feat: 3-bar meters, latching ceiling lamp, and rolling in/out/GR plot

Meters: per-channel |L | GR | R| layout (narrower bars). Ceiling lamp now
latches on a limiter catch and holds, clearing after 3s or on click.

Plot: per-channel selectable scrolling in/out/gain-reduction scope under the
meters, fed by new raw block-peak atomics (separate from the decayed bar
atomics). Histories for all four channels run continuously, so switching tabs
keeps each channel's history. Scroll is time-based with a flow-speed selector
(2/5/15/45 s window) so the window length is accurate regardless of frame rate,
with peak-preserving downsampling between columns.

reset() now zeroes the meters so transport restart shows silence rather than
stale values.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy.ps1

@@ -74,11 +74,22 @@ if (Test-Path -LiteralPath '$clapSrc') { Copy-Item -LiteralPath '$clapSrc' -Dest
     Start-Process powershell -Verb RunAs -Wait -ArgumentList '-NoProfile','-EncodedCommand',$enc
 }
 
-$check = Join-Path $vst3Dst "$vst3Name\Contents\x86_64-win\$vst3Name"
+# Verify each bundle was actually refreshed. A plugin currently loaded in a DAW keeps its
-if (Test-Path $check) {
+# binary locked, so the copy fails silently and leaves a STALE install — re-scanning then runs
-    Write-Host "VST3 installed OK -> $check" -ForegroundColor Green
+# old code. Compare install vs build timestamps to catch exactly that.
-    Write-Host "In FL Studio: Manage plugins -> 'Rescan previously failed plugins' -> Find installed plugins." -ForegroundColor Yellow
+function Test-Installed($label, $src, $dst) {
+    if (-not (Test-Path $src)) { return }  # nothing was built for this format
+    if (-not (Test-Path $dst)) { throw "$label install verification failed: $dst not found" }
+    $srcT = (Get-Item $src).LastWriteTime
+    $dstT = (Get-Item $dst).LastWriteTime
+    if ($dstT -lt $srcT) {
+        Write-Warning "$label is STALE (installed $dstT < built $srcT). It's almost certainly loaded in your DAW (file locked). Close the plugin/DAW and re-run deploy."
     }
     else {
-    throw "Install verification failed: $check not found"
+        Write-Host "$label installed OK -> $dst" -ForegroundColor Green
     }
+}
+
+Test-Installed "VST3" (Join-Path $vst3Src "Contents\x86_64-win\$vst3Name") (Join-Path $vst3Dst "$vst3Name\Contents\x86_64-win\$vst3Name")
+Test-Installed "CLAP" $clapSrc (Join-Path $clapDst $clapName)
+Write-Host "In FL Studio: Manage plugins -> 'Rescan previously failed plugins' -> Find installed plugins." -ForegroundColor Yellow

src/dsp/compressor.rs

@@ -152,6 +152,13 @@ impl Compressor {
         self.fixed_delay as u32
     }
 
+    /// Current gain reduction being applied, in dB (>= 0), excluding makeup. For metering.
+    /// This is the smoothed detector output `yl`, so it tracks the visible needle, not the
+    /// instantaneous static curve.
+    pub fn gain_reduction_db(&self) -> f32 {
+        self.yl
+    }
+
     /// Process one sample frame in place: `input[ch]` -> `output[ch]`.
     ///
     /// `input` and `output` are short stack slices (one value per channel), so this

src/dsp/limiter.rs

@@ -89,6 +89,12 @@ impl Limiter {
         self.fixed_delay as u32
     }
 
+    /// Current limiter gain reduction in dB (>= 0). `gain` is linear (<= 1); expressed here as a
+    /// positive dB amount for the ceiling lamp / metering.
+    pub fn gain_reduction_db(&self) -> f32 {
+        -20.0 * self.gain.max(1e-9).log10()
+    }
+
     /// Limit one frame in place: `input[ch]` -> `output[ch]`.
     ///
     /// `ceiling` is linear gain (e.g. `util::db_to_gain(ceiling_db)`); `release_coef` comes from a

src/dsp/mod.rs

@@ -1,8 +1,8 @@
 //! DSP building blocks for Codename 206.
 //!
-//! Stage 2 introduces the full-band compressor (also the engine that will be reused
+//! The signal chain: a `crossover` filterbank splits into bands, each band (plus the summed
-//! per band and for the 'All' aggregate channel — see README.md). Later stages add the
+//! 'All' channel) runs a `compressor`, and a `limiter` (with a true-peak `oversampler` detector)
-//! crossover filterbank, output limiter, and oversampler alongside it.
+//! is the final stage. `biquad` is the shared filter primitive the crossover is built from.
 
 pub mod biquad;
 pub mod compressor;

