feat(tracker): show CPU load percentage in the song panel

CHANGELOG.md

@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 ### Added
+- Show CPU load percentage in the song panel ([#192][i192])
 - Theme can be user configured, in theme.yml. This theme.yml should be placed in
   the usual sointu config directory (i.e.
   `os.UserConfigDir()/sointu/theme.yml`). See
@@ -332,3 +333,4 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 [i170]: https://github.com/vsariola/sointu/issues/170
 [i176]: https://github.com/vsariola/sointu/issues/176
 [i186]: https://github.com/vsariola/sointu/issues/186
+[i192]: https://github.com/vsariola/sointu/issues/192

tracker/broker.go

@@ -63,6 +63,7 @@ type (
 		Panic             bool
 		SongPosition      sointu.SongPos
 		VoiceLevels       [vm.MAX_VOICES]float32
+		CPULoad           float64
 
 		HasDetectorResult bool
 		DetectorResult    DetectorResult

tracker/gioui/songpanel.go

@@ -129,6 +129,14 @@ func (t *SongPanel) layoutSongOptions(gtx C, tr *Tracker) D {
 						layout.Rigid(func(gtx C) D {
 							return layoutSongOptionRow(gtx, tr.Theme, "Cursor step", NumUpDown(tr.Theme, t.Step, "Cursor step").Layout)
 						}),
+						layout.Rigid(func(gtx C) D {
+							cpuload := tr.Model.CPULoad()
+							label := Label(tr.Theme, &tr.Theme.SongPanel.RowValue, fmt.Sprintf("%.0f %%", cpuload*100))
+							if cpuload >= 1 {
+								label.Color = tr.Theme.SongPanel.ErrorColor
+							}
+							return layoutSongOptionRow(gtx, tr.Theme, "CPU load", label.Layout)
+						}),
 					)
 				})
 		}),

tracker/model.go

@@ -69,6 +69,7 @@ type (
 		linkInstrTrack bool
 
 		voiceLevels [vm.MAX_VOICES]float32
+		cpuLoad     float64
 
 		signalAnalyzer *ScopeModel
 		detectorResult DetectorResult
@@ -343,6 +344,7 @@ func (m *Model) ProcessMsg(msg MsgToModel) {
 			}))
 		}
 		m.panic = msg.Panic
+		m.cpuLoad = msg.CPULoad
 	}
 	if msg.HasDetectorResult {
 		m.detectorResult = msg.DetectorResult
@@ -377,6 +379,8 @@ func (m *Model) ProcessMsg(msg MsgToModel) {
 	}
 }
 
+func (m *Model) CPULoad() float64 { return m.cpuLoad }
+
 func (m *Model) SignalAnalyzer() *ScopeModel { return m.signalAnalyzer }
 func (m *Model) Broker() *Broker             { return m.broker }
 

tracker/player.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"math"
 	"slices"
+	"time"
 
 	"github.com/vsariola/sointu"
 	"github.com/vsariola/sointu/vm"
@@ -32,6 +33,8 @@ type (
 		frameDeltas map[any]int64 // Player.frame (approx.)= event.Timestamp + frameDeltas[event.Source]
 		events      NoteEventList
 
+		cpuload float64 // current CPU load of the player, used to adjust the render rate
+
 		synther sointu.Synther // the synther used to create new synths
 		broker  *Broker        // the broker used to communicate with different parts of the tracker
 	}
@@ -86,6 +89,9 @@ func NewPlayer(broker *Broker, synther sointu.Synther) *Player {
 // buffer. It is used to trigger and release notes during processing. The
 // context is also used to get the current BPM from the host.
 func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext) {
+	startTime := time.Now()
+	startFrame := p.frame
+
 	p.processMessages(context)
 	p.events.adjustTimes(p.frameDeltas, p.frame, p.frame+int64(len(buffer)))
 
@@ -145,6 +151,7 @@ func (p *Player) Process(buffer sointu.AudioBuffer, context PlayerProcessContext
 		}
 		// when the buffer is full, return
 		if len(buffer) == 0 {
+			p.updateCPULoad(time.Since(startTime), p.frame-startFrame)
 			p.send(nil)
 			return
 		}
@@ -345,7 +352,7 @@ func (p *Player) compileOrUpdateSynth() {
 
 // all sendTargets from player are always non-blocking, to ensure that the player thread cannot end up in a dead-lock
 func (p *Player) send(message interface{}) {
-	TrySend(p.broker.ToModel, MsgToModel{HasPanicPosLevels: true, Panic: p.synth == nil, SongPosition: p.songPos, VoiceLevels: p.voiceLevels, Data: message})
+	TrySend(p.broker.ToModel, MsgToModel{HasPanicPosLevels: true, Panic: p.synth == nil, SongPosition: p.songPos, VoiceLevels: p.voiceLevels, CPULoad: p.cpuload, Data: message})
 }
 
 func (p *Player) processNoteEvent(ev NoteEvent) {
@@ -405,3 +412,14 @@ func (p *Player) processNoteEvent(ev NoteEvent) {
 	p.synth.Trigger(oldestVoice, ev.Note)
 	TrySend(p.broker.ToModel, MsgToModel{TriggerChannel: instrIndex + 1})
 }
+
+func (p *Player) updateCPULoad(duration time.Duration, frames int64) {
+	if frames <= 0 {
+		return // no frames rendered, so cannot compute CPU load
+	}
+	realtime := float64(duration) / 1e9
+	songtime := float64(frames) / 44100
+	newload := realtime / songtime
+	alpha := math.Exp(-songtime) // smoothing factor, time constant of 1 second
+	p.cpuload = float64(p.cpuload)*alpha + newload*(1-alpha)
+}