Sets data of one or more data fields inside the glyph item. You have to
pass a table to this function that consists of one or more key-value pairs,
each setting a single data member.
The following keys are recognized in the table parameter:
YOffset-
Shift of the baseline, relative to the baseline of the containing line. Positive values shift upwards.
StartXOffset-
Horizontal displacement to apply before the glyph item. Positive values shift right.
EndXOffset-
Horizontal displacement to apply after th glyph item. Positive values shift right.