[Laszlo-user] Strange data-binding behavior

[André Bargull]

Hello Yang,
this isn't about databinding, it's more about states and constraints, 
see "http://www.openlaszlo.org/jira/browse/LPP-631".

Here is just another testcase which shows this misbehaviour and probably 
a workaround for you..."LzDelegate#disable()":
[code]
<canvas debug="true" >
 
  <class name="resizeview" width="100" height="80"
           onmousedown="this.resizer.apply()" 
onmouseup="this.resizer.remove()" >
    <resizestate name="resizer" apply="false" >
      <attribute name="height" value="$once{this.height}" />
    </resizestate>
  </class>
 
  <class name="testview" width="300" height="220" bgcolor="0xEAEAEA" >
    <attribute name="width" value="${this.redview.width+150}" />
    <simplelayout axis="y" spacing="20" />
    <resizeview name="redview" bgcolor="red" />
  </class>
 
  <simplelayout axis="y" spacing="50" />
 
  <testview name="tv1" >
    <state apply="true" >
      <attribute name="width" value="${this.blueview.width+150}" />
      <resizeview name="blueview" bgcolor="blue" />
    </state>
    <text options="ignorelayout" text="Both resizeviews will affect 
width" align="left" valign="bottom" />
  </testview>
 
  <button y="230" options="ignorelayout" text="Disable" >
    <handler name="onclick" >
      tv1.__LZdelegates[0].disable();
    </handler>
  </button>
 
  <button y="230" x="80" options="ignorelayout" text="Enable" >
    <handler name="onclick" >
      tv1.__LZdelegates[0].enable();
    </handler>
  </button>
 
  <testview name="tv2" >
    <attribute name="width" value="${this.blueview.width+150}" />
    <resizeview name="blueview" bgcolor="blue" />
   
    <text options="ignorelayout" text="Only the blue resizeview will 
affect width" align="left" valign="bottom" />
  </testview>
 
</canvas>
[/code]

Cheers,
André

Yang wrote:
> In the following, there is a lone button whose width is initially
> unset, and then is bound by applying a state. (This is the same as how
> the grid's header buttons works.) The width of the button should never
> change.
>
> However, if we update the data referenced by the button's datapath,
> the button will actually resize.
>
> <canvas>
>   <dataset name="d">hello world</dataset>
>   <view width="100" name="v">
>     <attribute name="doapply" type="boolean" value="$immediately{false}"/>
>     <button name="b" datapath="d:/text()">
>       <state apply="${parent.parent.doapply}">
>         <attribute name="width" value="${parent.width}"/>
>       </state>
>     </button>
>   </view>
>   <handler name="oninit">
>     LzTimer.addTimer( new LzDelegate( this, 'changeApply' ), 500 );
>     LzTimer.addTimer( new LzDelegate( this, 'changeData' ), 1000 );
>   </handler>
>   <method name="changeApply">
>     v.setAttribute('doapply', true);
>   </method>
>   <method name="changeData">
>     d.getPointer().setNodeText('bye');
>   </method>
> </canvas>
>
> Is this a bug? This was the smallest test case I could come up with.
>
> If you just set the state's apply to true, the button never even
> expands to width 100.
>
> Furthermore, if you try to add an onwidth handler (such as the
> following) to the button in an attempt to correct the width if it ever
> gets set to something wrong, the setWidth() seems to just be ignored:
>
> <handler name="onwidth">
>   if (this.width != parent.width) {
>     this.setWidth(parent.width);
>   }
> </handler>
>
> The only way I could work around this was to use add another
> timer/delegate/method (with timeout 1).
>
> BTW, is there any way to pass an anonymous block of code to a timer
> (instead of creating and naming a method)? And is there any way to
> pass arguments through a delegate (aside from the
> eventSender/eventName)?
>
> Thanks,
>
> Yang
-- 
Mit freundlichen Grüßen,
André Bargull
Intensis GmbH

Tel.: +49 (0)231 5522-900
Fax.: +49 (0)231 5522-901
E-Mail: a.bargull at intensis.de
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