src/editor.rs

@@ -0,0 +1,394 @@
+//! egui editor.
+//!
+//! Placeholder control layout for now — Stage 6 will keep adding visualisers (a rolling
+//! reduction/in/out plot next, then a gain-curve view and draggable crossover handles) and
+//! eventually replace the slider columns. Built to stay usable meanwhile: a resizable window with
+//! a vertical scroll area so every control is reachable at any size, global controls in a
+//! label|slider grid, and the four channels (low/mid/high/all) side by side.
+//!
+//! Meters: a per-channel `|L | GR | R|` cluster (output level left/right + mono gain reduction in
+//! the middle) plus a latching ceiling lamp, fed by the lock-free [`Meters`] state the audio
+//! thread publishes each block.
+
+use nih_plug::prelude::*;
+use nih_plug_egui::{
+    create_egui_editor,
+    egui::{self, pos2, vec2, Align2, Color32, CornerRadius, CursorIcon, FontId, Painter, Rect, Sense, Stroke, Vec2},
+    resizable_window::ResizableWindow,
+    widgets,
+};
+use std::sync::atomic::Ordering;
+use std::sync::Arc;
+
+use crate::meters::{Meters, NUM_CHANNELS};
+use crate::params::{Codename206Params, CompressorParams};
+use crate::Codename206;
+
+/// Bottom of the level meter's dB scale (top is 0 dBFS).
+const METER_FLOOR_DB: f32 = -60.0;
+/// Full-scale of the gain-reduction meter (bar fills downward from the top).
+const GR_FULL_DB: f32 = 24.0;
+/// Limiter gain reduction (dB) above which the ceiling lamp latches on.
+const LAMP_TRIGGER_DB: f32 = 0.1;
+/// How long the ceiling lamp stays lit after the most recent catch (seconds).
+const LAMP_HOLD_S: f64 = 3.0;
+/// Height of the meter panel.
+const METER_PANEL_H: f32 = 130.0;
+/// Height of the scrolling-plot panel.
+const PLOT_PANEL_H: f32 = 150.0;
+/// Number of frames held in the scrolling-plot history (~a few seconds at ~60 fps).
+const PLOT_N: usize = 256;
+
+const COLOR_IN: Color32 = Color32::from_rgb(90, 170, 235);
+const COLOR_OUT: Color32 = Color32::from_rgb(90, 200, 110);
+const COLOR_GR: Color32 = Color32::from_rgb(240, 150, 60);
+
+/// Rolling history for the in/out/GR plot — kept for ALL channels at once (cheap: ~12 KB), so
+/// switching the selected tab shows that channel's existing history rather than restarting blank.
+/// It's a per-channel ring sampled once per GUI frame (wall-clock, not sample-accurate).
+struct PlotHistory {
+    in_db: [[f32; PLOT_N]; NUM_CHANNELS],
+    out_db: [[f32; PLOT_N]; NUM_CHANNELS],
+    gr_db: [[f32; PLOT_N]; NUM_CHANNELS],
+    write: usize,
+    len: usize,
+}
+
+impl Default for PlotHistory {
+    fn default() -> Self {
+        Self {
+            in_db: [[METER_FLOOR_DB; PLOT_N]; NUM_CHANNELS],
+            out_db: [[METER_FLOOR_DB; PLOT_N]; NUM_CHANNELS],
+            gr_db: [[0.0; PLOT_N]; NUM_CHANNELS],
+            write: 0,
+            len: 0,
+        }
+    }
+}
+
+impl PlotHistory {
+    /// Append one frame of (in_db, out_db, gr_db) per channel.
+    fn push(&mut self, samples: &[(f32, f32, f32); NUM_CHANNELS]) {
+        for i in 0..NUM_CHANNELS {
+            self.in_db[i][self.write] = samples[i].0;
+            self.out_db[i][self.write] = samples[i].1;
+            self.gr_db[i][self.write] = samples[i].2;
+        }
+        self.write = (self.write + 1) % PLOT_N;
+        self.len = (self.len + 1).min(PLOT_N);
+    }
+}
+
+/// GUI-side editor state (not persisted): ceiling-lamp latch, selected plot channel, plot history,
+/// and the time-based scroll cadence (flow speed = how many seconds span the plot width).
+struct EditorState {
+    /// egui time (seconds) of the most recent ceiling catch, while the lamp is latched on.
+    /// `None` = lamp off (never caught, expired, or dismissed by a click).
+    ceiling_trigger: Option<f64>,
+    /// Channel shown in the plot (0..NUM_CHANNELS: low/mid/high/all).
+    selected: usize,
+    history: PlotHistory,
+    /// Seconds of history shown across the full plot width — the flow speed (smaller = faster).
+    window_s: f64,
+    /// egui time of the last column pushed to the history ring (the cadence clock).
+    last_push: f64,
+    /// Per-channel max accumulator (in_db, out_db, gr_db) for the column currently being built.
+    acc: [(f32, f32, f32); NUM_CHANNELS],
+}
+
+impl Default for EditorState {
+    fn default() -> Self {
+        Self {
+            ceiling_trigger: None,
+            selected: 0,
+            history: PlotHistory::default(),
+            window_s: 5.0,
+            last_push: 0.0,
+            acc: [(METER_FLOOR_DB, METER_FLOOR_DB, 0.0); NUM_CHANNELS],
+        }
+    }
+}
+
+/// Build the plugin editor over shared handles to the params and meter state.
+pub(crate) fn create(params: Arc<Codename206Params>, meters: Arc<Meters>) -> Option<Box<dyn Editor>> {
+    let egui_state = params.editor_state.clone();
+    create_egui_editor(
+        params.editor_state.clone(),
+        EditorState::default(),
+        |_, _| {},
+        move |egui_ctx, setter, state| {
+            // Keep frames coming so the meters animate and the lamp can time out while open.
+            egui_ctx.request_repaint();
+
+            // One column of controls for a single compressor channel.
+            let band_col = |ui: &mut egui::Ui, title: &str, p: &CompressorParams| {
+                ui.strong(title);
+                ui.label("Pre-gain");
+                ui.add(widgets::ParamSlider::for_param(&p.pre_gain_db, setter));
+                ui.add(widgets::ParamSlider::for_param(&p.detection, setter));
+                ui.label("Threshold");
+                ui.add(widgets::ParamSlider::for_param(&p.threshold_db, setter));
+                ui.label("Ratio");
+                ui.add(widgets::ParamSlider::for_param(&p.ratio, setter));
+                ui.label("Knee");
+                ui.add(widgets::ParamSlider::for_param(&p.knee_db, setter));
+                ui.label("Attack");
+                ui.add(widgets::ParamSlider::for_param(&p.attack_ms, setter));
+                ui.label("Release");
+                ui.add(widgets::ParamSlider::for_param(&p.release_ms, setter));
+                ui.label("Makeup");
+                ui.add(widgets::ParamSlider::for_param(&p.makeup_db, setter));
+                ui.add(widgets::ParamSlider::for_param(&p.bypass, setter));
+            };
+
+            // Resizable window; vertical scroll so every control stays reachable even when the
+            // window is small. (Placeholder layout — Stage 6 will replace it.)
+            ResizableWindow::new("editor")
+                .min_size(Vec2::new(480.0, 320.0))
+                .show(egui_ctx, egui_state.as_ref(), |ui| {
+                    egui::ScrollArea::vertical().show(ui, |ui| {
+                        ui.heading(Codename206::NAME);
+                        draw_meters(ui, &meters, state);
+                        ui.separator();
+                        draw_plot(ui, &meters, state);
+                        ui.separator();
+                        // Global controls stacked vertically so they never overflow sideways.
+                        egui::Grid::new("globals").num_columns(2).show(ui, |ui| {
+                            ui.label("Xover Lo/Mid");
+                            ui.add(widgets::ParamSlider::for_param(&params.crossover_low_hz, setter));
+                            ui.end_row();
+                            ui.label("Xover Mid/Hi");
+                            ui.add(widgets::ParamSlider::for_param(&params.crossover_high_hz, setter));
+                            ui.end_row();
+                            ui.label("Look-ahead");
+                            ui.add(widgets::ParamSlider::for_param(&params.look_ahead_ms, setter));
+                            ui.end_row();
+                            ui.label("Ceiling");
+                            ui.add(widgets::ParamSlider::for_param(&params.output_ceiling_db, setter));
+                            ui.end_row();
+                            ui.label("Lim Release");
+                            ui.add(widgets::ParamSlider::for_param(&params.limiter_release_ms, setter));
+                            ui.end_row();
+                        });
+                        ui.separator();
+                        ui.columns(4, |cols| {
+                            band_col(&mut cols[0], "LOW", &params.low);
+                            band_col(&mut cols[1], "MID", &params.mid);
+                            band_col(&mut cols[2], "HIGH", &params.high);
+                            band_col(&mut cols[3], "ALL", &params.all);
+                        });
+                    });
+                });
+        },
+    )
+}
+
+/// Draw the meter panel: one channel group per column as `|L | GR | R|` (output level left/right,
+/// mono gain reduction in the middle), plus the latching ceiling lamp driven by the limiter.
+fn draw_meters(ui: &mut egui::Ui, meters: &Meters, state: &mut EditorState) {
