ARC Hover Sidebar

An ARC-browser-style sidebar for Obsidian: sweep the mouse to the left edge of the window and the sidebar slides out; swipe right and it slides back.

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Demo

What it does

The sidebar is opened and collapsed through Obsidian's own leftSplit.expand() / collapse() API — not faked with CSS — so its width, colours and content layout are exactly the same as when you open it yourself.

It also reuses the theme's built-in "hover to reveal the ribbon" behaviour (by overriding a single CSS variable, leaving your theme files untouched).

Installation

Manual

1. Download main.js and manifest.json from this repository.
2. Put them in <vault>/.obsidian/plugins/arc-hover-sidebar/.
3. Add "arc-hover-sidebar" to <vault>/.obsidian/community-plugins.json.
4. Reload Obsidian and enable the plugin under Settings → Community plugins.

BRAT

BRAT can install it from this repository: add https://github.com/goodends/arc-hover-sidebar in BRAT's plugin list.

Settings

Settings → Community plugins → ARC Hover Sidebar

• Enable hover sidebar — master switch. When off, the plugin stops interfering with the sidebar entirely.
• Unified open/close — when on, a sidebar you opened yourself is also managed by the plugin, and always closes the same way: swipe horizontally past the sidebar's right edge.
• Sync ribbon — when on, the ribbon (the icon bar on the left) is hidden and shown together with the sidebar.

Tunable parameters (getters at the top of main.js)

Implementation notes

• The trigger is purely geometric — no velocity check (like ARC):
  • position: the mouse enters the leftmost edgeZone pixels of the window;
  • path: this frame moved leftwards and the path crossed the trigger zone (covers the case where the mouse crosses the whole zone within a single frame).
• Singleton guard: if a stale instance is still around when the plugin loads, it is unloaded first. Two instances fighting over the sidebar make it flicker open and closed.
• Cold-start guard: leftSplit does not exist before the layout is ready, so .collapsed must not be read in onload — doing so throws and the plugin fails to load.
• Polling fallback: expand() / collapse() take effect asynchronously and may not emit events around the transition, so a 400ms poll keeps the state in sync.
• Drag guard: the sidebar is not collapsed while you are dragging its resize handle — otherwise you could never resize it.
• Blur guard: switching to another application collapses the sidebar, and no hover expansion happens while the window is unfocused.

Known trade-offs

• Any mouse movement within edgeZone of the left edge pops the sidebar out. If you only wanted to click a ribbon icon, the sidebar comes out too — reduce edgeZone.
• A larger trigger zone means fast strokes near the left edge trigger it more easily: it is a trade-off between the hot zone and sensitivity.
• Desktop only (isDesktopOnly: true).

Development

There is no build step — main.js is the entire plugin. For local development, symlink the repository's main.js and manifest.json into <vault>/.obsidian/plugins/arc-hover-sidebar/; changes take effect after disabling and re-enabling the plugin in Obsidian.

Development conventions are described in CLAUDE.md.

License

MIT