gramps
0f62e55474
`Controls/SegmentMeter` draws a 24-segment ladder in ONE OnRender pass — no per-segment elements updating on the UI thread, which is the difference between a meter and a UI thread tax. Level and peak are display fractions (what was MEASURED), never gain settings; vertical for the bay ladders, horizontal for the master strip. Bands come from `Helpers/MeterScale` (nominal/caution/peak, DESIGN.md thresholds) and live as dependencies of the control, so the painting logic is pure and testable: the band a segment paints is the level it measured. Brushes resolve from the theme tokens via SetResourceReference, so the ladder cannot drift from DESIGN.md. Peak-hold is the reason the header exists: a bar that follows the moment hides clipping, and clipping is the one audio fault that cannot be fixed after the stream. Guard: MeterScaleTests — band edges (inclusive at −12 and −3, as the standard states the ranges), the −60…0 display scale, and peak-hold rising instantly then decaying at 0.35/s.
46 lines
1.9 KiB
C#
46 lines
1.9 KiB
C#
using System;
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namespace ytLive.Helpers;
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/// <summary>Which colour band a level falls in (DESIGN.md meter thresholds).</summary>
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public enum MeterBand
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{
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Nominal,
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Caution,
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Peak,
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}
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/// <summary>The mathematics of the dock's segment meter, kept out of the control so it can be
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/// tested: a segment ladder is only honest if the band it paints is the level it measured.
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///
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/// <para>Bands follow DESIGN.md: nominal to −12 dB, caution to −3 dB, peak above. The display
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/// fraction spreads −60…0 dBFS across 0…1 — the same scale <c>AudioLevelMeter.ToDisplay</c> uses,
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/// so the ladder and the old bars cannot disagree.</para></summary>
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public static class MeterScale
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{
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public const float FloorDb = -60f;
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public const float CautionDb = -12f;
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public const float PeakDb = -3f;
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/// <summary>dBFS → 0…1 across the whole ladder.</summary>
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public static float ToFraction(float dbfs)
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=> Math.Clamp(1f + Math.Clamp(dbfs, FloorDb, 0f) / 60f, 0f, 1f);
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/// <summary>The band boundaries are INCLUSIVE at the bottom edge (a meter reading exactly
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/// −12.0 dB is cautious, exactly −3.0 is peaking), matching the ranges as DESIGN.md states
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/// them: "−12 … −3" and "−3 … 0+".</summary>
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public static MeterBand BandFor(float dbfs)
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=> dbfs >= PeakDb ? MeterBand.Peak
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: dbfs >= CautionDb ? MeterBand.Caution
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: MeterBand.Nominal;
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/// <summary>Peak hold: jumps up instantly to a new maximum and falls back at
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/// <paramref name="decayPerSecond"/> — a moment-to-moment bar hides clipping, which is the one
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/// audio fault that cannot be fixed afterwards.</summary>
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public static float NextPeak(float held, float incoming, float seconds, float decayPerSecond = 0.35f)
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{
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if (incoming >= held) return incoming;
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return Math.Max(0f, held - decayPerSecond * Math.Max(0f, seconds));
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}
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}
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