Viewing and Editing truetype instructions in FontForge.

I shall not attempt to describe the mechanics of instructing truetype, if you want to understand it I refer you to the above links. (Microsoft has a similar set in but they are in word format).

This dialog shows the instructions associated with a glyph or truetype table (like fpgm or prep). If you move your mouse cursor over one of the instructions a brief help message will pop up describing that instruction. If you press the [Edit] button the dlg will change and you will be presented with a editable textarea containing the same instructions. You may modify these to your heart's content. Pressing the [Parse] will parse your modifications and (if they parse) return you to the "help" mode.

Instructions like MIRP may be entered either in FontForge's peculiar (but marginally more mnemonic) style: MIRP[rnd,white] or as MIRP[00110], and PUSHB_1 may be PUSHB[000].

You may also include an stack arguments on the same line as the instruction and FontForge will convert them into the appropriate pushes. So...

5 SRP0

is equivalent to

PUSHB_1
5
SRP0

You may also use the expression cvt(<val>) instead of a number. This will be replaced by the index in the 'cvt ' table of an entry which is (within one em-unit of) <val>. So cvt(100) would return the index in 'cvt ' of 100. If there is no such entry, FontForge will create one.

Editing the 'cvt ' table directly

This dialog shows the initial contents of the 'cvt ' table (before it has been modified by the 'prep' program). It is simply a list of signed 16bit values. You may change any value by clicking on it and typing a new value. You may add new entries (at the end) with the [change length] button.

(You may also use the "cvt(<val>)" notation described above to edit the cvt table.)