[HIDPI] element.setSize sets wrong editor's dimensions if border's width is in fraction of pixels

[Marek Lewandowski]

This come out from #14630.

There as a failing test:

Error details for tests/plugins/maximize/maximize
test maximize fire resize event with proper properties
Width should be restored.
Expected: 200 (number)
Actual:   202 (number)

When I started to investigate what's the cause of this - it took me all the way to ​setSize method, and then ​marginAndPaddingSize function.

The problem there was that resize plugin was setting editor size, using box model so that border width should be included as a part of with. But it did not consider that the width might ba a fraction of a pixel, as a result in mentioned test border width was something like ~0.9px - but it used it as 0px. Having width attribute set to 200px (because border were skipped) and including the border, the actual width of the element was 202px.

The issue was reproducible on all browsers for me.

[Marek Lewandowski]

Pushed to ​branch:t/16753.

I didn't create manual test for this, as it's hard to test with "eye" - instead the best way to test it is simply a unit test. However I don't think I'm able to stub hdpi settings, so I used explicitly border with a fraction of a pixel.

To test it it's nice to play around with different pixel ratio in OS - I've used 250%, 300% and 350%.

[Tomasz Jakut]

Test is failing in IE8. It seems that element.setSize still returns wrong dimensions in that browser:

Computed width
Expected: 198.2 (number)
Actual:   198 (number)

[Marek Lewandowski]

True, it rounds the width - I've updated ​branch:t/16753 accordingly.

[Tomasz Jakut]

LGTM. Fixed with ​git:https://github.com/ckeditor/ckeditor-dev/commit/722f86c.