feat: add limiter

src-tauri/src/commands.rs

@@ -291,3 +291,20 @@ pub async fn set_compressor(
             .map_err(|e| e.to_string())
     })
 }
+
+#[tauri::command]
+pub async fn set_limiter(
+    state: State<'_, AppState>,
+    id: u64,
+    channel: types::OutputChannel,
+    threshold: f32,
+    attack: u16,
+    release: u16,
+) -> Result<bool, String> {
+    state.with_device_mut(id, |device| {
+        device
+            .dsp
+            .set_limiter(channel, threshold, attack, release)
+            .map_err(|e| e.to_string())
+    })
+}

src-tauri/src/lib.rs

@@ -22,6 +22,7 @@ pub fn run() {
                 commands::set_current_preset_name,
                 commands::set_gate,
                 commands::set_compressor,
+                commands::set_limiter,
             ]
         )
         .run(tauri::generate_context!())

src/components/dsp408/LimiterSection/LimiterSection.css

@@ -0,0 +1,171 @@
+.limiter-section {
+  container-type: size;
+  position: absolute;
+  left: 0;
+  right: 0;
+  bottom: 0;
+
+  height: var(--dsp-control-heigth);
+
+  display: flex;
+  align-items: flex-end;
+  justify-content: center;
+
+  box-sizing: border-box;
+
+  background: var(--bg-panel);
+
+  z-index: 20;
+
+  border-top: var(--border-width) solid var(--border-hairline);
+}
+
+.limiter-panels {
+  height: 100%;
+  display: flex;
+  gap: var(--space-2);
+  overflow-x: auto;
+}
+
+.limiter-panel {
+  position: relative;
+  height: 10;
+
+  aspect-ratio: 0.5;
+  flex: 0 0 auto;
+
+  display: flex;
+  flex-direction: column;
+  align-items: stretch;
+  justify-content: flex-start;
+
+  border: var(--border-width) solid var(--border-hairline);
+  border-radius: var(--radius-md);
+  box-sizing: border-box;
+  background: var(--bg-void);
+}
+
+.limiter-panel__title {
+  flex: 0 0 auto;
+  width: 100%;
+  text-align: center;
+  font-family: var(--font-ui);
+  font-size: 4cqh;
+  font-weight: var(--font-weight-semibold);
+  padding-top: 2cqh;
+  padding-bottom: 2cqh;
+  border-bottom: var(--border-width) solid var(--border-hairline);
+
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.limiter-panel__grid {
+  flex: 1 1 auto;
+  min-height: 0;
+
+  display: grid;
+  grid-template-columns: repeat(2, 1fr);
+  grid-template-rows: repeat(2, 1fr);
+  grid-template-areas:
+    'threshold attack'
+    'threshold release';
+  gap: 2cqh;
+
+  padding: 2cqh;
+  box-sizing: border-box;
+}
+
+.limiter-panel__cell--threshold {
+  grid-area: threshold;
+}
+.limiter-panel__cell--attack {
+  grid-area: attack;
+}
+.limiter-panel__cell--release {
+  grid-area: release;
+}
+
+.limiter-panel__cell {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: flex-start;
+  min-height: 0;
+  min-width: 0;
+  gap: 1cqh;
+}
+
+.limiter-panel__cell-label {
+  flex: 0 0 auto;
+  font-family: var(--font-ui);
+  font-size: 2.5cqh;
+  color: var(--text-muted);
+  white-space: nowrap;
+}
+
+.limiter-linear-graph-section {
+  flex: 0 0 calc(100% - var(--dsp-control-heigth));
+  min-height: 0;
+
+  display: flex;
+  flex-direction: row;
+  gap: 1cqh;
+  padding: 0.5cqh;
+
+  box-sizing: border-box;
+  background: var(--bg-panel);
+}
+
+.limiter-graph-panel {
+  flex: 1 1 auto;
+  min-width: 0;
+  min-height: 0;
+
+  display: flex;
+  flex-direction: column;
+
+  border: var(--border-width) solid var(--border-hairline);
+  border-radius: var(--radius-md);
+}
+
+.limiter-meter-panel {
+  flex: 0 0 auto;
+  width: fit-content;
+  min-width: max-content;
+
+  display: flex;
+  flex-direction: column;
+
+  border: var(--border-width) solid var(--border-hairline);
+  border-radius: var(--radius-md);
+}
+
+.limiter-graph__title {
+  flex: 0 0 auto;
+
+  text-align: center;
+  padding: 1cqh;
+
+  font-family: var(--font-ui);
+  font-size: 2.5cqh;
+  font-weight: var(--font-weight-semibold);
+}
+
+.limiter-graph__meters {
+  flex: 1;
+  min-height: 0;
+
+  display: flex;
+  flex-direction: row;
+  align-items: stretch;
+
+  gap: 1cqh;
+  padding: 1cqh;
+}
+
+.limiter-graph-panel > .container {
+  flex: 1;
+  min-height: 0;
+}

