perf: reduce Fleet panel refresh and idle rendering work

CHANGELOG.md

@@ -1,5 +1,17 @@
 # changelog
 
+## unreleased - panel efficiency
+
+- preserved the installed popup's layout, fonts, themes, controls and navigation.
+- kept controls intact on timestamp-only refreshes and reused frozen brushes.
+- replaced frequent file checks with debounced notifications and a recovery timer.
+- paced live-glass handoff to its 60 Hz capture rate while retaining display-rate
+  entrance and exit motion; stopped capture workers before reopening.
+- bounded panel error logs and closed window-owned timers and capture resources.
+- added reproducible, isolated memory, refresh and navigation checks; see
+  [performance checks](docs/performance.md). collectors and account behavior are
+  unchanged.
+
 ## 0.4.1 - 2026-10-26
 
 - changed **Dashboard** to switch pages inside the existing tray popup. removed

docs/performance.md

@@ -0,0 +1,66 @@
+# panel performance checks
+
+Fleet keeps its existing native WPF panel, controls, fonts, themes and collectors.
+The panel reuses frozen brushes, keeps its controls on timestamp-only model
+updates, and watches cache-file notifications with a one-second recovery timer.
+The normal tray-window message path is unchanged. File notifications are debounced
+so creating and writing a request does not toggle the popup twice.
+
+Live glass still captures up to 60 frames per second. Its UI handoff now runs only
+at that rate, instead of subscribing continuously to display-rate rendering.
+Entrance and exit animations retain their display-rate animation. Closing stops
+and joins the capture worker; closing the window disposes its watcher, timers and
+capture resources. Error logging keeps two bounded files and omits exception
+messages that could contain input.
+
+## reproduce
+
+Use a synthetic `panel.json` generated with `panel_model.build`, including
+`summary`, `coverage`, `api_accounts` and dashboard history. Do not copy credentials
+or a user's raw logs into a fixture. Install `pythonnet` and `psutil` in a test
+environment. Both checks require Windows; neither collects provider data.
+
+```powershell
+python scripts/measure-panel.py PANEL_EXE SAMPLE_JSON OUTPUT_DIR 3
+python scripts/check-panel-performance.py PANEL_EXE SAMPLE_JSON OUTPUT_DIR
+python scripts/check-dashboard.py PANEL_EXE SAMPLE_JSON OUTPUT_DIR
+```
+
+Use different output directories for each binary and run. Keep all generated
+artifacts, virtual environments, package caches, TEMP and TMP on the requested
+scratch/output drive. Do not run performance checks concurrently.
+
+`measure-panel.py` starts real standalone panel processes with isolated caches,
+samples fresh-hidden, open and closed-after-open states, then requests graceful
+exit. Its windows stay offscreen and use the real open/close and capture paths.
+It reports private resident memory (USS), total working set, private commit,
+process CPU time, handles and threads separately. CPU time is per process, not a
+percentage of every logical processor.
+
+`check-panel-performance.py` hosts the same assembly in Python/CLR to exercise 100
+timestamp-only refreshes and 100 open/close/navigation cycles. It checks that
+changed content still replaces controls, and that coverage, settings, summary and
+account changes are not lost. Its memory samples include Python/CLR test overhead
+and must not be presented as the standalone app's footprint. Managed allocation
+totals include the host's other managed work. No check forces garbage collection
+or trims the working set.
+
+## acceptance and limits
+
+Compare identical fixtures, display settings, timing and process age. Separate
+startup memory from the memory after interaction. Check late-cycle ranges for
+private resident memory, working set, private commit, kernel handles, GDI objects
+and threads. A short plateau is evidence for that workload, not a guarantee about
+multi-day behavior.
+
+For appearance, render each binary with `--render` against the same synthetic
+model and background. Compare usage, dashboard, settings and expanded-provider
+pages in both themes. Static pixel parity does not by itself prove animation,
+multi-monitor, or live-background parity; use the dashboard interaction check and
+a real desktop smoke check as well.
+
+Unit tests should not depend on a developer's real Credential Manager entries.
+An unisolated provider-enablement test can discover an already-connected admin
+account. For reproducible local tests, mock `api_credentials.read` to return
+`None` around test discovery/execution; credential-specific tests use their own
+mocks. Never clear real credentials to make a test pass.

