I’m on up to day TW but icons have been missing for maybe a year, I just never got around to solving this problem.
Firefox looks okay in kdemenuedit, with the icon and everything, and FF icon shows up in task manager and in FF window decoration when Firefox is open, but in KDE menu and in a panel I created (ages ago) the icons are missing. They are circled red in the screenshot:
If I right-click the missing icons in the panel on the left or in KDE launcher and select “Edit application” the icon is present in the dialogue that pops up, but even if I change it to something else it doesn’t register with neither the panel nor with the launcher.
I suppose I don’t have the right FF icon file saved in the place the panel and launcher look for, but where is this place and what do they need exactly? I looked around the machine and there are all kinds of directories for storing icons - “hi res”, “16”, “32”, “256” and so on.
I added one at the top (empty panel), added applications widget and it still doesn’t have Firefox icon under “internet”, but dragging and dropping FF from the menu onto the panel creates a shortcut with an icon.
Assuming it’s there? Since it’s not referring to a definite target I’d say it must “fall back” on “system settings” i.e. generic KDE settings. Checking file list of firefox all the icons are in “/usr/share/icons/hicolor/”
There’s two files that migh be responsible: “/usr/share/icons/hicolor/index.theme” and “/usr/share/icons/hicolor/icon-theme-cache”. Searching “index.theme” there’s no hint to “firefox”. So that all seems to be generic KDE. “icon-theme-cache” is not a txt file but there’s traces of “firefox”.
So, maybe try deleting (or first renaming) “/usr/share/icons/hicolor/icon-theme-cache” and log out/in?
Firefox.desktop file has “Icon=firefox” entry as expected.
/usr/share/icons/hicolor/ has lots of directories indicating icons sizes and most of them have firefox in “apps” subdirectory. It is missing in “scalable”, however, and in some weird sizes with only one special app placing its special icon there, but otherwise it’s everywhere it’s expected to be.
Renaming icon-theme-cache didn’t affect anything and the file wasn’t recreated after logout-login.