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$Integrating TEX, MetaPost, JavaScript and PDF - Pragma ADE$

8 Font formats a b g l q . ; ? ffi Figure 1.3 The boundingbox of some italic glyphs. The rectangles around the shapes figure 1.2 and figure 1.3 are called boundingbox. The dashed line reflects the baseline where they eventually are aligned onto next to each other. The amount above the baseline is called height, and below is called depth. The piece of the shape above the baseline is the ascender and the bit below the descender. The width of the bounding box is not by definition the width of the glyph. In Type1 and OpenType fonts each shape has a so called advance width and that is the one that will be used. -0.747 -0.252 Very often glyphs get very small spaces inserted horizontally. -0.61523 V -0.06152 -0.0791-0.18018 -0.17578 -0.0791 ery often glyphs get very small spaces inserted horizontally. V -0.81 er 0.135 -0.747 -0.18018 -0.74707 -0.225 y often glyphs g -0.18 et v -0.36 er 0.135 y small spaces inserted horizontally. -0.225 -0.81 -0.74355 Very often glyphs get very small spaces inserted horizontally. Figure 1.4 Kerning in Latin Roman, Cambria, Pagella and Dejavu. Another traditional property of a font is kerning. In figure 1.4 you see this in action. These examples demonstrate that not all fonts need (or provide) the same kerns (in points). So, as a start, we have now met a couple of properties of a font. They can be summarized as follows: mapping to glyphs : characters are represented by a shapes that have recognizable properties so that readers know what they mean ligature building : a sequence of characters gets mapped onto one glyph dimensions : each glyph has a width, height and depth inter-glyph kerning : optionally a bit of positive or negative space has to be inserted between glyphs Regular font kerning is hardly noticeable and improves the overall look of the page. Typesetting applications sometimes are capable of inserting additional spaces between shapes. This more excessive kerning is not that much related to the font and is used for special purposes, like making a snippet of text stand out. In ConT E Xt this kind of kerning is available but it is a font independent feature. Keep in mind that when applying that kind of rather visible kerning you’d better not have ligatures and fancy replacements enabled as ConT E Xt already tries to deal with that as good as possible. -1.07578
1.3 The basic process In T E X a font is an abstraction: the engine only needs to know about the mapping from characters to glyphs, what the width, height and depth is, what sequences need to be translated into ligatures and when kerning has to be applied. If for the moment we forget about math, these are all the properties that matter and this is what the T E X font metric files that we see in the next section provide. Because one of the principles behind LuaT E X is that the core engine (the binary) stays small and that new functionality is provided in Lua code, the font subsystem largely looks like it always has been. As users will normally use a macro package most of the loading will be hidden from the user. It is however good to give a quick overview of how for instance pdfT E X deals with fonts using traditional metric files. input characters glyphs subset Figure 1.5 Several translation steps in a traditonal T E X flow. The input (bytes) gets translated into characters by the input parser. Normally this is a one-to-one translation but there are examples of some translation taking place. You can for instance make characters active and give them a meaning. So, the eight bit represention of an editors code page ë can become something else internally, for instance a regular e with an ¨ overlayed. It can also become another character, which in the code page would be shown as á but the user will not know this as by then this byte is already tokenized. Another example is multibyte translation, for instance utf sequences can get remapped to something that is known internally as being a character of some kind. The LuaTEX engine expects utf so a macro package has to make sure that translation to this encoding happens beforehand, for instance using a callback that intercepts the input from file. 1 So, the input character (sequence) becomes tokens representing a character. From these tokens TEX will start building a (linked) node list where each character becomes a node. In this node there is a reference to the current font. If you know TEX you will understand that a list can have more than characters: there can be skips, kerns, rules, references to images, boxes, etc. At some point TEX will handle this list over to a routine that will turn them into something that resembles a paragraph or otherwise snippet of text. In that stage hyphenation kicks in, ligatures get built and kerning is added. Character references become glyph indices. This list can finally be broken into lines. It is no secret that TEX can box and unbox material and that after unboxing some new formatting has to happen. The traditional engine has some optimizations that demand a partial reconstruction of the original list but in LuaTEX we removed this kind of optimization so there the process is somewhat simpler. We will see more of that later. 1 In ConTE Xt we talk of input regimes and these can be mixed, although in practice most users will stick to utf and never use regimes. 9 Font formats
