Undo the last shape stored in the whiteboard message buffer

jrobertson (James Robertson) — Mon, 07 Apr 2008 23:42:40 GMT

This ECMAScript implements an undo feature for the SVG whiteboard. When the user presses CTRL+Z the last shape in the message_buffer variable is removed.



  function undoLast() {

    ipos = getLastMethodPos(message_buffer,-1)

    if (ipos > 0)

      message_buffer = message_buffer.substring(0, ipos)

    else

      message_buffer = ''    

  }

  

  function getLastMethodPos(message, pos) {

    i = message.indexOf('    if (i >= 0) 

      result = getLastMethodPos(message, i)

    else

      result = pos 

    return result;

  }

Here's an example of the messages (containing shapes) stored in the message_buffer



"shape

polyline%20x%3D%27524%27%20y%3D%27198%27%20fill%3D%27none%27%20stroke%3D%27red%27%20id%3D

%27348553%27%20stroke-width%3D%272%27%20points%3D%27524%2C198%20523%2C198%20522%2C198%20521%2C198%20

513%2C198%20511%2C198%20503%2C198%20495%2C200%20493%2C200%20485%2C204%20483%2C205%20475%2C207%20474%

2C208%20470%2C212%20466%2C216%20465%2C217%20464%2C219%20463%2C220%20463%2C222%20463%2C223%20463%2C22

5%20463%2C226%20463%2C228%20464%2C230%20465%2C231%20466%2C233%20467%2C234%20471%2C238%20472%2C238%20

478%2C242%20484%2C246%20485%2C247%20488%2C247%20489%2C248%20491%2C248%20493%2C249%20496%2C249%20497%

2C249%20505%2C249%20515%2C249%20521%2C247%20531%2C245%20533%2C245%20539%2C243%20547%2C243%20548%2C24

3%20550%2C242%20555%2C237%20556%2C237%20557%2C235%20558%2C234%20558%2C233%20559%2C231%20559%2C230%20

560%2C228%20560%2C226%20560%2C222%20559%2C221%20559%2C220%20559%2C219%20559%2C217%20559%2C216%20558%

2C215%20558%2C214%20556%2C208%20555%2C206%20555%2C205%20553%2C199%20549%2C191%20547%2C185%20546%2C18

4%20544%2C176%20540%2C170%20539%2C168%20535%2C162%20534%2C161%20528%2C155%20528%2C154%20524%2C148%20

518%2C144%20517%2C143%20511%2C139%20509%2C138%20501%2C134%20499%2C133%20491%2C129%20489%2C129%20479%

2C129%20469%2C129%20467%2C129%20459%2C129%20457%2C129%20454%2C129%20452%2C129%20446%2C131%20438%2C13

1%20437%2C132%20435%2C132%20435%2C133%20434%2C133%20434%2C134%20433%2C134%20433%2C135%27%23%3A

34855var='type'>shapepolyline%20x%3D%27457%27%20y%3D%27175%27%20fill%3D%27none

%27%20stroke%3D%27red%27%20id%3D

%27348554%27%20stroke-width%3D%272%27%20points%3D%27457%2C175%20456%2C175%20455%2C176%20454%2C176%20

453%2C177%20452%2C177%20451%2C177%20449%2C178%20448%2C179%20442%2C181%20440%2C183%20438%2C184%20438%

2C185%20437%2C186%20436%2C187%20435%2C189%20435%2C191%20434%2C193%20434%2C194%20433%2C195%20433%2C19

6%20431%2C200%20431%2C201%20431%2C203%20431%2C205%20431%2C206%20431%2C207%20431%2C208%20431%2C209%20

431%2C210%20431%2C211%20431%2C212%20431%2C213%20431%2C214%20431%2C215%20431%2C216%20431%2C217%20432%

2C223%20432%2C224%20432%2C225%20432%2C226%20433%2C226%20433%2C227%20433%2C228%20433%2C229%20434%2C22

9%20434%2C230%20435%2C231%20435%2C233%20435%2C234%20436%2C235%20437%2C236%20437%2C237%20438%2C237%20

438%2C238%20438%2C239%20438%2C240%20439%2C240%20439%2C241%20443%2C245%20444%2C246%20444%2C247%20445%

2C247%20446%2C248%20447%2C248%20448%2C248%20448%2C249%20449%2C249%20450%2C250%20451%2C251%20452%2C25

2%20454%2C253%20455%2C253%20461%2C255%20462%2C255%20464%2C256%20466%2C256%20467%2C257%20469%2C257%20

469%2C258%20471%2C259%20472%2C259%20474%2C260%20475%2C260%20477%2C261%20478%2C261%20480%2C262%20481%

2C262%20481%2C263%20482%2C263%20483%2C263%20484%2C263%20485%2C263%20486%2C263%20489%2C263%20491%2C26

3%20492%2C263%20495%2C263%20496%2C263%20502%2C261%20504%2C261%20507%2C261%20509%2C261%20510%2C261%20

511%2C261%20512%2C261%20513%2C261%20515%2C261%20517%2C261%20518%2C261%20520%2C260%20523%2C260%20524%

2C260%20526%2C259%20528%2C259%20529%2C259%20534%2C258%20535%2C258%20536%2C257%20537%2C257%20538%2C25

7%20540%2C257%27%23%3A34855"

In the above example there are 2 methods calls ready to be sent to the server, the 2nd method would be removed after the undoLast() function had executed.

The methods are ready to be passed to the function getLatestMessages which passes the request through the ProjectX API, which then returns the results.

This code only removes the shape before it's sent to the server, I still need to write the code to delete a shape which is in the server whiteboardqueue, and remove the shape element from the web browser display (SVG DOM).

Deleting a redundant shape message from the whiteboard queue

jrobertson (James Robertson) — Sat, 05 Apr 2008 19:39:02 GMT

This code is used to remove a message from the whiteboard queue containing a shape which has recently moved it's position (x and y coordinates) on the board. Code extract from whiteboardqueue.rb



  def call_delete_shape(params)

    #get the shape's message id.

    doc = Document.new(params)

    shape_id = doc.root.elements["param[@var='id']"].text.to_s

    initialize_doc



    doc_xml = Document.new(decode2(@doc_file.root.to_s))

    id = doc_xml.root.elements["records/message/body/*[@id='#{shape_id}']"].parent.parent.attributes.get_attribute('id')

    delete_record(id)

    save_file

  end

*update 10:04pm*
Added the link to the project code http://github.com/jrobertson/whiteboardqueue/tree

DZone Snippets: whiteboardqueue code

Undo the last shape stored in the whiteboard message buffer

Deleting a redundant shape message from the whiteboard queue