native/FleetPanel/LiveBackdrop.cs

@@ -16,6 +16,7 @@ internal sealed class LiveBackdrop
         private readonly object gate = new object();
         private Thread thread;
         private volatile bool running;
+        private readonly ManualResetEventSlim stopping = new ManualResetEventSlim(false);
         private int left, top, width, height;
         private byte[] frame;
         private int frameWidth, frameHeight;
@@ -41,6 +42,7 @@ public void Start(int l, int t, int w, int h)
                 totalMs = 0;
             }
             running = true;
+            stopping.Reset();
             thread = new Thread(Run) { IsBackground = true, Name = "fleet-glass" };
             thread.Start();
         }
@@ -56,7 +58,15 @@ public void Move(int l, int t, int w, int h)
             }
         }
 
-        public void Stop() => running = false;
+        public void Stop()
+        {
+            running = false;
+            stopping.Set();
+            // A new open must not revive the previous worker before it exits.
+            // Wake its paced wait immediately; only an in-flight copy can remain.
+            thread?.Join();
+            thread = null;
+        }
 
         /// <summary>The newest frame, if one arrived since the last call.</summary>
         public bool TryTake(ref byte[] target, out int w, out int h, out double lum)
@@ -100,7 +110,7 @@ private void Run()
                     }
                     if (w <= 0 || h <= 0)
                     {
-                        Thread.Sleep(16);
+                        stopping.Wait(16);
                         continue;
                     }
                     var cw = Math.Max(1, w / ScreenCapture.Downscale);
@@ -128,7 +138,7 @@ private void Run()
                     clock.Stop();
                     if (!ok)
                     {
-                        Thread.Sleep(16);
+                        stopping.Wait(16);
                         continue;
                     }
                     // Sixty copies a second while something behind moves: under a blur that
@@ -144,7 +154,7 @@ private void Run()
                     }
                     if (rest >= 1)
                     {
-                        Thread.Sleep((int)Math.Ceiling(rest));
+                        stopping.Wait((int)Math.Ceiling(rest));
                     }
                     lock (gate)
                     {
@@ -174,16 +184,18 @@ private void Run()
 
         private static void Free(ref IntPtr dc, ref IntPtr dib)
         {
-            if (dib != IntPtr.Zero)
-            {
-                Native.DeleteObject(dib);
-                dib = IntPtr.Zero;
-            }
+            // Release the DC's selection before deleting its bitmap. GDI refuses
+            // DeleteObject while the bitmap is still selected into a live DC.
             if (dc != IntPtr.Zero)
             {
                 Native.DeleteDC(dc);
                 dc = IntPtr.Zero;
             }
+            if (dib != IntPtr.Zero)
+            {
+                Native.DeleteObject(dib);
+                dib = IntPtr.Zero;
+            }
         }
     }
 }

native/FleetPanel/Model.cs

@@ -11,6 +11,9 @@ namespace FleetPanel
     internal sealed class PanelData
     {
         public double Ts;
+        // Compare every field except the collection timestamp. Freshness, account
+        // status and coverage timestamps remain part of the displayed content.
+        public string ContentKey;
         public int Live;
         public int Cached;
         public List<Provider> Providers = new List<Provider>();
@@ -27,7 +30,8 @@ internal sealed class PanelData
         public static PanelData Load(string path)
         {
             var text = File.ReadAllText(path);
-            var root = new JavaScriptSerializer { MaxJsonLength = 8 * 1024 * 1024 }.DeserializeObject(text)
+            var serializer = new JavaScriptSerializer { MaxJsonLength = 8 * 1024 * 1024 };
+            var root = serializer.DeserializeObject(text)
                 as Dictionary<string, object>;
             var data = new PanelData();
             if (root == null)
@@ -150,6 +154,8 @@ public static PanelData Load(string path)
                 data.SkippedArchives = Num(coverage, "skipped_zst"); data.LogUpdated = Num(coverage, "updated");
                 data.LogSince = Num(coverage, "since");
             }
+            root.Remove("ts");
+            data.ContentKey = serializer.Serialize(root);
             return data;
         }