1052474 - Scrolling an iframe with a CSS transform doesn't work very well

Status: RESOLVED WORKSFORME

(Core :: Panning and Zooming, defect)

Description

[Kartikaya Gupta (email:[e-mail])]

Attachment: Test case

Load the attached test page in the B2G browser and try scrolling the iframe. Issues:
- You can only scroll if you put your finger down in the top-left quadrant of the iframe
- The iframe moves twice as fast as your finger
- Often there are unpainted areas visible at the bottom of the iframe

Comment 1

[Kartikaya Gupta (email:[e-mail])]

Attachment: Test page

Updated to use https so we don't run into mixed-content-blocking problems.

Comment 2

[Botond Ballo [:botond]]

(In reply to Kartikaya Gupta (email:[e-mail]) from comment #0)
> - You can only scroll if you put your finger down in the top-left quadrant
> of the iframe

Bug 993125 has similar symptoms.

Comment 3

[Kartikaya Gupta (email:[e-mail])]

Attachment: Layer tree

I don't understand why this layer tree is the way it is. Specifically both ContainerLayerComposite instances with a 2.0 scale also have a preScale of 0.5. And there's no postScale in sight. Where is the scaling actually happening?

Comment 4

[Botond Ballo [:botond]]

Going to start the apz-css-transforms work by looking at this. (Thanks for the simple example page!)

Comment 5

[Kartikaya Gupta (email:[e-mail])]

This works now \o/. Presumably it was fixed by the parts of the apz-css-transforms work that landed already, but I didn't bisect to verify.

It is a little janky while scrolling but that's a separate issue.