86 lines
4.6 KiB
TeX
86 lines
4.6 KiB
TeX
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%% Name: tfontenc.tex
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%% Purpose: font encoding overview
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%% Author: Vadim Zeitlin
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%% Modified by:
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%% Created: 03.11.99
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%% RCS-ID: $Id$
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%% Copyright: (c) Vadim Zeitlin
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%% Licence: wxWindows licence
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\section{Font encoding overview}\label{wxfontencodingoverview}
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wxWindows has support for multiple font encodings starting from release 2.2.
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By encoding we mean here the mapping between the character codes and the
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letters. Probably the most well-known encoding is (7 bit) ASCII one which is
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used almost universally now to represent the letters of the English alphabet
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and some other common characters. However, it is not enough to represent the
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letters of foreign alphabetes and here other encodings come into play. Please
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note that we will only discuss 8-bit fonts here and not
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\helpref{Unicode}{unicode}.
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Font encoding support is assured by several classes:
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\helpref{wxFont}{wxfont} itself, but also
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\helpref{wxFontEnumerator}{wxfontenumerator} and
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\helpref{wxFontMapper}{wxfontmapper}. wxFont encoding support is reflected by
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a (new) constructor parameter {\it encoding} which takes one of the following
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values (elements of enumeration type {\tt wxFontEncoding}):
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\begin{twocollist}
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\twocolitem{wxFONTENCODING\_SYSTEM}{The default encoding of the underlying
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operating system (notice that this might be a "foreign" encoding for foreign
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versions of Windows 9x/NT).}
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\twocolitem{wxFONTENCODING\_DEFAULT}{The applications default encoding as
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returned by \helpref{wxFont::GetDefaultEncoding}{wxfontgetdefaultencoding}. On
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program startup, the applications default encoding is the same as
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wxFONTENCODING\_SYSTEM, but may be changed to make all the fonts created later
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to use it (by default).}
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\twocolitem{wxFONTENCODING\_ISO8859\_1..15}{ISO8859 family encodings which are
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usually used by all non-Microsoft operating systems}
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\twocolitem{wxFONTENCODING\_KOI8}{Standard cyrillic encoding for the Internet
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(but see also wxFONTENCODING\_ISO8859\_5 and wxFONTENCODING\_CP1251)}
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\twocolitem{wxFONTENCODING\_CP1250}{Microsoft analogue of ISO8859-2}
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\twocolitem{wxFONTENCODING\_CP1251}{Microsoft analogue of ISO8859-5}
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\twocolitem{wxFONTENCODING\_CP1252}{Microsoft analogue of ISO8859-1}
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\end{twocollist}
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As you may see, Microsofts encoding partly mirror the standard ISO8859 ones,
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but there are (minor) differences even between ISO8859-1 (Latin1, ISO encoding
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for Western Europe) and CP1251 (WinLatin1, standard code page for English
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versions of Windows) and there are more of them for other encodings.
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The situation is particularly complicated with cyrillic encodings for which
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(more than) three incompatible encodings exist: KOI8 (the old standard, widely
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used on the Internet), ISO8859-5 (ISO standard for cyrillic) and CP1251
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(WinCyrillic).
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This abundance of (incompatible) encodigns should make it clear that using
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encodings is less easy than it might seem. The problems arise both from the
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fact that the standard encodigns for the given language (say Russian, which is
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written in cyrillic) are different on different platforms and because the
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fonts in the given encoding might just not be installed (this is especially a
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problem with Unix, or, in general, not Win32, systems).
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To allow to see clearer in this, \helpref{wxFontEnumerator}{wxfontenumerator}
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class may be used to enumerate both all available encodings and to find the
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facename(s) in which the given encoding exists. If you can find the font in
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the correct encoding with wxFontEnumerator then your troubles are over, but,
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unfortunately, sometimes this is not enough. For example, there is no standard
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way (I know of, please tell me if you do!) to find a font on a Windows system
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for KOI8 encoding (only for WinCyrillic one which is quite different), so
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\helpref{wxFontEnumerator}{wxfontenumerator} will never return one, even if
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the user has installed a KOI8 font on his system.
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To solve this problem, \helpref{wxFontMapper}{wxfontmapper} class is provided.
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This class stores the mapping between the encodings and the font face
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names<EFBFBD>which support them in a \helpref{wxConfig}{wxconfigoverview} object. Of
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course, it would be fairly useless if it tried to determine these mappings by
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itself, so, instead, it may (optionally) ask the user and remember his answers
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so that the next time the program will automatically choose the correct font.
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All these topics are illustrated by the \helpref{font sample}{samplefont},
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please refer to it and the documentation of the classes mentioned here for
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further explanations.
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