fixedSliderInputSize.R

# if added to a shiny server, fixes the range of the slider to a predetermined length

oldSliderCoordinates = reactiveValues(range1 = data$date %>% max %>% subtract(sliderSize), # initial slider location 1
                                        range2 = data$date %>% max) # initial slider location 2
  observe({
    range = input$dateRange[2] - input$dateRange[1]
    range %<>% as('numeric')
    
    if(range > sliderSize){
      if(input$dateRange[2]!= oldSliderCoordinates$range2){
        new1 =  input$dateRange[1]
        new2 = input$dateRange[1] + sliderSize
      } else {
        new1 = input$dateRange[2] - sliderSize
        new2 = input$dateRange[2]
      }
      
      oldSliderCoordinates$range1 = new1
      oldSliderCoordinates$range2 = new2
      updateSliderInput(session, 'dateRange', value = c(new1,new2))
    }
  })