1458177 - text shadow misbehaves with webrender async scene building

Status: RESOLVED FIXED

(Core :: Graphics: WebRender, defect, P1)

Description

[Toshihiro Yamada]

Attachment: screenshot of the page while the problem happens

STR
1. set gfx.webrender.all true
2. Open http://nihon.syoukoukai.com/modules/stories/index.php?lid=1265
3. Scroll the page or select some text.

Expected results
text with shadow displays normally.

Actual results
text shadow is different from original text. 

When gfx.webrender.all is false and gfx.webrender.enabled is true, the problem doesn't happen (As far as I tested)

Comment 1

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

I can repro this on macOS as well.

Comment 2

[Aria Beingessner [:Gankra]]

I can repro this on windows and linux as well.

Comment 3

[Aria Beingessner [:Gankra]]

str: 

data:text/html,<div style="width: 400px;text-shadow: 1px 1px 1px grey;">Hello there my name is alexis and this is my amazing test-case for shadows being broken under async scene building

literally just a multi-line text-shadow. analyzing now.

Comment 4

[Aria Beingessner [:Gankra]]

I was able to reproduce this in a capture, but the scene.ron looks fine. Converting that scene to a reftest produces something that doesn't reproduce the issue. In addition pressing keys to adjust the zoom level fixes the issue. It looks like we might be corrupting the resource or gpu caches?

kvark found it suspicious that the font entry had a different font_key from its own key: 

font_instances: {
  ..
  ((3), 57): (
    font_key: ((3), 56),
    ..
  )
}

font_templates: {
  ..
  ((3), 56): Native,
}

Comment 5

[Aria Beingessner [:Gankra]]

huh: on linux i'm seeing the color of the shadow being ignored for cache lookup when i turn on asyn-scene-building.

So if you open:

data:text/html,<div style="width: 400px;text-shadow: 1px 1px 2px black;">Hello there my name is alexis and this is my amazing test-case for shadows being broken under async scene building

and then (identical except for shadow color):

data:text/html,<div style="width: 400px;text-shadow: 1px 1px 2px white;">Hello there my name is alexis and this is my amazing test-case for shadows being broken under async scene building

the white shadow will appear black, as it will seemingly find the old black shadow from the other tab in the shadow(?) cache

Comment 7

[Toshihiro Yamada]

Confirmed fixed on try-build in Bug 1466549.