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

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

function buildVectorCamera(scene: MapScene): CameraState {
  return {
    centerWorldX: scene.exactCenterWorldX,
    centerWorldY: scene.exactCenterWorldY,
    viewportWidth: scene.viewportWidth,
    viewportHeight: scene.viewportHeight,
    visibleColumns: scene.visibleColumns,
    rotationRad: scene.rotationRad,
  }
}

export class GpsLayer implements MapLayer {
  projectPoint(scene: MapScene): ScreenPoint | null {
    if (!scene.gpsPoint) {
      return null
    }

    const camera = buildVectorCamera(scene)
    const worldPoint = calibratedLonLatToWorldTile(scene.gpsPoint, scene.zoom, scene.gpsCalibration, scene.gpsCalibrationOrigin)
    return worldToScreen(camera, worldPoint, false)
  }

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

  draw(context: LayerRenderContext): void {
    const { ctx, scene, pulseFrame } = context
    const gpsScreenPoint = this.projectPoint(scene)
    if (!gpsScreenPoint) {
      return
    }

    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()
  }
}