Backgrounds

A background is a small animated document that runs behind one region of the IDE. It comes from a plugin, so picking one is a click, not code.

Picking one#

Open the Theme tab and choose Background — it sits right after Wallpaper. Or, from a card in Settings → Plugins, press Pick background.

1. Choose a Region: Header, Tabs, Left panel, Main content or Right panel. A ● beside a region means it already holds something. The count on the right says how many backgrounds are built for that region.
2. Click a card. Every card is running the real thing, so what you see is what you get. The first card, None (Bare floor), clears the region.

The choice applies at once. Like everything else on the Theme tab it is part of your theme draft, so save the theme to keep it — see Saving, sharing and the share card.

It travels with the theme. A saved theme stores a reference to the plugin's background, not the background itself. Share the theme with someone who has the same plugin and they see the same thing. Without it, the page says This theme asks for <plugin>, which is not installed. and nothing runs.

What it shows through#

A background is behind the region, not on top of it. How much of it you see depends on the Glass page: turn the panel and surface opacity down and it comes through.

The Main content region exists only while the 3D view is on screen. While you're looking at the Theme tab, the page says Not running right now — close Settings to see it run.

A background or your own HTML — one per region#

Each region holds one thing: a plugin's background, or a document you wrote yourself on the Section CSS page (see Wallpaper and custom code). Not both.

If a region already runs hand-written HTML, the Background page won't overwrite it with a click. It says <Region> runs hand-written HTML. and offers Open Custom code to go and look at it, or Discard it to clear it and pick a background instead.

One difference worth knowing: a plugin background travels with an exported theme, as a reference. Hand-written HTML does not.

When it misbehaves#

A background is sandboxed — no network, no files, no clicks — but a badly written one can still stall the window with a loop that never ends. Semantix watches for that.

• After a stall, the next run holds every background back and says so: Backgrounds are held back this run., with how long the window stopped. Nothing is lost; your pick is still saved. Press Re-enable when you've fixed or replaced it.
• The master switch is Run custom HTML, at the foot of the Section CSS page. Off, every background and every hand-written document is remembered but not run, and the Background page shows Custom HTML is switched off. with Switch on beside it.

Backgrounds pause when they're off screen or the window is minimized, and stay still if your system asks for reduced motion.

Making your own#

A background is the simplest plugin there is: a plugin.json and one HTML file. See Writing a plugin.