All the eight values above are instead set in Element > Font Info > OS/2, including the РІР‚СљhheaРІР‚Сњ values. There is a restriction in FontForge that enforces that Ascent + Descent = Em Size, which is unnecessary. OpenType has a variety of internal metrics, stored in the hhea and OS/2 tables, that are used by many operating systems and applications to determine default line spacing:Р”Р‡ontLab (in the Font Info dialog) gives you specific fields to set all eight of these values - do not let FontLab set these values automatically! Glyphs makes it easier for you and simplifies this to two settings in the Font Info/Masters panel: РІР‚СљAscenderРІР‚Сњ and РІР‚СљDescenderРІР‚Сњ, which it uses to set all the others.Р”Р‡ontForge is particularly misleading: Element > Font Info > General has Ascent and Descent fields, but those are best ignored. There is no technical means of specifying a consistent default line spacing across all environments from within the font. Whenever possible, line spacing should be set explicitly by the user rather than relying on an applicationРІР‚в„ўs defaults. Many also have a way to explicitly set the line spacing to a certain amount. Others, such as InDesign, simply set it at a percentage of the point size, usually 120%. Some programs look inside the font for information. Each program has a built-in way of guessing at a good default line spacing, but those techniques differ. Most word processors and page layout programs have two ways of setting line spacing (how far apart vertically two lines of text will be).

How to set space in fontforge