add_tooltip not working in ggvis in R - r

Question

I want to add tooltip containing all variables.
But when I use this code I get following error:
Error in handlers$add(handler, key, tail) : Key / already in use
If I don't use add_tooltip the plot is created without any problem.
(The add_tooltip is near the bottom of server.R)
Please help, I am really frustrated.
I am creating a Shiny application with following ui and server:
ui.R:
library(ggplot2)
library(ggvis)
library(shiny) # load shiny at beginning at both scripts
shinyUI(fluidPage( # standard shiny layout, controls on the
# left, output on the right
titlePanel("Relative Velocity vs Distance Gap"), # give the interface a title
sidebarLayout(position="right",
sidebarPanel( # all the UI controls go in here
radioButtons(inputId = 'dfid', label = h4("Select Data:"),
choices = c("Coordinate Approach",
"Sum Approach")),
selectInput(inputId="vid", label=h4("Select Vehicle ID:"), choices = vehid)
),
mainPanel( # all of the output elements go in here
h3("Plot"), # title with HTML helper
plotOutput("plot") # this is the name of the output
# element as defined in server.R
)
)
))
server.R:
library(ggvis)
library(shiny) # load shiny at beginning at both scripts
shinyServer(function(input, output) { # server is defined within
# these parentheses
new.data <- reactive({switch(input$dfid, "Coordinate Approach"=df1, "Sum Approach"=df2)})
output$plot <- renderPlot({
new.data <- subset(new.data(), new.data()$Vehicle.ID==input$vid)
tittle <- unique(new.data$Vehicle.class)
mtc <- new.data
mtc$id <- 1:nrow(mtc)
all_values <- function(x) {
if(is.null(x)) return(NULL)
row <- mtc[mtc$id == x$id, ]
paste0(names(row), ": ", format(row), collapse = "<br />")
}
mtc %>% ggvis(x = ~relative.v, y = ~gap.dist, key:=~id) %>%
layer_points() %>%
add_tooltip(all_values, "hover")
#ggplot(data= new.data, mapping = aes(x=relative.v, y=gap.dist, color=as.factor(p))) +
# geom_point() + ggtitle(tittle) + labs(x='Relative Velocity (ft/s)', y='Gap (feet)') + theme_bw() #+ my.theme()
})
})
Another unrelated problem is that when I run the app, the shiny app runs in a window but ggvis plot is created in Viewer pane.
How can I render the plot in window within the Shiny app?