Yet the underlying text is unchanged bythe question of which glyphs come out the other end.Īll of which is a very long-winded way of saying “Unicode characters + OpenType layout = glyphs” or in design terms “text + formatting = display.” The beauty of this is that whenever you search, copy andpaste, change fonts or do other operations, the application is goingback to that underlying text. How many and which glyphs yousee is entirely font-dependent. One fontmight not have any ligatures, another might have just the “fi” ligature,and a third might have an “offi” ligature. The application asks its text engine to tell it whatglyphs to display for that text stream with ligatures on. Say, for example, you enter “o-f-f-i-c-e” and you have standardligatures on. When it comes to display, the application automatically does the additional processing and transformations to decide what glyphs to display for that character-based text stream, based on what layout features are “on” for that text. The underlying text that gets operated on by the application (spell-checked or copied or what-have-you) is the stream of characters. Most of the time when you’re working within an OpenType text model, your application (such as QuarkXPress or Adobe InDesign or Illustrator) deals with characters rather than glyphs. (In Adobe-speak, a Standard western font is anything that lacks central European language support, regardless of how many typographic goodies it has.) Contrariwise, a font might have a “Th” ligature, which is one glyph, but two characters (the “T” and the “h”), or an “off” ligature, which is again one glyph, but four characters (“o-f-f-i”). In a most extreme example, Poetica Std offers 57 different ampersands: one character but 57 glyphs. One of these would be the default glyph directly associated with that Unicode codepoint, while the others would be alternates or variants. A typeface might offer a regular cap A, a small cap A and a swash A-all of which are one character (cap “A,” U 0041), but three different glyphs. Sometimes a single character has several different representations in a font. OpenType and Unicode are not synonymous, but all OpenType fonts have a Unicode encoding.Ī glyph is a specific instantiation of that character in a given font, with a specific appearance. That Unicode codepoint may or may not be occupied in a given OpenType font, but it is reserved for that character and only that character (for example, the euro character is at Unicode U 20AC, capital “A” is U 0041 and the Cyrillic capital “Be” is U 0411). A character is the abstract idea of a letter or symbol, which has its own unique codepoint in the Unicode text encoding standard. If you want to know what can still go wrong, yet how it all works anyway, read on.Īt the heart of the OpenType font format lies the difference between characters and glyphs.
Similarly, support for Hungarian, Greek and Russian can be had in a single font and accessed by changing language keyboards or using the Glyph Panel found in Adobe’s Creative Suite (or the Quark, Mac OS or Windows equivalent). If you want extra fractions, swash alternates or small caps, you can get all those things in one well-chosen font, accessing them via formatting. Ligatures just appear as you type, and for the most part, designers don’t have to worry about it.
This FontLab screenshot shows which characters in the Latin Extended-B range of Unicode are supported by Hypatia Sans Pro Bold. If you needed pre-built fractions for 1/3, special symbols or Russian, the answers were similar: Change to a separate font and use a special chart to know what keys to strike to get a character codepoint in your text-a codepoint that would mean something entirely different in a regular Western font, which would be a problem if you ever changed fonts for that text. Heaven help you if you wanted to spell check this, or selected the whole paragraph and switched it to a different font, or copied the text into e-mail, or searched for the word “office,” or…well, you get the idea.
Using the Expert Set font for the Y plus the Regular font for the other letters would make the word look like “office” even though the underlying text characters were quite different. This meant that for the word “office” set with an “Y” ligature, the underlying text would end up as office. For example, the additional f-ligature glyphs (V, Y and Z) in Adobe Expert Set fonts used the codepoints usually assigned to the characters X, Y and Z.
If the glyphs in a particular Type 1 font didn’t map cleanly to the standard characters of the ISO-Adobe character set, then the glyphs would be placed in the numbered slots or codepoints normally used by something else. An "Expert Set" font: unrelated ligatures replace the letters V-Z.