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| 32 | <td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Fonts in Qt/Embedded</h1>
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| 33 |
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| 34 |
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| 35 | <p> <h2> Supported Formats
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| 36 | </h2>
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| 37 | <a name="1"></a><p> Qt/Embedded supports four font formats:
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| 38 | <p> <center><table cellpadding="4" cellspacing="2" border="0">
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| 39 | <tr bgcolor="#f0f0f0">
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| 40 | <td valign="top"><b>TrueType (TTF)</b>
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| 41 | <td valign="top">The scalable font technology now standard on MS-Windows and Apple
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| 42 | Macintosh, and becoming popular on X11.
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| 43 | <tr bgcolor="#d0d0d0">
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| 44 | <td valign="top"><b>Postscript Type1 (PFA/PFB)</b>
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| 45 | <td valign="top">Scalable fonts often used by printers, also popular on X11. These
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| 46 | are similar in functionality to TTF fonts and are not discussed
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| 47 | further in this document.
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| 48 | <tr bgcolor="#f0f0f0">
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| 49 | <td valign="top"><b>Bitmap Distribution Format<br>fonts (BDF)</b>
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| 50 | <td valign="top">A standard format for non-scalable fonts. A large number of BDF
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| 51 | fonts are supplied as part of standard X11 distributions - most of
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| 52 | these can be used with Qt/Embedded. You should <em>not</em> use these in a
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| 53 | production system: they are very slow to load and take up a <em>lot</em> of
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| 54 | storage space. Instead, render the BDF to a QPF.
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| 55 | <tr bgcolor="#d0d0d0">
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| 56 | <td valign="top"><b>Qt Prerendered Font (QPF)</b>
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| 57 | <td valign="top">A light-weight non-scalable font format specific to Qt/Embedded.
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| 58 | </table></center>
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| 59 | <p> Support for each of these font formats (except QPF which is always
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| 60 | enabled) can be enabled or disabled independently by using the <a href="emb-features.html">Qt/Embedded Features Definition</a>. There is
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| 61 | support in Qt/Embedded for writing a QPF font file from any font, so
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| 62 | you can initially enable TTF and BDF formats, save QPF files for the
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| 63 | fonts and sizes you need, then remove TTF and BDF support.
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| 64 | <p> See <a href="makeqpf.html">tools/makeqpf</a> for a tool that helps
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| 65 | produce QPF files from the TTF and BDF, or just run your application
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| 66 | with the <tt>-savefonts</tt> option.
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| 67 | <p> <h2> Memory Requirements
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| 68 | </h2>
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| 69 | <a name="2"></a><p> With TTF fonts, each character in the font at a given point size is
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| 70 | only rendered when first used in a drawing or metrics operation. With
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| 71 | BDF fonts all characters are rendered when the font is used.
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| 72 | With QPF fonts, the characters are stored in the same format that Qt
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| 73 | uses for drawing.
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| 74 | <p> For example, a 10-point Times font containing the ASCII characters uses
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| 75 | around 1300 bytes when stored in QPF format.
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| 76 | <p> Taking advantage of the way the QPF format is structured, Qt/Embedded
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| 77 | memory-maps the data rather than reading and parsing it.
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| 78 | This reduces RAM consumption even further.
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| 79 | <p> Scalable fonts use a larger amount of memory per font, but
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| 80 | these fonts provide a memory saving if many different sizes of each
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| 81 | font are needed.
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| 82 | <p> <h2> Smooth Fonts
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| 83 | </h2>
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| 84 | <a name="3"></a><p> TTF, PFA, and QPF fonts can be rendered as <em>smooth</em> anti-aliased
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| 85 | fonts to give superior readability, especially on low-resolution
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| 86 | devices. The difference between smooth and non-smooth fonts is
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| 87 | illustrated below (you may need to change your display to low
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| 88 | resolution to see the difference):
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| 89 | <p> <center><img src="unsmooth.png" alt="unsmooth"></center>
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| 90 | <p> <center><img src="smooth.png" alt="smooth"></center>
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| 91 | <p> <h2> Unicode
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| 92 | </h2>
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| 93 | <a name="4"></a><p> All fonts used by Qt/Embedded use the Unicode character encoding.
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| 94 | Most fonts available today use this encoding, but they usually don't
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| 95 | contain all the Unicode characters. A <em>complete</em> 16-point Unicode
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| 96 | font uses over 1 MB of memory.
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| 97 | <p> <h2> The font definition file
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| 98 | </h2>
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| 99 | <a name="5"></a><p> When Qt/Embedded applications run, they look for a file called
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| 100 | <tt>$QTDIR/lib/fonts/fontdir</tt> or
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| 101 | <tt>/usr/local/qt-embedded/lib/fonts/fontdir</tt>. This file defines the
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| 102 | fonts available to the application. It has the following format:
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| 103 | <blockquote>
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| 104 | <em>name</em> <em>file</em> <em>renderer</em> <em>italic</em> <em>weight</em> <em>size</em> <em>flags</em>
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| 105 | </blockquote>
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| 106 | where
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| 107 | <p> <center><table cellpadding="4" cellspacing="2" border="0">
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| 108 | <tr bgcolor="#a2c511"> <th valign="top">Field <th valign="top">Value
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| 109 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>name</em> <td valign="top"><tt>Helvetica</tt>, <tt>Times</tt>, etc.
