Posted by:
Si From Beat...
Re: inline, pre-IUP, and post-IUP deltas: Yes, pre-IUP and post-IUP deltas are immediately before and after the IUP instructions, respectively. Inline deltas are deltas that are "in line" with the links (or interpolates) in the sense that there is a link (or interpolate) to a point P, which is then "delta-ed," and finally there are more links from that same point. This effectively applies a delta to P and all points subsequently linked to from P. For instance, if we wanted to xdelta the (vertical) stem in a "Croatian d" (Unicode 0x0111), we'd have an entire "tree" of links, but we can get away with a single inline delta to move the entire stem. This means that for a delta to be applicable as inline delta, the point it is applied to must have been "touched" (linked to, or interpolated, etc.). If it hasn't been touched, then an inline delta doesn't make sense, and hence it's not allowed.
Sometimes we may want to apply a delta to a point P which has been touched, but without the knock-on effect of delta-ing all other points linked to from P. This may make it simpler to cleanup a bad pixel pattern on a round stroke. Again, such a delta is applied to a "touched" point P, but after all the other links and interpolates starting from P. Effectively, this means that the delta is applied pretty much right before the IUP (hence the name pre-IUP delta). So, again, if the point hasn't been touched, then a pre-IUP delta doesn't make sense. Moreover, merely applying a delta to a point doesn't "touch" it (which I've found out the hard way), hence a subsequent IUP would still interpolate it like other untouched points, but with results that are "difficult to explain." Therefore, a pre-IUP delta is not allowed unless it is applied to a touched point.
Hope this makes any sense at all.
Cheers & Happy New Year
Beat
