Topic List Previews (legacy)

That could be a temporary solution for now. Before I post something, I’m curious if anyone else can reproduce this problem?

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Would be good to identify another theme component with a tag picker …

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Another solution for the time being is just to use a new independent tag?

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Yes, that will work for now with this component since it’s just the one tag I need, thanks!


Emojis present in posts are not displayed in excerpts, at least in tiles mode. Is this a know problem?


Yeah, that was low priority. but thanks for the reminder. It’s fixed now in the TC, update to latest! Emojis FTW :upside_down_face:


@merefield Thank you so much! This was so fast, I’m considering running a subliminal Turing test. :wink:


Glad to see this move to mobile as well as to a theme component! The only thing I couldn’t get to work was


Is ‘true’ the correct value here? I tried absolute and relative links in the thumbnail field, but it wouldn’t show an image either way.

Thanks for your efforts!


So the way the first setting works is that it rescues the view if the thumbnail is not ultimately retrievable (the url fails). This works I believe.

What it doesn’t do is add a thumbnail where there wasn’t one in the first place.

That’s a bug with the second setting. I’ll take a look.

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That’s now fixed.

NB The Theme Component only allows one site wide default.

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Cool, thanks for the quick reponse!


Hi Robert,

we tried to switch to your theme component, but there was a small bug stopping us: We couldn’t adjust the ‘topic list thumbnail resolution level’. Thumbnails would always use the original image, so that they were warped. Could you please have a look?

Thanks so much!

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I checked and it seems to be working. Can you give me more detailed STR?

Is your sidekiq running? There’s a job in core that now creates the thumbnails. You need to be on latest tests passed (for TC not plugin!)

If you look at /latest.json on say, Firefox, you should see multiple entries for thumbnails in each topic that contain an image in the first post. Those are available based on a setting in the Theme Component to specify the range of thumbnail options and the Discourse core code itself. There is no code in the Theme Component aside from the settings that affects this set of available thumbnails.

One point to note however: the default thumbnail is only served at the original resolution. This is because it is not part of the new sidekiq process of creating thumbnails. However you are in control of that image and you can purposefully set it to a lower res image. Also it is shared only once and used multiple times.

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OK new feature for the Theme Component:

This is default ON, disable in theme component settings.


Love this feature! Only problem I seem to have is that it only shows a few from the category, even though there are plenty to use to fill grid of ten. Is there a time limit so it’s only showing the most recent images? Here’s an example, it’s pulling from the editor-pick tag, you can see there are lots of posts with this tag, but it’s only showing five, whereas when you go to latest it shows all ten.

Also, going back to our previous discussion, I first realized that having tags restricted to categories was causing the problem of tags not available in the dropdown, not tag groups. I also realized that making this tag not restricted to categories is not ideal because it’s only supposed to be used in certain categories (which is what I did on my sandbox for now). So if it’s not too much trouble, I would request that this goes back to the other style of category picker where you can type it in to get around this limitation as nobody is responding to the question I raised about this. Thanks!

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Yep, there is a limit. I may find a better way of doing it, but currently it’s a brute force filter of main list by Category.

I’m restricted by the API and paging limits.

Currently, reduce the number from elsewhere and you should see more in this Category.

Also unfortunately some of the array space is wasted by Topics that don’t have images … again that’s API … I can’t get back only Topics with Thumbnails in one retrieve, unless I’m mistaken.


Sorry, my bad! Everything is working fine now. Thanks again for your efforts!


OK, working on something exciting.

I’ve created a complimentary plugin for the Theme Component that adds additional functionality.

So far I’ve added working Thumbnail Picker to the Theme Component based install. For this piece of functionality to work you also need this cut-down plugin. (Please also update your TC)

The experimental plugin is here:

- git clone -b "theme_sidecar"

This adds two advantages:

  1. it modifies the criteria Discourse uses to determine which thumbnails are used by default and accepts more useful smaller thumbnails that would have otherwise been rejected (in my opinion the core criteria are too restrictive).
  2. adds a working thumbnail picker in the Topic meta editor so if you are not happy which one it chooses, you can override it. Functionally this is almost identical to the original plugin version, but it now works with the new Discourse thumbnail production logic.

My goal is to make the Theme Component as stable and feature rich enough to retire the original plugin.

Then, for a basic install you can just add the Theme Component.

If you are self-hosted or on a plan which allows you to add plugins, you can add the complementary plugin to add additional features.

Overall this will minimise maintenance whilst giving more people access to Topic List Previews.

The other significant advantage to the site admin, is that many more superficial changes to the front end won’t require a rebuild as you may only have to update the Theme Component.


after latest discourse update i coudn’t set thumbrails to posts.
is there a bug?

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Pretty exciting! I tried it out and I only see this:

Not sure if it’s related to this:

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