1573886 - backdrop-filter blur can have artifacts due to scaling

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P3)

Description

[Connor Brewster [:cbrewster]]

WebRender does blurring via multiple passes, first it scales the source down using scale tasks and then does a horizontal and vertical blur pass. To ensure that errors are not introduced due to scaling, the width and height of the source must be multiples of two.
https://searchfox.org/mozilla-central/rev/c7e8bc4996f979e5876b33afae3de3b1ab4f3ae1/gfx/wr/webrender/src/render_task.rs#1031

When blurring for backdrop-filter, we do not adjust the size so it is a multiple of two because this can add extra padding of transparent pixels to the source. This results in incorrect blur results.

We should do size adjustment but also track the original size so we don't include the extra transparent padding while computing the blur.

Comment 1

[Connor Brewster [:cbrewster]]

Attachment: backdrop-filter-blur-artifacts.html

Comment 2

[Connor Brewster [:cbrewster]]

Attachment: Bug 1573886 - Fix backdrop-filter blur errors due to incorrect scaling r?gw,nical,kvark

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/26094588b48e
Fix backdrop-filter blur errors due to incorrect scaling r=kvark

Comment 4

[Cristian Brindusan [:cbrindusan]]

https://hg.mozilla.org/mozilla-central/rev/26094588b48e