Re: dominant-baseline property

[Finn Bock]

[Manuel]

I just discovered something unusual in the spec. It describes the
dominant-baseline property in a number of places as:
'The "dominant-baseline" property is a compound value with three
components.'
It then goes on and lists the 3 components as
"dominant-baseline-identifier", "baseline-table" and
"baseline-table font-size" collectively referred to as a
"scaled-baseline-table". Or to put it differently - the computed
value of the "dominant-baseline" property is a value of type
"scaled-baseline-table".

[Andreas]

Not exactly. Read 7.13.5:

"The 'dominant-baseline' property is used to determine a
scaled-baseline-table. A scaled-baseline-table is a compound value
with three components..."

So, it's not the property itself which is a compound value, but
rather the property's enum value is used to determine the compound
value of the scaled-baseline-table.

[Manuel]

It also says in 7.13: The primary baseline alignment property is the 
"dominant-baseline" property. This property has a compound value with 
three components. 

And in 5.5.7: The value of this property is a compound value with three 
components: a baseline-identifier for the dominant-baseline, a 
baseline-table and a baseline-table font-size.

So there is some evidence in the spec that the authors meant that the 
computed value of the property is of type "scaled-baseline-table".

I agree, the spec does indeed indicate that the value isn't a simple 
enum. OTOH I have no idea how it should be handled in the property 
system. It isn't a normal compound property (no 
"dominant-baseline.baseline-identifier" sub property).

I'm far from being an expert on alignment, but my gut feeling would make 
the "scaled-baseline-table" datatype a class in layoutmgr, accessed from 
LayoutContext and updated at each LM level with the alignment properties.

If you allow me to turn the question around, what would be the benefit 
of having a scaled-baseline-table datatype in the property system? I 
guess that inheritance of values would be the main reason which is easy 
in the property system and somewhat harder in LayoutContext. The 
calculation is the remainging values seems easier to do during layout.

regards,
finn