rustdoc: clean up .logo-container layout CSS

[notriddle]

This commit should result in no appearance changes.

To make the logo container exactly the desired height, you want to get rid of the part of the box used for typographic descenders (you know, the part of g, y, and j that descends below the baseline). After all, it contains no text, but the space is still left open in the layout by default, because <img> is display:inline. The CSS used to employ three different tricks to accomplish this:

• By making .sidebar .logo-container a flex container, the image becomes a flex item and is blockified, without synthesizing any inline boxes. No inline boxes means no descenders.
• By giving .mobile-topbar .logo-container a max-height exactly the same as the height of the image plus the padding, the descender area gets cut off.
• By setting .sub-logo-container { line-height: 0 }, we ensure that the only box that contributes to the height of the line box is the image itself, and not any zero-content text boxes that neighbor it. See the logical height algorithm.

This commit gets rid of the first two hacks, leaving only the third, since it requires only one line of code to accomplish and doesn't require setting the value based on math.

[GuillaumeGomez]

Please add a GUI test with a bigger image to ensure the maximum size of the image doesn't grow beyond 45px as we originally specified please for mobile, and an equivalent test for non-mobile too.

[rustbot]

Some changes occurred in HTML/CSS/JS.

cc @GuillaumeGomez, @Folyd, @jsha

[GuillaumeGomez]

Since the image is imported like this, is there a need to add the tux.png one?

[notriddle]

No, it’s not needed.

[GuillaumeGomez]

Looks good to me, thanks! r=me once CI pass

[notriddle]

@bors r=GuillaumeGomez rollup

[bors]

📌 Commit 2189480 has been approved by GuillaumeGomez

It is now in the queue for this repository.