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List:       whatwg
Subject:    [whatwg] DND: spec not matching implementations
From:       "Anne van Kesteren" <annevk () opera ! com>
Date:       2012-02-17 9:31:55
Message-ID: op.v9tgrhcj64w2qv () annevk-macbookpro ! local
[Download RAW message or body]

The feedback that follows is based on our implementation experience with=
  =

drag & drop. The people that ought to be credited for the report below a=
re  =

Pawe=C5=82 Stanek, Giorgi Chavchanidze, Wilhelm Joys Andersen, and anony=
mous;  =

i.e. not me.


During our initial implementation of HTML5 drag and drop, we encountered=
  =

some situations where the current specification either does not reflect =
 =

useful behaviour of existing implementations, or is not yet complete  =

enough to base the implementation on it (eg. synthetic events). There ar=
e  =

also some limitations of the specification for which we feel a change is=
  =

best. The most minor cases are listed in this message. Other messages wi=
ll  =

follow with the details of more extensive changes.

* Firefox, Chrome and Opera only allow dragend to delete ranges during a=
  =

'move' if the range exists within an editable element. The spec needs to=
  =

change to reflect this - currently it expects this anywhere within a  =

non-editable document.

* Firefox, Chrome and Opera allow dropping in all text based inputs (tex=
t  =

search tel url email password number) not just text.

* Firefox, Chrome and Opera all make .effectAllowed writeable only when =
 =

the data store is in read/write mode, so that only the source node has t=
he  =

ability to set the effectAllowed.

* Opera and Firefox have chosen to implement modifiers at the point of  =

dropEffect initialization during dragenter and dragover: initially set  =

dropEffect to the default value specified in the spec table, then if the=
  =

platform requests something else with a modifier, set the dropEffect to =
 =

that modified value. Therefore those events see the modified dropEffect =
 =

(which seems to be the intention of the spec), and can also override it =
by  =

writing to the dropEffect property.

* When dragging selections, Firefox, Chrome and Opera populate text/html=
  =

with the minimal markup intersected by the selection (the smallest  =

possible markup that contains all of the selection, without any parent  =

elements that contain both ends of the selection).

* Opera populates text/html when dragging an element. This means that it=
  =

is possible to drag HTML into another application without needing  =

JavaScript.

* Opera recognises dropzone on parent elements of the immediate user  =

selection - the spec currently requires it to be the specific element,  =

which means that child elements of the dropzone are not within the  =

dropzone. This implementation is as simple as replacing this line in the=
  =

specification:
"If the immediate user selection is an element with a dropzone attribute=
  =

that matches the drag data store -> Set the current target element to th=
e  =

immediate user selection anyway."
With this line:
"If the immediate user selection is an element with a dropzone attribute=
  =

that matches the drag data store, or if the immediate user selection has=
  =

an ancestor element with a dropzone attribute that matches the drag data=
  =

store -> Set the current target element to the immediate user selection =
 =

anyway."

* When there is no body, Opera uses the root node as the fallback target=
  =

(when the immediate user selection does not cancel dragenter). If there =
is  =

no root node, Opera uses null. This allows documents with no body to  =

function correctly, where the spec reverts to using the document object.=
  =

This means that when subsequently moving the drag over another  =

non-cancelling element, it will once again fire dragenter at the documen=
t.  =

And again when the mouse drags over another non-cancelling element, etc.=
  =

etc.

Our proposal is to replace this:

"If the current target element is the body element"

with this:

If the current target element is the body element, or if there is no bod=
y  =

element and the current target is the html element

And then replace this:

"Otherwise; Fire a DND event named dragenter at the body element, if the=
re  =

is one, or at the Document object, if not. Then, and set the current  =

target element to the body element, regardless of whether that event was=
  =

canceled or not."

with this:

If the body element or html element exist; Fire a DND event named  =

dragenter at the first of the following objects that exists, and set the=
  =

current target element to that object regardless of whether that event w=
as  =

canceled or not:
* The body element
* The html element [interpreted as the root node in non-html documents]
Otherwise; set the current target element to null

(Note that it is possible for a document containing an immediate user  =

selection to have neither a body element nor a root element, if the  =

dragenter event handler for the immediate user selection deletes the roo=
t  =

element.)


-- =

Anne van Kesteren
http://annevankesteren.nl/
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