PeppyMeter Window

A skinnable analog VU meter window — a native Swift port of project-owner/PeppyMeter. It renders left/right audio levels on classic analog needle (circular) and bar (linear) meters composited from bundled image templates. Two implementations (classic/modern UI) share one mode-neutral engine, following the same standalone-window pattern as the spectrum-analyzer-window and Audio Analyzer windows.

Accessing

• Main-window right-click context menu → PeppyMeter
• Window menu → PeppyMeter
• Available in classic and modern UI modes.

What it shows

• Circular meters — one rotating needle per channel (stereo) or a single needle (mono), swinging between per-meter start/stop angles.
• Linear meters — a bar (or single moving indicator) per channel that grows with level.
• Right-click the window to pick any bundled meter or toggle Random (auto-switches on an interval).

The default catalog is the PeppyMeter 480×320 templates (25 meters: bar, vintage, blue, compass, chillout, big-bang, …). Higher-resolution sibling sets (800x480, plus the partial wide 1280x400 set) are bundled for sharper large-window/fullscreen rendering. Mixed .png/.jpg backgrounds are supported.

Audio path (levels)

PeppyMeter reuses the existing stereo tap — it does not add a new audio tap.

• PeppyMeterLevelModel registers a stereo consumer via WindowManager.shared.audioEngine.addStereoConsumer("peppyMeter") while the window is shown, so the tap stays idle when no meter is open (removed on hide/close/teardown).
• It observes .audioStereoPCMDataUpdated (userInfo left/right = 512 samples, sampleRate), computes per-channel level with AudioAnalysisDSP.rmsDBFS, and maps dBFS → PeppyMeter's 0…100 volume via PeppyMeterLevels.volume(fromDBFS:floor:) (default floor −42 dB).
• A 60 Hz timer applies VU ballistics (fast attack / slow release) and drives redraws, so the needle keeps falling toward zero on silence (when no notifications arrive). Redraws are skipped once the needles settle, so an idle meter costs nothing.

This is the same stereo path the Audio Analyzer's Levels/Delay panes use — see audio-analysis-window. Any change to the stereo tap must still be emitted by both AudioEngine and the StreamingAudioPlayer delegate route. The Cava spectrum window (cava) uses a separate full-rate, undecimated stereo tap (.audioStereoPCMFullDataUpdated, 2048 samples) because a spectrum needs the full band; the same both-playback-paths rule applies to it.

Rendering (CoreGraphics compositor)

PeppyMeterRenderer.draw(template:leftVolume:rightVolume:in:context:) composites background → needle(s)/indicator(s) → optional foreground, scaled-to-fit (aspect preserved, centered) into the window's content rect. Ported faithfully from PeppyMeter's circular.py, linear.py, needlefactory.py, and maskfactory.py.

• Coordinate space. meters.txt uses a top-left, y-down pixel space; CoreGraphics is bottom-left, y-up. Top-left points are converted with y_bl = H − y_topLeft (H = the meter's native background-image height).
• Circular needle. The needle image points up at angle 0; its pivot, in image-local coords, is (w/2, h/2 + distance) and is placed at the channel origin (origin_x, origin_y). angle = start + (volume/100)·(stop − start) degrees, CCW-positive (ctx.rotate(by:)). Stereo uses left/right.origin.* + left/right.start/stop.angle; mono uses mono.origin.* (angles fall back to the shared start.angle/stop.angle). Origins may sit off-canvas (e.g. vertical-circular).
• Linear bar. linearMasks is a cumulative pixel-width table (masks[n] = n·step.width.regular, then the overload zone adds step.width.overload steps). Volume picks a step index → reveal width w. A growing bar crops the indicator to w per direction (left-right, right-left, bottom-top, top-bottom; center-edges/edges-center are resolved per channel). A single indicator (indicator.type = single, e.g. chillout) instead moves the whole sprite by w. flip.left.x/flip.right.x mirror the indicator image (cached).

Rendering matches SkinRenderer's CoreGraphics approach; there is no Metal here.

Window compositing

Classic and modern PeppyMeter windows draw the animated meter content separately from the window chrome:

• PeppyMeterPresenter.onNeedsDisplay must call the view's requestMeterRedraw() method, not needsDisplay = true, for normal VU ticks. This invalidates only the meter content rect, so the static window border is not repainted at 60 Hz.
• Both views clip PeppyMeterDrawing.draw(...) to the chrome content rect. Keep this clip in place; some templates have artwork near their own edges and must never paint over the app window border. Modern skins do not add an extra PeppyMeter-specific gutter beyond the shared auxiliary chrome inset. In every render style the modern meter content rect expands through adjacent joined chrome strips (via NSRect.expandingThroughJoinedEdges) so no ~1px seam shows on a docked edge — this is not metal-only (issue #364). The helper is bounded to small edge-adjacent gaps so content cannot jump across a visible title bar/chrome gap.
• Do not add a PeppyMeter-specific outer padding around the modern meter content. That recreates the old heavy-border look. If a template needs spacing, handle it inside the meter compositor or template layout, not by shrinking the whole window content rect.
• Classic PeppyMeter draws the skin chrome after the meter content by using SkinRenderer.drawSpectrumAnalyzerWindowChromeOverlay(...). The normal spectrum chrome method fills the whole window and is not suitable as a border-only overlay.

