Editing Typeface (section)

==={{anchor|metrics}}Font metrics===
[[Image:Typography Line Terms.svg|thumb|410px|The word ''Sphinx'', set in [[Garamond|Adobe Garamond Pro]] to illustrate the concepts of [[baseline (typography)|baseline]], [[x-height]], body size, descent and ascent.]]

{{See also|Font#Metrics|Typographic unit|Metric typographic units}}

Most [[script (styles of handwriting)|scripts]] share the notion of a [[baseline (typography)|baseline]]: an imaginary horizontal line on which characters rest. In some scripts, parts of glyphs lie below the baseline. The ''descent'' spans the distance between the baseline and the lowest descending glyph in a typeface, and the part of a glyph that descends below the baseline has the name ''[[descender]]''. Conversely, the ''ascent'' spans the distance between the baseline and the top of the glyph that reaches farthest from the baseline. The ascent and descent may or may not include distance added by accents or diacritical marks.

In the [[Latin script|Latin]], [[Greek script|Greek]] and [[Cyrillic script|Cyrillic]] (sometimes collectively referred to as LGC) scripts, one can refer to the distance from the baseline to the top of regular lowercase glyphs ([[mean line]]) as the ''[[x-height]]'', and the part of a glyph rising above the x-height as the ''[[Ascender (typography)|ascender]]''. The distance from the baseline to the top of the ascent or a regular uppercase glyphs (cap line) is also known as the cap height.<ref>Cullen, Kristin. ''Layout Workbook: A Real-World Guide to Building Pages in Graphic Design,''  Jul 2005: 92</ref> The height of the ascender can have a dramatic effect on the readability and appearance of a font. The ratio between the x-height and the ascent or cap height often serves to characterize typefaces.

Typefaces that can be substituted for one another in a document without changing the document's text flow are said to be "metrically identical" (or "metrically compatible").<ref>{{cite book |page=375 |publisher=Butterworth-Heinemann |title=The Computer Graphics Metafile |date=20 May 2014 |first1=L.R. |last1=Henderson |first2=A.M. |last2=Mumford |isbn=9781483144849 |url=https://books.google.com/books?id=O0KeBQAAQBAJ&q=%22metrically+identical%22&pg=PA375}}</ref><ref>{{cite book |page=102 |title=CGM in the Real World |first1=Anne M. |last1=Mumford |first2=Mark |last2=Skall |publisher=Springer Science & Business Media |date=7 Mar 2013 |isbn=9783642736292 |url=https://books.google.com/books?id=iUCqCAAAQBAJ&q=%22metrically+identical%22&pg=PA102}}</ref><ref>{{cite book |title=Beginning Ubuntu Linux: Natty Narwhal Edition |page=286 |publisher=Apress |first1=Emilio |last1=Raggi |first2=Keir |last2=Thomas |first3=Sander |last3=van Vugt |date=17 Dec 2011 |isbn=9781430236276 |url=https://books.google.com/books?id=5i-c2yms6tUC&q=%22metrically+identical%22&pg=PA286}}</ref> Several typefaces have been created to be metrically compatible with widely used proprietary typefaces to allow the editing of documents set in such typefaces in digital typesetting environments where these typefaces are not available. For instance, the free and open-source [[Liberation fonts]] and [[Croscore fonts]] have been designed as metrically compatible substitutes for widely used [[Microsoft]] fonts.<ref name="fc-30-metric-aliases">{{cite web|last2=TAGOH|first2=Akira|last3=Steffens|first3=Jan|last4=Crozat|first4=Frederic|last1=Esfahbod|first1=Behdad|title=30-metric-aliases.conf|url=https://github.com/behdad/fontconfig/blob/master/conf.d/30-metric-aliases.conf|website=GitHub|publisher=fontconfig|access-date=1 May 2016}}</ref><ref>{{cite web |title=Liberation fonts and the tricky task of internationalization |first=Nathan |last=Willis |date=19 June 2012 |access-date=26 June 2017 |publisher=[[LWN.net]] |url=https://lwn.net/Articles/502371/}}</ref>