forked from minhngoc25a/freetype2
115 lines
3.8 KiB
Plaintext
115 lines
3.8 KiB
Plaintext
FreeType font driver for PCF fonts
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Francesco Zappa Nardelli
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<francesco.zappa.nardelli@ens.fr>
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Introduction
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************
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PCF (Portable Compiled Format) is a binary bitmap font format, largely used
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in X world. This code implements a PCF driver for the FreeType library.
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Glyph images are loaded into memory only on demand, thus leading to a small
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memory footprint.
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Information on the PCF font format can only be worked out from
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`pcfread.c', and `pcfwrite.c', to be found, for instance, in the XFree86
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(www.xfree86.org) source tree (xc/lib/font/bitmap/).
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Many good bitmap fonts in bdf format come with XFree86: they can be
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compiled into the pcf format using the `bdftopcf' utility.
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Supported hardware
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******************
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The driver has been tested on linux/x86 and sunos5.5/sparc. In both
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cases the compiler was gcc. When back in Paris, I will test it also
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on linux/alpha.
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Encodings
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*********
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The variety of encodings that accompanies pcf fonts appears to encompass the
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small set defined in freetype.h. On the other hand, each pcf font defines
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two properties that specify encoding and registry.
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I decided to make these two properties directly accessible, leaving to the
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client application the work of interpreting them. For instance:
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#include "pcftypes.h" /* include/freetype/internal/pcftypes.h */
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FT_Face face;
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PCF_Public_Face pcfface;
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FT_New_Face( library,..., &face );
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pcfface = (PCF_Public_Face)face;
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if ((pcfface->charset_registry == "ISO10646") &&
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(pcfface->charset_encoding) == "1")) [..]
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Thus the driver always export `ft_encoding_none' as
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face->charmap.encoding. FT_Get_Char_Index() behavior is unmodified, that
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is, it converts the ULong value given as argument into the corresponding
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glyph number.
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Known problems
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**************
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- dealing explicitly with encodings breaks the uniformity of freetype2
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api.
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- except for encodings properties, client applications have no
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visibility of the PCF_Face object. This means that applications
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cannot directly access font tables and are obliged to trust
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FreeType.
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- currently, glyph names and ink_metrics are ignored.
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I plan to give full visibility of the PCF_Face object in the next
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release of the driver, thus implementing also glyph names and
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ink_metrics.
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- height is defined as (ascent - descent). Is this correct?
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- if unable to read size information from the font, PCF_Init_Face
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sets available_size->width and available_size->height to 12.
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- too many english grammar errors in the readme file :-(
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License
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*******
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Copyright (C) 2000 by Francesco Zappa Nardelli
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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"Software"), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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Credits
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*******
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Keith Packard wrote the pcf driver found in XFree86. His work is at
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the same time the specification and the sample implementation of the
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PCF format. Undoubtedly, this driver is inspired from his work.
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