# Local performance and portal notes

Date: 2026-05-05

This repository carries a local patch aimed at improving initial directory
display latency in large folders, plus a system-level workaround for a COSMIC
portal FileChooser crash observed with Firefox and Chromium.

## Directory listing latency

The slow path was the initial construction of `Item` values in `src/tab.rs`.
On a test folder with about 2000 entries, raw filesystem enumeration and stat
calls completed in a few milliseconds, while COSMIC Files took multiple seconds
before showing the directory.

The local patch keeps initial item construction cheap:

- directory child counts are no longer computed synchronously in
  `item_from_entry` and `item_from_gvfs_info`;
- initial MIME detection uses extension-based `mime_guess`;
- regular files use a generic file icon during the initial scan instead of
  resolving the full MIME icon immediately.

This keeps folders and `.desktop` files special-cased, while avoiding expensive
per-file work for ordinary files during first paint.

Measured locally during investigation:

- before the MIME/icon changes: about 3.1 seconds for `~/Téléchargements`;
- after avoiding full MIME icon resolution during scan: below the temporary
  100 ms perf-log threshold for the same folder.

## File chooser portal workaround

Firefox and Chromium were failing to open `Save As` on the first attempt because
`xdg-desktop-portal-cosmic` crashed while handling `FileChooser`.

Logs showed:

```text
Backend call failed: Remote peer disconnected
xdg-desktop-portal-cosmic ... status=11/SEGV
```

The working local system workaround is to remove
`org.freedesktop.impl.portal.FileChooser` from:

```text
/usr/share/xdg-desktop-portal/portals/cosmic.portal
```

so the file chooser falls back to GTK. The resulting local `cosmic.portal`
keeps COSMIC for the other interfaces:

```ini
[portal]
DBusName=org.freedesktop.impl.portal.desktop.cosmic
Interfaces=org.freedesktop.impl.portal.Access;org.freedesktop.impl.portal.Screenshot;org.freedesktop.impl.portal.Settings;org.freedesktop.impl.portal.ScreenCast
UseIn=COSMIC
```

Backups created locally:

```text
/usr/share/xdg-desktop-portal/portals/cosmic.portal.bak-codex-20260505-filechooser
/usr/share/xdg-desktop-portal/cosmic-portals.conf.bak-codex-20260505
/usr/share/xdg-desktop-portal/cosmic-portals.conf.bak-codex-20260505-2
```

After editing portal files, restart:

```sh
systemctl --user restart xdg-desktop-portal.service xdg-desktop-portal-gtk.service
```

Package updates may overwrite `/usr/share/xdg-desktop-portal/portals/cosmic.portal`.
If `Save As` starts needing two attempts again, re-check that `FileChooser` has
not been reintroduced in `cosmic.portal`.