Explore the Shiny.inputBinding object and methods

inst/shiny-input-app/dev-shiny-input.Rmd

@@ -2,6 +2,10 @@
 output: github_document
 ---
 
+[shiny-debounce]: https://shiny.rstudio.com/reference/shiny/latest/debounce.html
+[updateText-shiny-input-binding]: https://github.com/rstudio/shiny/blob/a2a4e40821b9811a40e461f67e3622196d8aa726/srcjs/input_binding_text.js#L31-L41
+[checkboxInput-shiny-input-binding]: https://github.com/rstudio/shiny/blob/a2a4e40821b9811a40e461f67e3622196d8aa726/srcjs/input_binding_checkbox.js
+
 ```{r setup, include=FALSE}
 knitr::opts_chunk$set(eval = FALSE)
 
@@ -233,6 +237,8 @@ you need to find and replace all:
 
 ## Add a dependency to the typing input
 
+`r github_sha_link("0be8efb83bef664f707b8716eab1d5478de933c7")`
+
 To have `typing.js` included with our input,
 we use `htmltools::htmlDependency()` inside our input function.
 This guarantees that `typing.js` is loaded once per page
@@ -252,3 +258,62 @@ htmltools::htmlDependency(
 Now when you run the app,
 you'll see `"FIXME"` as the output of `input$typing`.
 That's our next step.
+
+## Explore the input binding
+
+Read through the comments of the input binding template.
+They explain the role of each function.
+
+In a nutshell,
+as a Shiny input author,
+your job is to tell Shiny a few key things:
+
+1. **`.find()`** — How to find your input elements on the page
+
+1. **`.subscribe()`** — What browser events will trigger an update from your input.
+
+   The template show how to listen `'change'` events,
+   but you may want to listen for a different event (or multiple events!),
+   like a button `'click'` or a `'keydown'` or `'keyup'` event.
+
+1. **`.getRatePolicy()`** — How often to send updates back to the server.
+
+   There are three options here: `'debounce'`, `'throttle'`, and `'direct'`.
+   See the [shiny debounce documentation][shiny-debounce] and my slides
+   for more info.
+
+1. **`.getValue()`** — What is the value of your input?
+
+   This method is called whenever a subscribed event happens, and if the value
+   of the input has changed it is reported back to Shiny. It's up to you,
+   though, in this function, to read the HTML to determine the current value of
+   the input and to construct the data that's sent back to the server.
+   
+1. **`.receiveMessage()`** - Let the input receive messages from the server.
+
+   This works just like custom message handles, except that you call
+   `shiny::sendInputMessage(inputId, data)` on the server side.
+   This method receives the data and can be used to update the state of the
+   input from values sent by the server.
+   
+   Ideally you would write an `update<InputName>()` function that wraps
+   `shiny::sendInputMessage()`. This is how [`updateTextInput()`][updateText-shiny-input-binding] and others
+   works.
+   
+   If you want the updated values to flow through the reactive graph
+   (you probably do), then you need to trigger a subscribed event after
+   you make the changes. This calls `.getValue()` which sets the input values
+   and reports back to the server.
+   
+1. **`.setValue()`** — This method takes a value sent from your input and
+   updates your HTML to match.
+   
+   This method is required to be able to restore the input from a bookmarked 
+   state. It also allows you to set the input's value without triggering
+   reactivity.
+
+### Read the input binding for `checkboxInput()`
+
+The input binding JavaScript for `checkboxInput()` is available
+in the [Shiny GitHub repository][checkboxInput-shiny-input-binding].
+Read through it and discuss what each method does.