We are using Topic List Previews with tiles in our main page. Yesterday we had to rebuild our instance for reasons unrelated to TPL. We were aware of the change of thumbnailing backend in Discourse core and we knew that upgrading could cause problems with thumbnails. Still, it had to be done.
Anyway, after rebuilding (including the Postgres upgrade), all thumbnails coming from oneboxes were gone. No problem, we rebaked all posts and then most thumbnails reappeared (good) but not all (intriguing and bad). We rebaked a couple more times just in case, but there are some remaining posts that won’t get their thumbnail in the main page even if the oneboxes render without problems in their topic page.
Some thumbnails of YouTube oneboxes were missing in the main page (only some) and then, after visiting the topic page, they would magically appear in the main page. However…
As discussed, thumbnailing production logic is now built into core.
What TLP used to have to do is no longer necessary, largely.
For reference, the core criteria for inclusion are the following:
def extract_images_for_post
# all images with a src attribute
@doc.css("img[src]") -
# minus emojis
@doc.css("img.emoji") -
# minus images inside quotes
@doc.css(".quote img") -
# minus onebox site icons
@doc.css("img.site-icon") -
# minus onebox avatars
@doc.css("img.onebox-avatar") -
# minus small onebox images (large images are .aspect-image-full-size)
@doc.css(".onebox .aspect-image img")
end
TLP modifies this slightly, but only to loosen it up. I’d like to drop this override completely if possible:
def extract_images_for_post
# all images with a src attribute
@doc.css("img[src]") -
# minus emojis
@doc.css("img.emoji") -
# minus images inside quotes
@doc.css(".quote img") -
# minus onebox site icons
@doc.css("img.site-icon") -
# minus onebox avatars
@doc.css("img.onebox-avatar") #Broader criteria than Discourse Core
end
As you can see I am reducing the amount of exclusions by allowing small onebox images as defined by core.
Rather than maintaining this in TLP, it would be good to get consensus and parity across the use cases, so I don’t have to maintain this in the plugin at all.
I just want to say that the previous thumbnailing of Soundcloud oneboxes provided great results, and this regression is really bothering for a site focusing on music like ours.
I don’t mind if we miss a YouTube thumbnail here and there.
Curious about how this will evolve. I agree that the goal is to fine tune thumbnailing in Discourse core to find the best common ground between the many requirements and wishes. Thank you to everyone working on this.
At a glance, I don’t think that’s a YouTube onebox. I suspect someone has used raw YouTube embedding code in the post. If you turn it into a onebox, the thumbnail should work.
Did this used to work with the old TLP plugin? Soundcloud oneboxes are iframes, so I struggle to see how we could pull a thumbnail image from them, even my updating our selection criteria. @merefield did TLP have some soundcloud-specific logic somewhere?
Yes, there was some custom logic around oneboxes, though this was not exclusively for SoundCloud:
if @has_oneboxes
cooked = PrettyText.cook(@post.raw)
if img
## We need something more specific to identify the image with
img_id = img
src = img.attribute("src").to_s
img_id = src.split('/').last.split('.').first if src
end
prior_oneboxes = []
Oneboxer.each_onebox_link(cooked) do |url, element|
if !img || (img && cooked.index(element).to_i < cooked.index(img_id).to_i)
html = Nokogiri::HTML::fragment(Oneboxer.cached_preview(url))
prior_oneboxes = html.css('img')
end
end
if prior_oneboxes.any?
prior_oneboxes = prior_oneboxes.reject do |html|
class_str = html.attribute('class').to_s
class_str.include?('site-icon') || class_str.include?('avatar')
end
if prior_oneboxes.any? && validate_image_for_previews(prior_oneboxes.first)
img = prior_oneboxes.first
end
end
end
This has been stripped out to defer to the core logic.
There wasn’t an immediate change. After rebuilding HTML there wasn’t an immediate change either, but then I went to check Sidekiq and I saw one related job scheduled. After waiting 4 minutes patiently, the thumbnail is now available and it is displayed in the main page. Thank you @david for such quick reply, and on a Sunday!
Absolutely. Sadly, I didn’t take any screenshot. The main page would show the image at the left of the onebox.
These are both tricky problems, and I think for now we will be leaving the behavior as-is. We may be able to add some improvements in future. I created a couple of #feature topics to track progress
I take no responsibility! Works well though.