Allow to deffer subroutine/constant calling

[mnbv09870987]

I am doing perl binding for SDL2 https://www.libsdl.org/download-2.0.php

in include/SDL_pixels.h there is next enum:

typedef enum
{
    SDL_PIXELFORMAT_UNKNOWN,
    ...
    SDL_PIXELFORMAT_RGBA8888 =
        SDL_DEFINE_PIXELFORMAT(SDL_PIXELTYPE_PACKED32, SDL_PACKEDORDER_RGBA,
                               SDL_PACKEDLAYOUT_8888, 32, 4),
   ...
    /* Aliases for RGBA byte arrays of color data, for the current platform */
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    SDL_PIXELFORMAT_RGBA32 = SDL_PIXELFORMAT_RGBA8888,
    SDL_PIXELFORMAT_ARGB32 = SDL_PIXELFORMAT_ARGB8888,
    SDL_PIXELFORMAT_BGRA32 = SDL_PIXELFORMAT_BGRA8888,
    SDL_PIXELFORMAT_ABGR32 = SDL_PIXELFORMAT_ABGR8888,
#else
    SDL_PIXELFORMAT_RGBA32 = SDL_PIXELFORMAT_ABGR8888,
    SDL_PIXELFORMAT_ARGB32 = SDL_PIXELFORMAT_BGRA8888,
    SDL_PIXELFORMAT_BGRA32 = SDL_PIXELFORMAT_ARGB8888,
    SDL_PIXELFORMAT_ABGR32 = SDL_PIXELFORMAT_RGBA8888,
#endif
    ....
} SDL_PixelFormatEnum;

I convert it like next:

# required forward declaration
sub SDL_PIXELFORMAT_RGBA8888();

$ffi->load_custom_type('::Enum', 'SDL_PixelFormatEnum',
	{ ret => 'int', package => 'SDL2::Pixels' },
	'SDL_PIXELFORMAT_UNKNOWN',
        ....
    [ SDL_PIXELFORMAT_RGBA8888 => SDL_DEFINE_PIXELFORMAT(
		SDL2::Pixels::SDL_PIXELTYPE_PACKED32, SDL2::Pixels::SDL_PACKEDORDER_RGBA,
		SDL2::Pixels::SDL_PACKEDLAYOUT_8888, 32, 4
	)],
	SDL2::Endian::SDL_BYTEORDER == SDL2::Endian::SDL_BIG_ENDIAN? (
	    [SDL_PIXELFORMAT_RGBA32 => SDL_PIXELFORMAT_RGBA8888],
	    [SDL_PIXELFORMAT_ARGB32 => SDL_PIXELFORMAT_ARGB8888],
	    [SDL_PIXELFORMAT_BGRA32 => SDL_PIXELFORMAT_BGRA8888],
	    [SDL_PIXELFORMAT_ABGR32 => SDL_PIXELFORMAT_ABGR8888],
	) : (
	    [SDL_PIXELFORMAT_RGBA32 => SDL_PIXELFORMAT_ABGR8888],
	    [SDL_PIXELFORMAT_ARGB32 => SDL_PIXELFORMAT_BGRA8888],
	    [SDL_PIXELFORMAT_BGRA32 => SDL_PIXELFORMAT_ARGB8888],
	    [SDL_PIXELFORMAT_ABGR32 => SDL_PIXELFORMAT_RGBA8888],
	)
);                           

because of ?: works first before load_custom_type is called. I get error:

Undefined subroutine &SDL2::Pixels::SDL_PIXELFORMAT_ABGR8888 called at ...

This patch allow to defer call to SDL_PIXELFORMAT_ABGR8888. Now declaration looks like:

	SDL2::Endian::SDL_BYTEORDER == SDL2::Endian::SDL_BIG_ENDIAN? (
	    sub{ [SDL_PIXELFORMAT_RGBA32 => SDL_PIXELFORMAT_RGBA8888] },
	    sub{ [SDL_PIXELFORMAT_ARGB32 => SDL_PIXELFORMAT_ARGB8888] },
	    sub{ [SDL_PIXELFORMAT_BGRA32 => SDL_PIXELFORMAT_BGRA8888] },
	    sub{ [SDL_PIXELFORMAT_ABGR32 => SDL_PIXELFORMAT_ABGR8888] },
	) : (
	    sub{ [SDL_PIXELFORMAT_RGBA32 => SDL_PIXELFORMAT_ABGR8888] },
	    sub{ [SDL_PIXELFORMAT_ARGB32 => SDL_PIXELFORMAT_BGRA8888] },
	    sub{ [SDL_PIXELFORMAT_BGRA32 => SDL_PIXELFORMAT_ARGB8888] },
	    sub{ [SDL_PIXELFORMAT_ABGR32 => SDL_PIXELFORMAT_RGBA8888] },
	)

and works without problem

[plicease]

Instead of removing this test, please substitute another unsupported type, like a scalar ref.

[plicease]

Suggested change

	if( ref $value eq 'CODE' ) {
	if(is_coderef $value) {

You will need to import is_coderef from Ref::Util

[plicease]

Need to document the new usage.

[plicease]

I'm not 100% sure this is the best way to handle enum aliasing tbh, I think there might be a better interface.

[plicease]

Also a test should be added to test passing a subref in as a value.

[plicease]

I think a more general approach would be something like:

$ffi->load_custom_type('::Enum', 'foo_t',
  'default',
  'better',
  ['best' => 12, alias => ['abc','xyz']],
);

[plicease]

I think I prefer #6 which doesn't rely on the load order. I think you should still be able to do what you need.