Cthulhu is no longer a fork. Now it is a screen reader written in Golang.

internal/sound/progress.go

@@ -0,0 +1,64 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package sound
+
+import (
+	"bytes"
+	"encoding/binary"
+	"math"
+	"strconv"
+	"strings"
+)
+
+const progressCuePrefix = "generated-progress-tone:"
+
+func ProgressCueName(percentage float64) string {
+	return progressCuePrefix + strconv.FormatFloat(percentage, 'g', -1, 64)
+}
+
+func progress_percentage(cue string) (float64, bool) {
+	if !strings.HasPrefix(cue, progressCuePrefix) {
+		return 0, false
+	}
+	percentage, err := strconv.ParseFloat(strings.TrimPrefix(cue, progressCuePrefix), 64)
+	return percentage, err == nil && !math.IsNaN(percentage) && !math.IsInf(percentage, 0) && percentage >= 0 && percentage <= 100
+}
+
+// Match NVDA's default ProgressBar event_valueChange and generateBeep:
+// 110 * 2^(percentage/25) Hz, 40 ms padded to the next integer cycle,
+// 44100 Hz stereo PCM, and a sine clipped after multiplying by two.
+// NVDA passes frequency through a C float and defaults each channel to 50%.
+// Reference: nvaccess/nvda a4a89720ccbf3973a0e1e50a76dd8bff38db3d15,
+// source/NVDAObjects/behaviors.py and nvdaHelper/local/beeps.cpp.
+func progress_tone_wav(percentage float64) []byte {
+	const sampleRate = 44100
+	frequency := float64(float32(110 * math.Pow(2, percentage/25)))
+	// sampleRate/hz is evaluated as a float in NVDA's C++ generator.
+	cycleLength := float64(float32(sampleRate) / float32(frequency))
+	samplesPerCycle := int(cycleLength)
+	sampleCount := int(0.040 / (1.0 / sampleRate))
+	sampleCount += samplesPerCycle - sampleCount%samplesPerCycle
+	dataSize := sampleCount * 4
+	buffer := bytes.NewBuffer(make([]byte, 0, 44+dataSize))
+	buffer.WriteString("RIFF")
+	_ = binary.Write(buffer, binary.LittleEndian, uint32(36+dataSize))
+	buffer.WriteString("WAVEfmt ")
+	_ = binary.Write(buffer, binary.LittleEndian, uint32(16))
+	_ = binary.Write(buffer, binary.LittleEndian, uint16(1))
+	_ = binary.Write(buffer, binary.LittleEndian, uint16(2))
+	_ = binary.Write(buffer, binary.LittleEndian, uint32(sampleRate))
+	_ = binary.Write(buffer, binary.LittleEndian, uint32(sampleRate*4))
+	_ = binary.Write(buffer, binary.LittleEndian, uint16(4))
+	_ = binary.Write(buffer, binary.LittleEndian, uint16(16))
+	buffer.WriteString("data")
+	_ = binary.Write(buffer, binary.LittleEndian, uint32(dataSize))
+	sinFrequency := 2 * math.Pi / cycleLength
+	for sample := 0; sample < sampleCount; sample++ {
+		value := int16(min(1.0, max(-1.0, math.Sin(float64(sample%sampleRate)*sinFrequency)*2)) * 7000)
+		_ = binary.Write(buffer, binary.LittleEndian, value)
+		_ = binary.Write(buffer, binary.LittleEndian, value)
+	}
+	return buffer.Bytes()
+}