Re: FreeType INSTCTRL behavior (Po Lu)

[Werner LEMBERG]

> Here is what the TrueType reference manual says: [...]

Found it!  It's not a bug but a feature.  From file
`src/truetype/ttobjs.c`, lines 1048ff:

```
    /* UNDOCUMENTED!  The MS rasterizer doesn't allow the following */
    /* graphics state variables to be modified by the CVT program.  */

    exec->GS.dualVector.x = 0x4000;
    exec->GS.dualVector.y = 0;
    exec->GS.projVector.x = 0x4000;
    exec->GS.projVector.y = 0x0;
    exec->GS.freeVector.x = 0x4000;
    exec->GS.freeVector.y = 0x0;

    exec->GS.rp0 = 0;
    exec->GS.rp1 = 0;
    exec->GS.rp2 = 0;

    exec->GS.gep0 = 1;
    exec->GS.gep1 = 1;
    exec->GS.gep2 = 1;
```

This is commit a2c7eb188892c6 from 2013, confirmed then by Microsoft
engineer Greg Hitchcock.

I've just filed

  https://github.com/MicrosoftDocs/typography-issues/issues/1012

so that it gets documented in the OpenType specification.


    Werner