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Font metrics returns both internal and external leading to layout. Layout now is responsible for calculating the normalLineHeight. It take consideration of external leading, and compensate if it does not exist. All these are controled by a preference switch. r=rbs, sr=attinasi,
251 lines
8.0 KiB
C++
251 lines
8.0 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: NPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Netscape Public License
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* Version 1.1 (the "License"); you may not use this file except in
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* compliance with the License. You may obtain a copy of the License at
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* http://www.mozilla.org/NPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is mozilla.org code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 1998
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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*
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the NPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the NPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef nsIFontMetrics_h___
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#define nsIFontMetrics_h___
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#include "nsISupports.h"
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#include "nsCoord.h"
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struct nsFont;
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class nsString;
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class nsIDeviceContext;
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class nsIAtom;
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// IID for the nsIFontMetrics interface
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#define NS_IFONT_METRICS_IID \
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{ 0xc74cb770, 0xa33e, 0x11d1, \
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{ 0xa8, 0x24, 0x00, 0x40, 0x95, 0x9a, 0x28, 0xc9 } }
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//----------------------------------------------------------------------
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/**
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* A native font handle
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*/
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typedef void* nsFontHandle;
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/**
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* Font metrics interface
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*
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* This interface may be somewhat misnamed. A better name might be
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* nsIFontList. The style system uses the nsFont struct for various font
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* properties, one of which is font-family, which can contain a *list* of
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* font names. The nsFont struct is "realized" by asking the device context
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* to cough up an nsIFontMetrics object, which contains a list of real font
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* handles, one for each font mentioned in font-family (and for each fallback
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* when we fall off the end of that list).
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*
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* The style system needs to have access to certain metrics, such as the
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* em height (for the CSS "em" unit), and we use the first Western font's
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* metrics for that purpose. The platform-specific implementations are
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* expected to select non-Western fonts that "fit" reasonably well with the
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* Western font that is loaded at Init time.
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*/
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class nsIFontMetrics : public nsISupports
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{
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public:
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NS_DEFINE_STATIC_IID_ACCESSOR(NS_IFONT_METRICS_IID)
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/**
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* Initialize the font metrics. Call this after creating the font metrics.
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* Font metrics you get from the font cache do NOT need to be initialized
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*
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* @see nsIDeviceContext#GetMetricsFor()
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*/
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NS_IMETHOD Init(const nsFont& aFont, nsIAtom* aLangGroup,
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nsIDeviceContext *aContext) = 0;
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/**
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* Destroy this font metrics. This breaks the association between
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* the font metrics and the device context.
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*/
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NS_IMETHOD Destroy() = 0;
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/**
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* Return the font's xheight property, scaled into app-units.
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*/
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NS_IMETHOD GetXHeight(nscoord& aResult) = 0;
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/**
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* Return the font's superscript offset (the distance from the
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* baseline to where a superscript's baseline should be placed). The
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* value returned will be a positive value.
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*/
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NS_IMETHOD GetSuperscriptOffset(nscoord& aResult) = 0;
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/**
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* Return the font's subscript offset (the distance from the
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* baseline to where a subscript's baseline should be placed). The
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* value returned will be a positive value.
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*/
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NS_IMETHOD GetSubscriptOffset(nscoord& aResult) = 0;
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/**
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* Return the font's strikeout offset (the distance from the
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* baseline to where a strikeout should be placed) and size
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* Positive values are above the baseline, negative below.
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*/
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NS_IMETHOD GetStrikeout(nscoord& aOffset, nscoord& aSize) = 0;
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/**
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* Return the font's underline offset (the distance from the
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* baseline to where a underline should be placed) and size.
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* Positive values are above the baseline, negative below.
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*/
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NS_IMETHOD GetUnderline(nscoord& aOffset, nscoord& aSize) = 0;
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/**
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* Returns the height (in app units) of the font. This is ascent plus descent
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* plus any internal leading
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*
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* This method will be removed once the callers have been moved over to the
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* new GetEmHeight (and possibly GetMaxHeight).
