+
+> This plugin is pretty ambitious, and is unfinished, so I'd recommend
+> playing with a normal IkiWiki installation for a bit, then trying
+> out this plugin when you've mastered the basics of IkiWiki. --[[smcv]]
+
+----
+
+You had wanted my feedback on the design of this. I have not looked at the
+code or tried it yet, but here goes. --[[Joey]]
+
+* Needing to create the albumimage "viewer" pages for each photo
+ seems like it will become a pain. Everyone will need to come up
+ with their own automation for it, and then there's the question
+ of how to automate it when uploading attachments.
+
+> There's already a script (ikiwiki-album) to populate a git
+> checkout with skeleton "viewer" pages; I was planning to make a
+> specialized CGI interface for albums after getting feedback from
+> you (since the requirements for that CGI interface change depending
+> on the implementation). I agree that this is ugly, though. -s
+
+* With each viewer page having next/prev links, I can see how you
+ were having the scalability issues with ikiwiki's data structures
+ earlier!
+
+> Yeah, I think they're a basic requirement from a UI point of view
+> though (although they don't necessarily have to be full wikilinks).
+> -s
+
+>> I think that with the new dependency types system, the dependencies for
+>> these can be presence dependencies, which will probably help with
+>> avoiding rebuilds of a page if the next/prev page is changed.
+>> (Unless you use img to make the thumbnails for those links, then it
+>> would rebuild the thumbnails anyway. Have not looked at the code.) --[[Joey]]
+
+* And doesn't each viewer page really depend on every other page in the
+ same albumsection? If a new page is added, the next/prev links
+ may need to be updated, for example. If so, there will be much
+ unnecessary rebuilding.
+
+> albumsections are just a way to insert headings into the flow of
+> photos, so they don't actually affect dependencies.
+>
+> One non-obvious constraint of ikiwiki's current design is that
+> everything "off-page" necessary to build any page has to happen
+> at scan time, which has caused a few strange design decisions,
+> like the fact that each viewer controls what album it's in.
+>
+> It's difficult for the contents of the album to just be a
+> pagespec, like for inline, because pagespecs can depend on
+> metadata, which is gathered in arbitrary order at scan time;
+> so the earliest you can safely apply a pagespec to the wiki
+> contents to get a concrete list of pages is at rebuild time.
+>
+> (This stalled my attempt at a trail plugin, too.) -s
+
+>> Not sure I understand why these need to look at pagespecs at scan time?
+>> Also, note that it is fairly doable to detect if a pagespec uses such
+>> metadata. Er, I mean, I have a cheezy hack in `add_depends` now that does
+>> it to deal with a similar case. --[[Joey]]
+
+* One thing I do like about having individual pages per image is
+ that they can each have their own comments, etc.
+
+> Yes; also, they can be wikilinked. I consider those to be
+> UI requirements. -s
+
+* Seems possibly backwards that the albumimage controls what album
+ an image appears in. Two use cases -- 1: I may want to make a locked
+ album, but then anyone who can write to any other page on the wiki can
+ add an image to it. 2: I may want an image to appear in more than one
+ album. Think tags. So it seems it would be better to have the album
+ directive control what pages it includes (a la inline).
+
+> See note above about pagespecs not being very safe early on.
+> You did merge my inline-with-pagenames feature, which is safe to use
+> at scan time, though.
+
+* Putting a few of the above thoughts together, my ideal album system
+ seems to be one where I can just drop the images into a directory and
+ have them appear in the album index, as well as each generate their own wiki
+ page. Plus some way I can, later, edit metadata for captions,
+ etc. (Real pity we can't just put arbitrary metadata into the images
+ themselves.) This is almost pointing toward making the images first-class
+ wiki page sources. Hey, it worked for po! :) But the metadata and editing
+ problems probably don't really allow that.
+
+> Putting a JPEG in the web form is not an option from my point of
+> view :-) but perhaps there could just be a "web-editable" flag supplied
+> by plugins, and things could be changed to respect it.
+>
+> In a way, what you really want for metadata is to have it in the album
+> page, so you can batch-edit the whole lot by editing one file (this
+> does mean that editing the album necessarily causes each of its viewers
+> to be rebuilt, but in practice that happens anyway). -s
+>
+>> Yes, that would make some sense.. It also allows putting one image in
+>> two albums, with different caption etc. (Maybe for different audiences.)
