realtime waveform

bitchat/Views/RealtimeScrollingWaveform.swift

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+import SwiftUI
+import Combine
+
+/// Real-time scrolling waveform for live recording.
+/// Provide a normalized amplitude [0,1]. The view maintains a sliding window of bars.
+struct RealtimeScrollingWaveform: View {
+    var amplitudeNorm: CGFloat
+    var bars: Int = 240
+    var barColor: Color = Color(red: 0, green: 1, blue: 0.5) // neon-ish green
+
+    @State private var samples: [CGFloat] = []
+    @State private var ticker = Timer.publish(every: 0.02, on: .main, in: .common).autoconnect()
+
+    var body: some View {
+        GeometryReader { geo in
+            Canvas { ctx, size in
+                let w = size.width
+                let h = size.height
+                guard w > 0 && h > 0 else { return }
+                let n = samples.count
+                guard n > 0 else { return }
+                let stepX = w / CGFloat(n)
+                let midY = h / 2
+                let stroke: CGFloat = 1.2
+
+                for i in 0..<n {
+                    let amp = max(0, min(1, samples[i]))
+                    // Amplify only higher amplitudes so quiet parts stay subtle
+                    let t: CGFloat = 0.6
+                    let k: CGFloat = 0.7
+                    let boosted = amp <= t ? amp : min(1, amp + k * (amp - t))
+                    let lineH = max(1, boosted * (h * 0.95))
+                    let x = CGFloat(i) * stepX + stepX / 2
+                    let yTop = midY - lineH / 2
+                    let yBot = midY + lineH / 2
+                    var path = Path()
+                    path.move(to: CGPoint(x: x, y: yTop))
+                    path.addLine(to: CGPoint(x: x, y: yBot))
+                    ctx.stroke(path, with: .color(barColor), lineWidth: stroke)
+                }
+            }
+            .onAppear {
+                if samples.isEmpty { samples = Array(repeating: 0, count: bars) }
+            }
+            .onChange(of: bars) { newVal in
+                let clamped = max(8, newVal)
+                samples = Array(samples.suffix(clamped))
+                if samples.count < clamped {
+                    samples.insert(contentsOf: Array(repeating: 0, count: clamped - samples.count), at: 0)
+                }
+            }
+            .onReceive(ticker) { _ in
+                let v = max(0, min(1, amplitudeNorm))
+                samples.append(v)
+                let overflow = samples.count - bars
+                if overflow > 0 { samples.removeFirst(overflow) }
+            }
+        }
+    }
+}