+    let labels = ["LOW", "MID", "HIGH", "ALL"];
+    let now = ui.ctx().input(|i| i.time);
+    let (rect, _) =
+        ui.allocate_exact_size(vec2(ui.available_width(), METER_PANEL_H), Sense::hover());
+    let p = ui.painter_at(rect);
+    p.rect_filled(rect, CornerRadius::ZERO, Color32::from_rgb(20, 20, 24));
+
+    let top = rect.top() + 10.0;
+    let bottom = rect.bottom() - 18.0; // leave a row for the labels
+    let cell_w = rect.width() / NUM_CHANNELS as f32;
+    // Three bars per cluster now, so they're narrower than the old two-bar layout.
+    let bar_w = (cell_w * 0.17).min(14.0);
+    let gap = (cell_w * 0.05).min(5.0);
+
+    for i in 0..NUM_CHANNELS {
+        let cell_left = rect.left() + i as f32 * cell_w;
+        let group_w = bar_w * 3.0 + gap * 2.0;
+        let bx = cell_left + (cell_w - group_w) * 0.5;
+
+        // L / R output level (upward); colour warns as it nears 0 dBFS.
+        let l_db = util::gain_to_db(meters.level_l[i].load(Ordering::Relaxed));
+        let r_db = util::gain_to_db(meters.level_r[i].load(Ordering::Relaxed));
+        let l_frac = ((l_db - METER_FLOOR_DB) / -METER_FLOOR_DB).clamp(0.0, 1.0);
+        let r_frac = ((r_db - METER_FLOOR_DB) / -METER_FLOOR_DB).clamp(0.0, 1.0);
+
+        // Mono gain reduction (downward from the top).
+        let gr_db = meters.gain_reduction_db[i].load(Ordering::Relaxed);
+        let gr_frac = (gr_db / GR_FULL_DB).clamp(0.0, 1.0);
+
+        v_bar(&p, bx, bar_w, top, bottom, l_frac, level_color(l_db), false);
+        v_bar(&p, bx + bar_w + gap, bar_w, top, bottom, gr_frac, Color32::from_rgb(240, 150, 60), true);
+        v_bar(&p, bx + 2.0 * (bar_w + gap), bar_w, top, bottom, r_frac, level_color(r_db), false);
+
+        p.text(
+            pos2(cell_left + cell_w * 0.5, rect.bottom() - 2.0),
+            Align2::CENTER_BOTTOM,
+            labels[i],
+            FontId::proportional(12.0),
+            Color32::from_gray(200),
+        );
+    }
+
+    // Ceiling lamp (top-right): latches on when the limiter catches a peak, then holds. It clears
+    // after LAMP_HOLD_S or when clicked. Re-arms while limiting is ongoing.
+    if meters.limiter_gr_db.load(Ordering::Relaxed) > LAMP_TRIGGER_DB {
+        state.ceiling_trigger = Some(now);
+    }
+    let center = pos2(rect.right() - 14.0, rect.top() + 14.0);
+    let lamp_rect = Rect::from_center_size(center, vec2(22.0, 22.0));
+    let resp = ui
+        .interact(lamp_rect, ui.id().with("ceiling_lamp"), Sense::click())
+        .on_hover_cursor(CursorIcon::PointingHand)
+        .on_hover_text("Ceiling reached — click to clear");
+    if resp.clicked() {
+        state.ceiling_trigger = None;
+    }
+    // Expire the latch once the hold time has passed.
+    if let Some(t) = state.ceiling_trigger {
+        if now - t >= LAMP_HOLD_S {
+            state.ceiling_trigger = None;
+        }
+    }
+    let lamp = if state.ceiling_trigger.is_some() {
+        Color32::from_rgb(255, 40, 40)
+    } else {
+        Color32::from_rgb(40, 12, 12)
+    };
+    p.circle_filled(center, 7.0, lamp);
+    p.text(
+        pos2(center.x - 14.0, center.y),
+        Align2::RIGHT_CENTER,
+        "CEILING",
+        FontId::proportional(11.0),
+        Color32::from_gray(180),
+    );
+}
+
+/// Draw the scrolling in/out/gain-reduction plot for the selected channel, plus the channel tabs.
+/// History for all channels is sampled every frame (wall-clock), so it scrolls continuously while
+/// the editor is open regardless of which tab is shown.
+fn draw_plot(ui: &mut egui::Ui, meters: &Meters, state: &mut EditorState) {
+    let now = ui.ctx().input(|i| i.time);
+    // (Re)initialise the cadence clock on first use or after a long gap (e.g. tab hidden).
+    if state.last_push <= 0.0 || now - state.last_push > state.window_s {
+        state.last_push = now;
+    }
+    // Accumulate this frame's block peaks into the column currently being built.
+    for i in 0..NUM_CHANNELS {
+        let in_db = util::gain_to_db(meters.plot_in[i].load(Ordering::Relaxed));
+        let out_db = util::gain_to_db(meters.plot_out[i].load(Ordering::Relaxed));
+        let gr = meters.plot_gr[i].load(Ordering::Relaxed);
+        state.acc[i].0 = state.acc[i].0.max(in_db);
+        state.acc[i].1 = state.acc[i].1.max(out_db);
+        state.acc[i].2 = state.acc[i].2.max(gr);
+    }
+    // Emit columns on a fixed time grid so the window length stays accurate regardless of the
+    // frame rate. The while loop is bounded by PLOT_N thanks to the resync above.
+    let dt_col = state.window_s / PLOT_N as f64;
+    let mut pushed = false;
+    while now - state.last_push >= dt_col {
+        state.history.push(&state.acc);
+        state.last_push += dt_col;
+        pushed = true;
+    }
+    if pushed {
+        state.acc = [(METER_FLOOR_DB, METER_FLOOR_DB, 0.0); NUM_CHANNELS];
+    }
+
+    // Channel tabs + flow-speed selector + legend.
+    let labels = ["LOW", "MID", "HIGH", "ALL"];
+    let speeds = [2.0f64, 5.0, 15.0, 45.0];
+    ui.horizontal(|ui| {
+        ui.label("Plot:");
+        for (i, l) in labels.iter().enumerate() {
+            ui.selectable_value(&mut state.selected, i, *l);
+        }
+        ui.separator();
+        ui.label("Speed:");
+        let mut speed_changed = false;
+        for &w in &speeds {
+            if ui.selectable_value(&mut state.window_s, w, format!("{w:.0}s")).changed() {
+                speed_changed = true;
+            }
+        }
+        if speed_changed {
+            // Cadence changed: start the history fresh so the time axis is consistent.
+            state.history = PlotHistory::default();
+            state.acc = [(METER_FLOOR_DB, METER_FLOOR_DB, 0.0); NUM_CHANNELS];
+            state.last_push = now;
+        }
+        ui.separator();
+        ui.colored_label(COLOR_IN, "in");
+        ui.colored_label(COLOR_OUT, "out");
+        ui.colored_label(COLOR_GR, "GR");
+    });
+
+    let (rect, _) =
+        ui.allocate_exact_size(vec2(ui.available_width(), PLOT_PANEL_H), Sense::hover());
+    let p = ui.painter_at(rect);
+    p.rect_filled(rect, CornerRadius::ZERO, Color32::from_rgb(16, 16, 20));
+
+    let (top, bottom, left, right) =
+        (rect.top() + 4.0, rect.bottom() - 4.0, rect.left() + 4.0, rect.right() - 4.0);
+    let width = right - left;
+    let y_for_db = |db: f32| -> f32 {
+        let frac = ((db - METER_FLOOR_DB) / -METER_FLOOR_DB).clamp(0.0, 1.0);
+        bottom - frac * (bottom - top)
+    };
+
+    // Gridlines (dB).
+    for &g in &[0.0f32, -12.0, -24.0, -48.0] {
+        let y = y_for_db(g);
+        p.line_segment([pos2(left, y), pos2(right, y)], Stroke::new(1.0, Color32::from_gray(40)));
+        p.text(
+            pos2(left + 2.0, y),
+            Align2::LEFT_BOTTOM,
+            format!("{g:.0}"),
+            FontId::proportional(9.0),
+            Color32::from_gray(90),
+        );
+    }
+
+    let c = state.selected.min(NUM_CHANNELS - 1);
+    let (write, len) = (state.history.write, state.history.len);
+    if len >= 2 {
+        let draw_series = |series: &[f32; PLOT_N], to_db: &dyn Fn(f32) -> f32, color: Color32| {
+            let mut pts = Vec::with_capacity(len);
+            for k in 0..len {
+                let idx = (write + PLOT_N - len + k) % PLOT_N;
+                let pos = (PLOT_N - len + k) as f32 / (PLOT_N - 1) as f32; // newest hugs the right
+                pts.push(pos2(left + pos * width, y_for_db(to_db(series[idx]))));
+            }
+            p.add(egui::Shape::line(pts, Stroke::new(1.5, color)));
+        };
+        draw_series(&state.history.in_db[c], &|db| db, COLOR_IN);
+        draw_series(&state.history.out_db[c], &|db| db, COLOR_OUT);
+        // GR hangs from the 0 dB line: a reduction of X dB is drawn at the -X gridline.
+        draw_series(&state.history.gr_db[c], &|gr| -gr, COLOR_GR);
+    }
+}
+
+/// Draw a vertical bar within `[top, bottom]`. `frac` is 0..1; `from_top` fills downward from the
+/// top (gain reduction) instead of upward from the bottom (level).
+fn v_bar(p: &Painter, x: f32, w: f32, top: f32, bottom: f32, frac: f32, fill: Color32, from_top: bool) {
+    let track = Color32::from_rgb(34, 34, 40);
+    p.rect_filled(Rect::from_min_max(pos2(x, top), pos2(x + w, bottom)), CornerRadius::ZERO, track);
+
+    let h = (bottom - top) * frac.clamp(0.0, 1.0);
+    let filled = if from_top {
+        Rect::from_min_max(pos2(x, top), pos2(x + w, top + h))
+    } else {
+        Rect::from_min_max(pos2(x, bottom - h), pos2(x + w, bottom))
+    };
+    p.rect_filled(filled, CornerRadius::ZERO, fill);
+}
+
+/// Level-bar colour: green below -6 dB, yellow approaching, red near 0 dBFS.
+fn level_color(db: f32) -> Color32 {
+    if db >= -1.0 {
+        Color32::from_rgb(235, 70, 60)
+    } else if db >= -6.0 {
+        Color32::from_rgb(230, 200, 70)
+    } else {
+        Color32::from_rgb(90, 200, 110)
+    }
+}

src/lib.rs

@@ -1,16 +1,20 @@
 use nih_plug::prelude::*;
-use nih_plug_egui::{
-    create_egui_editor,
-    egui::{self, Vec2},
-    resizable_window::ResizableWindow,
-    widgets, EguiState,
-};
 use std::sync::Arc;
 
 mod dsp;
-use dsp::compressor::{Compressor, CompressorSettings, MAX_LOOKAHEAD_MS};
+mod editor;
+mod meters;
+mod params;
+
+use dsp::compressor::{Compressor, MAX_LOOKAHEAD_MS};
 use dsp::crossover::Crossover;
 use dsp::limiter::Limiter;
+use meters::Meters;
+use params::{build_settings, Codename206Params};
+
+/// Peak-meter fall: after this long of silence the bars decay by 12 dB. (Matches nih-plug's
+/// gain-gui example feel.)
+const METER_DECAY_MS: f64 = 150.0;
 
 /// Band indices into the compressor array: low, mid, high, then the 'All' aggregate channel.
 const LOW: usize = 0;
@@ -18,17 +22,6 @@ const MID: usize = 1;
 const HIGH: usize = 2;
 const ALL: usize = 3;
 
-/// Level-detection mode for a compressor's detector.
-#[derive(Enum, PartialEq, Clone, Copy)]
-enum DetectionMode {
-    #[id = "peak"]
-    #[name = "Peak"]
-    Peak,
-    #[id = "rms"]
-    #[name = "RMS"]
-    Rms,
-}
-
 /// Codename 206 — Stage 3: 3-band crossover + per-band compressors summed into an 'All' channel.
 ///
 /// Signal: input → LR4 crossover → {low, mid, high} each through their own compressor → sum →
@@ -42,58 +35,11 @@ struct Codename206 {
     comps: [Compressor; 4],
     /// Output brickwall limiter (final stage).
     limiter: Limiter,
-}
+    /// Lock-free meter state shared with the editor.
-
+    meters: Arc<Meters>,
-#[derive(Params)]
+    /// Per-sample decay factor for the meter peak-hold (computed from the sample rate; raised to
-struct Codename206Params {
+    /// the block length when applied once per block in `process`).
-    #[persist = "editor-state"]
+    meter_decay_weight: f32,
-    editor_state: Arc<EguiState>,
-
-    /// Low/Mid crossover frequency.
-    #[id = "xover_lo"]
-    pub crossover_low_hz: FloatParam,
-    /// Mid/High crossover frequency.
-    #[id = "xover_hi"]
-    pub crossover_high_hz: FloatParam,
-    /// Global look-ahead time (constant reported latency — safe to adjust during playback).
-    #[id = "lookahead"]
-    pub look_ahead_ms: FloatParam,
-
-    /// Output brickwall ceiling (the limiter never lets output exceed this).
-    #[id = "ceiling"]
-    pub output_ceiling_db: FloatParam,
-    /// Output limiter release time.
-    #[id = "lim_rel"]
-    pub limiter_release_ms: FloatParam,
-
-    #[nested(id_prefix = "low", group = "Low")]
-    pub low: CompressorParams,
-    #[nested(id_prefix = "mid", group = "Mid")]
-    pub mid: CompressorParams,
-    #[nested(id_prefix = "high", group = "High")]
-    pub high: CompressorParams,
-    #[nested(id_prefix = "all", group = "All")]
-    pub all: CompressorParams,
-}
-
-#[derive(Params)]
-struct CompressorParams {
-    #[id = "detect"]
-    pub detection: EnumParam<DetectionMode>,
-    #[id = "thresh"]
-    pub threshold_db: FloatParam,
-    #[id = "ratio"]
-    pub ratio: FloatParam,
-    #[id = "knee"]
-    pub knee_db: FloatParam,
-    #[id = "attack"]
-    pub attack_ms: FloatParam,
-    #[id = "release"]
-    pub release_ms: FloatParam,
-    #[id = "makeup"]
-    pub makeup_db: FloatParam,
-    #[id = "bypass"]
-    pub bypass: BoolParam,
 }
 
