338354c4d0
Avoid synchronous child counts during item construction, use extension-based MIME detection for initial scans, and defer expensive MIME icon resolution by using generic file icons for ordinary files. Document the local xdg-desktop-portal FileChooser workaround for COSMIC portal crashes.
78 lines
2.7 KiB
Markdown
78 lines
2.7 KiB
Markdown
# Local performance and portal notes
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Date: 2026-05-05
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This repository carries a local patch aimed at improving initial directory
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display latency in large folders, plus a system-level workaround for a COSMIC
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portal FileChooser crash observed with Firefox and Chromium.
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## Directory listing latency
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The slow path was the initial construction of `Item` values in `src/tab.rs`.
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On a test folder with about 2000 entries, raw filesystem enumeration and stat
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calls completed in a few milliseconds, while COSMIC Files took multiple seconds
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before showing the directory.
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The local patch keeps initial item construction cheap:
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- directory child counts are no longer computed synchronously in
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`item_from_entry` and `item_from_gvfs_info`;
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- initial MIME detection uses extension-based `mime_guess`;
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- regular files use a generic file icon during the initial scan instead of
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resolving the full MIME icon immediately.
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This keeps folders and `.desktop` files special-cased, while avoiding expensive
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per-file work for ordinary files during first paint.
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Measured locally during investigation:
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- before the MIME/icon changes: about 3.1 seconds for `~/Téléchargements`;
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- after avoiding full MIME icon resolution during scan: below the temporary
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100 ms perf-log threshold for the same folder.
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## File chooser portal workaround
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Firefox and Chromium were failing to open `Save As` on the first attempt because
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`xdg-desktop-portal-cosmic` crashed while handling `FileChooser`.
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Logs showed:
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```text
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Backend call failed: Remote peer disconnected
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xdg-desktop-portal-cosmic ... status=11/SEGV
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```
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The working local system workaround is to remove
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`org.freedesktop.impl.portal.FileChooser` from:
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```text
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/usr/share/xdg-desktop-portal/portals/cosmic.portal
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```
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so the file chooser falls back to GTK. The resulting local `cosmic.portal`
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keeps COSMIC for the other interfaces:
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```ini
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[portal]
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DBusName=org.freedesktop.impl.portal.desktop.cosmic
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Interfaces=org.freedesktop.impl.portal.Access;org.freedesktop.impl.portal.Screenshot;org.freedesktop.impl.portal.Settings;org.freedesktop.impl.portal.ScreenCast
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UseIn=COSMIC
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```
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Backups created locally:
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```text
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/usr/share/xdg-desktop-portal/portals/cosmic.portal.bak-codex-20260505-filechooser
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/usr/share/xdg-desktop-portal/cosmic-portals.conf.bak-codex-20260505
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/usr/share/xdg-desktop-portal/cosmic-portals.conf.bak-codex-20260505-2
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```
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After editing portal files, restart:
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```sh
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systemctl --user restart xdg-desktop-portal.service xdg-desktop-portal-gtk.service
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```
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Package updates may overwrite `/usr/share/xdg-desktop-portal/portals/cosmic.portal`.
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If `Save As` starts needing two attempts again, re-check that `FileChooser` has
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not been reintroduced in `cosmic.portal`.
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