[ft-devel] various questions about implementing ttf

[Jan Bruns]

Hallo.

I'm currently writing on some ft-"equivalent" pascal lib.

I've decided to do this from scratch, 100% fresh code base.

Current state profile looks like:

interface: no thought
renderer: overly simple, bw, buggy, no dropout control
file-loader:
  loads composite glphys
  no pixel-bitmaps, yet
  format12-cmap only
  nothing about metrics, yet
  no variations, yet
hinter:
  well, most instructions seem to work,
  points are sometimes moved by small amounts


Questions that I currently have:

1. Are there fonts designed for the purpose of debuging interpreters?

2. Scaling:
  Really make the interpreter work on device-space units?
  Wouldn't it be more natural to scale by pointsize, and probably
  have some "intended ppem hint" about a final renderer transform
  just for fonts that are really interested in subpixel fitting?

3. CVT-table (from font-file):
  spec unclear (apple says 4 bytes per elem),
  OT/MS say FUnits and tabs often have odd multiples of 2
  How to scale? By device independent pointsize?

4. Interpreter/Hinter, initializations:
   How to Reset or keep states between program invocations?
   Fresh init for any invocation, or reset to what "prep" left?
   What about zone0 init?

5. Interpreter/Hinter, dual projection vector:
   Is it really used somewhere?  

6. Renderer, dropout control:
   Is the test "continue to intersect scanlines" a pixel-based
   process, like just checking if the neighbor scan line segments
   have been touched by a contour? Or do we already have more
   sophisticated tests implemented today?

7. more to follow...

Gruss

Jan Bruns


svn://abnuto.de/ttf