tabBox width doesn't expand to contain plot - r

Question

Starting with the code on this page: enter link description here, I would like to be able to control the size of the box plot on Tab 1 of the First tabBox. Hacking in a couple of sliders, and a uiOuput call in the code below, I can now easily control the height and width of the boxplot. But, while the tabBox nicely expands in height to contain the plot, it does not expand in width. At high values of width, the plot extends over the boundary of the box. I see similar results using a simple Box to contain the plot.
Is there a way to change the width of the Box/tabBox to get the desired effect?
library(shiny)
library(shinydashboard)
body <- dashboardBody(
fluidRow(
tabBox(
title = "First tabBox",
# The id lets us use input$tabset1 on the server to find the current tab
id = "tabset1",
tabPanel("Tab1", "First tab content", uiOutput('UI_test')),
tabPanel("Tab2", "Tab content 2")
),
tabBox(
side = "right",
selected = "Tab3",
tabPanel("Tab1", "Tab content 1"),
tabPanel("Tab2", "Tab content 2"),
tabPanel("Tab3", "Note that when side=right, the tab order is reversed.",
sliderInput('sldHt', 'Height', min=100, max=500,
value=200, step=10),
sliderInput('sldWd', 'Width', min=100, max = 500,
value=200, step=10)
)
)
),
fluidRow(
tabBox(
# Title can include an icon
title = tagList(shiny::icon("gear"), "tabBox status"),
tabPanel("Tab1",
"Currently selected tab from first box:",
verbatimTextOutput("tabset1Selected")
),
tabPanel("Tab2", "Tab content 2")
)
)
)
shinyApp(
ui = dashboardPage(
dashboardHeader(title = "tabBoxes"),
dashboardSidebar(),
body
),
server = function(input, output) {
# The currently selected tab from the first box
output$tabset1Selected <- renderText({
input$tabset1
})
output$UI_test = renderUI({
plotOutput('test',
height = input$sldHt,
width = input$sldWd)
})
output$test = renderPlot(
boxplot(len ~ dose, data = ToothGrowth,
boxwex = 0.25, at = 1:3 - 0.2,
subset = supp == "VC", col = "yellow",
main = "Guinea Pigs' Tooth Growth",
xlab = "Vitamin C dose mg",
ylab = "tooth length",
xlim = c(0.5, 3.5), ylim = c(0, 35), yaxs = "i"))
}
)