meters.txt & bundled assets

• Templates live in Sources/NullPlayer/Resources/PeppyMeter/<resolution>/ (currently 480x320/, 800x480/, and 1280x400/), auto-included by the existing .copy("Resources") in Package.swift — no Package.swift change to add a resolution folder. PeppyMeterLibrary discovers configured folders via BundleHelper.url(forResource:withExtension:subdirectory:) and chooses the best same-name template for the current draw size, falling back to the full 480x320 catalog.
• PeppyMeterConfig.parse reads the INI-style meters.txt; each section keeps a template only if it has a valid meter.type and its background image loads.
• Licensing. The bundled meter images + meters.txt are GPL-3.0 (from PeppyMeter). They live in their own folder with Resources/ThirdPartyLicenses/PeppyMeter_NOTICE.txt. The NullPlayer rendering engine (Sources/NullPlayer/PeppyMeter/) is an independent implementation.

Selection, random, persistence

PeppyMeterPresenter (mode-neutral) owns the level model, the random-switch timer, the current template, and the right-click menu. Settings persist to UserDefaults (independent of Remember State), via PeppyMeterSettings:

• peppyMeterCurrentMeter — selected meter name
• peppyMeterRandomEnabled — Random toggle
• peppyMeterRandomIntervalSeconds — switch interval (default 20 s)

Window visibility + frame are saved in AppStateManager session state (isPeppyMeterVisible / peppyMeterWindowFrame), mode-gated like the other center-stack windows.

WindowManager integration

Registered as CenterStackWindowKind.peppyMeter. showPeppyMeter / togglePeppyMeter / isPeppyMeterVisible / peppyMeterWindowFrame mirror the Audio Analyzer / Network Monitor methods exactly, and the controller is threaded through every window collection (docking, snapshots, always-on-top, UI Size, Hide Title Bars, compact-mode snapshots, mode teardown/rebuild) and the classic frame-repair path (repairClassicCenterStackFrames). It docks/snaps flush in the vertical stack, opens at main-window width, and is vertically stretchable like the spectrum/analyzer windows. Its default/minimum height is 1.75× the normal center-stack height, rounded to whole pixels, because the bundled meter templates are landscape-oriented. Saved legacy double-height PeppyMeter frames are normalized down to this landscape height on restore/repair.

Architecture / key files

Engine (mode-neutral — must not import Skin/ or ModernSkin/):

• PeppyMeter/PeppyMeterConfig.swift — meters.txt parser → [PeppyMeterTemplate]
• PeppyMeter/PeppyMeterLibrary.swift — template + image loading/caching; PeppyMeterSettings
• PeppyMeter/PeppyMeterRenderer.swift — CoreGraphics compositor (needle + linear geometry)
• PeppyMeter/PeppyMeterLevelModel.swift — stereo consumer + dBFS→volume + ballistics; PeppyMeterLevels
• PeppyMeter/PeppyMeterPresenter.swift — shared runtime + PeppyMeterDrawing + menu

Windows + protocol:

• App/PeppyMeterWindowProviding.swift — : ModeDependentWindow
• Windows/PeppyMeter/PeppyMeterWindowController.swift + PeppyMeterView.swift (classic chrome, SkinRenderer)
• Windows/ModernPeppyMeter/ModernPeppyMeterWindowController.swift + ModernPeppyMeterView.swift (modern chrome, ModernSkinRenderer)

Assets: Resources/PeppyMeter/{480x320,800x480,1280x400}/ (+ ThirdPartyLicenses/PeppyMeter_NOTICE.txt). Tests: Tests/NullPlayerAppTests/PeppyMeterConfigTests.swift (parser + mask table + dBFS→volume math and window geometry restore coverage).

Gotchas

• Mode independence. Windows/ModernPeppyMeter/ must never import from Skin/ or Windows/MainWindow/; the shared engine under Sources/NullPlayer/PeppyMeter/ stays mode-neutral (no skin imports). Only the classic shell may use Skin/.
• No new audio tap. PeppyMeter consumes the existing .audioStereoPCMDataUpdated stream. Don't add a dedicated tap; register/deregister the stereo consumer with show/hide so it's idle when closed.
• Don't invalidate chrome on VU ticks. Use requestMeterRedraw() for level animation updates. Full needsDisplay = true is reserved for skin changes, fullscreen transitions, resize, titlebar state, and other events where chrome really changed.
• GPL assets. The bundled meters are GPL-3.0 and isolated in Resources/PeppyMeter/. For a build that can't ship GPL assets, drop that folder — the renderer shows a "No meters bundled" placeholder.
• Coordinate flip. Get the top-left→bottom-left conversion right (needle pivot Y, linear anchor Y, rotation sign) — see ui-guide for the skin top-left vs macOS bottom-left rule.
• Native size varies. Some backgrounds are .jpg; the meter's canvas size comes from the background image, not a hardcoded 480×320.

See audio-analysis-window for the shared stereo path and visualizations for the visualization/meter index.