Views in Shiny apps — aobview-shiny • aobview

aobviewOutput() places a view in a Shiny app's UI and renderAobview() draws one there from the server: its expression returns a view from view() or view_add() (or NULL for none). The scene and its data travel to the browser over the Shiny session's own connection, and the renderer is loaded once for every view in the app (allboa/design decision 0009). The 'shiny' package is needed (it is suggested, not imported).

Usage

aobviewOutput(outputId, width = "100%", height = "480px")

renderAobview(expr, env = parent.frame(), quoted = FALSE)

aobview_selection(outputId, session = shiny::getDefaultReactiveDomain())

aobview_selected(
  outputId,
  source = NULL,
  session = shiny::getDefaultReactiveDomain()
)

aobview_view_state(outputId, session = shiny::getDefaultReactiveDomain())

Arguments

outputId: The output's id.
width, height: CSS sizes, such as "100%" or "480px"; a number is pixels.
expr: An expression that returns a view (an "aob_view") or NULL.
env: The environment in which to evaluate expr.
quoted: Is expr a quoted expression (with quote())?
session: The Shiny session.
source: With several objects in the view, the name of the one to return rows of, as for selected().

Value

aobviewOutput(): a UI element. renderAobview(): a render function for output$<outputId>. aobview_selection(): a data frame (source, layer, row) with attributes at and trigger, or NULL until the output has rendered a view. aobview_selected(): rows of the viewed object, or NULL. aobview_view_state(): a list, or NULL.

Details

Transport. A browser can reach only the Shiny app's server, so a view in Shiny is embedded: while Shiny runs, transport = "auto" never serves (over getOption("aobview.embed_max") the tiles are embedded with a warning), and rendering a served view is an error.

Selections. Every vector layer of a rendered view can be selected, as in a served view: a click on a feature selects it and only it, Shift (or Cmd) and click adds or removes it, and a click on nothing or Escape clears. The page sends each change as the input value input$<outputId>_aob_select and the settled camera as input$<outputId>_aob_view (protocol 1 messages, decision 0007). A select message is a list with scene (the serial of the render it was made on), seq, trigger ("click", "toggle" or "clear"), at (the pressed point in view CRS units) and items, one per layer with its layer id and rows, which are 0-based row indices into that layer's data, not rows of your object: read them through the functions below. aobview_selection(), aobview_selected() and aobview_view_state() read those inputs, so they are reactive, and return what selection(), selected() and view_state() return for a served view: the selected rows of the objects that were viewed, mapped through the rendered view. A new render (a NULL one too) clears the selection, and the functions re-run when it happens; a message from an older render is ignored. They return NULL until the output has rendered a view (and after a NULL render). They work inside a module (outputId as given to the module's output); a module's output is never confused with an output of the same id elsewhere in the app.

Files. view() writes a page to the temporary directory as usual; for a view rendered here that page is deleted when the output renders again and when the session ends, since the scene travels as the render value. A page written to a file you named is left alone.

Examples

if (FALSE) { # interactive() && requireNamespace("shiny", quietly = TRUE)
bases <- data.frame(base = c("Casey", "Davis", "Mawson"))
bases$geom <- wk::xy(c(110.53, 77.97, 62.87), c(-66.28, -68.58, -67.60),
                     crs = "OGC:CRS84")
ui <- shiny::fluidPage(aobviewOutput("map"), shiny::tableOutput("picked"))
server <- function(input, output, session) {
  output$map <- renderAobview(view(bases, zcol = "base"))
  output$picked <- shiny::renderTable(aobview_selected("map"))
}
shiny::shinyApp(ui, server)
}