src/components/dsp408/LimiterSection/LimiterSection.tsx

@@ -0,0 +1,238 @@
+// LimiterSection.tsx
+import VerticalSlider from '../Slider/VerticalSlider';
+import { OutputChannel } from '../../../types/dsp408State';
+import { DSP } from '../../../types/types';
+import ChannelGroup from '../ChannelGroup/ChannelGroup';
+import { LinearGraph } from '../LinearGraph/LinearGraph';
+import MeterBar from '../../MeterBar/MeterBar';
+import { useMemo, useState } from 'react';
+import './LimiterSection.css';
+
+const LIMITER_SLIDER_PARAMS = [
+  { key: 'threshold', label: 'Threshold', min: -90, max: 20, step: 0.5, unit: ' dB' },
+  { key: 'attack', label: 'Attack', min: 1, max: 999, step: 1, unit: ' ms' },
+  { key: 'release', label: 'Release', min: 10, max: 3000, step: 1, unit: ' ms' },
+] as const;
+
+// ASSUMPTION: output meter indices follow the 4 input channels (0-3), i.e.
+// Out1 -> 4, Out2 -> 5, etc. Same mapping as CompressorSection — adjust if
+// dsp.meters.channels ordering differs.
+const OUTPUT_METER_INDEX: Record<OutputChannel, number> = {
+  [OutputChannel.Out1]: 4,
+  [OutputChannel.Out2]: 5,
+  [OutputChannel.Out3]: 6,
+  [OutputChannel.Out4]: 7,
+  [OutputChannel.Out5]: 8,
+  [OutputChannel.Out6]: 9,
+  [OutputChannel.Out7]: 10,
+  [OutputChannel.Out8]: 11,
+} as const;
+
+type LimiterParamKey = 'threshold' | 'attack' | 'release';
+
+type LimiterValues = {
+  threshold: number;
+  attack: number;
+  release: number;
+};
+
+type SetLimiterFn = (
+  outputChannel: OutputChannel,
+  threshold: number,
+  attack: number,
+  release: number
+) => Promise<boolean>;
+
+function LimiterPanel({
+  channel,
+  dsp,
+  setLimiter,
+  onLiveValue,
+}: {
+  channel: OutputChannel;
+  dsp: DSP;
+  setLimiter: SetLimiterFn;
+  onLiveValue: (channel: OutputChannel, key: LimiterParamKey, value: number) => void;
+}) {
+  const outputState = dsp.state.current_config.output_states[channel];
+  // ASSUMPTION: limiter settings live at output_states[channel].limiter
+  const lim = outputState.limiter as LimiterValues;
+
+  const commit = (overrides: Partial<LimiterValues>) => {
+    const next = { ...lim, ...overrides };
+    return setLimiter(channel, next.threshold, next.attack, next.release);
+  };
+
+  return (
+    <div className="limiter-panel">
+      <div className="limiter-panel__title">{outputState.name}</div>
+
+      <div className="limiter-panel__grid">
+        {LIMITER_SLIDER_PARAMS.map((param) => (
+          <div className={`limiter-panel__cell limiter-panel__cell--${param.key}`} key={param.key}>
+            <VerticalSlider
+              min={param.min}
+              max={param.max}
+              step={param.step}
+              unit={param.unit}
+              value={lim[param.key]}
+              onInput={(value) => onLiveValue(channel, param.key, value)}
+              onChange={(value) => commit({ [param.key]: value } as Partial<LimiterValues>)}
+              style={{ width: '100%', flex: '1 1 auto' }}
+            />
+            <div className="limiter-panel__cell-label">{param.label}</div>
+          </div>
+        ))}
+      </div>
+    </div>
+  );
+}
+
+// Hard-knee brickwall limiter transfer curve, in dB.
+function limiterOutputDb(input: number, threshold: number): number {
+  return input <= threshold ? input : threshold;
+}
+
+function LimiterSection({ dsp, set_limiter }: { dsp: DSP; set_limiter: SetLimiterFn }) {
+  const outputs = [
+    OutputChannel.Out1,
+    OutputChannel.Out2,
+    OutputChannel.Out3,
+    OutputChannel.Out4,
+    OutputChannel.Out5,
+    OutputChannel.Out6,
+    OutputChannel.Out7,
+    OutputChannel.Out8,
+  ];
+
+  const [activeChannel, setActiveChannel] = useState<OutputChannel>(outputs[0]);
+  const [liveLim, setLiveLim] = useState<Partial<Record<OutputChannel, LimiterValues>>>({});
+
+  const handleLiveValue = (channel: OutputChannel, key: LimiterParamKey, value: number) => {
+    setActiveChannel(channel);
+    setLiveLim((prev) => {
+      const base =
