption>
* <p>
* Notice that LineHeightSpan will change the line height of the entire paragraph, even though it
* covers only part of the paragraph.
* </p>
*/
class Standard implements LineHeightSpan, ParcelableSpan {
private final @Px int mHeight;
/**
* Set the line height of the paragraph to <code>height</code> physical pixels.
*/
public Standard(@Px @IntRange(from = 1) int height) {
Preconditions.checkArgument(height > 0, "Height:" + height + "must be positive");
mHeight = height;
}
/**
* Constructor called from {@link TextUtils} to restore the span from a parcel
*/
public Standard(@NonNull Parcel src) {
mHeight = src.readInt();
}
/**
* Returns the line height specified by this span.
*/
@Px
public int getHeight() {
return mHeight;
}
@Override
public int getSpanTypeId() {
return getSpanTypeIdInternal();
}
/** @hide */
@Override
public int getSpanTypeIdInternal() {
return TextUtils.LINE_HEIGHT_SPAN;
}
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
writeToParcelInternal(dest, flags);
}
/** @hide */
@Override
public void writeToParcelInternal(@NonNull Parcel dest, int flags) {
dest.writeInt(mHeight);
}
@Override
public void chooseHeight(@NonNull CharSequence text, int start, int end,
int spanstartv, int lineHeight,
@NonNull Paint.FontMetricsInt fm) {
final int originHeight = fm.descent - fm.ascent;
// If original height is not positive, do nothing.
if (originHeight <= 0) {
return;
}
final float ratio = mHeight * 1.0f / originHeight;
fm.descent = Math.round(fm.descent * ratio);
fm.ascent = fm.descent - mHeight;
}
}
}
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