Repeat offsets

The repeatOffset point is defined for glyphs that are designed to tessellate, such as the wiggly line that follows the symbol, or any of the glyphs in the Multi-segment lines range.

These glyphs are registered such that they may have negative side bearings on either or both the left- and right-hand sides. When entered in a run of text, the advance width produces the correct tessellation. However, in some situations it may not be possible to use a run of text to draw such a line, or the API in use may not provide easy access to the advance width of a glyph (e.g. when using the HTML canvas element).

In these situations, correct tessellation can be achieved by positioning the origin of subsequent glyphs in a tessellating line at the horizontal position defined by the repeatOffset point for a given glyph.

Here, for example, is an illustration of the glyph wiggleTrill:

The vertical dashed lines show the left- and right-hand side bearings for this glyph. The repeatOffset anchor’s coordinates are at the x position of the right-hand side bearing and y = 0. Positioning another trillWiggle glyph at the position of the repeatOffset anchor produces correct tessellation, like this: