Stretching Your Shiny Leaflet Maps: Achieving "Height=100%" within navbarPage
Let's face it, Shiny apps with maps can be stunning but sometimes feel cramped within the confines of a navbarPage. The desire to have that leaflet map fill the entire available space is a common one. This article dives into the techniques you can use to achieve a "height=100%" leaflet map within a navbarPage structure.
The Problem: Cramped Maps in navbarPage
The issue stems from the default behavior of navbarPage. It creates a layout with a fixed-height navigation bar at the top, and the content area below often feels constricted. This can be especially frustrating when working with interactive maps that require ample space for exploration.
Example:
library(shiny)
library(leaflet)
ui <- navbarPage(
"My App",
tabPanel("Map",
leafletOutput("mymap", height = "100%")
)
)
server <- function(input, output) {
output$mymap <- renderLeaflet({
leaflet() %>%
addTiles()
})
}
shinyApp(ui, server)
This code creates a simple Shiny app with a map in a tabPanel within navbarPage. However, the map doesn't fill the entire screen. It's limited by the available space left after the fixed navigation bar.
Solutions: Expanding the Canvas
Here are two common approaches to tackle this issue:
1. CSS Magic: Resizing the Leaflet Container
Leveraging CSS is a straightforward way to achieve the desired height. This involves adjusting the height property of the leaflet container within the navbarPage structure.
Modified Example:
library(shiny)
library(leaflet)
ui <- navbarPage(
"My App",
tabPanel("Map",
div(style = "height: calc(100vh - 50px);", # Adjust the '50px' as needed
leafletOutput("mymap")
)
)
)
server <- function(input, output) {
output$mymap <- renderLeaflet({
leaflet() %>%
addTiles()
})
}
shinyApp(ui, server)
Explanation:
- The key here is the
divelement with thestyleattribute. calc(100vh - 50px)calculates the height as 100% of the viewport height, minus 50 pixels to account for the navbar's height. This ensures the map adjusts dynamically with the screen size.
2. Dynamically Adjusting with JavaScript
For finer control and situations where the navigation bar height might vary, you can use JavaScript to resize the leaflet map.
Modified Example:
library(shiny)
library(leaflet)
ui <- navbarPage(
"My App",
tabPanel("Map",
tags$head(
tags$script("
$(document).ready(function() {
$('#mymap').height($(window).height() - $('#navbarPage').height());
});
$(window).resize(function() {
$('#mymap').height($(window).height() - $('#navbarPage').height());
});
")
),
leafletOutput("mymap")
)
)
server <- function(input, output) {
output$mymap <- renderLeaflet({
leaflet() %>%
addTiles()
})
}
shinyApp(ui, server)
Explanation:
- The JavaScript code within the
tags$headis executed on page load ($(document).ready) and whenever the window is resized ($(window).resize). - The script dynamically calculates the height of the leaflet map (
#mymap) by subtracting the navigation bar height (#navbarPage) from the viewport height ($(window).height()).
Additional Tips
- CSS Styling: You can use CSS to further customize the map's appearance, such as adding borders or padding.
- Responsiveness: Remember to consider responsiveness for different screen sizes. You might need to adjust CSS or JavaScript to ensure the map looks good across devices.
- Performance: Be mindful of performance with JavaScript. Frequent resizing can impact responsiveness, so try to optimize your code.
Conclusion
By implementing these techniques, you can successfully integrate large, full-height leaflet maps within your navbarPage Shiny applications. Remember to choose the solution that best suits your specific requirements and preferences.
