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/*******************************************************************************
* Copyright (c) 2000, 2011 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package org.eclipse.swt.graphics;
import org.eclipse.swt.internal.*;
import org.eclipse.swt.internal.win32.*;
/**
* Instances of this class provide measurement information
* about fonts including ascent, descent, height, leading
* space between rows, and average character width.
* <code>FontMetrics</code> are obtained from <code>GC</code>s
* using the <code>getFontMetrics()</code> method.
*
* @see GC#getFontMetrics
* @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
*/
public final class FontMetrics {
/**
* On Windows, handle is a Win32 TEXTMETRIC struct
* (Warning: This field is platform dependent)
* <p>
* <b>IMPORTANT:</b> This field is <em>not</em> part of the SWT
* public API. It is marked public only so that it can be shared
* within the packages provided by SWT. It is not available on all
* platforms and should never be accessed from application code.
* </p>
*
* @noreference This field is not intended to be referenced by clients.
*/
public TEXTMETRIC handle;
/**
* Prevents instances from being created outside the package.
*/
FontMetrics() {
}
/**
* Compares the argument to the receiver, and returns true
* if they represent the <em>same</em> object using a class
* specific comparison.
*
* @param object the object to compare with this object
* @return <code>true</code> if the object is the same as this object and <code>false</code> otherwise
*
* @see #hashCode
*/
@Override
public boolean equals (Object object) {
if (object == this) return true;
if (!(object instanceof FontMetrics)) return false;
TEXTMETRIC metric = ((FontMetrics)object).handle;
return handle.tmHeight == metric.tmHeight &&
handle.tmAscent == metric.tmAscent &&
handle.tmDescent == metric.tmDescent &&
handle.tmInternalLeading == metric.tmInternalLeading &&
handle.tmExternalLeading == metric.tmExternalLeading &&
handle.tmAveCharWidth == metric.tmAveCharWidth &&
handle.tmMaxCharWidth == metric.tmMaxCharWidth &&
handle.tmWeight == metric.tmWeight &&
handle.tmOverhang == metric.tmOverhang &&
handle.tmDigitizedAspectX == metric.tmDigitizedAspectX &&
handle.tmDigitizedAspectY == metric.tmDigitizedAspectY &&
// handle.tmFirstChar == metric.tmFirstChar &&
// handle.tmLastChar == metric.tmLastChar &&
// handle.tmDefaultChar == metric.tmDefaultChar &&
// handle.tmBreakChar == metric.tmBreakChar &&
handle.tmItalic == metric.tmItalic &&
handle.tmUnderlined == metric.tmUnderlined &&
handle.tmStruckOut == metric.tmStruckOut &&
handle.tmPitchAndFamily == metric.tmPitchAndFamily &&
handle.tmCharSet == metric.tmCharSet;
}
/**
* Returns the ascent of the font described by the receiver. A
* font's <em>ascent</em> is the distance from the baseline to the
* top of actual characters, not including any of the leading area,
* measured in pixels.
*
* @return the ascent of the font
*/
public int getAscent() {
return DPIUtil.autoScaleDown(handle.tmAscent - handle.tmInternalLeading);
}
/**
* Returns the average character width, measured in pixels,
* of the font described by the receiver.
*
* @return the average character width of the font
* @since 3.107
*/
public double getAverageCharacterWidth() {
return getAverageCharWidth();
}
/**
* Returns the average character width, measured in pixels,
* of the font described by the receiver.
*
* @return the average character width of the font
* @deprecated Use getAverageCharacterWidth() instead
*/
public int getAverageCharWidth() {
return DPIUtil.autoScaleDown(handle.tmAveCharWidth);
}
/**
* Returns the descent of the font described by the receiver. A
* font's <em>descent</em> is the distance from the baseline to the
* bottom of actual characters, not including any of the leading area,
* measured in pixels.
*
* @return the descent of the font
*/
public int getDescent() {
return DPIUtil.autoScaleDown(handle.tmDescent);
}
/**
* Returns the height of the font described by the receiver,
* measured in pixels. A font's <em>height</em> is the sum of
* its ascent, descent and leading area.
*
* @return the height of the font
*
* @see #getAscent
* @see #getDescent
* @see #getLeading
*/
public int getHeight() {
return DPIUtil.autoScaleDown(handle.tmHeight);
}
/**
* Returns the leading area of the font described by the
* receiver. A font's <em>leading area</em> is the space
* above its ascent which may include accents or other marks.
*
* @return the leading space of the font
*/
public int getLeading() {
/*
* HiHPI rounding problem (bug 490743 comment 17):
*
* API clients expect this invariant:
* getHeight() == getLeading() + getAscent() + getDescent()
*
* Separate rounding of each RHS term can break the invariant.
*
* An additional problem is that ascent and descent are more important to
* be as close as possible to the real value. Any necessary rounding
* adjustment should go into leading, that's why compute this as a derived
* value here:
*/
return getHeight() - getAscent() - getDescent();
}
/**
* Returns an integer hash code for the receiver. Any two
* objects that return <code>true</code> when passed to
* <code>equals</code> must return the same value for this
* method.
*
* @return the receiver's hash
*
* @see #equals
*/
@Override
public int hashCode() {
return handle.tmHeight ^ handle.tmAscent ^ handle.tmDescent ^
handle.tmInternalLeading ^ handle.tmExternalLeading ^
handle.tmAveCharWidth ^ handle.tmMaxCharWidth ^ handle.tmWeight ^
handle.tmOverhang ^ handle.tmDigitizedAspectX ^ handle.tmDigitizedAspectY ^
// handle.tmFirstChar ^ handle.tmLastChar ^ handle.tmDefaultChar ^ handle.tmBreakChar ^
handle.tmItalic ^ handle.tmUnderlined ^ handle.tmStruckOut ^
handle.tmPitchAndFamily ^ handle.tmCharSet;
}
/**
* Invokes platform specific functionality to allocate a new font metrics.
* <p>
* <b>IMPORTANT:</b> This method is <em>not</em> part of the public
* API for <code>FontMetrics</code>. It is marked public only so that
* it can be shared within the packages provided by SWT. It is not
* available on all platforms, and should never be called from
* application code.
* </p>
*
* @param handle the <code>TEXTMETRIC</code> containing information about a font
* @return a new font metrics object containing the specified <code>TEXTMETRIC</code>
*
* @noreference This method is not intended to be referenced by clients.
*/
public static FontMetrics win32_new(TEXTMETRIC handle) {
FontMetrics fontMetrics = new FontMetrics();
fontMetrics.handle = handle;
return fontMetrics;
}
}
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