[Devel] Bug in ttinterp.c ???

[Rogier van Dalen]

As I was instructing a TT font I have made, I found FreeType behaving 
strangely on a few glyphs. It seems to have to do with the MSIRP 
instruction.

The font is at
http://home.kabelfoon.nl/~slam/fonts/Legendum_hinted.ttf
(the instruction code is at 
http://home.kabelfoon.nl/~slam/fonts/Legendum.tti (This has been 
produced with my instruction compiler, but the code surely is 
straightforward enough) )

The capitals I and T look strange with ftview, whereas both the Windows 
(2000 & 95) scaler and my own, home-grown scaler work as they should. 
Let's take T (glyph 57).

At g0018, the program calls function 6. At f0398, the MSIRP tries to 
move a point horizontally at a distance from point 0 in the twilight 
zone. The y coordinate, however, seems to be set to the twilight point y 
coordinate, which is 0. It seems to me this has got something to do with 
the /* XXX: UNDOCUMENTED! behaviour */ part in Ins_MSIRP, which I don't 
understand at all. This seems to happen at all sizes.

Hopefully someone will be able to see what is wrong or point out what 
I'm doing wrong...

Rogier