app.R

suppressMessages({
	library(shiny)
	library(ggplot2)
	library(dplyr)
	library(tidyr)
	library(viridis)
	library(Rcpp)
})
init_x <<- c(-1,1)
init_y <<- c(-1,1)

cppFunction('
int mandelfoo(double x, double y,int maxit) {
  int it=0;
  double x2,y2,modulus;
  double myx,myy;
  myx=x;myy=y;
  while (it < maxit) {
    x2 = myx*myx;
    y2 = myy*myy;
    modulus = x2 + y2;
    if (modulus > 4) { return(it); }
    it++;
    myy = 2 * myx * myy + y;
    myx = x2 - y2 + x;
  }
  return(it);
}')

mandeldeez <- function(x,y,maxit=100) {
  retv <- mapply(mandelfoo,x,y,MoreArgs=list(maxit=maxit))
}
server <- function(input, output, session) {
	viewport <- reactiveValues(xmin=min(init_x),
														 xmax=max(init_x),
														 ymin=min(init_y),
														 ymax=max(init_y))
     # When a double-click happens, check if there's a brush on the plot.
     # If so, zoom to the brush bounds; if not, reset the zoom.
     observeEvent(input$plot_click, {
       brush <- input$plot_brush
       if (!is.null(brush)) {
         viewport$xmin <- brush$xmin
         viewport$xmax <- brush$xmax
         viewport$ymin <- brush$ymin
         viewport$ymax <- brush$ymax
       } else {
         viewport$xmin <- min(init_x)
         viewport$xmax <- max(init_x)
         viewport$ymin <- min(init_y)
         viewport$ymax <- max(init_y)
       }
     })

		xyzs <- reactive({
			parm <- tidyr::crossing(tibble(x=seq(viewport$xmin,viewport$xmax,length.out=input$dpi)),
															tibble(y=seq(viewport$ymin,viewport$ymax,length.out=input$dpi))) %>%
				mutate(mi=mandeldeez(x,y,input$resolution))
		})
		output$theplot <- renderPlot({
			ph <- xyzs() %>%
				ggplot(aes(x=x,y=y,fill=mi)) + 
				scale_fill_viridis(option='B',direction=-1) + 
				geom_tile(size=0) +
				coord_equal() + 
				theme_void() + 
				geom_raster() + 
				guides(color=FALSE,fill=FALSE)
			ph
		},
		height=700,width=1400)
		# should have coords in bookmark. rats.
		setBookmarkExclude(c('bookmark'))
		observeEvent(input$bookmark,{
			session$doBookmark()
		})
}

ui <- shinyUI(
	fluidPage(theme=shinythemes::shinytheme("spacelab"),
	tags$head(
				tags$script(src='test.js'),
				tags$style(".table .alignRight {color: black; text-align:right;}"),
				tags$link(rel="stylesheet", type="text/css", href="style.css")
	),
	titlePanel("Mandelbroit"),
	sidebarLayout(position="left",
								sidebarPanel(sliderInput("resolution","Depth: ",min=10,max=300,value=100,step=5),
														 sliderInput("dpi", "DPI: ",min=90,max=900,value=300,step=10),
														 bookmarkButton(id='bookmark'),
														 hr(),
														 width=2),
    mainPanel(
			width=10,
			plotOutput('theplot',
								 dblclick="plot_click",
								 brush=brushOpts(id="plot_brush",resetOnNew=TRUE),
								 height='100%',width='100%')
			)  # mainPanel
  ) # sidebarLayout
,title="Mandelbroit Thingy"))

enableBookmarking(store='url')
foo <- shinyApp(ui = ui, server = server)