| 1 | /****************************************************************************
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| 2 | **
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| 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation (qt-info@nokia.com)
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:FDL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| 15 | **
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| 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at qt-info@nokia.com.
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \page qt-embedded-fonts.html
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| 30 |
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| 31 | \title Qt for Embedded Linux Fonts
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| 32 | \ingroup qt-embedded-linux
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| 33 |
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| 34 | \l {Qt for Embedded Linux} uses the
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| 35 | \l{http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
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| 36 | font engine to produce font output. The formats supported depends on
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| 37 | the locally installed version of the FreeType library. In addition,
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| 38 | \l{Qt for Embedded Linux} supports the Qt Prerendered Font formats (\l QPF and \l QPF2):
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| 39 | light-weight non-scalable font formats specific to \l {Qt for Embedded Linux}.
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| 40 | QPF2 is the native format of \l{Qt for Embedded Linux}. QPF is the legacy
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| 41 | format used by Qt/Embedded 2.x and 3.x. Several of the formats may be rendered
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| 42 | using anti-aliasing for improved readability.
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| 43 |
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| 44 | When \l{Qt for Embedded Linux} applications run, they look for fonts in
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| 45 | Qt's \c lib/fonts/ directory. \l {Qt for Embedded Linux} will automatically detect
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| 46 | prerendered fonts and TrueType fonts. For compatibility, it will also read the
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| 47 | legacy \c lib/fonts/fontdir file.
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| 48 |
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| 49 | Support for other font formats can be added. To make a suggestion,
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| 50 | please create a task in our bug tracker at \l
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| 51 | {http://bugreports.qt.nokia.com}{http://bugreports.qt.nokia.com}.
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| 52 |
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| 53 | \tableofcontents
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| 54 |
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| 55 | \table 100%
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| 56 | \row
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| 57 | \o
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| 58 | \bold {Optimization}
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| 59 |
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| 60 | The \l FreeType, \l QPF2 and \l QPF formats are features that can be
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| 61 | disabled using the
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| 62 | \l{Fine-Tuning Features in Qt}{feature definition system},
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| 63 | reducing the size of Qt and saving resources.
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| 64 |
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| 65 | Note that at least one font format must be defined.
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| 66 |
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| 67 | See the \l {Fine-Tuning Features in Qt} documentation for
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| 68 | details.
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| 69 |
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| 70 | \o
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| 71 | \inlineimage qt-embedded-fontfeatures.png
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| 72 | \endtable
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| 73 |
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| 74 | All supported fonts use the Unicode character encoding. Most fonts
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| 75 | available today do, but they usually don't contain \e all the
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| 76 | Unicode characters. A complete 16-point Unicode font uses over 1
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| 77 | MB of memory.
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| 78 |
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| 79 | \target FreeType
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| 80 | \section1 FreeType Formats
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| 81 |
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| 82 | The \l {http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
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| 83 | library (and therefore \l{Qt for Embedded Linux}) can support the following font formats:
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| 84 |
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| 85 | \list
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| 86 | \o TrueType (TTF)
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| 87 | \o PostScript Type1 (PFA/PFB)
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| 88 | \o Bitmap Distribution Format (BDF)
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| 89 | \o CID-keyed Type1
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| 90 | \o Compact Font Format (CFF)
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| 91 | \o OpenType fonts
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| 92 | \o SFNT-based bitmap fonts
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| 93 | \o Portable Compiled Format (PCF)
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| 94 | \o Microsoft Windows Font File Format (Windows FNT)
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| 95 | \o Portable Font Resource (PFR)
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| 96 | \o Type 42 (limited support)
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| 97 | \endlist
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| 98 |
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| 99 | It is possible to add modules to the \l
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| 100 | {http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
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| 101 | font engine to support other types of font files. For more
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| 102 | information, see the font engine's own website: \l
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| 103 | http://freetype.sourceforge.net/freetype2/index.html.
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| 104 |
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| 105 | Glyphs rendered using FreeType are shared efficiently between applications,
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| 106 | reducing memory requirements and speeding up text rendering.