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*/
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NS_IMETHOD GetHeight(nscoord &aHeight) = 0;
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#if defined(XP_WIN)
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#define FONT_LEADING_APIS_V2 1
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#endif
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#if defined(XP_UNIX) || defined(XP_PC) || defined(XP_MAC) || defined(XP_BEOS)
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#define NEW_FONT_HEIGHT_APIS 1
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#endif
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#ifdef NEW_FONT_HEIGHT_APIS
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#ifndef FONT_LEADING_APIS_V2
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/**
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* Returns the normal line height (em height + leading).
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*/
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NS_IMETHOD GetNormalLineHeight(nscoord &aHeight) = 0;
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#endif /* not FONT_LEADING_APIS_V2 */
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#endif /* NEW_FONT_HEIGHT_APIS */
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#ifdef FONT_LEADING_APIS_V2
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/**
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* Returns the amount of internal leading (in app units) for the font. This
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* is computed as the "height - (ascent + descent)"
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*/
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NS_IMETHOD GetInternalLeading(nscoord &aLeading) = 0;
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/**
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* Returns the amount of external leading (in app units) as suggested by font
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* vendor. This value is suggested by font vendor to add to normal line-height
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* beside font height.
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*/
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NS_IMETHOD GetExternalLeading(nscoord &aLeading) = 0;
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#else
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/**
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* Returns the amount of internal leading (in app units) for the font. This
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* is computed as the "height - (ascent + descent)"
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*/
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NS_IMETHOD GetLeading(nscoord &aLeading) = 0;
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#endif /* FONT_LEADING_APIS_V2 */
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#ifdef NEW_FONT_HEIGHT_APIS
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/**
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* Returns the height (in app units) of the Western font's em square. This is
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* em ascent plus em descent.
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*/
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NS_IMETHOD GetEmHeight(nscoord &aHeight) = 0;
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/**
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* Returns, in app units, the ascent part of the Western font's em square.
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*/
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NS_IMETHOD GetEmAscent(nscoord &aAscent) = 0;
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/**
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* Returns, in app units, the descent part of the Western font's em square.
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*/
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NS_IMETHOD GetEmDescent(nscoord &aDescent) = 0;
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/**
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* Returns the height (in app units) of the Western font's bounding box.
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* This is max ascent plus max descent.
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*/
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NS_IMETHOD GetMaxHeight(nscoord &aHeight) = 0;
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#endif /* NEW_FONT_HEIGHT_APIS */
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/**
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* Returns, in app units, the maximum distance characters in this font extend
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* above the base line.
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*/
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NS_IMETHOD GetMaxAscent(nscoord &aAscent) = 0;
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/**
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* Returns, in app units, the maximum distance characters in this font extend
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* below the base line.
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*/
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NS_IMETHOD GetMaxDescent(nscoord &aDescent) = 0;
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/**
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* Returns, in app units, the maximum character advance for the font
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*/
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NS_IMETHOD GetMaxAdvance(nscoord &aAdvance) = 0;
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/**
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* Returns the font associated with these metrics
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*/
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NS_IMETHOD GetFont(const nsFont *&aFont) = 0;
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/**
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* Returns the language group associated with these metrics
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*/
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NS_IMETHOD GetLangGroup(nsIAtom** aLangGroup) = 0;
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/**
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* Returns the font handle associated with these metrics
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*/
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NS_IMETHOD GetFontHandle(nsFontHandle &aHandle) = 0;
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#if defined(_WIN32) || defined(XP_OS2)
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/**
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* Returns the average character width
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*/
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NS_IMETHOD GetAveCharWidth(nscoord& aAveCharWidth) = 0;
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#endif
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/**
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* Returns the often needed width of the space character
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*/
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NS_IMETHOD GetSpaceWidth(nscoord& aSpaceCharWidth) = 0;
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};
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#endif /* nsIFontMetrics_h___ */
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