implement caption and meta-information for images #119

[laurensmartina]

Fixes #119

[matthijskooijman]

I think I might be misunderstanding how all of this fits together, so I asked some questions inline. Maybe we should look at this together this afternoon.

[matthijskooijman]

I left a bunch of inline comments which I also fixed in two fixup commits that I'll push in a minute.

I did find some other problems that are still unfixed right now and might need us to rethink our approach. In particular:

• The <figure> tag is a block-level tag, while <img> is inline, so adding the figure creates invalid HTML, causing at least my Firefox to drop the <figure>, it seems.
• Any layout CSS applied to the image might break. In particular, the default theme supports e.g. the .left class to make the image floating and have text wrap around it, but this breaks when wrapped inside <figure>.
• Inside the wymeditor, the caption is not shown, which makes it a bit harder to preview changes.

Not sure if there is an easy fix for these, so maybe we should be storing <figure> tags after all?

[matthijskooijman]

One additional thing I found is that you now explicitly exclude any HTML inside wymeditor, which I had expected to be not needed since this should live as text (rather than HTML) inside a textarea. However, I found that we actually changed this to HTML in b6f630e to actually allow the global dewikify to process this. However, this results in actual (non-escaped) HTML to end up in the <textarea> tag, which is not technically correct HTML (though it seems browsers will allow it in practice).

Also note that this editor starts out as an <editor> tag and is later transformed into a textarea tag by this bit of code. This makes the current code in this PR fragile: If it would happen to run before rather than after this transformation, the .wymeditor class would not exist yet and it would add captions inside the wymeditor too.

I think it might be better to just revert to storing text rather than HTML, but manually run dewikify (and maybe other things needed) on the HTML before converting it to text and inserting it into the editor.

I also wonder if we really need this editor tag at all, maybe it would be simpler and more transparent to just use <textarea class="wymeditor"> instead of <editor> in the forms directly? Does not really look any less readable to me either?