opacity does not affect text

[fryguybob]

(Imported from http://code.google.com/p/diagrams/issues/detail?id=78. Original issue from byor...@gmail.com on April 5, 2012, 02:09:03 AM UTC)

Consider the following code:

{-# LANGUAGE NoMonomorphismRestriction #-}

import Diagrams.Prelude
import Diagrams.Backend.Cairo.CmdLine

import Data.Colour

t1 = text "H" # fcA (black withOpacity 0.5) <> square 1 # lw 0

t2 = text "H" # opacity 0.5 <> square 1 # lw 0

main = defaultMain (t1 ||| t2)

I would expect both H's to be grey, but only the one on the left is. The way the cairo backend handles setting the fill and stroke colors is sort of a hack, and it looks like it's coming around to bite us here.

[byorgey]

This was incidentally fixed by the recent refactoring of the cairo backend. It's still not solved in the most general way though.