[luatex] Attributes of font kerns.

[Paul Isambert]

Hello all,

The manual (section 2.5.1) notes that some nodes inherit the attributes' 
values of the surrounding nodes, and not the values in force when they 
are created; for instance, ligatures have the values of their 
components, even though ligature nodes are created well after their 
components (in the "ligaturing" callback).

Other `asynchronous' nodes receive the current values; for instance, 
font kern nodes added in the "kerning" callback do not inherit the 
values of the surrounding nodes. However, the manual states (same 
section) that `this area needs studying', and Manuel and I thought it 
would be worth discussing here.

My contribution is that font kerns should behave like ligatures and 
inherit the surrounding values; the resulting horizontal list would be 
more homogenous that way, even though the only area where I can see it 
make a difference is underlining and associates (using attributes to 
determine what should be underlined).

Perhaps some of you have reasons for keeping the font kerns' values in 
line with the current values?
[If you don't, I'll be forced to solemnly petition Taco with a feature 
request.]

Best,
Paul