CSS 'transformation: skew()' should take <angle> type as parameters

[Jinwoo-Song]

Current implementation is taking type as parameter so skew()
does not work properly. Let the skew() to get as specification
described.

Fixes #6237.

r? @pcwalton
cc @yichoi

[nox]

Review status: all files reviewed, 2 unresolved discussions, all commit checks successful.
Reviewed files:

• components/style/properties.mako.rs @ r1
• tests/ref/basic.list @ r1
• tests/ref/transform_skew_a.html @ r1
• tests/ref/transform_skew_ref.html @ r1

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^{components/style/properties.mako.rs, line 3267 [r1] (raw file):}
The spec says "specifies a 2D skew by [ax,ay] for X and Y. If the second parameter is not provided, it has a zero value."

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^{components/style/properties.mako.rs, line 3461 [r1] (raw file):}
Out of curiosity, why do we need to subtract it from PI_2 here and in the Rotate case?

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Comments from the review on Reviewable.io

[Jinwoo-Song]

Review status: 3 of 4 files reviewed, 2 unresolved discussions, all commit checks successful.

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^{components/style/properties.mako.rs, line 3267 [r1] (raw file):}
Done. You're right! I fixed the code.

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^{components/style/properties.mako.rs, line 3461 [r1] (raw file):}
It seems that it's to apply the clockwise angle. If we do not subtract, the rotation and skew are done in the counter-clockwise.

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Comments from the review on Reviewable.io

[nox]

@bors-servo: r+

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Review status: all files reviewed, all discussions resolved, all commit checks successful.
Reviewed files:

• components/style/properties.mako.rs @ r2

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Comments from the review on Reviewable.io

[bors-servo]

📌 Commit 2c83111 has been approved by nox

[bors-servo]

⌛ Testing commit 2c83111 with merge 2356273...

[bors-servo]

💔 Test failed - mac2

[nox]

This isn't working.

failures:
    transform_skew_a.html == transform_skew_ref.html

[nox]

The problem is that tan(0.3rad) ≠ 0.3 and tan(0.5rad) ≠ 0.5.

[nox]

[nox]

Review status: all files reviewed, 4 unresolved discussions, some commit checks failed.

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^{components/style/properties.mako.rs, line 3170 [r2] (raw file):}
Nit: rename theta_x and theta_y to alpha and beta like in the spec, and include link to it:

http://dev.w3.org/csswg/css-transforms/#SkewDefined

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^{components/style/properties.mako.rs, line 3171 [r2] (raw file):}
beta.tan()

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^{components/style/properties.mako.rs, line 3172 [r2] (raw file):}
alpha.tan()

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^{components/style/properties.mako.rs, line 3461 [r2] (raw file):}
Remove the subtraction from PI_2 here and you don't need to negate the angles in ComputedMatrix::skew().

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Comments from the review on Reviewable.io

[bors-servo]

☔ The latest upstream changes (presumably #6161) made this pull request unmergeable. Please resolve the merge conflicts.

[Jinwoo-Song]

Review status: all files reviewed, 4 unresolved discussions, some commit checks failed.

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^{components/style/properties.mako.rs, line 3170 [r2] (raw file):}
Done.

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^{components/style/properties.mako.rs, line 3461 [r2] (raw file):}
Done.

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Comments from the review on Reviewable.io

[Jinwoo-Song]

I'll update the patch to apply nox's comments. As the latest upstream code has been changed, I need to change rust-geom package as well. Rebased patch will be uploaded after below patch is merged.
servo/euclid#77

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Review status: all files reviewed, 4 unresolved discussions, some commit checks failed.

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^{components/style/properties.mako.rs, line 3171 [r2] (raw file):}
Done.

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^{components/style/properties.mako.rs, line 3172 [r2] (raw file):}
Done.

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Comments from the review on Reviewable.io

[nox]

I think you forgot to push the changes here. :)

[Jinwoo-Song]

Yes, I did not push the changes yet. I'll do it after the patch in rust-geom is landed for updating the cargo file.

[nox]

@Jinwoo-Song Ping?

[bors-servo]

🔒 Merge conflict

[nox]

Fixed at master...nox:skew, but is currently blocked by servo/surfman#28.

[nox]

Superseded by #7605, thanks for the patch @Jinwoo-Song!