 impl Default for Codename206 {
@@ -104,131 +50,12 @@ impl Default for Codename206 {
             crossover: Crossover::new(),
             comps: [Compressor::new(), Compressor::new(), Compressor::new(), Compressor::new()],
             limiter: Limiter::new(),
+            meters: Arc::new(Meters::default()),
+            meter_decay_weight: 1.0,
         }
     }
 }
 
-impl Default for Codename206Params {
-    fn default() -> Self {
-        Self {
-            editor_state: EguiState::from_size(760, 520),
-
-            crossover_low_hz: FloatParam::new(
-                "Crossover Lo/Mid",
-                200.0,
-                FloatRange::Skewed { min: 30.0, max: 1_000.0, factor: FloatRange::skew_factor(-1.0) },
-            )
-            .with_value_to_string(formatters::v2s_f32_hz_then_khz(0))
-            .with_string_to_value(formatters::s2v_f32_hz_then_khz()),
-
-            crossover_high_hz: FloatParam::new(
-                "Crossover Mid/Hi",
-                2_500.0,
-                FloatRange::Skewed { min: 500.0, max: 18_000.0, factor: FloatRange::skew_factor(-1.0) },
-            )
-            .with_value_to_string(formatters::v2s_f32_hz_then_khz(0))
-            .with_string_to_value(formatters::s2v_f32_hz_then_khz()),
-
-            look_ahead_ms: FloatParam::new(
-                "Look-ahead",
-                2.0,
-                FloatRange::Linear { min: 0.0, max: MAX_LOOKAHEAD_MS },
-            )
-            .with_unit(" ms")
-            .with_value_to_string(formatters::v2s_f32_rounded(2)),
-
-            output_ceiling_db: FloatParam::new(
-                "Ceiling",
-                0.0,
-                FloatRange::Linear { min: -24.0, max: 0.0 },
-            )
-            .with_unit(" dB")
-            .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            limiter_release_ms: FloatParam::new(
-                "Limiter Release",
-                100.0,
-                FloatRange::Skewed { min: 1.0, max: 1_000.0, factor: FloatRange::skew_factor(-2.0) },
-            )
-            .with_unit(" ms")
-            .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            low: CompressorParams::default(),
-            mid: CompressorParams::default(),
-            high: CompressorParams::default(),
-            all: CompressorParams::default(),
-        }
-    }
-}
-
-impl Default for CompressorParams {
-    fn default() -> Self {
-        Self {
-            detection: EnumParam::new("Detection", DetectionMode::Peak),
-
-            threshold_db: FloatParam::new(
-                "Threshold",
-                -18.0,
-                FloatRange::Linear { min: -60.0, max: 0.0 },
-            )
-            .with_unit(" dB")
-            .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            ratio: FloatParam::new(
-                "Ratio",
-                2.0,
-                FloatRange::Skewed { min: 1.0, max: 20.0, factor: FloatRange::skew_factor(-1.0) },
-            )
-            .with_value_to_string(Arc::new(|v| format!("{v:.2} : 1")))
-            .with_string_to_value(Arc::new(|s| {
-                s.split(':').next().and_then(|x| x.trim().parse::<f32>().ok())
-            })),
-
-            knee_db: FloatParam::new("Knee", 6.0, FloatRange::Linear { min: 0.0, max: 24.0 })
-                .with_unit(" dB")
-                .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            attack_ms: FloatParam::new(
-                "Attack",
-                10.0,
-                FloatRange::Skewed { min: 0.0, max: 100.0, factor: FloatRange::skew_factor(-2.0) },
-            )
-            .with_unit(" ms")
-            .with_value_to_string(formatters::v2s_f32_rounded(2)),
-
-            release_ms: FloatParam::new(
-                "Release",
-                100.0,
-                FloatRange::Skewed { min: 1.0, max: 1_000.0, factor: FloatRange::skew_factor(-2.0) },
-            )
-            .with_unit(" ms")
-            .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            makeup_db: FloatParam::new("Makeup", 0.0, FloatRange::Linear { min: -12.0, max: 24.0 })
-                .with_smoother(SmoothingStyle::Linear(20.0))
-                .with_unit(" dB")
-                .with_value_to_string(formatters::v2s_f32_rounded(1)),
-
-            bypass: BoolParam::new("Bypass", false),
-        }
-    }
-}
-
-/// Build the per-block compressor settings for one channel's params (makeup filled per sample).
-fn build_settings(p: &CompressorParams, lookahead: usize, sample_rate: f32) -> CompressorSettings {
-    CompressorSettings {
-        threshold_db: p.threshold_db.value(),
-        ratio: p.ratio.value(),
-        knee_db: p.knee_db.value(),
-        attack_coef: Compressor::time_to_coef(p.attack_ms.value(), sample_rate),
-        release_coef: Compressor::time_to_coef(p.release_ms.value(), sample_rate),
-        makeup_db: 0.0,
-        lookahead_samples: lookahead,
-        use_rms: p.detection.value() == DetectionMode::Rms,
-        bypass: p.bypass.value(),
-    }
-}
-
 impl Codename206 {
     fn lookahead_samples(&self) -> usize {
         (self.params.look_ahead_ms.value() * 0.001 * self.sample_rate).round() as usize
@@ -269,68 +96,7 @@ impl Plugin for Codename206 {
     }
 
