Attach a Publication-Ready Figure Download to a Plot Card

Registers the downloadHandler that serves the export block rendered by av_ui_plot_card(export = TRUE). Width, height, resolution and file format are read from that block; the figure itself is written with ggplot2::ggsave() using ragg::agg_png (better antialiasing than grDevices::png) or grDevices::cairo_pdf (embeds the font outlines, so the PDF renders identically off-machine).

Usage

av_server_plot_download(
  output_id,
  plot_builder,
  input,
  output,
  session = shiny::getDefaultReactiveDomain(),
  file_label = output_id
)

Arguments

output_id

Character. The Shiny output id of the plot card (e.g. "dashboard_ecdf"). Must match the output_id given to av_ui_plot_card().

plot_builder

A zero-argument function returning the ggplot object to export. Not a shiny::reactive(): see Details.

input

The Shiny input object.

output

The Shiny output object.

session

The Shiny session (default: the current reactive domain). Used to confirm the written geometry via shiny::showNotification().

file_label

Character. Stem of the downloaded file name (default: output_id). The date is appended automatically.

Value

The output object, invisibly. Called for the side effect of registering <output_id>_export_download.

Details

plot_builder must be a plain function(), not a shiny::reactive(). Export re-evaluates it with av_scale_factor = 1 so the print figure is not typeset at the browser container's scale; a reactive that the card already rendered is still valid at that moment and hands back its cached, browser-scaled build, which silently ships a figure with on-screen typography (half-size text on a narrow card).

It must return the ggplot object, never a plotly widget. For cards rendered via render_av_plotly() the ggplot is otherwise consumed inside the render expression, so hoist it into its own function and feed both consumers from there:

p_dir <- function() av_plot_distribution(rv$obj, style = "directionality")
output$dashboard_directionality <- render_av_plotly(
  "dashboard_directionality", av_finalize_plotly(p_dir())
)
av_server_plot_download("dashboard_directionality", p_dir, input, output)

Passing a plotly object raises an error naming the card, since a widget carries no ggplot layer stack that ggsave() could re-render.

Examples

if (interactive()) {
  server <- function(input, output, session) {
    obj <- av_import_csv(
      system.file("extdata", "bcl11a_rs1427407_example.csv", package = "AlphaVaR")
    )
    p_ecdf <- function() av_plot_distribution(obj, style = "ecdf")
    output$dashboard_ecdf <- render_av_plot("dashboard_ecdf", p_ecdf())
    av_server_plot_download("dashboard_ecdf", p_ecdf, input, output)
  }
}