Text shaping

Text shaping is the process of converting text to glyph indices and positions as part of text rendering.^[1] It is complementary to font rendering as part of the text rendering process; font rendering is used to generate the glyphs, and text shaping decides which glyphs to render and where they should be put on the image plane.^[2] Unicode is generally used to specify the text to be rendered.

Text shaping results in substantially better results on Latin script; for some scripts with complex text layout such as Arabic script, text shaping is necessary for text to be readable at all.^[3]

Most graphical user interface systems, including those in MacOS, iOS,^[4] and Microsoft Windows have their own native text rendering engines that include text shaping. Microsoft's Uniscribe framework permits the use of pluggable shaping engines.^[5] Monotype's WorldType system also provides shaping functions.^[6]

In the open source world, HarfBuzz is a popular text shaping engine. According to HarfBuzz's developers, HarfBuzz is used by a range of software products including Android, Chrome, ChromeOS, Firefox, GNOME, GTK+, KDE, Qt, LibreOffice, OpenJDK, XeTeX, PlayStation, Microsoft Edge, Adobe Photoshop, Illustrator, InDesign, and Godot Engine.^[7]

Text shaping engines require descriptions of shaping properties and rules packaged in a format known as a shaping model. Shaping models include OpenType Layout, Graphite, and Apple Advanced Typography.^[8]

• Font rasterization
• Kerning
• Ligature (typography)
• Layout engine
• Complex text layout
• Line wrap and word wrap
• Pagination

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