bug#39649: 27.0.60; tab-line doesn't scroll

[Lars Ingebrigtsen]

Juri Linkov <juri@linkov.net> writes:

> But the bug creeps in only when there is space between tabs:
>
> (format-mode-line (concat " " (propertize "tab1" 'face
> 'tab-line-tab-current) " x"))
> #(" tab1 x" 1 5 (face tab-line-tab-current))
>
> (format-mode-line (concat " " (propertize "tab1" 'face
> 'tab-line-tab-current) " x") 'tab-line)
> #(" tab1 x" 0 1 (face tab-line) 1 5 (face tab-line) 5 7 (face tab-line))
>
> Here the face 'tab-line' overwrites the face 'tab-line-tab-current'.

The mode-line formatting machinery doesn't support having a mixture of
text properties over a single string -- for efficiency, it assumes that
the same properties are used over the entire string.  If you want
something else, you unfortunately have to use :propertize or a list of
strings.

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