Bug 214970 - [iOS] Calling preventDefault() in a pointerdown event handler for an <img> does not prevent system drag
Summary: [iOS] Calling preventDefault() in a pointerdown event handler for an <img> do...
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: UI Events (show other bugs)
Version: Safari Technology Preview
Hardware: Unspecified Unspecified
: P2 Normal
Assignee: Nobody
URL:
Keywords: InRadar
Depends on:
Blocks:
 
Reported: 2020-07-30 08:48 PDT by Antoine Quint
Modified: 2020-07-30 08:51 PDT (History)
3 users (show)

See Also:

Attachments
Test (289 bytes, text/html)
2020-07-30 08:48 PDT, Antoine Quint 		no flags Details
View All Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Antoine Quint 2020-07-30 08:48:14 PDT 
Consider this simple markup:

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAGQAAABkCAQAAADa613fAAAAaUlEQVR42u3PQREAAAgDoK1/aI3g34MGNJMXKiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiIiJyWXmfZAEMq/KNAAAAAElFTkSuQmCC" onpointerdown="event.preventDefault()">

On macOS, the fact that `event.preventDefault()` is called while handling the `pointerdown` event makes it so that the image cannot be dragged. On iOS the image is draggable after a long press, but I think it should not be to match both the macOS behavior and developer expectation.
Comment 1 Radar WebKit Bug Importer 2020-07-30 08:48:37 PDT 
<rdar://problem/66329423>
Comment 2 Antoine Quint 2020-07-30 08:48:50 PDT 
Created attachment 405572 [details]
Test
Comment 3 Antoine Quint 2020-07-30 08:50:11 PDT 
This came up while fixing bug 214968.
Comment 4 Antoine Quint 2020-07-30 08:51:23 PDT 
Useful information from Wenson: the UI process (UIDragInteraction) mediates when to begin a drag on iOS, we’d probably just need to prod it when default is prevented for pointerdown.