Plots not printed over multiple pages - r

Question

I have developed app to allow users to download all the plots in the app to PDF file. The code somewhat works, but not as I expected.
The number of plots are dynamic (as it depends on the data). I have use marrangeGrob function but all my plots are still on the same page, instead of seeing one on each page
Is there a setting I have missed? Also, I would like to adjust the height and the width for each chart as well (make the width shorter and the height longer), is there an option to do so?
Here is my code:
library(shiny)
library(data.table)
library(tidyverse)
library(shinydashboard)
### UI & Module -------------------
plotUI <- function(id) {
ns <- NS(id)
plotOutput(ns("myplot"))
}
plotServer <- function(id,groups) {
moduleServer(
id,
function(input, output, session) {
filtered.data <- reactive(iris %>% filter(Species == groups))
create_graph <- reactive(filtered.data() %>% ggplot(aes(x = Sepal.Length, y = Sepal.Width)) +geom_col())
output$myplot <- renderPlot(create_graph())
return(list(graph = create_graph))
}
)
}
### UI part -----------------------
ui <- dashboardPage(
title="test",
dashboardHeader(),
dashboardSidebar(downloadButton('download')),
dashboardBody(uiOutput('tablist'))
)
### Server part ----------------------------
server = function(input, output) {
groups <- reactive(unique(iris$Species))
ntabs <- reactive(length(groups()))
allplots <- reactiveVal()
observeEvent(ntabs(),{
plot <- lapply(1:ntabs(), function (i) {
plotServer(paste0("plot",i),groups()[i])
})
allplots(plot)
})
output$tablist = renderUI({
addtabs <- lapply(1:ntabs(),function (i) {
tabPanel(
groups()[i],
plotUI(paste0("plot",i)),
)
})
do.call(tabsetPanel, addtabs)
})
output$download <- downloadHandler(
filename = function() {
paste0("plots-", Sys.Date(), ".pdf")
}, content = function(file) {
plot.list <- allplots()
ggsave(file,marrangeGrob(lapply(plot.list, function(x) x$graph()),
ncol = 1, nrow = length(plot.list)))
}
)
}
### Running part ----------------------------
shinyApp(ui, server,enableBookmarking = "server")

Answer 1

If we specify ncol = 1 and nrow = 1, every plot goes in a separate page because the layout gets "recycled".
output$download <- downloadHandler(
filename = function() {
paste0("plots-", Sys.Date(), ".pdf")
}, content = function(file) {
plot.list <- allplots()
ggsave(file, marrangeGrob(
grobs = plot.list |> lapply(\(x) x$graph()),
ncol = 1,
nrow = 1
))
}
)