+>>
+>> It would probably be possible to add a new dependency type, and thus
+>> make ikiwiki smart about noticing whether the metadata has actually
+>> changed, and only update those viewers where it has. But the dependency
+>> type stuff is still very new, and not plugin friendly .. so only just
+>> possible, --[[Joey]]
+
+----
+
+Trying to use the "special extension" design:
+
+Suppose that each viewer is a JPEG-or-GIF-or-something, with extension
+".albumimage". We have a gallery "memes" with three images, badger,
+mushroom and snake.
+
+> An alternative might be to use ".album.jpg", and ".album.gif"
+> etc as the htmlize extensions. May need some fixes to ikiwiki to support
+> that. --[[Joey]]
+
+Files in git repo:
+
+* index.mdwn
+* memes.mdwn
+* memes/badger.albumimage (a renamed JPEG)
+* memes/badger/comment_1._comment
+* memes/badger/comment_2._comment
+* memes/mushroom.albumimage (a renamed GIF)
+* memes/mushroom.meta (sidecar file with metadata)
+* memes/snake.albumimage (a renamed video)
+
+Files in web content:
+
+* index.html
+* memes/index.html
+* memes/96x96-badger.jpg (from img)
+* memes/96x96-mushroom.jpg (from img)
+* memes/96x96-snake.jpg (from img, hacked up to use totem-video-thumbnailer :-) )
+* memes/badger/index.html (including comments)
+* memes/badger.jpg
+* memes/mushroom/index.html
+* memes/mushroom.gif
+* memes/snake/index.html
+* memes/snake.mov
+
+ispage("memes/badger") (etc.) must be true, to make the above rendering
+happen, so albumimage needs to be a "page" extension.
+
+To not confuse other plugins, album should probably have a filter() hook
+that turns .albumimage files into HTML? That'd probably be a reasonable
+way to get them rendered anyway.
+
+> I guess that is needed to avoid preprocess, scan, etc trying to process
+> the image, as well as eg, smiley trying to munge it in sanitize.
+> --[[Joey]]
+
+do=edit&page=memes/badger needs to not put the JPG in a text box: somehow
+divert or override the normal edit CGI by telling it that .albumimage
+files are not editable in the usual way?
+
+Every image needs to depend on, and link to, the next and previous images,
+which is a bit tricky. In previous thinking about this I'd been applying
+the overly strict constraint that the ordered sequence of pages in each
+album must be known at scan time. However, that's not *necessarily* needed:
+the album and each photo could collect an unordered superset of dependencies
+at scan time, and at rebuild time that could be refined to be the exact set,
+in order.
+
+> Why do you need to collect this info at scan time? You can determine it
+> at build time via `pagespec_match_list`, surely .. maybe with some
+> memoization to avoid each image in an album building the same list.
+> I sense that I may be missing a subtelty though. --[[Joey]]
+
+Perhaps restricting to "the images in an album A must match A/*"
+would be useful; then the unordered superset could just be "A/*". Your
+"albums via tags" idea would be nice too though, particularly for feature
+parity with e.g. Facebook: "photos of Joey" -> "tags/joey and albumimage()"
+maybe?
+
+If images are allowed to be considered to be part of more than one album,
+then a pretty and usable UI becomes harder - "next/previous" expands into
+"next photo in holidays/2009/germany / next photo in tagged/smcv / ..."
+and it could get quite hard to navigate. Perhaps next/previous links could
+be displayed only for the closest ancestor (in URL space) that is an
+album, or something?
+
+> Ugh, yeah, that is a problem. Perhaps wanting to support that was just
+> too ambitious. --[[Joey]]
+
+Requiring renaming is awkward for non-technical Windows/Mac users, with both
+platforms' defaults being to hide extensions; however, this could be
+circumvented by adding some sort of hook in attachment to turn things into
+a .albumimage at upload time, and declaring that using git/svn/... without
+extensions visible is a "don't do that then" situation :-)
+
+> Or extend `pagetype` so it can do the necessary matching without
+> renaming. Maybe by allowing a subdirectory to be specified along
+> with an extension. (Or allow specifying a full pagespec,
+> but I hesitate to seriously suggest that.) --[[Joey]]
+
+Ideally attachment could also be configured to upload into a specified
+underlay, so that photos don't have to be in your source-code control
+(you might want that, but I don't!).
+
+Things that would be nice, and are probably possible:
+
+* make the "Edit page" link on viewers divert to album-specific CGI instead
+ of just failing or not appearing
+* some way to deep-link to memes/badger.jpg with a wikilink, without knowing a
+ priori that it's secretly a JPEG