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Who needs a glyph palette?

v1.2 (30 April 2010) / v1.0 (16 April 2010)

This note goes back to, and continues, a previous note. The question then was: Suppose that an application grants direct access to glyphs via a glyph palette – as known from InDesign and requested for Photoshop too.[1] Suppose that a designer inserts a glyph into a text via this glyph palette. And suppose that the designer applies one or more OpenType layout features to this text. Did the designer make an explicit choice when inserting this specific glyph, so that layout features applied to the glyph should have no effect? Or did the designer use the glyph palette to insert a character not available on his keyboard, so that layout features applied to it should indeed have an effect?

Characters and glyphs

The question as formulated above already points to an answer as it distinguishes inserting a glyph from inserting a character.
Today's layout and font technology presupposes a distinction of character and glyph. This is not merely a distinction of two items. It is a distinction of two levels – character level, or content, and glyph level, or representation.
It should be evident that the idea of using a glyph palette to insert a glyph (a meaningless shape) into text (a string of characters that convey meaning) is conceptually flawed in that it ignores that character and glyph belong to separate levels, and that while these levels relate to each other, this is not a 1:1 relation: A character can be represented by one or more glyphs. And a glyph, alone or in combination with other glyphs, can represent more than just one character.
Of course InDesign knows that inserting a glyph into a text string is wrong and tries to infer which character each glyph serves to represent. Selecting a glyph from the glyph palette will insert a character and apply the layout feature necessary to produce the specific glyph. The problem is that this bottom–up approach, from glyph level to character level, at best produces ambiguous results and none at worst – as happens when a glyph merely contributes, in connection with other glyphs, to representing a character and, in connection with yet other glyphs, contributes to representing another character, etc. InDesign's bottom–up approach means starting from the wrong end. A top-down approach, from character level to glyph level, instead would produce unambiguous results.

Character palette not glyph palette

This note is not supposed to question the need for easy access to characters and variant representations thereof. What it questions is the idea that an application should give direct access to a font's glyphs. The latter may work as long as layout and font technology take for granted that a glyph represents exactly one character. Unicode (the character level) and OpenType (mapping character level to glyph level) have jointly moved past this.
In short, there is no place for a glyph palette in a Unicode-savvy application – be this InDesign or Photoshop.[2] There is, however, a place for a character palette that exposes each character addressed by a font (see 'cmap' table) in its various representations (see 'GSUB' table). Mind that a character palette does not show characters but representations thereof. Each representation, default or variant, in turn may draw on one glyph or more. But the latter is a font implementation issue that users should not be bothered with.



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