1328059 - Text on the page blinks after hard-refresh when I edit irrelevant CSS rules in devtools

Status: REOPENED

(Core :: CSS Parsing and Computation, defect, P3)

Description

[arni2033]

>>>   My Info:   Win7_64, Nightly 49, 32bit, ID 20160526082509
STR_1:
1. Open http://otto.yndenz.com/ , reload it using Ctrl+Shift+R
2. Inspect element "#menu-filter-brand", find rule "height: 40px;" in ruleview, click on "40px"
3. Press Up key, wait 5 seconds
4. Press Down key, wait 5 seconds

AR:  After Step 3 and Step 4 icons (set by font) on the page blink. Font file is requested
     multiple times. New requests appear in Netmonitor, and each of them says "cached"
ER:  Icons shouldn't blink

This is regression from bug 964613 (between 2014-04-17 and 2014-04-18). Regression range:
> https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=e71ed4135461&tochange=7fe3ee0cf8be@ John Daggett (:jtd):
It seems that this is a regresion caused by your change. Please have a look.

Comment 1

[Mats Palmgren (inactive)]

Unfortunately, the site appears to be gone now.
Loading the URL shows the text "File not found" with no other content.

Comment 2

[castiel743]

The issue appears to be reproducible on any site with downloadable fonts. Could you check STR_2?

>>>   My Info:   Win7_64, Nightly 53, 32bit, ID 20170107030205 (2017-01-07)
STR_2:
1. Open http://otto.yndenz.com/ , reload it using Ctrl+Shift+R
2. Inspect element "#bugzilla-body", find rule "margin: 10px auto 15px;" in ruleview, click on "10px"
3. Press Up key, wait 5 seconds
4. Press Down key, wait 5 seconds

AR:  After Step 3 and Step 4 text on the page blinks. Font file is requested multiple times.
     New requests appear in Netmonitor/console, and each of them says "cached"
ER:  Text shouldn't blink

Comment 3

[castiel743]

The issue appears to be reproducible on any site with downloadable fonts. Could you check STR_2?
(please hide comment 2, it's incorrect.

>>>   My Info:   Win7_64, Nightly 53, 32bit, ID 20170107030205 (2017-01-07)
STR_2:
1. Open bug 1268736 , reload it using Ctrl+Shift+R
2. Inspect element "#bugzilla-body", find rule "margin: 10px auto 15px;" in ruleview, click on "10px"
3. Press Up key, wait 5 seconds
4. Press Down key, wait 5 seconds

AR:  After Step 3 and Step 4 text on the page blinks. Font file is requested multiple times.
     New requests appear in Netmonitor/console, and each of them says "cached"
ER:  Text shouldn't blink

Comment 4

[Mats Palmgren (inactive)]

I can reproduce the STR in comment 2 in Nightly 53.0a1 (2017-01-07) (64-bit) on Linux.

The Network tab adds new requests for some FireSans woff fonts in step 3/4.
They are listed as "Transferred: Cached".
There is also a noticeable flash on the page that happens - it's more noticeable
when the page is scrolled down a bit to begin with.

Comment 5

[Mats Palmgren (inactive)]

The claimed regression range (in comment 0) is:
> This is regression from bug 964613 (between 2014-04-17 and 2014-04-18). Regression range:
> https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=e71ed4135461&tochange=7fe3ee0cf8be
I haven't confirmed it, but it seems plausible.

Comment 6

[Mats Palmgren (inactive)]

It does seem odd that we'd trigger font requests when editing a CSS rule
that contains no font properties.  So that's why I figured the root cause
might be in the style system.  It might also be something that the devtools
code does.

Comment 7

[Mats Palmgren (inactive)]

> I can reproduce the STR in comment 2 in Nightly 53.0a1 (2017-01-07) (64-bit) on Linux.

Bah, I meant comment 3 of course.