Final by default?

[Iain Buclaw]

On 17 March 2014 08:06, Walter Bright <newshound2 at digitalmars.com> wrote:
> On 3/17/2014 12:39 AM, Iain Buclaw wrote:
>>
>> If I recall, he was saying that you must pass
>> -fversion=CAIRO_HAS_PNG_SUPPORT to
>> every file that imports it was the problem, because you want PNG support,
>> not stubs.
>
>
> Stub out the functions for PNG support. Then just call them, they will do
> nothing if PNG isn't supported. There is NO NEED for the callers to set
> version.
>
>
>
>> It's more an example where you need a build system in place for a simple
>> hello
>> world in cairoD if you don't want to be typing too much just to get your
>> test
>> program built. :)
>
>
> If you need to -fversion=CAIRO_HAS_PNG_SUPPORT for every file that imports
> it, you have completely misunderstood the design I suggested.
>
> 1. Encapsulate the feature in a function.
>
> 2. Implement the function in module X. Module X is the ONLY module that
> needs the version. In module X, define the function to do nothing if version
> is false.
>
> 3. Nobody who imports X has to define the version.
>
> 4. Just call the function as if the feature always exists.
>
> 5. If you find you still need a version in the importer, then you didn't
> fully encapsulate the feature. Go back to step 1.

Right, but going back full circle to the original comment:

"For example cairoD wraps the cairo C library. cairo can be compiled
without or with PNG support. Historically cairoD used
version(CAIRO_HAS_PNG_SUPPORT) for this."

Requires that cairoD have this encapsulation you suggest, but also
requires detection in some form of configure system that checks:

1) Is cairo installed? (Mandatory, fails without)
2) Does the installed version of cairo have PNG suport (If true, set
build to compile a version of module X with
version=CAIRO_HAS_PNG_SUPPORT)