The fact that the highlight-thickness can only be changed in "free" mode isn't really obvious visually in the toolbar, so attempt to provide at least some indication of the `disabled`-state by "dimming" the slider.
The free highlighting is enabled when the mouse pointer isn't on some text.
Then we draw a shape with smoothed borders corresponding to the movement of
the mouse.
Printing/saving and changing the thickness will come later.
The doorhanger for highlighting has a basic color picker composed of 5 predefined colors
to set the default color to use.
These colors can be changed thanks to a preference for now but it's something which could
be changed in the Firefox settings in the future.
Each highlight has in its own toolbar a color picker to just change its color.
The different color pickers are so similar (modulo few differences in their styles) that
this patch introduces a new class ColorPicker which provides a color picker component
which could be reused in future editors.
All in all, a large part of this patch is dedicated to color picker itself and its style
and the rest is almost a matter of wiring the component.
It fixes few errors in the CSS for HCM.
It now complies to the specs from UI/UX.
Only the foreground must change in HCM and not the background, similarly to what
we had for the alt-text button before moving it.
When PR 17015 removed the `disabled` handling for the "Save"-button it left a bunch of now unused CSS rules behind, which seems like a simply oversight.
Rather than shipping "dead" CSS rules, let's remove those until such a time that they're actually needed.
*For many non-English locales the translated strings will be longer, which is easy to forget about during development/review.*
Note how for some locales (e.g. Swedish) the altText-button end up looking horizontally "cramped", hence it seems reasonable to add a bit of inline padding to improve this.
It's a part of the UX specifications. There's a drawing issue in Firefox
(see bug https://bugzilla.mozilla.org/1853288) but setting the
background-clip property to content-box seems to be a good workaround.
There are 2 rotation we've to deal with: the viewer one and the editor one.
The previous implementation was a bit complex and having to deal with these
rotation would have potentially increase it.
So this patch aims to simplify the implementation and deal with all the possible
cases.
The main idea is to transform the mouse deltas according to the rotations and then
apply the resizing in the page coordinates system.
When resizing an editor we're currently using unidirectional cursors, please refer to https://developer.mozilla.org/en-US/docs/Web/CSS/cursor
Given that editors can (generally) be resized to become either smaller or larger, it seems overall more appropriate to use bidirectional cursors to make this clearer to the user.
Note that as mentioned in the MDN article some environments, which seems to apply to e.g. Windows 11, doesn't differentiate between the two cursor formats and simply use bidirectional ones unconditionally.
One additional benefit of these changes is that the relevant CSS rules become slightly more compact.
