Files: previews — a toggle that shows a thumbnail per image and video, made by ffmpeg on the machine's GPU where it has one, cached under the data dir

A previews button on the Files tab turns the icon column into a 256 px thumbnail for
every image and video row, loaded as rows scroll near. internal/thumbs probes what the
machine can do rather than assuming it: ffmpeg and ffprobe, every /dev/dri/renderD*
opened and exercised, vainfo's decode profiles per node where it exists. A video goes to
the first GPU that lists its codec, with ffmpeg's own software fallback behind it and a
CPU retry behind that; images decode on the CPU, JPEGs at a reduced DCT size. Previews
are kept under <data dir>/thumbs/ keyed by path, size and mtime, with undecodable files
remembered too. Root mode makes them through the same root helper the file reads use.
Where ffmpeg is missing the tab offers to install it; where a render node exists but is
closed to the daemon's user, it offers a drop-in adding the group and a restart.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/files/files.go

@@ -24,19 +24,21 @@ import (
 	"time"
 
 	"hamlab/internal/priv"
+	"hamlab/internal/thumbs"
 )
 
 type Entry struct {
-	Name   string `json:"name"`
-	Type   string `json:"type"` // dir | file | link | other
-	Size   int64  `json:"size"`
-	Mode   string `json:"mode"` // "-rw-r--r--"
-	Perm   string `json:"perm"` // "0644"
-	Mtime  int64  `json:"mtime"`
-	User   string `json:"user"`
-	Group  string `json:"group"`
-	Target string `json:"target,omitempty"` // link target
-	Broken bool   `json:"broken,omitempty"` // dangling link
+	Name    string `json:"name"`
+	Type    string `json:"type"` // dir | file | link | other
+	Size    int64  `json:"size"`
+	Mode    string `json:"mode"` // "-rw-r--r--"
+	Perm    string `json:"perm"` // "0644"
+	Mtime   int64  `json:"mtime"`
+	User    string `json:"user"`
+	Group   string `json:"group"`
+	Target  string `json:"target,omitempty"`  // link target
+	Broken  bool   `json:"broken,omitempty"`  // dangling link
+	Preview string `json:"preview,omitempty"` // "image" | "video": the Files tab can show a thumbnail of it
 }
 
 type Listing struct {
@@ -146,6 +148,9 @@ func entryOf(dir, name string, lst os.FileInfo) Entry {
 	default:
 		e.Type = "other"
 	}
+	if e.Type == "file" || (e.Type == "link" && !e.Broken) {
+		e.Preview = thumbs.Kind(name)
+	}
 	return e
 }