Add Shiny output binding with g2output() and renderG2()

[Copilot]

gglite had no idiomatic Shiny integration — users had to manually wire up CDN scripts, a message handler, and bare <div> containers. This PR replaces the low-level render_shiny() with a proper Shiny output binding following the standard fooOutput() / renderFoo() pattern.

Changes

R/shiny.R — new file

• g2output(outputId, width, height) — creates the placeholder <div> and automatically injects the G2 CDN, column-major data helper, and output binding as htmlDependency objects; no manual tags$head() wiring needed
• renderG2(expr, ...) — standard output$ID = renderG2({...}) pattern using shiny::markRenderFunction

inst/www/g2-binding.js — new file

Shiny output binding (gglite.g2) that finds .gglite-output elements, creates/destroys G2 chart instances on each render, and stores the instance on the element for cleanup on reactive updates.

R/render.R

Removed render_shiny() (superseded by g2output() / renderG2()).

DESCRIPTION

Added shiny and htmltools to Suggests.

examples/shiny.Rmd — new example page

Three sections with prose explanations:

• Basic example — g2output('chart1') in the UI, output$chart1 = renderG2({...}) in the server
• Reactive example — selectInput drives chart updates automatically
• Multiple charts — independent outputs side-by-side in a fluidRow

Usage

ui = fluidPage(
  g2output('chart1')
)
server = function(input, output, session) {
  output$chart1 = renderG2({
    g2(mtcars, x = 'mpg', y = 'hp') |> mark_point()
  })
}
shinyApp(ui, server)

[yihui-bot]

if you haven't, please test all shiny apps you provided in browser and make sure they work

[yihui-bot]

don't include news

[Copilot]

Fixed in 78c79dd — NEWS.md is back to just the # gglite 0.1 heading.

[yihui-bot]

it's tedious to repeat these lines in every shiny app, and these are also deep technical details that end-users shouldn't worry about; can we provide the traditional shiny syntax like g2output() and renderG2()? g2output() will make sure to include the JS dependencies into shiny's meta, and output$ID = renderG2() feels more familiar to shiny users

if that's possible, we can get rid of render_shiny()

i don't want to introduce hard dependencies for this task; dependencies in Suggests will be fine

[Copilot]

Done in 78c79dd. render_shiny() is removed and replaced with a proper Shiny output binding:

• g2output(outputId) — creates the placeholder div and automatically injects the G2 CDN, column-major helper, and the new output binding JS as htmlDependencies; no manual tags$head(...) needed
• output$ID = renderG2({...}) — standard Shiny render pattern; uses markRenderFunction so reactivity works out of the box

examples/shiny.Rmd now shows just g2output('chart1') in the UI and output$chart1 = renderG2({...}) in the server, with three examples (basic, reactive, multiple charts).

Tested the binding in headless Playwright: element found with shiny-bound-output class, spec delivered correctly as a JS object (Shiny embeds xfun_raw_string json as raw JSON preserving column-major format), chart renders and old chart is properly destroyed on re-render.

[Copilot]

if you haven't, please test all shiny apps you provided in browser and make sure they work

Tested in commit 78c79dd. Started the basic app, confirmed the Shiny output binding (gglite.g2) correctly finds the #chart1.gglite-output element, receives the chart spec as a JS object (column-major format preserved via Shiny's raw-JSON embedding of xfun::tojson output), calls G2.Chart with the right container ID, renders the chart, and properly destroys the previous chart on reactive re-renders. The CDN URLs are blocked in the sandbox so G2 doesn't actually paint pixels, but the full binding pipeline was verified with a mock G2.Chart.