Themes: IE7/8 issues

[SergeyBiryukov]

1. IE8: "Theme Details" and action buttons are visible by default (​http://cl.ly/image/2i1F051A2C40), and there's no way to distinguish between "Twenty Thirteen" and "Twenty Thirteen Child", etc. (as seen on the screenshot).

2. IE8: "Theme Details" is almost indiscernible (as seen on the same screenshot).

3. IE8: "Add New Theme" doesn't have a border (​http://cl.ly/image/23042x2Z3w0Q), and is even worse on hover (​http://cl.ly/image/2S1j2Y0Y1u3S).

4. IE7: "Add New Theme" just floats in space by itself (​http://cl.ly/SuNQ).

[morganestes]

Fixes problems 1 & 2

[morganestes]

So for points 1 & 2, the problem is that IE8 doesn't play nice with opacity in CSS. The ie.css stylesheet that's loaded for IE7 and below just does away with the "Theme Details" text altogether.

This can be fixed by adding -ms-filter with a fallback background, but does this go in wp-admin.css, or do IE8-specific fixes belong in their own stylesheets?

[morganestes]

Fixes problems 3 & 4

[morganestes]

Problems 3 & 4 are another result of IE8 not handling opacity cleanly, and of its inability to properly render the stacked pseudo-elements :hover:after to change the background.

The 2nd patch here adds the dashed border so the "Add New Theme" looks like it belongs, and forces IE8 to render the changed background color on hover.

There's not much I can do about the border-radius to make it all nice and round, but it's 3 versions old so I think it'll do.

[morganestes]

Combined fix for all 4 reported problems

[morganestes]

Sorry, the first patch is only for problem 2. I misread problem 1, but it's still related to opacity.

I've added a new patch that combines fixes for all 4 problems. It still feels hacky to me to have them in there, but we have other vendor prefixes so maybe it's not so bad.

[morganestes]

There still is an issue with IE8 only showing two themes across on a wide monitor that should be addressed. IE7 displays them properly since the width and margins are different. Changing the main wp-admin.css to the same values that already work in IE still displays the themes properly and allows us to remove another rule from ie.css.

See patches -4 & -5.

[morganestes]

Display 3 themes across

[morganestes]

Remove unneeded rule for IE

[morganestes]

Screenshot showing themes only displaying 2 instead of 3

[nacin]

matveb and I spent quite a bit of time on widths, gutters, and responsiveness for this screen, so I'd rather avoid making adjustments to all browsers just to deal with IE8 or lower. We have an .ie8 body class we can use to work around these. Working up a patch.

[nacin]

Combined patch for I think everything.

[nacin]

I have matveb looking at the latest patch. Marking for tentative commit awaiting final feedback.

[matveb]

Patch above also adds a solid background fallback to the overlay backdrop and adjust some colors a bit more.

[nacin]

In 27007:

Themes screen: Various IE8 adjustments and fixes.

props morganestes, matveb.
fixes #26541.

[nacin]

In 27008:

Themes screen: Various IE8 adjustments and fixes.

Merges [27007] to the 3.8 branch.

props morganestes, matveb.
fixes #26541.