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| 107 |
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| 108 | \omit
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| 109 | \l {Qt for Embedded Linux} will by default use the system FreeType library if it exists.
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| 110 | Otherwise it will use a copy of the FreeType library in Qt, which by default only
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| 111 | supports TrueType fonts to reduce footprint.
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| 112 | \endomit
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| 113 |
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| 114 | \target QPF2
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| 115 | \section1 Qt Prerendered Font (QPF2)
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| 116 |
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| 117 | The Qt Prerendered Font (QPF2) is an architecture-independent,
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| 118 | light-weight and non-scalable font format specific to \l{Qt for Embedded Linux}.
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| 119 |
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| 120 | Nokia provides the cross-platform \l makeqpf tool, included in the
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| 121 | \c tools directory of both \l {Qt} and \l{Qt for Embedded Linux}, which allows
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| 122 | generation of QPF2 files from system fonts.
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| 123 |
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| 124 | QPF2 supports anti-aliasing and complex writing systems, using information
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| 125 | from the corresponding TrueType font, if present on the system. The format
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| 126 | is designed to be mapped directly to memory. The same format is used to
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| 127 | share glyphs from non-prerendered fonts between applications.
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| 128 |
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| 129 | \target QPF
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| 130 | \section1 Legacy Qt Prerendered Font (QPF)
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| 131 |
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| 132 | Nokia provides support for the legacy QPF format for compatibility
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| 133 | reasons. QPF is based on the internal font engine data structure of Qt/Embedded
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| 134 | versions 2 and 3.
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| 135 |
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| 136 | Note that the file name describes the font, for example \c helvetica_120_50.qpf
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| 137 | is 12 point Helvetica while \c helvetica_120_50i.qpf is 12 point Helvetica \e italic.
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| 138 |
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| 139 | \omit
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| 140 | \section1 Memory Requirements
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| 141 |
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| 142 | Taking advantage of the way the QPF format is structured, Qt for
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| 143 | Embedded Linux memory-maps the data rather than reading and parsing it.
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| 144 | This reduces RAM consumption even further.
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| 145 |
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| 146 | Scalable fonts use a larger amount of memory per font, but
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| 147 | these fonts provide a memory saving if many different sizes of each
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| 148 | font are needed.
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| 149 | \endomit
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| 150 |
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| 151 | \section1 The Legacy \c fontdir File
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| 152 |
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| 153 | For compatibility reasons \l{Qt for Embedded Linux} supports the \c fontdir
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| 154 | file, if present. The file defines additional fonts available to the
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| 155 | application, and has the following format:
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| 156 |
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| 157 | \snippet doc/src/snippets/code/doc_src_emb-fonts.qdoc 0
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| 158 |
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| 159 | \table 100%
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| 160 | \header \o Field \o Description
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| 161 | \row \o \bold name
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| 162 | \o The name of the font format, e.g.,\c Helvetica, \c Times, etc.
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| 163 | \row \o \bold file
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| 164 | \o The name of the file containing the font, e.g., \c
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| 165 | helvR0810.bdf, \c verdana.ttf, etc.
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| 166 | \row \o \bold renderer
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| 167 | \o Specifies the font engine that should be used to render the
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| 168 | font, currently only the FreeType font engine (\c FT) is
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| 169 | supported.
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| 170 | \row \o \bold italic
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| 171 | \o Specifies whether the font is italic or not; the accepted
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| 172 | values are \c y or \c n.
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| 173 | \row \o \bold weight
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| 174 | \o Specifies the font's weight: \c 50 is normal, \c 75 is bold,
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| 175 | etc.
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| 176 | \row \o \bold size
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| 177 | \o Specifies the font size, i.e., point size * 10. For example, a
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| 178 | value of 120 means 12pt. A value of 0 means that the font is
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| 179 | scalable.
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| 180 | \row \o \bold flags
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| 181 | \o The following flag is supported:
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| 182 | \list
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| 183 | \o \c s: smooth (anti-aliased)
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| 184 | \endlist
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| 185 | All other flags are ignored.
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| 186 | \endtable
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| 187 | */
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