Text rendering: Combining diacritical characters have inverted y-shift

[Severin Meyer]

Inkscape 0.92.2 5c3e80d, 2017-08-06
openSUSE Leap 42.3

Inkscape does not seem to correctly render text with combining diacritical characters (https://en.wikipedia.org/wiki/Combining_character).

The problem arises when the anchor of the combining character is at a different y-position than the anchor of the base character. In that case, Inkscape inverts the y-shift.

Based on a few test measurements, the shift is the exact opposite, so I assume there is a simple +- mismatch somewhere in the code.

For testing I used the "Source Sans Pro" font, which has a comprehensive anchor implementation (https://github.com/adobe-fonts/source-sans-pro).