LayoutGlyph start/end seems broken

[dtzxporter]

Using 0.12 in iced, the .start/.end values seem to keep resetting for a common run like: "0 Asset tooth 0".
The glyphs won't point to the correct span in the original line.

[rkanati]

I ran into the same problem; Buffer::layout_cursor was always returning a fallback value, because start and end values of the LayoutGlyphs from the Buffer were wrong, as if they were relative to the beginning of words or spans of whitespace, e.g. the string "Hello world" produced LayoutGlyph::start values like so: 0 1 2 3 4 0 0 1 2 3 4.

Changing the Shaping from Basic to Advanced seems to avoid the bug.

[rkanati]

The culprit seems to be fn shape_skip in shape.rs, and looking at the blame it seems like these values were always set wrong here.