GlowRendererView

//
//  GlowRendererView.swift
//  UnwrapLive26
//
//  Created by Michael Charland on 2026-01-10.
//

import SwiftUI

struct GlowAttribute: TextAttribute {}

struct GlowRenderer: TextRenderer {
    var color: Color

    func draw(layout: Text.Layout, in context: inout GraphicsContext) {
        for line in layout {
            for run in line {
                if run[GlowAttribute.self] != nil {
                    for radius in stride(from: 8.0, through: 1.0, by: -3.0) {
                        var glowContext = context
                        glowContext.addFilter(.blur(radius: radius))
                        glowContext.fill(
                            Rectangle().path(
                                in: run.typographicBounds.rect.insetBy(
                                    dx: -radius,
                                    dy: -radius / 2
                                )
                            ),
                            with: .color(color)
                        )
                    }
                }
                context.draw(run)
            }
        }
    }
}

struct GlowRendererView: View {
    @State private var startTime = Date.now

    var body: some View {
        TimelineView(.animation) { timeline in
            let elapsed = timeline.date.timeIntervalSince(startTime)
            let glowIntensity = abs(sin(elapsed)) * 0.2 + 0.1

            let demo = Text("demo")
                .customAttribute(GlowAttribute())

            Text("This is a \(demo) of the custom highlight renderer.")
                .font(.system(size: 72))
                .lineSpacing(40)
                .textRenderer(GlowRenderer(color: .yellow.opacity(glowIntensity)))
        }
    }
}

#Preview {
    GlowRendererView()
}