Bug 27310 – Incorrect animation when trying to duplicate effect of transform-origin

• Component: CSS
• Status: RESOLVED FIXED

[Chris Marrin]

Created attachment 32798 [details]
testcase showing bug

See the attached testcase. You can duplicate the effect of the Z component of transform-origin using something like this:

    -webkit-transform: translateZ(200px) rotateY(90deg) translateZ(-200px)

This basically offset the axis of rotation by 200 pixels. But when animating this in hardware on Snow Leopard, it uses matrix animation, which produces the wrong results. It looks like the translation value is changing during the animation. This is due to how CA does matrix animation. This case correctly falls back to software animation in Leopard. In Snow Leopard it can still use hardware animation because it can use the valueFunction feature to animate the components separately. But we mistakenly chooses matrix animation instead.

[Chris Marrin]

Created attachment 32799 [details]
Patch with test

[Simon Fraser (smfr)]

Comment on attachment 32799 [details]
Patch with test

> Index: WebCore/ChangeLog
> ===================================================================
> --- WebCore/ChangeLog	(revision 45934)
> +++ WebCore/ChangeLog	(working copy)
> @@ -1,3 +1,19 @@
> [phone]  Chris Marrin  <[e-mail]>
> +
> +        Reviewed by NOBODY (OOPS!).
> +
> +        https://bugs.webkit.org/show_bug.cgi?id=27310

There's a new format being used here now. See earlier entries.

> +        This fixes the bug by always doing component animation
> +        as long as the function lists match. This allows CA
> +        to animate the components and then recompose the result
> +        into the correct matrix.

It would be nice to describe the bug that is being fixed here too.

> Index: LayoutTests/animations/transform-origin-vs-functions.html
> ===================================================================

> +      //document.addEventListener('webkitAnimationStart', start, false);

You should remove that if it's not necessary.
r=me with those fixes.

[Chris Marrin]

Sending        LayoutTests/ChangeLog
Adding         LayoutTests/animations/transform-origin-vs-functions-expected.txt
Adding         LayoutTests/animations/transform-origin-vs-functions.html
Sending        WebCore/ChangeLog
Sending        WebCore/platform/graphics/mac/GraphicsLayerCA.mm
Transmitting file data .....
Committed revision 45953.

[Simon Fraser (smfr)]

This caused bug 27356.