如何在“闪亮”的可拖动面板中绘制图

Question

到目前为止，我正在构建一个shiny应用程序，其简化如下。

library(shiny)

foo <- function(draggable = FALSE) {
  ui <- shinyUI(
    bootstrapPage(
      absolutePanel(
        id = "controls", 
        class = "panel panel-default", 
        draggable = draggable, 
        width = 330, 
        height = "auto",
        plotOutput(outputId="plots",
                   brush = brushOpts(id = "plot_brush",
                                     resetOnNew = FALSE),
                   dblclick = "plot_click")
      )
    )
  )

  server <- shinyServer(function(input, output, session) {

    x <- mtcars$mpg
    y <- mtcars$hp

    highlightColor <- "red"

    output$plots <- renderPlot({
      plot(x = x, y = y)
      brush <- input$plot_brush
      if(!is.null(brush)) {
        id <- intersect(
          which(x >= brush$xmin & x <= brush$xmax),
          which(y >= brush$ymin & y <= brush$ymax)
        )
        xx <- x[id]
        yy <- y[id]
        points(xx, yy ,col = highlightColor)
      }
    })
  })

  shinyApp(ui = ui, server = server)
}

图中的点可以通过笔刷突出显示。同时，我也想使该图可拖动。但是，如果该图是可拖动的，则无法再对其进行刷刷。

# the plot cannot be dragged, but the brush works fine
foo(draggable = FALSE)

# the plot can be dragged, but the brush does **not** work
foo(draggable = TRUE)

所以我想知道，是否有可能在不牺牲涂刷功能的情况下使图形可拖动？ （例如，当光标到达图形的边缘时，请按向左键，然后可以拖动图；如果光标位于图内，请按向左键，可以刷图）