Re: new trickery

[Hans Hagen <pragma@wxs.nl>]

On 3/15/2013 7:11 PM, Idris Samawi Hamid ادريس   سماوي حامد wrote:
> On Fri, 15 Mar 2013 05:07:02 -0600, Hans Hagen <pragma@wxs.nl> wrote:
>
>>     \start
>>         fijn fietsen 123
>>         \type{[+os]}\addfeature{f:oldstyle}
>>         fijn fietsen 123
>>         \type{[+sc]}\addfeature{f:smallcaps}
>>         fijn fietsen 123
>>         \type{[=os]}\replacefeature{f:oldstyle}
>>         fijn fietsen 123
>>         \type{[=sc]}\replacefeature{f:smallcaps}
>>         fijn fietsen 123
>>     \stop
>
> So I hope I have this right:
>
> \addfeature adds a set of features {<feature1>,<feature2>,...<featureN>}
> to the currently defined/enabled stack of OT features

no, it adds a *predefined* featureset to the set of the current font but 
forgets them when a group is left

> \subtractfeature subtracts a set of features from the currently
> defined/enabled stack

idem but subtraction

> These two seem clear enough. I'm not so clear on the next one:
>
> \replacefeature replaces all the _added_ features (not the default ones
> defined, e.g., in the typescripts I presume) with only those in the
> argument of \replacefeature. Is that right?

This reverts back to the features that are set when the font is defined 
and adds the given set. Resetting the stack in your speak.

> \resetfeature pops all features added to the stack (again, I'm assuming
> this does not include the default ones defined, e.g., in the typescripts).

This reverts back to the features that are set when the font is defined.

> Question: Does/Will this mechanism completely replace \addff et al, or
> will these mechanism ignore each other (e.g., \resetfeature does not pop
> those defined by \addff).

I dont' know ... in fact, they share code deep down in the machinery but 
indeed it might make sense to remove them (or at least depricate them).

Hans

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