Theme-Modifikatoren: Eine kurze Einführung

Da Themes immer ambitionierter werden, haben wir nach Wegen gesucht, ihnen die Möglichkeit zu geben, das Kernverhalten auf der Serverseite zu manipulieren. Obwohl sie niemals die gleiche Kontrolle wie Plugins erhalten werden, können wir einige vordefinierte Hooks bereitstellen, die Themes manipulieren können.

Wir stellen vor: Theme-Modifikatoren :partying_face:

Sie werden mit dem Schlüssel modifiers in der about.json-Datei Ihres Themes angegeben.

Für eine 100% aktuelle Liste der Modifikatoren, siehe das Datenbankschema am Ende von theme_modifier_set.rb, aber hier ist eine kurze Zusammenfassung dessen, was wir bisher haben:

  • serialize_topic_excerpts boolean (Standard: false) - fügt beim Serialisieren von Themenlisten immer Auszüge hinzu

  • csp_extensions String-Array - fügt dem CSP Direktiven hinzu. Funktioniert genauso wie die alte Methode „extend_content_security_policy“ der Theme-Einstellung. Aber denken Sie daran, einfache \u003cscript src=\"\"\u003e-Tags sind automatisch erlaubt.

  • svg_icons String-Array - eine Liste von Icons, die in den Icon-Subset aufgenommen werden sollen

  • topic thumbnails Array von Dimensionen - fordert zusätzliche Auflösungen im Topic-Thumbnail-Set an. Beachten Sie, dass diese asynchron generiert werden. Sie müssen also auf das ursprüngliche Bild zurückgreifen, falls Ihre angeforderte Größe nicht bereitgestellt wird. Weitere Informationen finden Sie in der Commit-Nachricht

  • serialize_post_user_badges String-Array - eine Liste von Badges-Namen (die Einträgen in der Badges-Tabelle entsprechen), die zusammen mit den Post-Daten serialisiert werden sollen. Bei Konfiguration fügt das System die angegebenen Benutzer-Badges jedem Post für das Client-seitige Rendern hinzu.

Ein Theme, das diese neuen Hooks intensiv nutzt, ist Topic List Thumbnails – schauen Sie sich den Code an, um zu sehen, wie es funktioniert.

Einstellungsabhängige Modifikatoren

Theme-Modifikatoren können auch so konfiguriert werden, dass sie ihren Wert aus einer Theme-Einstellung beziehen. Dies ermöglicht es Site-Betreibern, das Modifikatorverhalten zu überschreiben, ohne den Code des Themes bearbeiten zu müssen. Um einen Modifikator von einer Einstellung abhängig zu machen, verwenden Sie diese Syntax in Ihrer about.json:

{
  "modifiers": {
    "modifier_name": {
      "type": "setting",
      "value": "setting_name"
    }
  }
}

Wenn Sie beispielsweise eine Theme-Einstellung namens show_excerpts haben und diese den Modifikator serialize_topic_excerpts steuern soll:

In settings.yml:

show_excerpts:
  default: false

In about.json:

{
  "modifiers": {
    "serialize_topic_excerpts": {
      "type": "setting",
      "value": "show_excerpts"
    }
  }
}

Wenn die Einstellung show_excerpts geändert wird, aktualisiert sich der Modifikatorwert automatisch entsprechend. Dies bietet Site-Betreibern Flexibilität, das Theme-Verhalten über die Admin-UI anzupassen.


\u003csmall\u003eDieses Dokument wird versioniert – schlagen Sie Änderungen auf github vor.\u003c/small\u003e

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David, probably a bit lazy of me to ask but is there any way to access this in a plugin:

Themes can request additional thumbnail sizes by using a modifier in their about.json file:

I will be attempting to migrate the TLP plugin to this new schema and it would be good to have the same access to features from a plugin, at least in the meantime.

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There isn’t at the moment, but I’ll look into it :eyes:

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David, what’s the right approach for BULK recreation of thumbnails?

I’ve just tried utilising on one of my sites and it seems to have processed about 10% of the Topics … then given up (or turned its nose up at the rest). Why I think it’s the former is that the Topics for whom Thumbnails were produced were the latest 10%.

