Drag and drop events on views do not have e.dataTransfer

[juliangutman]

The html5 drag and drop events on views do not have the dataTransfer property on the event object. Likely because jQuery does not in its default state copy that property to the jQuery event from the browser event.

As per the jQuery documentation:

OtherProperties

Certain events may have properties specific to them. Those can be accessed as properties of the event.originalEvent object. To make special properties available in all event objects, they can be added to the jQuery.event.props array. This is not recommended, since it adds overhead to every event delivered by jQuery.

Example:

// add the dataTransfer property for use with the native drop event
// to capture information about files dropped into the browser window
jQuery.event.props.push("dataTransfer");

[raycohen]

@juliangutman Can you be a little more specific about what you are suggesting? It seems that the data you need can be accessed via event.originalEvent.dataTransfer. Is that not acceptable?

[juliangutman]

Fair point, it could be done that way.

I was simply suggesting that considering that the drag and drop series of events were the only ones for which a crucial event property was not available on the augmented jQuery event object, it might make sense to add:

jQuery.event.props.push("dataTransfer");

somewhere in the ember source. If not, at least have a note in the api docs around the fact that dataTransfer needs to be accessed via the originalEvent. I spent a bit of time and frustration trying to understand why I couldn't get the dataTransfer property and only after looking through the jQuery documentation did I find that section and luckily the example included the dataTransfer property specifically.

[raycohen]

Looks like there is a way to get html5 event attributes copied over by jQuery with less of a performance hit. If you push directly onto jquery.event.props then every event jQuery sees is going to get a slight performance hit for it. (Consider how fast lots of mouse and scroll events can be generated)

Instead, you can add per-event via jQuery.event.fixHooks so only that type of event will trigger the extra code.

Consider this example, where props is a list of extra properties, and filter can do custom logic with the event:
https://github.com/jquery/jquery/blob/9bb3494ce99889e05a7333e38e4da9579ce6af8e/src/event.js#L462

And these discussions:
http://bugs.jquery.com/ticket/8789

http://bugs.jquery.com/ticket/5249

so for extra events and properties we want to support, we'd add something like this:

jQuery.event.fixHooks.drop = {
  props: ['dataTransfer']
}

[juliangutman]

Very awesome. Appreciate you looking into this and sending over the
references. Apologies for being sloppy and not digging a bit deeper
myself.

Julian

On Jun 26, 2012, at 12:31 AM, raycohen
reply@reply.github.com
wrote:

Looks like there is a way to get html5 event attributes copied over by jQuery with less of a performance hit. If you push directly onto jquery.event.props then every event jQuery sees is going to get a slight performance hit for it. (Consider how fast lots of mouse and scroll events can be generated)

Instead, you can add per-event via jQuery.event.fixHooks so only that type of event will trigger the extra code.

Consider this example, where props is a list of extra properties, and filter can do custom logic with the event:
https://github.com/jquery/jquery/blob/9bb3494ce99889e05a7333e38e4da9579ce6af8e/src/event.js#L462

And these discussions:
http://bugs.jquery.com/ticket/8789

http://bugs.jquery.com/ticket/5249

so for extra events and properties we want to support, we'd add something like this:

jQuery.event.fixHooks.drop = {
 props: ['dataTransfer']
}

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#1073 (comment)

[raycohen]

ping: @wagenet

Since the event delegator is handling drag & drop events, this would be handy. Thoughts?

[wagenet]

@raycohen Since you seem to be fairly familiar with how this should work is this something you'd be willing to attempt a PR for?

[juliangutman]

Sure, I'd be glad to give it a shot.

On Tuesday, June 26, 2012 at 1:08 AM, Peter Wagenet wrote:

@raycohen Since you seem to be fairly familiar with how this should work is this something you'd be willing to attempt a PR for?

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#1073 (comment)

[raycohen]

jQuery.event.fixHooks only became available in jQuery 1.7. Ember still supports 1.6.

Is it ok for the code (and the tests) to check the existence of fixHooks before proceeding?

I'm also a bit concerned that fixHooks is not documented as part of the public API for jQuery.

[wagenet]

I think we can bump to requiring 1.7 for master so this fix should probably target master then. Maybe @wycats can provide some insight about fixHooks since he's on the jQuery team as well.

[scottgonzalez]

jQuery.event.fixHooks is the correct way to fix this. If you want to support older versions of jQuery, you should be able to just push on to jQuery.event.props. It'll affect all events, but I'm pretty sure it'll solve the problem.

[wycats]

Can someone submit a pull request that uses fixHooks and bumps us to 1.7?

[wagenet]

This has been merged it looks like.