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| 110 | <tr bgcolor="#d0d0d0"> <td valign="top"><em>file</em> <td valign="top"><tt>helvR0810.bdf</tt>, <tt>verdana.ttf</tt>, etc.
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| 111 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>renderer</em> <td valign="top"><tt>BDF</tt> or <tt>FT</tt>
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| 112 | <tr bgcolor="#d0d0d0"> <td valign="top"><em>italic</em> <td valign="top"><tt>y</tt> or <tt>n</tt>
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| 113 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>weight</em> <td valign="top"><tt>50</tt> is normal, <tt>75</tt> is bold, etc.
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| 114 | <tr bgcolor="#d0d0d0"> <td valign="top"><em>size</em> <td valign="top"><tt>0</tt> for scalable or point size * 10 (i.e. <tt>120</tt>
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| 115 | for 12pt)
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| 116 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>flags</em> <td valign="top"><ul>
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| 117 | <li> <tt>s</tt>: smooth (anti-aliased)
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| 118 | <li> <tt>u</tt>: Unicode range when saving (default is Latin-1)
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| 119 | <li> <tt>a</tt>: ASCII range when saving (default is Latin-1)
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| 120 | </ul>
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| 121 | </table></center>
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| 122 | <p> The font definition file does not specify QPF fonts; these are loaded
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| 123 | directly from the directory containing the <tt>fontdir</tt> file, and must
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| 124 | be named <em>name</em>_<em>size</em>_<em>weight</em><em>italicflag</em>.qpf, where
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| 125 | <p> <center><table cellpadding="4" cellspacing="2" border="0">
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| 126 | <tr bgcolor="#a2c511"> <th valign="top">Field <th valign="top">Value
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| 127 | <tr bgcolor="#d0d0d0"> <td valign="top"><em>name</em> <td valign="top"><tt>helvetica</tt>, <tt>times</tt>, etc. (in lowercase)
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| 128 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>size</em> <td valign="top">point size * 10 (i.e. <tt>120</tt> for 12pt)
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| 129 | <tr bgcolor="#d0d0d0"> <td valign="top"><em>italicflag</em> <td valign="top"><tt>i</tt> for italic, otherwise nothing.
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| 130 | <tr bgcolor="#f0f0f0"> <td valign="top"><em>weight</em> <td valign="top"><tt>50</tt> is normal, <tt>75</tt> is bold, etc.
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| 131 | </table></center>
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| 132 | <p> If an application is run with the <tt>-savefonts</tt> command-line option,
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| 133 | then whenever a font other than a QPF font is used, a corresponding QPF file
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| 134 | is saved. This allows you to easily find the font usage of your applications
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| 135 | and to generate QPF files so that you can eventually reduce the memory
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| 136 | usage of your applications by disabling TTF and BDF support from Qt/Embedded,
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| 137 | or by modifying the initialization of <tt>qws_savefonts</tt> in
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| 138 | <tt>kernel/qapplication_qws.cpp</tt> of the Qt/Embedded library source code.
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| 139 | In extreme cases of memory-saving, it is possible to save partially-rendered
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| 140 | fonts (i.e. only the characters in "Product Name<sup>TM</sup>") if you are
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| 141 | certain that these are the only characters you will need from the font.
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| 142 | See QMemoryManager::savePrerenderedFont() for this functionality.
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| 143 | <p> <h2> Notes
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| 144 | </h2>
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| 145 | <a name="6"></a><p> The font definition file, naming conventions for font files, and the format
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| 146 | of QPF files may change in versions of Qt/Embedded after 3.
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| 147 | <p>
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| 148 | To generate QPF files of different rotations, the program must be re-run with
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| 149 | an orientation that matches the desired rotation of the QPF output. An example to
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| 150 | generate all 4 rotations of fonts would be to run the following at a real framebuffer:
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| 151 | <pre>
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| 152 | for dpy in LinuxFb Transformed:Rot90 Transformed:Rot180 Transformed:Rot270
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| 153 | do
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| 154 | QWS_DISPLAY=$dpy ./makeqpf "$@"
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| 155 | done
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| 156 | </pre><p> If programs are only ever run in one orientation on a device, only the one
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| 157 | appropriate set of fonts is needed.
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| 158 | <p>
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| 159 | When enabled, Qt/Embedded uses the powerful FreeType2 library to implement
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| 160 | TrueType and Type1 support.
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| 161 | <p>
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| 162 | <!-- eof -->
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| 163 | <p><address><hr><div align=center>
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| 164 | <table width=100% cellspacing=0 border=0><tr>
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| 165 | <td>Copyright © 2007
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| 166 | <a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a>
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| 167 | <td align=right><div align=right>Qt 3.3.8</div>
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| 168 | </table></div></address></body>
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| 169 | </html>
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