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/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Free Documentation License Usage
** 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. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\page qt-embedded-fonts.html
\title Qt for Embedded Linux Fonts
\ingroup qt-embedded-linux
Qt normally uses \tt{fontconfig} to provide access to system fonts. If
\tt{fontconfig} is not available, e.g. in dedicated embedded systems where
space is at a premium, Qt will fall back to using \c QBasicFontDatabase. In
this case, Qt applications will look for fonts in Qt's \c lib/fonts/
directory. Qt will automatically detect prerendered fonts and TrueType fonts.
Qt 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. When using QBasicFontDatabase,
Qt also supports the Qt Prerendered Font format (\l QPF2),
a light-weight non-scalable font formats.
QPF2 is the native format of Qt for Embedded Linux 4.x.
\image qt-embedded-fontfeatures.png
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 can support the following font formats:
\list
\li TrueType (TTF)
\li PostScript Type1 (PFA/PFB)
\li Bitmap Distribution Format (BDF)
\li CID-keyed Type1
\li Compact Font Format (CFF)
\li OpenType fonts
\li SFNT-based bitmap fonts
\li Portable Compiled Format (PCF)
\li Microsoft Windows Font File Format (Windows FNT)
\li Portable Font Resource (PFR)
\li 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
Qt 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.
Qt comes with the cross-platform \l makeqpf tool, included in the
\c tools directory, 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)
Qt 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
*/
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