Basic, read-only audiotrondHEADmain

Audiotrond exists and properly displays music being played through MPD.
The display includes title, artist, album, and progress bar, and text
scrolls if too long to fit on the screen. Backlight support exists; the
display backlight fades smoothly on and off when the music starts and
stops. After being stopped for a little while, audiotrond switches to a
clock. Currently, audiotrond lacks user interaction support, so it keeps
the keypad backlight off.

1 files changed, 249 insertions, 0 deletions

diff --git a/mpdDisplay.go b/mpdDisplay.go
new file mode 100644
index 0000000..93fb552
--- /dev/null
+++ b/mpdDisplay.go
@@ -0,0 +1,249 @@
+// Copyright 2022 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+package main
+
+import (
+	"math"
+	"time"
+
+	"golang.org/x/text/transform"
+
+	"benjamin.barenblat.name/audiotrond/cfa635"
+)
+
+var (
+	encoder = cfa635.NewEncoder()
+)
+
+func encode(s string) []byte {
+	r, _, err := transform.String(encoder, s)
+	if err != nil {
+		panic(err)
+	}
+	return []byte(r)
+}
+
+func setPlaybackIcon(model *model, lcdState *cfa635.LCDState) {
+	switch model.State {
+	case stopped:
+		lcdState[0][19] = 0xd0
+	case playing:
+		lcdState[0][19] = 0x10
+	case paused:
+		lcdState[0][19] = pauseIconSprite
+	}
+}
+
+func rotate(s []byte, width int, start, now time.Time) []byte {
+	const delay int = 10
+	const rotationRate float64 = 1 / float64(333*time.Millisecond)
+
+	if len(s) <= width {
+		return s
+	}
+
+	ticks := int(float64(now.Sub(start).Nanoseconds()) * rotationRate)
+
+	if len(s) < 2*width {
+		// Just scroll back and forth.
+		period := len(s) - width + delay
+		ticks %= 2 * period
+
+		i := 0
+		if ticks <= delay {
+		} else if ticks <= period {
+			i = ticks - delay
+		} else if ticks <= period+delay {
+			i = len(s) - width
+		} else {
+			i = 2*period - ticks
+		}
+		return s[i : i+width]
+	}
+
+	// Actually rotate.
+	for i := 0; i < 7; i++ {
+		s = append(s, byte(' '))
+	}
+
+	period := len(s) + delay
+	ticks %= period
+
+	i := 0
+	if ticks > delay {
+		i = ticks - delay
+	}
+	return append(s[i:], s[:i]...)[:width]
+}
+
+func setTrackInfo(model *model, now time.Time, lcdState *cfa635.LCDState) {
+	// Cut off the track one character short so we don't overwrite the
+	// playback icon.
+	copy(lcdState[0][:], rotate(encode(model.Track), 19, model.LastTrackInfoUpdate, now))
+	copy(lcdState[1][:], rotate(encode(model.Artist), 20, model.LastTrackInfoUpdate, now))
+	copy(lcdState[2][:], rotate(encode(model.Album), 20, model.LastTrackInfoUpdate, now))
+}
+
+func setTimeElapsed(model *model, lcdState *cfa635.LCDState) int {
+	elapsed := fmtTime(model.Elapsed, model.Duration)
+	copy(lcdState[3][:], elapsed)
+	return len(elapsed)
+}
+
+func setTimeRemaining(model *model, lcdState *cfa635.LCDState) int {
+	remaining := fmtTime(model.Elapsed-model.Duration, model.Duration)
+	copy(lcdState[3][20-len(remaining):], remaining)
+	return len(remaining)
+}
+
+func setProgressBar(model *model, barStart, barEnd int, lcdState *cfa635.LCDState) {
