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/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** GNU Free Documentation License
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file.
**
** Other Usage
** Alternatively, this file may be used in accordance with the terms
** and conditions contained in a signed written agreement between you
** and Nokia.
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qt-embedded-fonts.html
\title Qt for Embedded Linux Fonts
\ingroup qt-embedded-linux
\l {Qt for Embedded Linux} uses the
\l{http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
font engine to produce font output. The formats supported depends on
the locally installed version of the FreeType library. In addition,
\l{Qt for Embedded Linux} supports the Qt Prerendered Font formats (\l QPF and \l QPF2):
light-weight non-scalable font formats specific to \l {Qt for Embedded Linux}.
QPF2 is the native format of \l{Qt for Embedded Linux}. QPF is the legacy
format used by Qt/Embedded 2.x and 3.x. Several of the formats may be rendered
using anti-aliasing for improved readability.
When \l{Qt for Embedded Linux} applications run, they look for fonts in
Qt's \c lib/fonts/ directory. \l {Qt for Embedded Linux} will automatically detect
prerendered fonts and TrueType fonts. For compatibility, it will also read the
legacy \c lib/fonts/fontdir file.
Support for other font formats can be added. To make a suggestion,
please create a task in our bug tracker at \l
{http://bugreports.qt-project.org}{http://bugreports.qt-project.org}.
\tableofcontents
\table 100%
\row
\o
\bold {Optimization}
The \l FreeType, \l QPF2 and \l QPF formats are features that can be
disabled using the
\l{Fine-Tuning Features in Qt}{feature definition system},
reducing the size of Qt and saving resources.
Note that at least one font format must be defined.
See the \l {Fine-Tuning Features in Qt} documentation for
details.
\o
\inlineimage qt-embedded-fontfeatures.png
\endtable
All supported fonts use the Unicode character encoding. Most fonts
available today do, but they usually don't contain \e all the
Unicode characters. A complete 16-point Unicode font uses over 1
MB of memory.
\target FreeType
\section1 FreeType Formats
The \l {http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
library (and therefore \l{Qt for Embedded Linux}) can support the following font formats:
\list
\o TrueType (TTF)
\o PostScript Type1 (PFA/PFB)
\o Bitmap Distribution Format (BDF)
\o CID-keyed Type1
\o Compact Font Format (CFF)
\o OpenType fonts
\o SFNT-based bitmap fonts
\o Portable Compiled Format (PCF)
\o Microsoft Windows Font File Format (Windows FNT)
\o Portable Font Resource (PFR)
\o Type 42 (limited support)
\endlist
It is possible to add modules to the \l
{http://freetype.sourceforge.net/freetype2/index.html}{FreeType 2}
font engine to support other types of font files. For more
information, see the font engine's own website: \l
http://freetype.sourceforge.net/freetype2/index.html.
Glyphs rendered using FreeType are shared efficiently between applications,
reducing memory requirements and speeding up text rendering.
\omit
\l {Qt for Embedded Linux} will by default use the system FreeType library if it exists.
Otherwise it will use a copy of the FreeType library in Qt, which by default only
supports TrueType fonts to reduce footprint.
\endomit
\target QPF2
\section1 Qt Prerendered Font (QPF2)
The Qt Prerendered Font (QPF2) is an architecture-independent,
light-weight and non-scalable font format specific to \l{Qt for Embedded Linux}.
Nokia provides the cross-platform \l makeqpf tool, included in the
\c tools directory of both \l {Qt} and \l{Qt for Embedded Linux}, which allows
generation of QPF2 files from system fonts.
QPF2 supports anti-aliasing and complex writing systems, using information
from the corresponding TrueType font, if present on the system. The format
is designed to be mapped directly to memory. The same format is used to
share glyphs from non-prerendered fonts between applications.
\target QPF
\section1 Legacy Qt Prerendered Font (QPF)
Nokia provides support for the legacy QPF format for compatibility
reasons. QPF is based on the internal font engine data structure of Qt/Embedded
versions 2 and 3.
Note that the file name describes the font, for example \c helvetica_120_50.qpf
is 12 point Helvetica while \c helvetica_120_50i.qpf is 12 point Helvetica \e italic.
\omit
\section1 Memory Requirements
Taking advantage of the way the QPF format is structured, Qt for
Embedded Linux memory-maps the data rather than reading and parsing it.
This reduces RAM consumption even further.
Scalable fonts use a larger amount of memory per font, but
these fonts provide a memory saving if many different sizes of each
font are needed.
\endomit
\section1 The Legacy \c fontdir File
For compatibility reasons \l{Qt for Embedded Linux} supports the \c fontdir
file, if present. The file defines additional fonts available to the
application, and has the following format:
\snippet doc/src/snippets/code/doc_src_emb-fonts.qdoc 0
\table 100%
\header \o Field \o Description
\row \o \bold name
\o The name of the font format, e.g.,\c Helvetica, \c Times, etc.
\row \o \bold file
\o The name of the file containing the font, e.g., \c
helvR0810.bdf, \c verdana.ttf, etc.
\row \o \bold renderer
\o Specifies the font engine that should be used to render the
font, currently only the FreeType font engine (\c FT) is
supported.
\row \o \bold italic
\o Specifies whether the font is italic or not; the accepted
values are \c y or \c n.
\row \o \bold weight
\o Specifies the font's weight: \c 50 is normal, \c 75 is bold,
etc.
\row \o \bold size
\o Specifies the font size, i.e., point size * 10. For example, a
value of 120 means 12pt. A value of 0 means that the font is
scalable.
\row \o \bold flags
\o The following flag is supported:
\list
\o \c s: smooth (anti-aliased)
\endlist
All other flags are ignored.
\endtable
*/
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