+        prev[channel] ?? (dsp.state.current_config.output_states[channel].limiter as LimiterValues);
+      return { ...prev, [channel]: { ...base, [key]: value } };
+    });
+  };
+
+  const handleSetLimiter: SetLimiterFn = async (channel, threshold, attack, release) => {
+    setActiveChannel(channel);
+    const success = await set_limiter(channel, threshold, attack, release);
+
+    if (success) {
+      setLiveLim((prev) => {
+        if (!(channel in prev)) return prev;
+        const next = { ...prev };
+        delete next[channel];
+        return next;
+      });
+    }
+
+    return success;
+  };
+
+  const activeOutputState = dsp.state.current_config.output_states[activeChannel];
+  const activeLim = liveLim[activeChannel] ?? (activeOutputState.limiter as LimiterValues);
+
+  const curvePoints = useMemo(() => {
+    const { threshold } = activeLim;
+    const steps = 120;
+    const points: [number, number][] = [];
+    for (let i = 0; i <= steps; i++) {
+      const x = -60 + (60 * i) / steps;
+      points.push([x, limiterOutputDb(x, threshold)]);
+    }
+    return points;
+  }, [activeLim.threshold]);
+
+  return (
+    <>
+      <div className="limiter-linear-graph-section">
+        <div className="limiter-graph-panel">
+          <div className="limiter-graph__title">{activeOutputState.name} - Limiter</div>
+
+          <LinearGraph
+            xMin={-60}
+            xMax={0}
+            yMin={-60}
+            yMax={0}
+            xLabel="in dB"
+            yLabel="out dB"
+            formatX={(v) => Math.round(v).toString()}
+            formatY={(v) => Math.round(v).toString()}
+            draw={({ ctx, toPx }) => {
+              // Unity reference line
+              ctx.strokeStyle = '#6b7280';
+              ctx.lineWidth = 1;
+              ctx.setLineDash([4, 4]);
+              const [ux0, uy0] = toPx(-60, -60);
+              const [ux1, uy1] = toPx(0, 0);
+              ctx.beginPath();
+              ctx.moveTo(ux0, uy0);
+              ctx.lineTo(ux1, uy1);
+              ctx.stroke();
+              ctx.setLineDash([]);
+
+              // Threshold marker
+              ctx.strokeStyle = '#fbbf24';
+              ctx.lineWidth = 1;
+              ctx.setLineDash([2, 3]);
+              const [tx0, ty0] = toPx(activeLim.threshold, -60);
+              const [tx1, ty1] = toPx(activeLim.threshold, 0);
+              ctx.beginPath();
+              ctx.moveTo(tx0, ty0);
+              ctx.lineTo(tx1, ty1);
+              ctx.stroke();
+              ctx.setLineDash([]);
+
+              // Limiter curve
+              ctx.strokeStyle = '#f87171';
+              ctx.lineWidth = 2;
+              ctx.lineJoin = 'round';
+              ctx.beginPath();
+              curvePoints.forEach(([x, y], i) => {
+                const [px, py] = toPx(x, y);
+                if (i === 0) ctx.moveTo(px, py);
+                else ctx.lineTo(px, py);
+              });
+              ctx.stroke();
+            }}
+          />
+        </div>
+
+        <div className="limiter-meter-panel">
+          <div className="limiter-graph__meters">
+            {outputs.map((output) => {
+              const outputState = dsp.state.current_config.output_states[output];
+              const idx = OUTPUT_METER_INDEX[output];
+
+              return (
+                <MeterBar key={output} label={outputState.name} meter={dsp.meters.channels[idx]} />
+              );
+            })}
+          </div>
+        </div>
+      </div>
+
+      <div className="limiter-section">
+        <div className="limiter-panels">
+          <ChannelGroup title="Output">
+            {outputs.map((output) => (
+              <LimiterPanel
+                key={String(output)}
+                channel={output}
+                dsp={dsp}
+                setLimiter={handleSetLimiter}
+                onLiveValue={handleLiveValue}
+              />
+            ))}
+          </ChannelGroup>
+        </div>
+      </div>
+    </>
+  );
+}
+
+export default LimiterSection;

