Intent to Ship: Preserving dropEffect Values from dragover to drop Events

[Chromestatus]

Contact emails

ror...@microsoft.com

Specification

https://www.w3.org/TR/2011/WD-html5-20110113/dnd.html#dom-datatransfer-dropeffect

Summary

The HTML5 Drag and Drop API allows web applications to handle drag-and-drop operations through a series of events: `dragstart`, `dragenter`, `dragover`, `dragleave`, `drop`, and `dragend`. During these events, the [`dataTransfer.dropEffect`](https://www.w3.org/TR/2011/WD-html5-20110113/dnd.html#dom-datatransfer-dropeffect) property indicates which operation (copy, move, link, or none) should be performed. According to the [HTML5 specification](https://www.w3.org/TR/2011/WD-html5-20110113/dnd.html#dndevents), the `dropEffect` value set by web applications during the last `dragover` event should be preserved and available in the subsequent `drop` event. However, Chromium-based browsers were overwriting the web application's `dropEffect` value with the browser's own negotiated operation before the `drop` event fired, breaking specification compliance and limiting developer control over drag-and-drop behavior.

Blink component

Blink>DataTransfer

Web Feature ID

draganddrop

Motivation

The current behavior: - Violates the HTML5 specification: Contradicts the standardized behavior defined in the HTML5 Drag and Drop API - Breaks developer control: Removes the ability for web applications to manage their own drag-and-drop operations - Creates unpredictable UX: The operation indicated during drag (via cursor feedback) may not match what's available in the drop handler - Forces workarounds: Developers must store `dropEffect` values in global variables or custom data attributes rather than using the standard API - Limits functionality: Makes it impossible to build spec-compliant file managers, code editors, and other applications requiring sophisticated drag-and-drop

Initial public proposal

No information provided

Search tags

draganddrop, dropEffect

TAG review

No information provided

TAG review status

Not applicable

Risks

Interoperability and Compatibility

No information provided

Gecko: Shipped/Shipping

WebKit: No signal (https://github.com/WebKit/standards-positions/issues/596)

Web developers: Strongly positive (https://issues.chromium.org/issues/40068941) 42 upvotes on the associated Chromium issue

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

Debuggability

No new functionality needed for debuggability

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

Yes
This is a blink level change independent of platform implementation.

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

Yes
There are few manual WPTs like https://wpt.live/html/editing/dnd/drop/025.html which cover this feature. Chromium has internal web tests / unit tests as well for this feature.

Flag name on about://flags

No information provided

Finch feature name

PreserveDropEffect

Rollout plan

Will ship enabled for all users

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/40068941

Estimated milestones

Shipping on desktop	146
Shipping on Android	146
Shipping on WebView	146

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).

No information provided

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5140028068069376?gate=6545001561587712

This intent message was generated by Chrome Platform Status.