In mslegrand/pointR: pointR

knitr::opts_chunk$set(echo = TRUE)
library(svgR)

Details about the Strategies

Notes on SVG

For initial SVG development it is convenient to keep the svgR in a seperate file Thus we - put svgR code in a seperate file: shinyInputControl_svg.R - create a wrapper to source the svg - call that wrapper from the constructor for shinyInputControl

Notes on Updating

What is updating

Updating is the act of sending a message from the server to the client. The message contains info to recreate appearence and value

What is the purpose of updating?

The purpose of updating is to perform 2 objectives:

• set a new value for the control
• change the control's appearence

What are the steps of updating?

• Starts in the server by calling the function updateShinyInputControl
• A message is formed to be sent to the client
• To send the message a call is made via session\$sendInputMessage
• The client receives the message in the function receiveMessage
• In receiveMessage
  • extract the value
  • reset the value via set value
  • reset the appearence (via node manipulations)

Three Strategies to Update

I. Braindead: (minimal js)

    1. Recreate the svgTree with using new params 
    2. Form message = value + svg
    3. send to the client
    4. client replaces tree and updates value

II. Mixedup:

    1. Recreate the svg with using new params 
    2. get id of svg node that is affected
    3. Extract affected node from svg to send
    4. Form message = value + replacement-node + id of node
    5. send to the client
    6. find node given id and replace with replacement-node

III. Traditional: (uses more js)

    1. Form message = value
    2. Send to client
    3. Use javascript to update appearence base on value.

We recommend the Kindergarden strategy to begin with.

Notes on registerInputHandler

On the client side

• svg sends a message to the shinyInputControl, probably clicked
• clicked resets the value via setValue
• The setValue function triggers a change message
• Inside the subscribe function a callback has been registered to send a message containg the value to the server

On the server side

Inputhandler

• The message from the client is received by the inputhandler
  • The inputhandler was defined when we called registerInputHandler
• The inputhandler allows for preprocessing of the data before attaching it to the input\$controlId
  • This preprocessing is need for lists, etc.
  • The inputhandler returns a value to be assigned to input\$controlId

How is the appearnce of the control changed?

The appearance of the control can be changed in one of two ways:

On the client side

Prior to sending the value to the server via setValue use javascript to modify the appearance. For example, one might do this inside the :clicked function.

On the server side

Inside the inputhandler function, after receiving the value, call an update with the new value to force the client to redraw the control with that new value.

Some supported events by SVG

• SVG Mouse events
  • onclick
  • onmousedown
  • onmouseup
  • onmouseover
  • onmousemove
  • onmouseout
• SVG UIEvents
  • onfocusin
  • onfocusout
  • onactivate
• SVG Misc
  • onload
  • onunload
  • onabort
  • onerror
  • onresize
  • onscroll
  • onzoom
  • onbegin
  • onend
  • onrepeat

mslegrand/pointR documentation built on July 4, 2022, 9:57 p.m.