+	fraction := float64(model.Elapsed) / float64(model.Duration)
+
+	// Convert the fraction played to the number of columns that should be
+	// colored in the bar. Each cell has 6 columns; leave one extra column
+	// free at the left of the bar so it doesn't crash into the time
+	// elapsed.
+	c := int(math.Round(fraction * (6*float64(barEnd-barStart) - 1)))
+	if c == 0 {
+		return
+	}
+
+	// There are precomposed block glyphs of widths 1-5 that leave a blank
+	// column at the beginning. Use one of those in the first cell.
+	w := c
+	if w > 5 {
+		w = 5
+	}
+	lcdState[3][barStart] = byte(0xdb - w)
+	c -= w
+	if c == 0 {
+		return
+	}
+
+	// Fill in the full cells in the bar.
+	x := barStart + 1
+	for ; c >= 6; x, c = x+1, c-6 {
+		lcdState[3][x] = progressBarSpriteFull
+	}
+	if c == 0 {
+		return
+	}
+
+	// Fill in the last, partial bar.
+	lcdState[3][x] = byte(progressBarSprite1 - 1 + c)
+}
+
+const (
+	ellipsisSprite = iota
+	pauseIconSprite
+	progressBarSprite1
+	progressBarSprite2
+	progressBarSprite3
+	progressBarSprite4
+	progressBarSprite5
+	progressBarSpriteFull
+)
+
+func initializeMPDDisplay(lcd *cfa635.Module) error {
+	// Load sprites.
+
+	if err := lcd.SetCharacter(ellipsisSprite, &[...]byte{
+		0b00_000000,
+		0b00_000000,
+		0b00_000000,
+		0b00_000000,
+		0b00_000000,
+		0b00_000000,
+		0b00_010101,
+		0b00_000000,
+	}); err != nil {
+		return err
+	}
+
+	if err := lcd.SetCharacter(pauseIconSprite, &[...]byte{
+		0b00_000000,
+		0b00_011011,
+		0b00_011011,
+		0b00_011011,
+		0b00_011011,
+		0b00_011011,
+		0b00_000000,
+		0b00_000000,
+	}); err != nil {
+		return err
+	}
+
+	for w := 1; w <= 6; w++ {
+		r := byte((1<<w - 1) << (6 - w))
+		if err := lcd.SetCharacter(progressBarSprite1-1+w, &[...]byte{
+			r,
+			r,
+			r,
+			r,
+			r,
+			r,
+			r,
+			0b00_000000,
+		}); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func brightnessStep(pm float64, then, now time.Time, old float64) float64 {
+	const brightnessRampRate float64 = 20.0 / float64(500*time.Millisecond)
+
+	dt := float64(now.Sub(then).Nanoseconds())
+	return old + pm*dt*brightnessRampRate
+}
+
+func setBrightness(model *model, now time.Time, old *view) float64 {
+	var z time.Time
+	if old.Mtime == z {
+		return old.DisplayBrightness
+	}
+
+	if model.State == playing || now.Sub(model.LastStateChange).Seconds() < 15 {
+		if old.DisplayBrightness >= 20 {
+			return 20
+		}
+		return brightnessStep(+1, old.Mtime, now, old.DisplayBrightness)
+	} else {
+		if old.DisplayBrightness == 0 {
+			return 0
+		}
+		return math.Max(0, brightnessStep(-1, old.Mtime, now, old.DisplayBrightness))
+	}
+}
+
+func mpdView(model *model, now time.Time, old *view) *view {
+	var new view
+	new.LCD = cfa635.ClearedLCDState()
+	setPlaybackIcon(model, new.LCD)
+	setTrackInfo(model, now, new.LCD)
+	if model.Duration > 0 {
+		barStart := setTimeElapsed(model, new.LCD)
+		barEnd := 20 - setTimeRemaining(model, new.LCD)
+		setProgressBar(model, barStart, barEnd, new.LCD)
+	}
+
+	new.DisplayBrightness = setBrightness(model, now, old)
+
+	new.Mtime = now
+
+	return &new
+}