Intent to Ship: Correctly set "dropEffect" for "dragEnter", "dragLeave" and "dragOver" events

[Chromestatus]

Contact emails

gas...@microsoft.com, gerc...@microsoft.com

Specification

https://html.spec.whatwg.org/multipage/dnd.html#dndevents

Summary

The drag and drop specifications require the "dataTransfer"'s object "dropEffect" attribute to have certain predetermined values on "dragEnter", "dragOver" and "dragLeave". Drag enter and drag over should have a "dropEffect" based on the current "effectAllowed", and "dragLeave" should always have a "none" "dropEffect". Currently, Chromium doesn't adhere to these rules. With the launch of this feature, Chromium will start respecting the specification and assigning the correct values to this attribute so that web developers can start relying on it.

Blink component

Blink>DataTransfer

Web Feature ID

draganddrop

Motivation

Many bug reports have been filed over the years by developers being affected by the lack of a correct dropEffect implementation: https://issues.chromium.org/issues?q=title:*dropEffect*

Initial public proposal

No information provided

TAG review

No information provided

TAG review status

Not applicable

Risks

Interoperability and Compatibility

None. Drop effect is reported as working properly in Firefox and Safari

Gecko: Shipped/Shipping

WebKit: Shipped/Shipping

Web developers: Strongly positive Visiting the crbug query linked in the "Motivation" section will show strong sentiment from web developers in wanting this fixed.

Other signals:

WebView application risks

Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications?

None. Should any implementation issue be found, we have a feature flag acting as a kill switch (SetDefaultDropEffect).

Debuggability

No additional functionality is needed to be added to debug this feature

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

Yes

Is this feature fully tested by web-platform-tests?

Yes
* WPT: "dropEffect" and "effectAllowed" are tested in: https://wpt.fyi/results/html/editing/dnd/drop?label=master&label=experimental&aligned * Other tests: We have unit tests (drag_and_drop_interactive_uitest.cc) and blink web tests (third_party/blink/web_tests/fast/dnd/*) verifying the correct functioning of this behavior.

Flag name on about://flags

None

Finch feature name

SetDefaultDropEffect

Non-finch justification

The feature will be shipped enabled by default to be used as a kill-switch in case a severe issue is discovered.

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/434151262

Estimated milestones

Shipping on desktop	148
Shipping on Android	148

Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (e.g. links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (e.g., changing to naming or structure of the API in a non-backward-compatible way).

N/A

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/6325617459068928?gate=6549835522113536

This intent message was generated by Chrome Platform Status.

[Alex Russell]

LGTM1.

Thanks for fixing long-standing compat issues. Deeply appreciated.

Best,

Alex

[Dan Clark]

LGTM2

[Mike Taylor]

LGTM3

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