Using images in tabs (was: bug#37385: 27.0.50; Crash on multibyte assertion violation)

[Juri Linkov]

> Stepping a notch back, I cannot say I like this "non-ASCII art"
> implementation for tabs.  It has two annoying problems:
>
>   . it looks unprofessional on GUI frames
>   . it requires you to determine whether the frame/font used for the
>     menu can display this character, which is not easy
>
> Why not use an image of a plus sign on GUI frames, and a simple ASCII
> "+" on TTY frames and frames that have no image support?  I think the
> result will be much better.

The biggest advantage of using “Unicode art” is its scalability for free,
i.e. scalable fonts keep the size of the character used in the close button
proportional to the font size of text in tabs.

I tried a small image with small font size and the result is not bad:

But a small image with big font size looks too clumsy:

I don't know if the patch to vertically center line content
recently sent here by Jesse, could improve the look to align
the button image to the center of the text line in tabs.

Another advantage of “Unicode art” is that on moving the mouse over the
close button the foreground color of its Unicode text changes to red
simply by using mouse-face.  I don't know how to do the same with images: