1464371 - Missing top few part lines of fixed-width font rendering on github with webrender

Status: RESOLVED WORKSFORME

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

Description

[:gerard-majax]

STR:
 1. Load a page with fixed-width font rendering (like console output) https://github.com/doe300/VC4CL/issues/31#issuecomment-391678487

Expected:
 No missing pixel

Actual:
 There's a slight few lines of pixels missing on some part of the rendering. In this example, it's around "[VC4CL] Allocated 48 bytes of buffer: handle 7, device address 3199127552, host address 0x76f08000"

A Firefox-level screenshot does not expose the issue, so this might likely be WebRender-level.

This is on Ubuntu 18.04, uptodate, with nightly since several days / weeks now (20180525005138 currently). GPU is Intel Core i7-8650U, UHD Graphics 620.

Comment 1

[:gerard-majax]

Attachment: Firefox-level screenshot, not exposing any rendering issue

Comment 2

[:gerard-majax]

Attachment: System-level screenshot, with bogus rendering visible

Comment 3

[:gerard-majax]

Attachment: Firefox-level screenshot, not exposing any rendering issue

Comment 4

[Aria Beingessner [:Gankra]]

I'm having trouble reproducing this on my Ubuntu machine; I expect it depends on some specific details of your system. Looks sort of like our shaders might be rounding wrong? Hmm.

Marking P3-backlog because it doesn't render the browser unusable and seems linux-specific while we're currently only focusing on ensuring windows works well for our first few releases.

Comment 5

[:gerard-majax]

Bad news: starting mozregression with build from 2018-01-01, I see the bogus line as well.

Comment 6

[:gerard-majax]

Would there be any "standard" way for me to help on that, on a nightly build? That is, without having to rebuild my own. Prefs, MOZ_LOG, anything?

Comment 7

[Aria Beingessner [:Gankra]]

You can follow these instructions to produce a capture of webrender's state to help us identify the issue: https://github.com/servo/webrender/wiki/WebRender-in-Firefox#create-a-capture-of-firefox

Comment 8

[:gerard-majax]

(In reply to Alexis Beingessner [:Gankro] from comment #7)
> You can follow these instructions to produce a capture of webrender's state
> to help us identify the issue:
> https://github.com/servo/webrender/wiki/WebRender-in-Firefox#create-a-
> capture-of-firefox

Thanks, but it looks like it's broken: CTRL+SHIFT+3 does nothing.

Comment 9

[Dzmitry Malyshau [:kvark]]

FWIW, I'm not able to repro the issue on latest FF Nightly and CTRL+SHIFT+3 works for me as expected (goes to ~/wr-capture)

Comment 10

[:gerard-majax]

Ok, so on linux with french keyboard it's actually CTRL+AltGr+3

Comment 11

[:gerard-majax]

So, I should have shared you the content of wr-capture when sitting on the github page exposing the issue :)

Comment 12

[:gerard-majax]

FYI, this kind of issue just made me miss a |É| and thought it was a |E|, which is quite a bad news when it comes to localization reviews :(

Comment 13

[Aria Beingessner [:Gankra]]

wonderful, I can reproduce this locally with your capture!

Comment 14

[Aria Beingessner [:Gankra]]

I reduced your capture down to a simple test-case, so it should hopefully be easy to fix now: https://github.com/servo/webrender/pull/2810

Comment 15

[:gerard-majax]

(In reply to Alexis Beingessner [:Gankro] from comment #14)
> I reduced your capture down to a simple test-case, so it should hopefully be
> easy to fix now: https://github.com/servo/webrender/pull/2810

So, that PR got merged, but I still see weirdnesses, is it expected?

Comment 16

[Aria Beingessner [:Gankra]]

No, it was closed. Glenn determined the issue was gecko feeding busted dimensions to webrender, so now the question is how/why. Unfortunately I don't have any idea how to investigate that part of the system without any way to reproduce this locally.

Comment 17

[:gerard-majax]

(In reply to Alexis Beingessner [:Gankro] from comment #16)
> No, it was closed. Glenn determined the issue was gecko feeding busted
> dimensions to webrender, so now the question is how/why. Unfortunately I
> don't have any idea how to investigate that part of the system without any
> way to reproduce this locally.

Maybe there's some way to add some extra debugging and I try that from a treeherder build ?

Comment 18

[:gerard-majax]

FYI, not that I want to be pushy, but this already got me into doing wrong reviews on github several times now, so it's not just some polish :/

Comment 19

[:gerard-majax]

From IRC:
 - 2560x1440, 14' screen
 - GNOME's scaling set to 100% (defaults to 150 or 200)
 - Gecko zoom untouched

Comment 20

[:gerard-majax]

(In reply to Alexandre LISSY :gerard-majax from comment #19)
> From IRC:
>  - 2560x1440, 14' screen
>  - GNOME's scaling set to 100% (defaults to 150 or 200)
>  - Gecko zoom untouched

At 110% of Gecko's zoom, it seems better. At 90%, feels like there's still some pixels missing, but the line exists (just thinner).

Comment 21

[:gerard-majax]

I don't know when (I've been away for more than one month), but with recent nightlies, this seems to be fixed.

Comment 22

[Aria Beingessner [:Gankra]]

Yep, Jan's link is the fix. gg lee!