     fn editor(&mut self, _async_executor: AsyncExecutor<Self>) -> Option<Box<dyn Editor>> {
-        let params = self.params.clone();
+        editor::create(self.params.clone(), self.meters.clone())
-        let egui_state = self.params.editor_state.clone();
-        create_egui_editor(
-            self.params.editor_state.clone(),
-            (),
-            |_, _| {},
-            move |egui_ctx, setter, _state| {
-                // One column of controls for a single compressor channel.
-                let band_col = |ui: &mut egui::Ui, title: &str, p: &CompressorParams| {
-                    ui.strong(title);
-                    ui.add(widgets::ParamSlider::for_param(&p.detection, setter));
-                    ui.label("Threshold");
-                    ui.add(widgets::ParamSlider::for_param(&p.threshold_db, setter));
-                    ui.label("Ratio");
-                    ui.add(widgets::ParamSlider::for_param(&p.ratio, setter));
-                    ui.label("Knee");
-                    ui.add(widgets::ParamSlider::for_param(&p.knee_db, setter));
-                    ui.label("Attack");
-                    ui.add(widgets::ParamSlider::for_param(&p.attack_ms, setter));
-                    ui.label("Release");
-                    ui.add(widgets::ParamSlider::for_param(&p.release_ms, setter));
-                    ui.label("Makeup");
-                    ui.add(widgets::ParamSlider::for_param(&p.makeup_db, setter));
-                    ui.add(widgets::ParamSlider::for_param(&p.bypass, setter));
-                };
-
-                // Resizable window; vertical scroll so every control stays reachable even when the
-                // window is small. (Placeholder layout — Stage 6 will replace it.)
-                ResizableWindow::new("editor")
-                    .min_size(Vec2::new(480.0, 320.0))
-                    .show(egui_ctx, egui_state.as_ref(), |ui| {
-                        egui::ScrollArea::vertical().show(ui, |ui| {
-                            ui.heading(Self::NAME);
-                            // Global controls stacked vertically so they never overflow sideways.
-                            egui::Grid::new("globals").num_columns(2).show(ui, |ui| {
-                                ui.label("Xover Lo/Mid");
-                                ui.add(widgets::ParamSlider::for_param(&params.crossover_low_hz, setter));
-                                ui.end_row();
-                                ui.label("Xover Mid/Hi");
-                                ui.add(widgets::ParamSlider::for_param(&params.crossover_high_hz, setter));
-                                ui.end_row();
-                                ui.label("Look-ahead");
-                                ui.add(widgets::ParamSlider::for_param(&params.look_ahead_ms, setter));
-                                ui.end_row();
-                                ui.label("Ceiling");
-                                ui.add(widgets::ParamSlider::for_param(&params.output_ceiling_db, setter));
-                                ui.end_row();
-                                ui.label("Lim Release");
-                                ui.add(widgets::ParamSlider::for_param(&params.limiter_release_ms, setter));
-                                ui.end_row();
-                            });
-                            ui.separator();
-                            ui.columns(4, |cols| {
-                                band_col(&mut cols[0], "LOW", &params.low);
-                                band_col(&mut cols[1], "MID", &params.mid);
-                                band_col(&mut cols[2], "HIGH", &params.high);
-                                band_col(&mut cols[3], "ALL", &params.all);
-                            });
-                        });
-                    });
-            },
-        )
     }
 
     fn initialize(
@@ -345,6 +111,10 @@ impl Plugin for Codename206 {
             .map(NonZeroU32::get)
             .unwrap_or(2) as usize;
 
+        // Per-block decay so the meters fall ~12 dB over METER_DECAY_MS of silence.
+        self.meter_decay_weight =
+            0.25f64.powf((self.sample_rate as f64 * METER_DECAY_MS / 1000.0).recip()) as f32;
+
         for comp in &mut self.comps {
             comp.prepare(self.sample_rate, channels, MAX_LOOKAHEAD_MS);
         }
@@ -370,6 +140,8 @@ impl Plugin for Codename206 {
             comp.reset();
         }
         self.limiter.reset();
+        // Transport restart / sample-rate change: drop stale meter values to silence.
+        self.meters.clear();
     }
 
     fn process(
@@ -401,6 +173,15 @@ impl Plugin for Codename206 {
         let limiter_release =
             Compressor::time_to_coef(self.params.limiter_release_ms.value(), self.sample_rate);
 
+        // Only do the (cheap) metering work when the editor is actually open.
+        let metering = self.params.editor_state.is_open();
+        let num_samples = buffer.samples();
+        let mut lvl_l = [0.0f32; meters::NUM_CHANNELS];
+        let mut lvl_r = [0.0f32; meters::NUM_CHANNELS];
+        let mut inp = [0.0f32; meters::NUM_CHANNELS]; // mono input peak (for the scrolling plot)
+        let mut gr = [0.0f32; meters::NUM_CHANNELS];
+        let mut lim_gr = 0.0f32;
+
         let mut in_frame = [0.0f32; 2];
         let mut band_in = [[0.0f32; 2]; 3];
         let mut band_out = [[0.0f32; 2]; 3];
@@ -410,6 +191,7 @@ impl Plugin for Codename206 {
 
         for mut frame in buffer.iter_samples() {
             let n = frame.len().min(2);
+            let r = (n - 1).min(1); // right-channel index (== left when mono)
             for ch in 0..n {
                 in_frame[ch] = *frame.get_mut(ch).unwrap();
             }
@@ -422,28 +204,69 @@ impl Plugin for Codename206 {
                 band_in[HIGH][ch] = hi;
             }
 
-            // Compress each band (per-sample smoothed makeup), then sum.
+            // Drive + compress each band (per-sample smoothed pre-gain & makeup), then sum.
             summed[..n].fill(0.0);
             for b in 0..3 {
+                let pre = util::db_to_gain(band_params[b].pre_gain_db.smoothed.next());
+                for ch in 0..n {
+                    band_in[b][ch] *= pre;
+                }
                 band_set[b].makeup_db = band_params[b].makeup_db.smoothed.next();
                 self.comps[b].process(&band_in[b][..n], &mut band_out[b][..n], &band_set[b]);
                 for ch in 0..n {
                     summed[ch] += band_out[b][ch];
                 }
+                if metering {
+                    inp[b] = inp[b].max(band_in[b][0].abs().max(band_in[b][r].abs()));
+                    lvl_l[b] = lvl_l[b].max(band_out[b][0].abs());
+                    lvl_r[b] = lvl_r[b].max(band_out[b][r].abs());
+                    gr[b] = gr[b]
+                        .max(if band_set[b].bypass { 0.0 } else { self.comps[b].gain_reduction_db() });
+                }
             }
 
-            // 'All' aggregate channel over the summed bands.
+            // 'All' aggregate channel over the summed bands (driven before its compressor).
+            let all_pre = util::db_to_gain(self.params.all.pre_gain_db.smoothed.next());
+            for ch in 0..n {
+                summed[ch] *= all_pre;
+            }
             all_set.makeup_db = self.params.all.makeup_db.smoothed.next();
             self.comps[ALL].process(&summed[..n], &mut out_frame[..n], &all_set);
 
             // Output brickwall limiter.
             self.limiter.process(&out_frame[..n], &mut lim_frame[..n], ceiling, limiter_release);
 
