fix(imageCache): improve cache management & file handling

quickshell/Common/CacheUtils.qml

@@ -7,17 +7,62 @@ import qs.Common
 Singleton {
     id: root
 
+    // Filenames present on disk, so CachingImage never points an Image at a
+    // missing cache file (Qt logs that as a "Cannot open" warning).
+    property var cachedFiles: ({})
+
+    Component.onCompleted: scan()
+
+    function scan() {
+        Proc.runCommand("imagecache_scan", ["ls", "-1", Paths.stringify(Paths.imagecache)], function (output, exitCode) {
+            const map = {};
+            if (exitCode === 0 && output) {
+                const lines = output.split("\n");
+                for (var i = 0; i < lines.length; i++) {
+                    const name = lines[i].trim();
+                    if (name)
+                        map[name] = true;
+                }
+            }
+            root.cachedFiles = map;
+        });
+    }
+
+    function hasCachedFile(name) {
+        return name ? root.cachedFiles[name] === true : false;
+    }
+
+    function recordCachedFile(name) {
+        if (name)
+            root.cachedFiles[name] = true;
+    }
+
+    function forgetCachedFile(name) {
+        if (name && root.cachedFiles[name] !== undefined)
+            delete root.cachedFiles[name];
+    }
+
     function clearImageCache() {
         Quickshell.execDetached(["rm", "-rf", Paths.stringify(Paths.imagecache)]);
         Paths.mkdir(Paths.imagecache);
+        root.cachedFiles = ({});
     }
 
     function clearOldCache(ageInMinutes) {
-        Quickshell.execDetached(["find", Paths.stringify(Paths.imagecache), "-name", "*.png", "-mmin", `+${ageInMinutes}`, "-delete"]);
+        // Rescan on delete completion since we can't know which files matched.
+        Proc.runCommand("imagecache_prune", ["find", Paths.stringify(Paths.imagecache), "-name", "*.png", "-mmin", `+${ageInMinutes}`, "-delete"], function (output, exitCode) {
+            root.scan();
+        });
     }
 
     function clearCacheForSize(size) {
         Quickshell.execDetached(["find", Paths.stringify(Paths.imagecache), "-name", `*@${size}x${size}.png`, "-delete"]);
+        const suffix = `@${size}x${size}.png`;
+        const map = {};
+        for (const key in root.cachedFiles)
+            if (!key.endsWith(suffix))
+                map[key] = true;
+        root.cachedFiles = map;
     }
 
     function getCacheSize(callback) {