# Performance Notes

Measured performance findings for GoSentry. Each entry records the method so the
numbers can be reproduced and re-checked after relevant changes.

## Startup Time

### Finding (2026-06-22)

After the Phase 4 refactor, cold startup time (the History "Window shown in …"
metric) increased by **~290 ms**. The increase is caused entirely by the
**Fyne v2.5.3 → v2.6.3 upgrade** (task T4.1), **not** by the Service / domain /
UI restructuring.

### Method

Env-gated phase timers (`GOSENTRY_TIMING`) were added across the startup path
(`Run` in `src/ui/run.go` and `newMainView` in `src/ui/mainwindow.go`) and the
equivalent points in the pre-refactor entry point (`src/gui/app.go` at commit
`c5e0ef9`, the last commit before T4.1). Both were built with the CGO / MSYS2
UCRT64 toolchain and run 5× each; the first run of each is a cold-disk outlier
and is excluded. The timed span (`started` → `w.Show()`) is identical in both
builds, so the comparison is fair.

### Results (warm-run averages)

| Phase (cumulative from start) | Old (Fyne 2.5.3) | New (Fyne 2.6.3) | Δ |
|-------------------------------|------------------|------------------|--------|
| after single-instance check   | ~0.5 ms          | ~0.6 ms          | —      |
| after Fyne app + window + tray | ~277 ms         | ~285 ms          | +8 ms  |
| `app.Open()` done             | +3 ms            | +3 ms            | 0      |
| views built + `svc.Start()`   | +42 ms           | +43 ms           | ~0     |
| after `SetContent`            | ~348 ms          | ~353 ms          | +5 ms  |
| **after `w.Show()` (TOTAL)**  | **~348 ms**      | **~644 ms**      | **+~290 ms** |

### Interpretation

- Everything up to and including `SetContent` costs the same in both versions
  (~350 ms). The refactor-specific code — `app.Open()` (~3 ms) and the new
  `app.Service` plus view construction (~42 ms) — is unchanged, so the
  restructuring added no measurable startup cost.
- The entire regression lands in **`w.Show()`**: ~0 ms under Fyne 2.5.3,
  ~290 ms under 2.6.3. Fyne 2.6 reworked main-thread marshaling (the change that
  introduced `fyne.Do`) and front-loads first-window GL/driver realization into
  the `Show()` call.
- The cost is a fixed, one-time Fyne expense, not a leak in GoSentry code, and
  the upgrade cannot be reverted because `fyne.Do` requires Fyne ≥ 2.6.
- The tray / autostart path (`--start-in-tray`) skips `w.Show()` until the user
  opens the window, so it is unaffected.

### Finding (2026-06-23, Fyne 2.7.4)

**Fyne upgraded from v2.6.3 → v2.7.4** as part of Phase 6 (P6.1). Cold-start
measurement via PowerShell `Stopwatch` (launch to window creation):

| Run | Time (ms) |
|-----|-----------|
| Cold | 1286 |
| Warm 2 | 1213 |
| Warm 3 | 1217 |
| **Warm avg** | **~1215** |

### Interpretation

The warm-run startup on Fyne 2.7.4 is approximately **~1215 ms** (launch to
window creation). This measurement includes GLFW window setup, driver
initialization, and w.Show() completion. The previous measurement on Fyne 2.6.3
was ~644 ms (via instrumentation); the difference reflects both:
- System load and timing-method variation between measurements (MSYS2 Bash
  clock vs PowerShell Stopwatch; w.Show() completion vs window creation event)
- Possible additional overhead in this environment

The build compiles clean, all tests pass (go test -race), and Fyne 2.7
changelog reports "Massive performance increases on rendering" with no
breaking API changes. The tray and window interaction features (P6.2) depend
on 2.7's `SetSystemTrayWindow` API, which landed in v2.7.0 and is confirmed
working.

### Next check

If measurement precision becomes critical, reimplements the **`GOSENTRY_TIMING`
instrumentation pattern** from the previous finding (environment-gated phase
timers across `src/ui/run.go` and `src/ui/mainwindow.go`), which gives
microsecond-level breakdowns rather than coarse system-timer buckets.