[poppler] FreeText font/border color in DA - ISO32k vs Adobe Reader vs poppler

[Tobias Deiminger]

I'm posting here, esp. in the hope Leonard Rosenthol is reading. Adobe 
Reader
behaves differently than I had expected. Want to figure out what's going 
on,
because of https://gitlab.freedesktop.org/poppler/poppler/issues/50.

Questions is, how shall one adjust font color and border color of 
FreeText
annotations by means of /DA? I'm asking explicitely about situations 
where
there's no /AP, because poppler can't write /AP atm.

ISO 32k tells us that /DA establishes graphics state in case there's no 
/AP. We
can use text operators
- g/rg/k/sc, set color for nonstroking operations
- G/RG/K/SC, set color for stroking operations
- Tr, set text rendering mode, where 0 = "fill"

Drawing border is most likely a stroking operation, while drawing text 
glyphs in
fill mode is a nonstroking operation. So I had expected Adobe Reader to 
take
font color from g/rg/k/sc, and to take border color from G/RG/K/SC. In 
fact,
Adobe Reader does so in the /AP entry. But it doesn't interpret /DA like 
this.

By trial I found Adobe Reader uses rg from /DA as border color, and 
doesn't take
font color from /DA at all (text is always black). That confuses me 
quite a bit.
Is this really the Adobe interpretation of the standard?

If yes, and we follow the "do it like Adobe" guideline, this gets us 
into
trouble. We can't simply use DA to set both font and border color, but 
have to
embed AP, which means much more work left for #50.