fixed and improved ui

Common/Client/go/wshub/history.go

@@ -422,6 +422,26 @@ func (hw *historyWriter) window() float64 {
 	return hw.windowSec
 }
 
+// coversWindow reports whether the archive file for key currently spans at
+// least sec seconds. When true, backfillCaptureHead can reconstruct a capture's
+// front out of the archive, so the trigger need not wait for the ring to cover
+// the whole window on its own.
+func (hw *historyWriter) coversWindow(key string, sec float64) bool {
+	if !hw.enabled() || !(sec > 0) {
+		return false
+	}
+	hw.mu.RLock()
+	hf, ok := hw.files[key]
+	hw.mu.RUnlock()
+	if !ok {
+		return false
+	}
+	hf.mu.RLock()
+	span := hf.tNewest - hf.tOldest
+	hf.mu.RUnlock()
+	return span >= sec
+}
+
 // setWindow points the archive at the timespan the clients are looking at, and
 // re-sizes the files that no longer match it. It reports whether any file's
 // geometry changed, which invalidates what clients know about the archive.