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Re: [css-fonts] Test for rem/em dimensions based on :root font-size

From: Philip Jägenstedt <foolip@google.com>
Date: Tue, 10 Sep 2019 11:05:26 +0200
Message-ID: <CAARdPYeB=j0NFX9RYyt2bVqwxtJnxVpQ921U4vzHKLKLmoQ2uQ@mail.gmail.com>
To: Jon Ronnenberg <jon.ronnenberg@gmail.com>
Cc: public-test-infra <public-test-infra@w3.org>
Hi Jon,

I see that https://crbug.com/308862 has a lot of stars, so this is probably
an important issue to resolve. Thanks for pushing it!

Tests for parts of the web platform not yet tested are always appreciated!
You've already found our main documentation site
https://web-platform-tests.org/ and the ambition is that this should be
enough to get you through the process. However, the repo is a little
daunting with a lot of open issues and PRs, so having someone who you can
poke for reviews and help, well, helps.

A reftest is probably the right tool for this if it depends on a fixed
viewport width, as reftests are always run at 800x600. Given a page that
results in different rendering in different browsers it should be fairly
straightforward to turn it into a reftest.

I tried rem-height.html from the bug, but it actually seems to give the
same result in Chrome and Firefox on Linux. Can you provide screenshots of
that or another test case showing the differences between browsers?

On Sun, Sep 8, 2019 at 11:17 PM Jon Ronnenberg <jon.ronnenberg@gmail.com>

> 6 years ago I filed a bug in
> https://bugs.chromium.org/p/chromium/issues/detail?id=308862 and lately
> it has been picked up by both Chromium developers and web developers.
> The short description is that, using percentage value in :root{ font-size
> }  below a certain threshold does not translate to correct rem/em values in
> blink and webkit. It does work as advertised on w3, in Edge and Firefox. <
> https://www.w3.org/TR/css-values-3/#rem
> <https://www.w3..org/TR/css-values-3/#rem>>
> I have look at the test cases in <
> https://github.com/web-platform-tests/wpt/tree/master/css/css-values> and
> searched in issues <
> https://github.com/web-platform-tests/wpt/issues?utf8=%E2%9C%93&q=is%3Aissue+REM+font-size>
> but have not found anything that suggest that there exist a test for this
> issue.
> Myself and others have provided several test cases in the chromium issue <
> https://bugs.chromium.org/p/chromium/issues/detail?id=308862> and I am
> wondering if it is feasible to translate a simple one of them into a test
> in the web-platform-tests Project.
> I don't have any experience writing these kind of tests and would need
> help to get started. I imagine that it could be a reftest <
> https://web-platform-tests.org/writing-tests/reftests.html> which could
> be run automatically.
> Is there interest in this kind of test, is it the right place for such a
> test and how do I get started?
Received on Tuesday, 10 September 2019 09:06:00 UTC

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