Page 1: explaining luatex and mkiv Fonts ou
Page 4 and 5: 2 Contents 5.4 Goodies 73 5.5 Analy
Page 6 and 7: 4 Contents
Page 8 and 9: 6 Introduction In this manual we wi
Page 12 and 13: 10 Font formats When T E X ships ou
Page 14 and 15: 12 A.4 A.3 Font formats multiple ac
Page 16 and 17: 14 Font formats can be rules that t
Page 18 and 19: 16 Font formats /fonts/tfm/vendor/t
Page 20 and 21: 18 Modes raw tfm normalized tfm raw
Page 22 and 23: 20 Modes shown next: kern cyrl dflt
Page 24 and 25: 22 Modes ccmp cyrl mkd абвгде
Page 26 and 27: 24 Modes dlig latn gag abcdefghijkl
Page 28 and 29: 26 Modes liga latn nsm abcdefghijkl
Page 30 and 31: 28 Modes salt latn mol abcdefghijkl
Page 32 and 33: 30 Modes glyph 256 font 42: U+00074
Page 38 and 39: 36 Modes optimizer that can apply a
Page 40 and 41: 38 Modes ا خǇَ﮲ ف﮲َ step
Page 42 and 43: 40 Modes dir +TRT glyph 256 font 49
Page 44 and 45: 42 Modes and now we get: 123 normal
Page 46 and 47: 44 Modes MkIV run can be faster tha
Page 48 and 49: 46 Lookups \font \MyFontG = lmr12 s
Page 50 and 51: 48 Lookups 3.4 Name Say that we wan
Page 52 and 53: 50 Lookups We add another specifier
Page 54 and 55: 52 Methods \definefont [MyFont] [Bo
Page 56 and 57: 54 Methods } copyright = "ConTeXt d
Page 58 and 59: 56 Features of all, all we get to s
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58 Features in base mode. A single
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60 Features accumulate within a wor
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62 Features features analyze=yes, c
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64 Features \definedfont[lmroman10-
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66 Features single substitutions or
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68 F -0.492 eatures result ffi feat
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70 Features font 80: lmroman10-regu
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72 Features font 46: cambria.ttf @
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74 Features } } This goodie file is
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76 Features { name = "msbm10.tfm",
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78 Features \starttypescript[somefo
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80 Features \setupbodyfont [mojcasf
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82 Features } normalweight = "extra
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84 Features "QF.waqf", "SKTH.waqf",
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86 Features featureset=smallcaps] O
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88 Features } }, When defining the
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90 Features local defaultfraction =
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92 Features } } ["LMRoman-Bold"] =
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94 Features In fact, in addition to
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96 Features } This time the applica
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98 Features step 1 I don't wanna kn
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100 Features If you’re lucky your
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102 Scripts
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However, when we go the other way,
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122 Math the regular a--z character
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While there are lots of text fonts,
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8 Extensions 8.1 Introduction One o
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[default] [itlc=5] This is demonstr
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132 Extensions \definefontfeature [
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134 Extensions characters to improv
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136 Extensions U+00079 0.05 y 0.05
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138 Extensions protrusion classes T
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140 Extensions [fonts.composing.def
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142 } Extensions top = { x = -250,
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144 Extensions
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146 Hooks
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148 ) Appendix (LIG C l O 10) (KRN
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150 ) Appendix (KRN O 177 R 0.056)
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152 Appendix Notice Copyright 2003-
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154 Appendix ... KPX seven.prop hyp
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156 Appendix name = , features = ,
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158 Appendix [] = "", ... default =
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160 Appendix A.10 Discretionary nod
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