Rebaking posts doesn’t seem to cut it. In fact, I did run a bulk rebake and wonder if that upset it …

I notice that image_url can be populated, but there are no thumbnails.

Any advice, appreciated!

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That column doesn’t do anything, and will be dropped very soon. image_upload_id is the one you want.

There should be no need for this. I deliberately designed it so that people can install new themes without having to mess around on the console. Thumbnails are generated asynchronously when needed. For example:

  • you add a new theme, which requests new resolutions
  • a user requests a topic, we serve the thumbnails that exist. If any sizes don’t exist, we schedule a sidekiq job.
  • next time someone requests the topic, the correct thumbnails will exist

If the requested thumbnail size is larger than the original, we won’t bother generate the thumbnail.

So the critical thing to bear in mind for this to work is:

There’s an example of this fallback logic in the thumbnail theme component I made - feel free to steal logic from there.

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The fallback is serialised as thumbnailsl[0]? Yes, I’m already handling that. (nice implementation btw, very easy to handle)

Is it possible some images are ‘not making the grade’ or fitting the criteria?

The behaviour we have in the TLP plugin will pick up one-box thumbnails. That’s not happening in every case here I think.

For example, if you get time, take a look at these examples:

I don’t think these thumbnails make the cut. The thumbnails are serialized as null

Yes that’s deliberate - we had a number of requests to remove small onebox thumbnails. For example, people were ending up with their github avatar as a topic thumbnail - which is rarely intended

https://github.com/discourse/discourse/commit/956d15d13fd8056cbf60ca64ebbd1edca00d0125

Note that for oneboxes where the image is the actual content (such as instagram/twitter/etc photos), they will be selected.

As for the youtube video, I fixed that yesterday.

https://github.com/discourse/discourse/commit/0c6f30d92a4090aa7447e2e579a17a180e49ce17

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Ah great, thanks for confirmation.

That’s odd, build was more recent, but some still seem to be being overlooked.

Yeah, that’s partly why I ended up implementing a thumbnail picker for the situations where the automated choice wasn’t optimal. I may still want to modify that behaviour, but I will try to do so in the plugin.

Thanks for your time David!

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OK, I’ve worked it out. After a somewhat fruitless byebug session I could not work out why older YT posts were not getting thumbnails.

Then is dawned on me. It’s because of this:

So I suggest that actually it might be necessary to rebake after setting this to a rather larger number (365?).

I think I’m right in saying that if something is not uploaded locally, it won’t have a thumbnail created? …

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:+1: correct, this only works for local uploads… we may need to rethink that “max days old” setting :thinking:

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I have a plan, will try and get it implemented this week. One question - do you need the values to be dynamic?

i.e. Will the resolutions be defined at boot? Or at runtime (e.g. via site settings)?

The former is easier… but the latter might be possible as well :thinking:

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Thanks for taking a look.

I just need a fixed way, exactly like the theme component.

A site setting would be nice though.

I will add for full disclosure: id like to migrate away from the plugin so parity with theme component solution would be more than enough.

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@merefield here you go:

Hopefully the commit message explains how it works, but let me know if you have any questions

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Excellent. Just added it to TLP and looks like it’s working! Thanks for your help!

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4 posts were split to a new topic: Getting thumbnails from json endpoints

Can we make it work for images from remote server as well? For example, images from Blogger, Picasa, or Amazon S3?

Because Discourse supports hosting on Amazon S3 for big and large image site, now if everything needs to be hosted on the local server directly then this design methodology seems to be a drawback.

With this update, it’s not an easy fix for my site since we’re using other server to host the images. Now it’s too difficult to move to an affiliated server with many posts, while it’s too big for hosting on local sever.

This is only designed to work on Discourse ‘uploads’. Those can be on S3, or some other service, if you use

We recommend using the download_remote_images site setting to automatically download images which are hotlinked from other sites.

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Hi David, anything special one needs to do to ensure Pro icons can be used in a TC?

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Nothing special, no. It should work just the same as using pro icons elsewhere in Discourse. I guess you are using this plugin to enable pro icons?

If it doesn’t work let me know and I’ll take a look :eyes:

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Yep we are. We’ll have another dig. Thanks for response late your eve!

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