Twenty Ten: retrofit with "get first gallery image" technique for gallery post format

[lancewillett]

The goal is to replace the custom code in loop.php with a simpler, cleaner core function. Will probably need to provide back compat fallback for pre 3.6 versions, though.

See #22960 for the new image grabber function and #15385 for converting Twenty Ten to using get_template_part().

My comment in http://core.trac.wordpress.org/ticket/22907#comment:4 applies here, too. What back compat do we need to test, and can the code be moved into a function to keep the template file cleaner?

Quick test with 3.4.2 and Twenty Ten. Created a new gallery post, pasted in [gallery ids="619,618,617"] as the content (grabbed 3 IDs from Media Library).

Works great on index, no errors. On single, the view is empty, though.

Tested with 3.5.1 and Twenty Ten, same post content. Exact opposite result: looks great on single, but empty view on index.

Replying to lancewillett:

Tested with 3.5.1 and Twenty Ten, same post content. Exact opposite result: looks great on single, but empty view on index.

Scratch that, this was with 3.6 trunk latest.

Tests out great in 3.5.1 and 3.6 (previously I didn't have the patch attached correctly).

3.4.2 -- gallery is missing the images on single view (index looks fine).

Patch doesn't tough the single view though. In 3.4 only images attached to the post were working with the gallery shortcode. The ability to add other pictures was just added in 3.5.

Cool. Works for me, then.

Thoughts on moving to a function instead of code right in the template?

Move to function, provide fallback for missing IDs

.1 moves to functions.php to simplify the template file a bit, and provides better fallback for shortcodes without "ids" attributes.

.2 patch fixes comment block for accuracy for new function and changes function to always return an array value.

In 23826:

Twenty Ten: improve how gallery image IDs are retrieved for use in the Gallery post format template. Props to obenland for original patch, fixes #23617.

[24093] introduced a new $html argument to get_post_galleries which defaults to true and breaks gallery counts (displays always 1 without a thumbnail). 23617.3.diff​ addresses this, and also changes the function we check in function_exists to the one that is actually used.

In 24195:

Twenty Ten: call get_post_galleries() correctly now that it has new arguments, and use a more accurate function_exists call. Props kovshenin, closes #23617.