After commit c018f5fd29 Fenrir is being switched over to go. If you do not want to be part of the testing process, please switch to master.

internal/sound/progress.go

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+// Fenrir console screen reader.
+// Copyright (c) 2026 Storm Dragon
+// SPDX-License-Identifier: GPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify it
+// under the terms of the GNU General Public License as published by the Free
+// Software Foundation, either version 3 of the License, or (at your option)
+// any later version.
+//
+// This program is distributed in the hope that it will be useful, but WITHOUT
+// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+// more details.
+//
+// You should have received a copy of the GNU General Public License along with
+// this program. If not, see <https://www.gnu.org/licenses/gpl-3.0.html>.
+
+// Tone synthesis adapted from Cthulhu (Storm Dragon and Angus Kola).
+package sound
+
+import "math"
+
+// A small gain lift for progress tones, independent of normal cue volume.
+const progressGain = 1.03 * 1.02
+
+// Precompute integer percentages before opening the stream. Admission and the
+// audio callback only move pointers; fractional progress rounds to the nearest
+// percent. The cache is bounded to 101 short clips (about 1.6 MiB).
+func progress_clips() [101]*clip {
+	var clips [101]*clip
+	for percentage := range clips {
+		clips[percentage] = progress_tone(float64(percentage))
+	}
+	return clips
+}
+
+// Match Cthulhu's NVDA-style tones: 110 * 2^(percent/25) Hz, clipped sine,
+// 40 ms padded to an integer cycle, 7000/32768 amplitude per channel. Generate
+// at its 44100 Hz rate, then interpolate onto our shared 48000 Hz stream.
+func progress_tone(percentage float64) *clip {
+	return progress_tone_shape(percentage, false)
+}
+
+// The triangle variant shares progress's pitch, duration and resampling.
+func progress_tone_shape(percentage float64, triangle bool) *clip {
+	const sourceRate = 44100
+	frequency := float32(110 * math.Pow(2, percentage/25))
+	cycleLength := float64(float32(sourceRate) / frequency)
+	samplesPerCycle := int(cycleLength)
+	count := sourceRate * 40 / 1000
+	count += samplesPerCycle - count%samplesPerCycle
+	source := make([]float32, count)
+	for index := range source {
+		phase := float64(index) * 2 * math.Pi / cycleLength
+		wave := min(1.0, max(-1.0, math.Sin(phase)*2))
+		if triangle {
+			wave = 2 / math.Pi * math.Asin(math.Sin(phase))
+		}
+		value := int16(wave * 7000)
+		source[index] = float32(value) / 32768
+	}
+	frames := (count*sampleRate + sourceRate - 1) / sourceRate
+	samples := make([]float32, frames*2)
+	for frame := range frames {
+		position := float64(frame) * sourceRate / sampleRate
+		left := min(int(position), count-1)
+		right := min(left+1, count-1)
+		value := source[left] + (source[right]-source[left])*float32(position-math.Floor(position))
+		samples[frame*2], samples[frame*2+1] = value, value
+	}
+	return &clip{samples: samples}
+}
+
+// Play_progress coalesces progress separately from ordinary cues. Progress
+// never replaces startup/review sounds and never cuts a progress tone short.
+func (s *Service) Play_progress(percentage float64) bool {
+	if s == nil || s.closed.Load() || s.finishing.Load() || math.IsNaN(percentage) || math.IsInf(percentage, 0) || percentage < 0 || percentage > 100 {
+		return false
+	}
+	item := s.tones[int(math.Round(percentage))]
+	if item == nil {
+		return false
+	}
+	s.progress.Store(item)
+	return true
+}
+
+// Discard_progress drops waiting tones after passive redraws or prompts while
+// letting the short tone already playing finish.
+func (s *Service) Discard_progress() {
+	if s != nil {
+		s.progress.Store(nil)
+	}
+}
+
+// Clear_progress drops pending/playing tones at input, menu capture, and
+// session handoff without touching any ordinary sound cue.
+func (s *Service) Clear_progress() {
+	if s == nil {
+		return
+	}
+	s.progress.Store(nil)
+	s.cancelProgress.Store(true)
+}