position_fixed reftest identical to its reference

[SimonSapin]

Sorry I’m late to the party, but I notice that src/test/ref/position_fixed_a.html and src/test/ref/position_fixed_b.html (added in #1440) are identical.

This really doesn’t work, as a reftest. The idea is to use the feature being tested in the test page, and have a reference page that does not use the feature but should render identically. A bug in the feature being tested will (hopefully) make the test render differently from its reference.

@ibnc, please try to modify these files to make them a reftest. Sometimes coming up with a reference is hard, especially when we have so few layout primitives that are implemented yet. Maybe the reference here could use negative margins. (Do we support those?) If a reftest proves too difficult, please remove the files.

[ibnc]

Nice catch!

I can't seem to find what I actually read on ref tests again; regardless I must of misunderstood it. Thank for clarifying!

I'll see what I can come up with.

[metajack]

@ibnc https://developer.mozilla.org/en-US/docs/Creating_reftest-based_unit_tests

[ibnc]

Thanks @metajack! I assume we use 800 x 1000 windows for our ref tests as well?

[Ms2ger]

Assume 600×600, please, for mobile. I'll update the wiki.

[metajack]

I think we use 800x600 currently, which is the default window size in servo. Note that this size was chosen arbitrarily, and probably not for any particular reason.

[mbrubeck]

These files have moved to these new locations:

• tests/wpt/mozilla/tests/css/position_fixed_a.html
• tests/wpt/mozilla/tests/css/position_fixed_b.html

Fixing this will require changing these HTML+CSS files so that the test ("a") file uses position: fixed, while the reference ("b") file uses some other styling to achieve the same desired output. See the link above for more details, and tests/wpt/README.md for instructions on running and editing the tests.

[mitchhentges]

I've got this, probably