+            if metering {
+                inp[ALL] = inp[ALL].max(summed[0].abs().max(summed[r].abs()));
+                lvl_l[ALL] = lvl_l[ALL].max(out_frame[0].abs());
+                lvl_r[ALL] = lvl_r[ALL].max(out_frame[r].abs());
+                gr[ALL] = gr[ALL]
+                    .max(if all_set.bypass { 0.0 } else { self.comps[ALL].gain_reduction_db() });
+                lim_gr = lim_gr.max(self.limiter.gain_reduction_db());
+            }
+
             for ch in 0..n {
                 *frame.get_mut(ch).unwrap() = lim_frame[ch];
             }
         }
 
+        // Publish one decimated value per meter for this block. The decay weight is per-sample,
+        // so raise it to the block length to keep the fall time constant independent of buffer size
+        // (we apply it once per block, not once per sample).
+        if metering {
+            let w = self.meter_decay_weight.powi(num_samples as i32);
+            for i in 0..meters::NUM_CHANNELS {
+                meters::decay_store(&self.meters.level_l[i], lvl_l[i], w);
+                meters::decay_store(&self.meters.level_r[i], lvl_r[i], w);
+                meters::decay_store(&self.meters.gain_reduction_db[i], gr[i], w);
+                // Raw block peaks for the scrolling plot (editor keeps its own history).
+                meters::store_instant(&self.meters.plot_in[i], inp[i]);
+                meters::store_instant(&self.meters.plot_out[i], lvl_l[i].max(lvl_r[i]));
+                meters::store_instant(&self.meters.plot_gr[i], gr[i]);
+            }
+            meters::decay_store(&self.meters.limiter_gr_db, lim_gr, w);
+        }
+
         ProcessStatus::Normal
     }
 }

src/meters.rs

@@ -0,0 +1,84 @@
+//! Lock-free meter state shared from the audio thread to the editor.
+//!
+//! `process()` is the single writer (one store per value per block — decimated, not per sample);
+//! the editor is the single reader (once per frame). All access is wait-free via atomics, so the
+//! realtime thread never blocks. Values are plain scalars (no streaming history yet) — enough for
+//! the per-channel level + gain-reduction bars and the ceiling lamp.
+
+use nih_plug::prelude::AtomicF32;
+use std::sync::atomic::Ordering;
+
+/// Metered channels: low, mid, high, then the 'All' aggregate — same order as the compressors.
+pub const NUM_CHANNELS: usize = 4;
+
+pub struct Meters {
+    /// Left output level per channel as a **linear** peak. Peak-with-decay.
+    pub level_l: [AtomicF32; NUM_CHANNELS],
+    /// Right output level per channel (== left for mono signals). Stored separately so the planned
+    /// `|L|GR|R|` layout is a pure editor change; the current bars render `max(L, R)`.
+    pub level_r: [AtomicF32; NUM_CHANNELS],
+    /// Compressor gain reduction per channel in **dB (>= 0)**. Mono by design — detection is
+    /// stereo-linked, so the same gain applies to both channels.
+    pub gain_reduction_db: [AtomicF32; NUM_CHANNELS],
+    /// Output limiter gain reduction in **dB (>= 0)** — drives the ceiling lamp.
+    pub limiter_gr_db: AtomicF32,
+
+    // --- Scrolling plot feed: instantaneous block peaks, NOT decayed. The editor samples these
+    // each frame into its own history ring. Per channel: input level (entering the compressor),
+    // output level, and gain reduction.
+    /// Mono input level per channel (linear peak, post pre-gain, pre-compressor).
+    pub plot_in: [AtomicF32; NUM_CHANNELS],
+    /// Mono output level per channel (linear peak, post-compressor).
+    pub plot_out: [AtomicF32; NUM_CHANNELS],
+    /// Gain reduction per channel in dB (>= 0).
+    pub plot_gr: [AtomicF32; NUM_CHANNELS],
+}
+
+impl Default for Meters {
+    fn default() -> Self {
+        Self {
+            level_l: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            level_r: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            gain_reduction_db: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            limiter_gr_db: AtomicF32::new(0.0),
+            plot_in: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            plot_out: std::array::from_fn(|_| AtomicF32::new(0.0)),
+            plot_gr: std::array::from_fn(|_| AtomicF32::new(0.0)),
+        }
+    }
+}
+
+impl Meters {
+    /// Zero every meter. Called from the plugin's `reset()` (transport restart / sample-rate
+    /// change) so the display starts from silence rather than stale values. Real-time safe.
+    pub fn clear(&self) {
+        for i in 0..NUM_CHANNELS {
+            self.level_l[i].store(0.0, Ordering::Relaxed);
+            self.level_r[i].store(0.0, Ordering::Relaxed);
+            self.gain_reduction_db[i].store(0.0, Ordering::Relaxed);
+            self.plot_in[i].store(0.0, Ordering::Relaxed);
+            self.plot_out[i].store(0.0, Ordering::Relaxed);
+            self.plot_gr[i].store(0.0, Ordering::Relaxed);
+        }
+        self.limiter_gr_db.store(0.0, Ordering::Relaxed);
+    }
+}
+
+/// Store an instantaneous value (no smoothing) — used for the scrolling-plot feed, which the
+/// editor smooths/decimates on its own.
+pub fn store_instant(meter: &AtomicF32, value: f32) {
+    meter.store(value, Ordering::Relaxed);
+}
+
+/// Update a meter atomic with a new block value using peak-hold-with-decay: jump instantly to a
+/// louder value, ease back down by `decay_weight` (0..1, closer to 1 = slower fall). Keeps meters
+/// from flickering while staying responsive to transients.
+pub fn decay_store(meter: &AtomicF32, block_value: f32, decay_weight: f32) {
+    let current = meter.load(Ordering::Relaxed);
+    let next = if block_value > current {
+        block_value
+    } else {
+        current * decay_weight + block_value * (1.0 - decay_weight)
+    };
+    meter.store(next, Ordering::Relaxed);
+}

