[Bug 39216] Re: Progress bar too thick for status bar

[Daniel Borgmann]

Firefox doesn't show a "narrower style" of the progress bar, it has its own progress bar implementation which just looks like a Gtk progress bar.

This is not a theme issue AFAICT, the applications should probably be fixed individually. Epiphany apparently solved the problem by forcing the status bar to be high enough to contain the progress bar even when the progress bar is hidden. Applications can also adjust the size of the progress bar, as can be seen in XChat.
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Progress bar too thick for status bar
https://launchpad.net/malone/bugs/39216