src/components/dsp408/LinearGraph/LinearGraph.tsx

@@ -170,9 +170,9 @@ export const LinearGraph = forwardRef<LinearGraphHandle, LinearGraphProps>(funct
     ctx.clearRect(0, 0, cssW, cssH);
 
     const plot = {
-      x: pad.left,
+      x: pad.left + cq.w * 2,
       y: pad.top,
-      width: Math.max(1, cssW - pad.left - pad.right),
+      width: Math.max(1, cssW - pad.left - pad.right - cq.w * 2),
       height: Math.max(1, cssH - pad.top - pad.bottom),
     };
 

src/hooks/useDSP408.ts

@@ -59,6 +59,12 @@ export type DSP408Device = {
     knee: number,
     threshold: number
   ) => Promise<boolean>;
+  setLimiter: (
+    outputChannel: OutputChannel,
+    threshold: number,
+    attack: number,
+    release: number
+  ) => Promise<boolean>;
 };
 
 // ============================================================
@@ -702,6 +708,67 @@ export function useDSP408(
     });
   }
 
+  // ==========================================================
+  // Limiter
+  // ==========================================================
+  async function setLimiter(
+    dsp: DSP,
+    outputChannel: OutputChannel,
+    threshold: number,
+    attack: number,
+    release: number
+  ): Promise<boolean> {
+    return withPollingPaused(dsp, async () => {
+      try {
+        const success = await invoke<boolean>('set_limiter', {
+          id: dsp.id,
+          channel: outputChannel,
+          threshold,
+          attack,
+          release,
+        });
+
+        if (!success) {
+          notify('Failed to change limiter settings', 'error', dsp.name);
+          return false;
+        }
+
+        updateDSP(setDsps, dsp.id, (d) => {
+          if (!d.state) return d;
+
+          const currentConfig = d.state.current_config;
+
+          return {
+            ...d,
+            state: {
+              ...d.state,
+              current_config: {
+                ...currentConfig,
+                output_states: {
+                  ...currentConfig.output_states,
+                  [outputChannel]: {
+                    ...currentConfig.output_states[outputChannel],
+                    limiter: {
+                      threshold,
+                      attack,
+                      release,
+                    },
+                  },
+                },
+              },
+            },
+          };
+        });
+
+        notify('Limiter updated', 'success', dsp.name);
+        return true;
+      } catch (err) {
+        notify(`Limiter update failed: ${String(err)}`, 'error', dsp.name);
+        return false;
+      }
+    });
+  }
+
   // ==========================================================
   // Return API
   // ==========================================================
@@ -730,6 +797,12 @@ export function useDSP408(
         knee: number,
         threshold: number
       ) => setCompressor(dsp, outputChannel, ratio, attack, release, knee, threshold),
+      setLimiter: (
+        outputChannel: OutputChannel,
+        threshold: number,
+        attack: number,
+        release: number
+      ) => setLimiter(dsp, outputChannel, threshold, attack, release),
     };
   }
 

src/pages/DspPage/DspPage.tsx

@@ -8,6 +8,7 @@ import CompressorSection from '../../components/dsp408/CompressorSection/Compres
 import { DSP408Device } from '../../hooks/useDSP408';
 import './DspPage.css';
 import GateSection from '../../components/dsp408/GateSection/GateSection';
+import LimiterSection from '../../components/dsp408/LimiterSection/LimiterSection';
 import LoadingOverlay from '../../components/LoadingOverlay/LoadingOverlay';
 import { InputChannel, OutputChannel } from '../../types/dsp408State';
 
@@ -183,6 +184,9 @@ function DSPPage({ dsp, dsp408 }: { dsp: DSP; dsp408: DSP408Device }) {
       case 'compressor':
         return <CompressorSection dsp={dsp} set_compressor={dsp408.setCompressor} />;
 
+      case 'limiter':
+        return <LimiterSection dsp={dsp} set_limiter={dsp408.setLimiter} />;
+
       default:
         return null;
     }