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Annex B. Localization – Technical Aspects ❘ 33Guidelines for determining default boundaries between certain significant text elements:grapheme clusters (“user characters”), words and sentences.The individual technical standards are:UTS 6: A Standard Compression Scheme for UnicodeSpecifications of a compression scheme for Unicode and sample implementation.UTS 10: Unicode Collation AlgorithmSpecifications for how to compare two Unicode strings while conforming to the requirements ofthe Unicode Standard. The UCA also supplies the Default Unicode Collation Element Table(DUCET) as the data specifying the default collation order for all Unicode characters.UTS 18: Unicode Regular Expression GuidelinesGuidelines on how to adapt regular expression engines to use Unicode.All Unicode Technical Reports are accessible from the Unicode.org web site. 12FontsFont Development ToolsSome FOSS tools for developing fonts are available. Although not as many as their proprietarycounterparts, they are adequate to get the job done, and are continuously being improved. Someinteresting examples are:1. XmBDFEd. 13 Developed by Mark Leisher, XmBDFEd is a Motif-based tool for developing BDF fonts. Itallows one to edit bit-map glyphs of a font, do some simple transformations on the glyphs, transferinformation between different fonts, and so on.2. FontForge 14 (formerly PfaEdit 15 ). Developed by George Williams, FontForge is a tool for developingoutline fonts, including Postscript Type1, TrueType, and OpenType. Scanned images of letters canbe imported and their outline vectors automatically traced. The splines can be edited, and transformationslike skewing, scaling, rotating, thickening may be applied and much more. It provides sufficientfunctionalities for editing Type1 and TrueType fonts properties. OpenType tables can also beedited in its recent versions. One weak point, however, is hinting. It guarantees Type1 hints quality,but not for TrueType.3. TTX/FontTools. 16 Just van Rossum’s TTX/FontTools is a tool to convert OpenType and TrueType fontsto and from XML. FontTools is a library for manipulating fonts, written in Python. It supports TrueType,OpenType, AFM and, to a certain extent, Type 1 and some Mac-specific formats. It allows one todump OpenType tables, examine and edit them with XML or plain text editor, and merge themback to the font.Font ConfigurationThere have been several font configuration systems available in GNU/Linux desktops. The mostfundamental one is the X Window font system itself. But, due to some recent developments, anotherfont configuration called fontconfig has been developed to serve some specific requirements of moderndesktops. These two font configurations will be discussed briefly.First, however, let us briefly discuss the X Window architecture, to understand font systems. X Window 17is a client-server system. X servers are the agents that provide service to control hardware devices, suchas video cards, monitors, keyboards, mice or tablets, as well as passes user input events from the devices12Unicode.org, ‘Unicode Technical Reports’; available from www.unicode.org/reports/index.html.13Leisher, M., ‘The XmBDFEd Font Editor‘; available from crl.nmsu.edu/~mleisher/xmbdfed.html.14Williams, G., ‘PfaEdit’; available from pfaedit.sourceforge.net.15van Rossum, J., S ‘TTX/FontTools’; available from fonttools.sourceforge.net/.16Note the difference with Microsoft’s “Windows” trademark. X Window is without ‘s’.17Taylor, O., ‘Pango’; available from www.pango.org.