Merge pull request 'perf(web): cache macro images in local PWA (1.1.2)' (#12) from perf/local-image-cache into main

config.py

@@ -1,6 +1,6 @@
 # Configuration and constants for MacroPad Server
 
-VERSION = "1.1.1"
+VERSION = "1.1.2"
 DEFAULT_PORT = 40000
 SETTINGS_FILE = "settings.json"
 

version.txt

@@ -1 +1 @@
-1.1.1
+1.1.2

web/js/app.js

@@ -34,8 +34,10 @@ class MacroPadApp {
         // Guards against out-of-order macro fetches
         this._macroReqId = 0;
 
-        // Blob object URLs created for macro images (revoked on re-render)
-        this._objectUrls = [];
+        // Cache of image URL -> Promise<objectURL>. Macro images are
+        // content-addressed by uuid filename, so they are immutable; caching
+        // avoids re-fetching every image on each re-render.
+        this._imageCache = new Map();
 
         // Set once a local-mode auth failure has been surfaced, to avoid
         // reconnect loops and repeated toasts.
@@ -451,16 +453,12 @@ class MacroPadApp {
         return headers;
     }
 
-    // Fetch a macro image with the auth header and display it as a blob
-    // object URL, so no credential is ever placed on an <img> src.
+    // Fetch a macro image with the auth header and display it as a blob object
+    // URL, so no credential is ever placed on an <img> src. The fetched blob is
+    // cached (images are immutable per URL) and reused across re-renders.
     async loadMacroImage(url, img, placeholder) {
         try {
-            const res = await fetch(url, { headers: this.getAuthHeaders() });
-            if (!res.ok) throw new Error('image request failed');
-            const blob = await res.blob();
-            const objectUrl = URL.createObjectURL(blob);
-            // Track for best-effort revocation on the next render.
-            this._objectUrls.push(objectUrl);
+            const objectUrl = await this._getImageUrl(url);
             img.src = objectUrl;
         } catch (e) {
             // Fall back to the placeholder if the image can't be loaded.
@@ -469,6 +467,23 @@ class MacroPadApp {
         }
     }
 
+    // Returns a cached Promise<objectURL> for an image URL, fetching once and
+    // retaining it for the page's lifetime (immutable content, nothing to
+    // invalidate); de-duplicates concurrent requests too.
+    _getImageUrl(url) {
+        let entry = this._imageCache.get(url);
+        if (entry) return entry;
+        entry = (async () => {
+            const res = await fetch(url, { headers: this.getAuthHeaders() });
+            if (!res.ok) throw new Error('image request failed');
+            const blob = await res.blob();
+            return URL.createObjectURL(blob);
+        })();
+        entry.catch(() => this._imageCache.delete(url));
+        this._imageCache.set(url, entry);
+        return entry;
+    }
+
     // Rendering (safe DOM construction only - no user value reaches innerHTML)
     renderTabs() {
         const container = document.getElementById('tabs-container');
@@ -492,12 +507,6 @@ class MacroPadApp {
         const container = document.getElementById('macro-grid');
         if (!container) return;
 
-        // Best-effort: revoke object URLs from the previous render to avoid leaks.
-        if (this._objectUrls && this._objectUrls.length) {
-            this._objectUrls.forEach((u) => URL.revokeObjectURL(u));
-        }
-        this._objectUrls = [];
-
         container.textContent = '';
 
         const macroEntries = Object.entries(this.macros);

web_server.py

@@ -338,7 +338,11 @@ class WebServer:
             # Only serve files that resolve to inside the macro_images directory
             if (os.path.commonpath([requested, images_real]) == images_real
                     and os.path.isfile(requested)):
-                return FileResponse(requested)
+                # Macro images are content-addressed (uuid filenames) and thus
+                # immutable, so let the browser cache them aggressively.
+                return FileResponse(requested, headers={
+                    "Cache-Control": "private, max-age=31536000, immutable"
+                })
             raise HTTPException(status_code=404, detail="Image not found")
 
         @app.websocket("/ws")