Difference between revisions of "Script-and-inputOutputField.x3d"

Revision as of 21:19, 6 August 2008

<?xml version="1.0" encoding="UTF-8"?>
   <X3D profile='Full' >
 <Scene DEF='scene'>
   <Viewpoint position='20 0 40'/>
   <Shape>
     <Text DEF='text' string='"Initialize called: FALSE" "readFoo() called: FALSE" "foo value send: FALSE" "foo function called: FALSE" "set_foo function called: FALSE" "foo_changed function called: FALSE"'/>
   </Shape>
   <Script DEF='s1' directOutput='true'>
     <field accessType='initializeOnly' name='text' type='SFNode'>
       <Text USE='text'/>
     </field>
     <field accessType='inputOutput' name='foo' type='SFFloat' value='5'/>
     <field accessType='inputOnly' name='readFoo' type='SFTime'/><![CDATA[ecmascript:
 //-----------------------------
 function initialize (value) {
   line = 'Initialized called: TRUE; foo value: ' + foo;
   text.string[0] = line;
  }
 //-----------------------------
 function readFoo (value) {     
  text.string[1] = 'readFoo called: TRUE, value: ' + foo;
 }       
 //-----------------------------
 function foo (value) {     
  text.string[3] = 'foo function called: TRUE; ' + value;
 }       
 //-----------------------------
 function set_foo (value) {     
  text.string[4] = 'set_foo function called: TRUE; ' + value;
 }       
 //-----------------------------
 function foo_changed (value) {     
  text.string[5] = 'foo_changed function called: TRUE; ' + value;
 }       
 ]]>
   </Script>
   <TimeSensor DEF='ts' cycleInterval='3' loop='true'/>
   <Script DEF='s2' directOutput='true'>
     <field accessType='initializeOnly' name='text' type='SFNode'>
       <Text USE='text'/>
     </field>
     <field accessType='inputOnly' name='fooCatcher' type='SFFloat'/><![CDATA[ecmascript:
 //-----------------------
 function fooCatcher (value) {
   text.string[2] = 'Foo value send: TRUE; value: ' + value;
 }
 ]]>
   </Script>
   <ROUTE fromNode='ts' fromField='fraction_changed' toNode='s1' toField='set_foo'/>
   <ROUTE fromNode='ts' fromField='cycleTime' toNode='s1' toField='readFoo'/>
   <ROUTE fromNode='s1' fromField='foo_changed' toNode='s2' toField='fooCatcher'/>
 </Scene>
</X3D>

Browser Results

Specification Notes

Basic Problem:

A) The X3D-spec (not VRML) supports intputOutput Fields in Scripts (http://www.web3d.org/x3d/specifications/ISO-IEC-19775-X3DAbstractSpecification_Revision1_to_Part1/Part01/components/scripting.html#Scriptlanguages)

B) Field values can be read or written in the Script code (http://www.web3d.org/x3d/specifications/ISO-IEC-19775-X3DAbstractSpecification_Revision1_to_Part1/Part01/components/scripting.html#Accessingfieldsandevents)

C) Events received by the Script node are passed to the appropriate scripting language method in the script. The method's name depends on the language type used. (http://www.web3d.org/x3d/specifications/ISO-IEC-19775-X3DAbstractSpecification_Revision1_to_Part1/Part01/components/scripting.html#Eventhandling)

D) ECMAScript X3D-binding: If the function represents an inputOutput field, the name of the function shall be the same name as the field declaration, without the set_ or _changed modifiers (http://www.web3d.org/x3d/specifications/ISO-IEC-19777-1-(X3DLanguageBindings-ECMAScript/Part1/concepts.html#ReceivingEvents)

E) ECMAScript: variable and function both are objects in the same namespace. (http://www.ecma-international.org/publications/standards/Ecma-262.htm)

=> There is variable/function-shadowing problem ((E) brakes (D)) which prevents reading/writing (B) or receiving of events (C)

Solution:

_S1_) Leave the X3D-Spec like it is (This breaks the ECMAScirpt spec (E))

There are ways to abuse the ECMAScript impl. (e.g SpiderMonkey) to work this way but still breaks the spec. (and slows down the object access) However there are some major browser that did exactly this

code snip:

   Script {
   inputOutput SFBool foo TRUE
     ...
     function initialize () {
          Browser.println( 'value: '+ foo);
     }
     ...
     function foo (value,timeStamp) {
         Browser.println( 'value: '+ value);
      }

_S2_) Change the X3D-Spec, use set_foo for the event handler

change the name of the function for inputOuput from "same as field" to "set_" prefix

code snip:

   Script {
   inputOutput SFBool foo TRUE
     ...
     function initialize () {
          Browser.println( 'value: '+ foo);
     }
     ...
     function set_foo (value,timeStamp) {
         Browser.println( 'value: '+ value);
      }

_S3_) Change the X3D-Spec, use foo_value/set_foo or foo_changed to access the value

change the field-value access funciton

code snip:

   Script {
   inputOutput SFBool foo TRUE
     ...
     function initialize () {
          Browser.println( 'value: '+ foo_value);
     }
     ...
     function foo (value,timeStamp) {
         Browser.println( 'value: '+ value);
      }

conclusion:

It is a mess right now and I would suggest that we change the spec to change the event-handling function form foo to set_foo;

Something like:

ECMASCRIPT: 4 Concepts: 4.3.5.4 Receiving events

OLD:

Events sent to the containing node are passed to the corresponding ECMAScript function in the script. The function's name is the same as the field and is passed two arguments. If the function represents an inputOutput field, the name of the function shall be the same name as the field declaration, without the set_ or _changed modifiers

NEW:

Events sent to the containing node are passed to the corresponding ECMAScript function in the script. Two arguments, the value and the timestamp, are passed while calling the function. For inputOnly fields the function's name is the same as the field. If the function represents an inputOutput field, the name of the function shall be the same name as the field declaration plus a set_ prefix.