From 0fe9a2ce63547ffdb21b6eb328b35b1e04577b44 Mon Sep 17 00:00:00 2001
From: Sander Schobers <sander@schobers.eu>
Date: Mon, 18 May 2020 21:01:17 +0200
Subject: [PATCH] Added FPS counter.

---
 play/fps.go | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 play/fps.go

diff --git a/play/fps.go b/play/fps.go
new file mode 100644
index 0000000..3ea40d4
--- /dev/null
+++ b/play/fps.go
@@ -0,0 +1,56 @@
+package play
+
+import (
+	"fmt"
+	"time"
+
+	"opslag.de/schobers/geom"
+	"opslag.de/schobers/zntg"
+
+	"opslag.de/schobers/zntg/ui"
+)
+
+type FPS struct {
+	ui.ControlBase
+
+	update zntg.Animation
+	i      int
+	frames []int
+	total  int
+}
+
+func (f *FPS) Shown() {
+	f.update.Interval = 20 * time.Millisecond
+	f.update.Start()
+	f.i = 0
+	f.frames = make([]int, 51)
+	f.total = 0
+}
+
+func (f *FPS) Hidden() {
+	f.update.Pause()
+}
+
+func (f *FPS) font(ctx ui.Context) ui.Font {
+	font := ctx.Fonts().Font("debug")
+	if font != nil {
+		return font
+	}
+	return ctx.Fonts().Font("default")
+}
+
+func (f *FPS) Render(ctx ui.Context) {
+	_, n := f.update.AnimateDelta()
+	for i := 0; i < n; i++ {
+		f.total += f.frames[f.i]
+		f.i = (f.i + 1) % len(f.frames)
+		f.total -= f.frames[f.i]
+		f.frames[f.i] = 0
+	}
+	f.frames[f.i]++
+
+	font := f.font(ctx)
+	fps := fmt.Sprintf("FPS: %d", f.total)
+	ctx.Renderer().Text(font, geom.PtF32(5, 5), ctx.Style().Palette.Background, fps)
+	ctx.Renderer().Text(font, geom.PtF32(4, 4), ctx.Style().Palette.Text, fps)
+}