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Re: [whatwg] Proposed addition to Drag and Drop API

From: Alex Bain <alex@alexba.in>
Date: Mon, 2 Jul 2012 10:06:47 -0700
To: Daniel Cheng <dcheng@chromium.org>
Message-ID: <E90A31B2677D40198E83EC5CAA839638@alexba.in>
Cc: whatwg@lists.whatwg.org, Ryosuke Niwa <rniwa@webkit.org>, Tony Chang <tony@chromium.org>
I did a bit of reading about what the WhatWG spec says setDragImage should do and wanted to ensure I understand what the spec is saying and how Webkit is behaving.

Spec: http://www.whatwg.org/specs/web-apps/current-work/multipage/dnd.html#dom-datatransfer-setdragimage

The spec says defines "setDragImage" as: setDragImage(element, x, y) 

Element argument is defined as: "If the element argument is an img element, then set the drag data store bitmap to the element's image (at its intrinsic size); otherwise, set the drag data store bitmap to an image generated from the given element (the exact mechanism for doing so is not currently specified)."

This says, if I'm understanding it correctly, that I can provide any element as the first argument and a bitmap image will be generated as a drag image. This would allow me to accomplish what I'm trying to do (setting a small drag element to represent a larger draggable container). However, in my testing, Webkit will not render anything unless the element specified is an image.

Am I misunderstanding the spec, or might this be a bug in the implementation?


- Alex 

On Friday, June 29, 2012 at 4:37 PM, Alex Bain wrote:

> @Ryosuke - I do not have a concrete proposal but would be interested in helping to work one out. I had idly considered a content attribute but think that specifying an element (perhaps via a function called setDragElement()) would be a simple implementation.
> @Daniel - I had thought that was possible but in my testing I was not able to get it to work. I had tried referencing an existing element as well as creating a new element but neither were visible while dragging [in Chrome].
> On Friday, June 29, 2012 at 4:30 PM, Daniel Cheng wrote:
> > Can't you use setDragImage() and pass it the element that holds the post title?
> > 
> > Daniel 
> > 
> > 
> > On Fri, Jun 29, 2012 at 4:27 PM, Ryosuke Niwa <rniwa@webkit.org (mailto:rniwa@webkit.org)> wrote:
> > > On Fri, Jun 29, 2012 at 4:24 PM, Alex Bain <alex@alexba.in (mailto:alex@alexba.in)> wrote:
> > > > I would prefer not to visually drag the entire post around (which is what happens if I set draggable to true on the post container). My goal is to set draggable on a container element and only show a small element when the user starts dragging.
> > > 
> > > Ah, that's an interesting use case. Thanks for clarification. Do you have a concrete proposal for this? (e.g. adding new content attribute / element).
> > > 
> > > - Ryosuke 
> > > 
> > 
Received on Monday, 2 July 2012 17:07:20 UTC

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