mini-prog/miniprogram/engine/layer/gpsLayer.ts

import { type CameraState } from '../camera/camera'
import { lonLatToWorldTile } from '../../utils/projection'
import { worldToScreen } from '../camera/camera'
import { type MapLayer, type LayerRenderContext } from './mapLayer'
import { type MapScene } from '../renderer/mapRenderer'
import { type ScreenPoint } from './trackLayer'

export class GpsLayer implements MapLayer {
  projectPoint(scene: MapScene, camera: CameraState): ScreenPoint {
    const worldPoint = lonLatToWorldTile(scene.gpsPoint, scene.zoom)
    const screenPoint = worldToScreen(camera, worldPoint, false)
    return {
      x: screenPoint.x + scene.translateX,
      y: screenPoint.y + scene.translateY,
    }
  }

  getPulseRadius(pulseFrame: number): number {
    return 18 + 6 * (0.5 + 0.5 * Math.sin(pulseFrame / 6))
  }

  draw(context: LayerRenderContext): void {
    const { ctx, camera, scene, pulseFrame } = context
    const gpsScreenPoint = this.projectPoint(scene, camera)
    const pulse = this.getPulseRadius(pulseFrame)

    ctx.save()
    ctx.beginPath()
    ctx.fillStyle = 'rgba(33, 158, 188, 0.22)'
    ctx.arc(gpsScreenPoint.x, gpsScreenPoint.y, pulse, 0, Math.PI * 2)
    ctx.fill()

    ctx.beginPath()
    ctx.fillStyle = '#21a1bc'
    ctx.arc(gpsScreenPoint.x, gpsScreenPoint.y, 9, 0, Math.PI * 2)
    ctx.fill()

    ctx.beginPath()
    ctx.strokeStyle = '#ffffff'
    ctx.lineWidth = 3
    ctx.arc(gpsScreenPoint.x, gpsScreenPoint.y, 13, 0, Math.PI * 2)
    ctx.stroke()

    ctx.fillStyle = '#0b3d4a'
    ctx.font = 'bold 16px sans-serif'
    ctx.textAlign = 'left'
    ctx.textBaseline = 'bottom'
    ctx.fillText('GPS', gpsScreenPoint.x + 14, gpsScreenPoint.y - 12)
    ctx.restore()
  }
}