src/params.rs

@@ -0,0 +1,213 @@
+//! Plugin parameters and their layout.
+//!
+//! Holds the global controls plus four `CompressorParams` blocks (low/mid/high + the 'All'
+//! aggregate channel). `build_settings` translates a channel's params into the per-block
+//! [`CompressorSettings`] the DSP consumes.
+
+use nih_plug::prelude::*;
+use nih_plug_egui::EguiState;
+use std::sync::Arc;
+
+use crate::dsp::compressor::{Compressor, CompressorSettings, MAX_LOOKAHEAD_MS};
+
+/// Level-detection mode for a compressor's detector.
+#[derive(Enum, PartialEq, Clone, Copy)]
+pub enum DetectionMode {
+    #[id = "peak"]
+    #[name = "Peak"]
+    Peak,
+    #[id = "rms"]
+    #[name = "RMS"]
+    Rms,
+}
+
+#[derive(Params)]
+pub struct Codename206Params {
+    #[persist = "editor-state"]
+    pub editor_state: Arc<EguiState>,
+
+    /// Low/Mid crossover frequency.
+    #[id = "xover_lo"]
+    pub crossover_low_hz: FloatParam,
+    /// Mid/High crossover frequency.
+    #[id = "xover_hi"]
+    pub crossover_high_hz: FloatParam,
+    /// Global look-ahead time (constant reported latency — safe to adjust during playback).
+    #[id = "lookahead"]
+    pub look_ahead_ms: FloatParam,
+
+    /// Output brickwall ceiling (the limiter never lets output exceed this).
+    #[id = "ceiling"]
+    pub output_ceiling_db: FloatParam,
+    /// Output limiter release time.
+    #[id = "lim_rel"]
+    pub limiter_release_ms: FloatParam,
+
+    #[nested(id_prefix = "low", group = "Low")]
+    pub low: CompressorParams,
+    #[nested(id_prefix = "mid", group = "Mid")]
+    pub mid: CompressorParams,
+    #[nested(id_prefix = "high", group = "High")]
+    pub high: CompressorParams,
+    #[nested(id_prefix = "all", group = "All")]
+    pub all: CompressorParams,
+}
+
+#[derive(Params)]
+pub struct CompressorParams {
+    /// Drive into the compressor: scales the signal **before** detection, so it both pushes the
+    /// channel further into compression and feeds the downstream sum/limiter harder. Combined with
+    /// makeup (post-comp), this gives full per-channel input/output gain-staging.
+    #[id = "pregain"]
+    pub pre_gain_db: FloatParam,
+    #[id = "detect"]
+    pub detection: EnumParam<DetectionMode>,
+    #[id = "thresh"]
+    pub threshold_db: FloatParam,
+    #[id = "ratio"]
+    pub ratio: FloatParam,
+    #[id = "knee"]
+    pub knee_db: FloatParam,
+    #[id = "attack"]
+    pub attack_ms: FloatParam,
+    #[id = "release"]
+    pub release_ms: FloatParam,
+    #[id = "makeup"]
+    pub makeup_db: FloatParam,
+    #[id = "bypass"]
+    pub bypass: BoolParam,
+}
+
+impl Default for Codename206Params {
+    fn default() -> Self {
+        Self {
+            editor_state: EguiState::from_size(760, 520),
+
+            crossover_low_hz: FloatParam::new(
+                "Crossover Lo/Mid",
+                200.0,
+                FloatRange::Skewed { min: 30.0, max: 1_000.0, factor: FloatRange::skew_factor(-1.0) },
+            )
+            .with_value_to_string(formatters::v2s_f32_hz_then_khz(0))
+            .with_string_to_value(formatters::s2v_f32_hz_then_khz()),
+
+            crossover_high_hz: FloatParam::new(
+                "Crossover Mid/Hi",
+                2_500.0,
+                FloatRange::Skewed { min: 500.0, max: 18_000.0, factor: FloatRange::skew_factor(-1.0) },
+            )
+            .with_value_to_string(formatters::v2s_f32_hz_then_khz(0))
+            .with_string_to_value(formatters::s2v_f32_hz_then_khz()),
+
+            look_ahead_ms: FloatParam::new(
+                "Look-ahead",
+                2.0,
+                FloatRange::Linear { min: 0.0, max: MAX_LOOKAHEAD_MS },
+            )
+            .with_unit(" ms")
+            .with_value_to_string(formatters::v2s_f32_rounded(2)),
+
+            output_ceiling_db: FloatParam::new(
+                "Ceiling",
+                0.0,
+                FloatRange::Linear { min: -24.0, max: 0.0 },
+            )
+            .with_unit(" dB")
+            .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            limiter_release_ms: FloatParam::new(
+                "Limiter Release",
+                100.0,
+                FloatRange::Skewed { min: 1.0, max: 1_000.0, factor: FloatRange::skew_factor(-2.0) },
+            )
+            .with_unit(" ms")
+            .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            low: CompressorParams::default(),
+            mid: CompressorParams::default(),
+            high: CompressorParams::default(),
+            all: CompressorParams::default(),
+        }
+    }
+}
+
+impl Default for CompressorParams {
+    fn default() -> Self {
+        Self {
+            pre_gain_db: FloatParam::new(
+                "Pre-gain",
+                0.0,
+                FloatRange::Linear { min: -24.0, max: 36.0 },
+            )
+            .with_smoother(SmoothingStyle::Linear(20.0))
+            .with_unit(" dB")
+            .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            detection: EnumParam::new("Detection", DetectionMode::Peak),
+
+            threshold_db: FloatParam::new(
+                "Threshold",
+                -18.0,
+                FloatRange::Linear { min: -60.0, max: 0.0 },
+            )
+            .with_unit(" dB")
+            .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            ratio: FloatParam::new(
+                "Ratio",
+                2.0,
+                FloatRange::Skewed { min: 1.0, max: 20.0, factor: FloatRange::skew_factor(-1.0) },
+            )
+            .with_value_to_string(Arc::new(|v| format!("{v:.2} : 1")))
+            .with_string_to_value(Arc::new(|s| {
+                s.split(':').next().and_then(|x| x.trim().parse::<f32>().ok())
+            })),
+
+            knee_db: FloatParam::new("Knee", 6.0, FloatRange::Linear { min: 0.0, max: 24.0 })
+                .with_unit(" dB")
+                .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            attack_ms: FloatParam::new(
+                "Attack",
+                10.0,
+                FloatRange::Skewed { min: 0.0, max: 100.0, factor: FloatRange::skew_factor(-2.0) },
+            )
+            .with_unit(" ms")
+            .with_value_to_string(formatters::v2s_f32_rounded(2)),
+
+            release_ms: FloatParam::new(
+                "Release",
+                100.0,
+                FloatRange::Skewed { min: 1.0, max: 1_000.0, factor: FloatRange::skew_factor(-2.0) },
+            )
+            .with_unit(" ms")
+            .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            makeup_db: FloatParam::new("Makeup", 0.0, FloatRange::Linear { min: -24.0, max: 24.0 })
+                .with_smoother(SmoothingStyle::Linear(20.0))
+                .with_unit(" dB")
+                .with_value_to_string(formatters::v2s_f32_rounded(1)),
+
+            bypass: BoolParam::new("Bypass", false),
+        }
+    }
+}
+
+/// Build the per-block compressor settings for one channel's params (makeup filled per sample).
+pub fn build_settings(
+    p: &CompressorParams,
+    lookahead: usize,
+    sample_rate: f32,
+) -> CompressorSettings {
+    CompressorSettings {
+        threshold_db: p.threshold_db.value(),
+        ratio: p.ratio.value(),
+        knee_db: p.knee_db.value(),
+        attack_coef: Compressor::time_to_coef(p.attack_ms.value(), sample_rate),
+        release_coef: Compressor::time_to_coef(p.release_ms.value(), sample_rate),
+        makeup_db: 0.0,
+        lookahead_samples: lookahead,
+        use_rms: p.detection.value() == DetectionMode::Rms,
+        bypass: p.bypass.value(),
+    }
+}