894345 - [New Tab Page] Fix drag/drop behavior when rearranging sites

Status: RESOLVED FIXED

(Firefox :: Tabbed Browser, defect)

Description

[Tim Taubert [:ttaubert] (inactive)]

While investigating some improvements to the about:newtab drag-and-drop tests, I stumbled over broken d&d behavior, implemented by dropTargetShim.js.

The problem is that the shim disables all pointer events for the grid (as necessary) but fails to call event.preventDefault() on dragenter and dragover so that the drag operation always fails (as far as the d&d service is concerned). about:newtab successfully drops the site anyway but I'm sure this could hit us or add-on authors in the future again, so we should fix that.

Comment 1

[Tim Taubert [:ttaubert] (inactive)]

Attachment: fix drag/drop behavior when rearranging sites

This patch implements the d&d correctly as it uses preventDefault() to communicate with the d&d service on dragenter/over and drop. I think may not have completely understood how it all works back when I implemented it first. I certainly do now.

The sites.js change removes unused code I found.

The change to _whenTransitionEnded() in transformations.js was necessary due to some strange behavior when other properties that were transitioned as well (but we didn't really care about) finished earlier than expected. This aborted the transition a little too early, unpredictibly, somtimes.

Comment 2

[Tim Taubert [:ttaubert] (inactive)]

Almighty try is pleased:

https://tbpl.mozilla.org/?tree=Try&rev=233f2eaf6c3a

Comment 3

[Jared Wein [:jaws] (please needinfo? me)]

Comment on attachment 776332 [details] [diff] [review]
fix drag/drop behavior when rearranging sites

Review of attachment 776332 [details] [diff] [review]:
-----------------------------------------------------------------

::: browser/base/content/newtab/dropTargetShim.js
@@ +218,4 @@
>      let node = aTarget.node;
>      let event = document.createEvent("DragEvents");
>  
> +    // Let the event not bubble to avoid recursion.

// The event should not bubble to prevent recursion.

Comment 4

[Tim Taubert [:ttaubert] (inactive)]

https://hg.mozilla.org/integration/fx-team/rev/0a2cc86d61b7

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/0a2cc86d61b7