mpvpaper: picker regenerates thumbnails already present on disk

[haimingz]

Summary

The Video Wallpaper picker regenerates thumbnails that already exist on disk every time the picker is opened or reloaded.

Environment

• Noctalia: v5.0.0-beta.9-dirty
• Video Wallpaper: noctalia/mpvpaper 1.1.1
• Cache directory: ~/.cache/noctalia/mpvpaper

Reproduction

1. Configure a video directory containing one or more non-GIF videos.
2. Open the Video Wallpaper picker and wait until thumbnails are generated.
3. Close and reopen (or reload) the picker.

Actual behavior

The picker starts a new mpv --frames=1 --vo=image extraction for every video and overwrites its existing JPG cache entry.

On my system, the cache already contained 348 JPGs, yet opening the picker started 9 active extraction processes and created new .jpg.d temporary directories.

Expected behavior

If cachePath(video.path) exists, use it immediately and do not queue an mpv extraction.

Cause

In mpvpaper/panel.luau, queueThumb() only checks the panel-local thumbPaths and thumbPending tables:

if thumbPaths[video.path] ~= nil or thumbPending[video.path] then
  return
end
table.insert(thumbQueue, video.path)
pumpThumbQueue()

Those tables start empty when the panel is loaded, so an existing on-disk cache is never restored.

A minimal fix is to check the disk cache before enqueueing:

local cached = cachePath(video.path)
if noctalia.fileExists(cached) then
  thumbPaths[video.path] = cached
  return
end

This retains the current cache-key behavior; it intentionally does not invalidate a source video replaced at the same path.