debounce tracklist row rendering when fast scrolling

ui/util/eventcounter.go

@@ -0,0 +1,43 @@
+package util
+
+import (
+	"time"
+)
+
+type EventCounter struct {
+	buf []time.Time
+	ptr int
+}
+
+func NewEventCounter(maxN int) *EventCounter {
+	buffer := make([]time.Time, maxN)
+	return &EventCounter{
+		buf: buffer,
+	}
+}
+
+func (e *EventCounter) Add() {
+	e.buf[e.ptr] = time.Now()
+	e.ptr = (e.ptr + 1) % len(e.buf)
+}
+
+func (e *EventCounter) NumEventsSince(t time.Time) int {
+	i := e.ptr - 1
+
+	count := 0
+	for {
+		if i < 0 {
+			i = len(e.buf) - 1
+		}
+		if !e.buf[i].IsZero() && e.buf[i].After(t) {
+			count++
+		} else {
+			break
+		}
+		if count == len(e.buf) {
+			break
+		}
+		i--
+	}
+	return count
+}