When changing the volume via shortcuts or mousewheel over the volume plamoid, a volume indicator is shown at the middle of the screen. This indicator has only two wave-symbols and its hard to see the actual volume between mute/one bar/two bars. There could be a text with a percentage below or above the symbol, so you can tell the actual difference between i.e 20% and 40%.
There is also a "progressbar" under the icon that indicates the volume percentage.
I do not have such a progress bar. Can this be theme dependend, if i see the bar?
Indeed, it works in Air, Breeze (variants) and oxygen, but is broken in eleonora and tibanna. I guess possibly many other non-default themes may be broken.
I'm not really sure, but those 2 themes you mentioned (eleonora, tibanna) looks just too old, are those even compatible with Plasma 5? As it works with default themes, this looks like the issue in theme itself.
Here is Eleonora. https://store.kde.org/p/998866/ Im am not really used to the Plasma Theming process. Does the theme need to be updated for the current plasma version to include all features like "volume control with progress bar" or are you just using some part of the theme like "progress bar"? I think it would be nice to support themes, which do not need to be optimized for single plasmoids, but if a generic "progress bar" widget in the theme is broken, it's obviously the theme's fault.
Yes, it's generic slider. The same element is used also in battery plasmoid, to show percentage of each battery. Does it work fine there?
I do not know, as this is a desktop pc, but i see that the theme is 7 years old. I guess you cannot expect a 7 year old theme to contain all the elements needed for current plasma.