740235 - Prevent about:home from creating a full window component alpha layer

Status: RESOLVED FIXED

(Firefox :: General, defect)

Description

[Bas Schouten (:bas.schouten)]

The google interface at about:home in our nightlies appears to create a full window size component alpha layer. From the looks of the page that seems needlessly complicated. It's possible we're doing something suboptimal.

Comment 1

[Robert O'Callahan (:roc) (email my personal email if necessary)]

It's the fixed background:

html {
  background-color: hsl(0,0%,90%);
  background-image: url(chrome://browser/content/abouthome/noise.png),
                    -moz-linear-gradient(hsla(0,0%,100%,.7), hsla(0,0%,100%,.4));
}

I can't actually tell what the background images are doing ... the background looks like a solid color to me.

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

oh, there's a "background-attachment: fixed;" rule in aboutHome.css that I accidentally trimmed.

I'm pretty sure we don't need that rule, at least.

Comment 3

[Frank Yan (:fryn)]

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #1)
> I can't actually tell what the background images are doing ... the
> background looks like a solid color to me.

It's not a solid color. It's a noise texture, but yes it is subtle and intentionally so.
See the following sites for other examples of this type of noise texture in their backgrounds:
https://www.youtube.com/
http://cl.ly/2F3M1T0L3E3h2C3A3f2X

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #2)
> oh, there's a "background-attachment: fixed;" rule in aboutHome.css that I
> accidentally trimmed.
> 
> I'm pretty sure we don't need that rule, at least.

No, we don't. Does removing that rule fix this bug?

Comment 4

[Frank Yan (:fryn)]

Attachment: patch

The background-attachment shouldn't be `fixed` anyway.

Comment 5

[Marco Bonardo [:mak]]

Comment on attachment 610565 [details] [diff] [review]
patch

Review of attachment 610565 [details] [diff] [review]:
-----------------------------------------------------------------

I thought was part of the design specs, good to know it's not.

Btw, it's still unclear, if this is really a perf problem, of which size? This is becoming more common on the Web (the transparent texture) as pointed out, is there a problem at the platform level or just it's something we should evangelize against?
And finally, if just removing the fixed is enough to solve the perf problem.

Comment 6

[Robert O'Callahan (:roc) (email my personal email if necessary)]

The problem is not the texture, it's 'background-attachment:fixed'.

It's not a big problem. Probably no-one would have noticed if Bas hadn't been doing some testing. But making about:home a bit faster to render, with a bit less memory usage, is worth it.

We could fix this case with an optimization in the engine. The reason we use extra resources here is so that we create a separate layer for the fixed background so that scrolling is snappy if you scroll the page. about:home usually doesn't need a scrollbar so we can expect that scrolling won't happen. We could detect that and turn off the separate layer for that case. But we have no data to indicate whether that would be worth doing in general.

Comment 7

[Frank Yan (:fryn)]

(In reply to Robert O'Callahan (:roc) (Mozilla Corporation) from comment #6)
> The problem is not the texture, it's 'background-attachment:fixed'.

Great! I'm glad you and Bas caught this, since background-attachment should have been `scroll` design-wise anyway, but we didn't notice it, since as you noted "about:home usually doesn't need a scrollbar". :)

Thanks, mak, for the review. :)

https://hg.mozilla.org/integration/fx-team/rev/7cc16b3f172d

Should this get ported to aurora?

Comment 8

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Might as well, it's minimal risk.

Comment 9

[Frank Yan (:fryn)]

Comment on attachment 610565 [details] [diff] [review]
patch

[Approval Request Comment]
User impact if declined: Slower rendering and more memory usage for about:home.
Risk to taking this patch: None.
String changes made by this patch: None.

Comment 10

[Tim Taubert [:ttaubert] (inactive)]

https://hg.mozilla.org/mozilla-central/rev/7cc16b3f172d

Comment 11

[Alex Keybl [:akeybl]]

Comment on attachment 610565 [details] [diff] [review]
patch

[Triage Comment]
Very simple, low-risk change in support of about:home perf. Approved for Aurora 13.

Comment 12

[Marco Bonardo [:mak]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/01fbbc855886

Comment 13

[u279076]

Is there a test QA can use to verify this fix?

Comment 14

[Frank Yan (:fryn)]

(In reply to Anthony Hughes, Mozilla QA (irc: ashughes) from comment #13)
> Is there a test QA can use to verify this fix?

I don't know, but it's not necessary, imho.