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Subject: Re[4]: [cgmo-webcgm] Issue: addEventListener
Hi all,
First, a few questions to Ulrich...
- Could you provide us with a few lines of JS that would illustrate
how your default event listener works in your viewer?
- Is the 'onload' the only default event listener you support?
Dieter... please see inline...
Monday, March 21, 2005, 11:54:06 AM, Dieter wrote:
DW> I think that an onLoad event needs to be installed somehow with the viewer
DW> rather than with the document.
You may be right, but this may not be easy to do. (not sure yet).
DW> Consider the following (assuming that the addEventListener method is moved
DW> up to the metafile interface:
Ok.
DW> <script language="JavaScript">
DW> function handleLoad(evt)
DW> {
DW> window.alert( "load finished" );
DW> }
DW> function init()
DW> {
DW> var cgmDoc =
DW> document.getElementById("ivx1").getWebCGMDocument();
DW> cgmDoc.src = 'first.cgm';
DW> cgmDoc.addEventListener( "load", handleLoad );
DW> cgmDoc.src = 'second.cgm'; }
DW> </script>
DW> As of now, handleLoad wouldn't be called for first.cgm,
Correct.
DW> and it would be removed by closing first.cgm before opening second.cgm,
I'm not so sure about that, I think an implementation could keep the
information around. Ralf (co-worker), let me know if I'm wrong.
DW> so it wouldn't be called for second.cgm either, right?
I think it could get called for second.cgm, but still, the problem
exists for first.cgm.
DW> It would be good to know how the SVG folks handle this case.
Both HTML and SVG support the predefined event listeners: onload,
onclick, onmousemove etc...
<html onload="do something"...>
or
<svg onload="do something"...>
So, while reading the file, an implementation can add the event
handler _before_ the document is finished loading _and_ execute it
before the first rendering.
DW> Some solution might be to install a default handler with the viewer,
DW> and the viewer installs it on the opening document as early as possible.
Default handlers or listeners?
In the case of handlers, you are in fact suggesting that we agree on a
function name, and that upon loading the viewer calls that function if
it present in the HTML script, right?
Could some other approach be:
- add onload="function to call" inside the CGM itself?
- or add onload="function to call" as some sort of parameter to the
object tag?
- or simply document that for the 'load' event, you need to set the
event listener before setting 'src'; and that 'load' doesn't work if
the source filename is set on the object tag.
Thoughts?
--
Benoit mailto:benoit@itedo.com
DW> Dieter
DW> -----Original Message-----
DW> From: Ulrich Laesche [mailto:ulrich@ematek.de]
DW> Sent: Monday, March 21, 2005 4:24 PM
DW> To: cgmo-webcgm@lists.oasis-open.org
DW> Subject: FW: Re[2]: [cgmo-webcgm] Issue: addEventListener
DW> Sorry, I hit the wrong reply button.
DW> -----Original Message-----
DW> From: Benoit Bezaire [mailto:benoit@itedo.com]
DW> Sent: Montag, 21. Marz 2005 15:58
DW> To: Ulrich Laesche
DW> Subject: Re[2]: [cgmo-webcgm] Issue: addEventListener
DW> Hi Ulrich,
DW> I was wondering if you could CC the group? I want to CC the group (I
DW> think they should be involved). Do you mind resending, and doing a
DW> reply all.
DW> --
DW> Benoit mailto:benoit@itedo.com
DW> Monday, March 21, 2005, 8:15:37 AM, Ulrich wrote:
UL>> Hi Benoit,
UL>> Once installed, the event handler should be triggered on a Reload
DW> Picture
UL>> occurrance, right? Still, this doesn't solve the problem you described
UL>> below (unless you want to load an image twice to execute some onload
UL>> actions).
UL>> So far, we (Ematek) always assumed the onload event handler in the
DW> script
UL>> being present by default (like in your SVG sample). Apparently the spec
DW> now
UL>> says that no event handler is present by default and that it needs to be
UL>> installed prior to become active.
UL>> We could assume that the load action is not finished before the second
DW> line
UL>> of the script is recognized (when moving the load handler to the
DW> Metafile
UL>> interface, cgmDoc.addEventListener( "load", handleLoad )). However,
DW> this is
UL>> mere speculation and may work or not depending on the implementation or
UL>> performance.
UL>> What does the SVG standard propose in this respect? As the Event
DW> handling
UL>> mechanism should work with all other events the onload should either be
UL>> handled the same way (with some reasonable behavior assumptions) or
DW> become a
UL>> different method.
UL>> Regards
UL>> Ulrich
UL>> -----Original Message-----
UL>> From: Benoit Bezaire [mailto:benoit@itedo.com]
UL>> Sent: Donnerstag, 17. Marz 2005 18:41
UL>> To: CGMO WebCGM TC
UL>> Subject: [cgmo-webcgm] Issue: addEventListener
UL>> Hi CGMO,
UL>> We came upon a problem while working on addEventListener... If you
UL>> consider the following ECMAScript:
UL>> <script language="JavaScript">
UL>> function handleLoad(evt)
UL>> {
UL>> window.alert( "load finished" );
UL>> }
UL>> function init()
UL>> {
UL>> var cgmDoc =
UL>> document.getElementById("ivx1").getWebCGMDocument();
UL>> cgmDoc.src = 'appstructure.cgm';
UL>> cgmPic = cgmDoc.firstPicture;
UL>> cgmPic.addEventListener( "load", handleLoad );
UL>> }
UL>> </script>
UL>> The problem is that the "load" event will never be triggered because
UL>> by the time you get to the addEventListener, the document is already
UL>> fully loaded.
UL>> Do people know if moving the addEventListner to the WebCGMMetafile
UL>> interface solves the problem? Ulrich, your guys worked on this,
UL>> right?
UL>> Assuming the source file was set on the <object> tag and that the
UL>> addEventListener method was on the WebCGMMetafile, would the
UL>> following code work?
UL>> function init()
UL>> {
UL>> var cgmDoc =
UL>> document.getElementById("ivx1").getWebCGMDocument();
UL>> cgmDoc.addEventListener( "load", handleLoad );
UL>> }
UL>> I'm thinking no... I tried this with an SVG viewer and it didn't
UL>> work (but it could be a bug). I can only get the load event to be
UL>> tricked if the event listener is already in the SVG file:
UL>> <svg onload="do something"...>
UL>> Is there a way to catch the 'load' event in a WebCGM viewer
UL>> implementation?
UL>> --
UL>> Benoit mailto:benoit@itedo.com
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