source: trunk/doc/src/platforms/emb-fonts.qdoc@ 569

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/*!
    \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.nokia.com}{http://bugreports.qt.nokia.com}.

    \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
*/