Allow users to provide absolute css units to editor.resize function

[hub33k]

What is the purpose of this pull request?

Bug fix

Does your PR contain necessary tests?

All patches that change the editor code must include tests. You can always read more
on PR testing,
how to set the testing environment and
how to create tests
in the official CKEditor documentation.

This PR contains

• Unit tests
• Manual tests

Did you follow the CKEditor 4 code style guide?

Your code should follow the guidelines from the CKEditor 4 code style guide which helps keep the entire codebase consistent.

• PR is consistent with the code style guide

What is the proposed changelog entry for this pull request?

*[#1883](https://github.com/ckeditor/ckeditor4/issues/1883): Allow users to pass absolute css units to `editor.resize` function.

What changes did you make?

Allow users to pass absolute css units to editor.resize function.

Which issues does your PR resolve?

Closes #1883.

[jacekbogdanski]

Approach with unifying units for both methods seems right 👍 Note, that we are missing manual test for element.setSize and unit tests for both changed files. Please, add missing test coverage.

Also, please add a changelog entry suggestion in the top comment.

[jacekbogdanski]

Is typeof size != 'string' && condition required at this point?

[hub33k]

Yes, if user passes percent value as width then size is still type of string. I can simplify it.

[jacekbogdanski]

Using developer tools to test this issue is not the most optimal approach as we cannot test it on mobiles. It also requires additional test steps. Maybe we could go with more complex test e.g. by adding CSS style inputs?

[jacekbogdanski]

#4010 (comment)

You are right, sorry I point you to wrong direction, didn't now that convertToPx works soo picky and seems to handle only absolute units. I'm wondering if we would be able to improve convertToPx, so it also correctly handles relative units like percentage and also viewport, initial etc.

It may be possible that it will be easier to fix the issue directly inside editor#resize method than fight with convertToPx, because converting units like % or viewport size could require iterating to parent. It seems like convertToPx may require some rewriting or docs rewording though, as it incorrectly implies that handles CSS length value, which is not 100% true.

Could you check if we can operate on CSS lengths instead inside editor#resize method or successfully fix convertToPx method? The latter may be more complicated, but more useful in the long run.

[jacekbogdanski]

There is additional issue with CKEDITOR.tools.convertToPx method which seems to work only with CSS units. You can verify it by calling CKEIDTOR.tools.convertToPx( 900 ). Please, see the review comments.

[jacekbogdanski]

LGTM 👍

I removed the manual test scenarios for inner resize as it gives hilarious feedback when used without caution and as it doesn't take part in unit conversion it's not important for this test. Also removed quarter-millimeters to simplify testing as this unit is not widely supported.