LlamaCasty/Controls/SegmentMeter.cs

using System;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using ytLive.Helpers;

namespace ytLive.Controls;

/// <summary>A segmented level ladder for the audio dock.
///
/// <para>Drawn in ONE <see cref="OnRender"/> pass. Twenty-four <c>Rectangle</c>s per meter would
/// mean hundreds of elements updating on the UI thread; a single drawing call does not. The
/// consumer updates <see cref="Level"/> at ~20 Hz — music-level smoothness is not needed and the
/// paint cost should never compete with the compositor.</para>
///
/// <para>Level is a 0…1 display fraction (see <see cref="MeterScale"/>), never a gain setting: the
/// ladder shows what was measured.</para></summary>
public sealed class SegmentMeter : FrameworkElement
{
    public static readonly DependencyProperty LevelProperty = DependencyProperty.Register(
        nameof(Level), typeof(double), typeof(SegmentMeter),
        new FrameworkPropertyMetadata(0d, FrameworkPropertyMetadataOptions.AffectsRender));

    /// <summary>Peak-hold mark, 0…1. Falls back slowly so a clip stays visible long enough to see.</summary>
    public static readonly DependencyProperty PeakProperty = DependencyProperty.Register(
        nameof(Peak), typeof(double), typeof(SegmentMeter),
        new FrameworkPropertyMetadata(0d, FrameworkPropertyMetadataOptions.AffectsRender));

    public static readonly DependencyProperty SegmentsProperty = DependencyProperty.Register(
        nameof(Segments), typeof(int), typeof(SegmentMeter),
        new FrameworkPropertyMetadata(24, FrameworkPropertyMetadataOptions.AffectsRender));

    public static readonly DependencyProperty OrientationProperty = DependencyProperty.Register(
        nameof(Orientation), typeof(Orientation), typeof(SegmentMeter),
        new FrameworkPropertyMetadata(Orientation.Vertical, FrameworkPropertyMetadataOptions.AffectsRender));

    public double Level { get => (double)GetValue(LevelProperty); set => SetValue(LevelProperty, value); }
    public double Peak { get => (double)GetValue(PeakProperty); set => SetValue(PeakProperty, value); }
    public int Segments { get => (int)GetValue(SegmentsProperty); set => SetValue(SegmentsProperty, value); }
    public Orientation Orientation { get => (Orientation)GetValue(OrientationProperty); set => SetValue(OrientationProperty, value); }

    public SegmentMeter()
    {
        // Token-driven, not literal: the ladder cannot drift from DESIGN.md.
        SetResourceReference(NominalBrushProperty, "Brush.Meter.Nominal");
        SetResourceReference(CautionBrushProperty, "Brush.Meter.Caution");
        SetResourceReference(PeakBrushProperty, "Brush.Meter.Peak");
        SetResourceReference(DimBrushProperty, "Brush.SurfaceContainerHighest");
    }

    private static readonly DependencyProperty NominalBrushProperty = DependencyProperty.Register(
        "NominalBrush", typeof(Brush), typeof(SegmentMeter), new FrameworkPropertyMetadata(Brushes.Cyan, FrameworkPropertyMetadataOptions.AffectsRender));
    private static readonly DependencyProperty CautionBrushProperty = DependencyProperty.Register(
        "CautionBrush", typeof(Brush), typeof(SegmentMeter), new FrameworkPropertyMetadata(Brushes.Orange, FrameworkPropertyMetadataOptions.AffectsRender));
    private static readonly DependencyProperty PeakBrushProperty = DependencyProperty.Register(
        "PeakBrush", typeof(Brush), typeof(SegmentMeter), new FrameworkPropertyMetadata(Brushes.Red, FrameworkPropertyMetadataOptions.AffectsRender));
    private static readonly DependencyProperty DimBrushProperty = DependencyProperty.Register(
        "DimBrush", typeof(Brush), typeof(SegmentMeter), new FrameworkPropertyMetadata(Brushes.DimGray, FrameworkPropertyMetadataOptions.AffectsRender));

    private Brush NominalBrush => (Brush)GetValue(NominalBrushProperty);
    private Brush CautionBrush => (Brush)GetValue(CautionBrushProperty);
    private Brush PeakBrush => (Brush)GetValue(PeakBrushProperty);
    private Brush DimBrush => (Brush)GetValue(DimBrushProperty);

    private const double Gap = 2;

    protected override void OnRender(DrawingContext dc)
    {
        var count = Math.Max(1, Segments);
        var vertical = Orientation == Orientation.Vertical;
        var extent = vertical ? ActualHeight : ActualWidth;
        var thickness = vertical ? ActualWidth : ActualHeight;
        if (extent <= 0 || thickness <= 0) return;

        var segmentSize = (extent - Gap * (count - 1)) / count;
        if (segmentSize <= 0) return;

        var lit = Math.Clamp(Level, 0, 1) * count;

        for (var i = 0; i < count; i++)
        {
            // Segment 0 sits at the bottom (vertical) or the left (horizontal).
            var fraction = (i + 1) / (double)count;
            var brush = fraction >= MeterScale.ToFraction(MeterScale.PeakDb) ? PeakBrush
                      : fraction >= MeterScale.ToFraction(MeterScale.CautionDb) ? CautionBrush
                      : NominalBrush;

            if (i >= lit) brush = DimBrush;

            var offset = i * (segmentSize + Gap);
            var rect = vertical
                ? new Rect(0, extent - offset - segmentSize, thickness, segmentSize)
                : new Rect(offset, 0, segmentSize, thickness);
            dc.DrawRectangle(brush, null, rect);
        }

        // Peak-hold: a 2px marker at the held level, drawn above the ladder.
        var peak = Math.Clamp(Peak, 0, 1);
        if (peak <= 0) return;
        var line = vertical
            ? new Rect(0, extent - peak * extent - 1, thickness, 2)
            : new Rect(peak * extent - 1, 0, 2, thickness);
        dc.DrawRectangle(PeakBrush, null, line);
    }
}