examples/demos/src/main/scala/canvasapp/ScratchPad.scala


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package canvasapp


import org.scalajs.dom

import scalajs.js.annotation.JSExport

@JSExport
object ScratchPad extends{
  @JSExport
  def main(canvas: dom.HTMLCanvasElement) = {
    /*setup*/
    val renderer = canvas.getContext("2d")
                         .asInstanceOf[dom.CanvasRenderingContext2D]

    canvas.width = canvas.parentElement.clientWidth
    canvas.height = canvas.parentElement.clientHeight

    renderer.fillStyle = "#f8f8f8"
    renderer.fillRect(0, 0, canvas.width, canvas.height)

    /*code*/
    renderer.fillStyle = "black"
    var down = false
    canvas.onmousedown =
      (e: dom.MouseEvent) => down = true

    canvas.onmouseup =
      (e: dom.MouseEvent) => down = false

    canvas.onmousemove = {
      (e: dom.MouseEvent) =>
        val rect =
          canvas.getBoundingClientRect()
        if (down) renderer.fillRect(
          e.clientX - rect.left,
          e.clientY - rect.top,
          10, 10
        )
    }
  }
}