Why is Linux Mint corrupting certain application icons?

Question

Linux Mint 18.3, in both Cinnamon and KDE desktops, is doing something strange to the icons for LibreOffice (and only that application). I tested the most recent versions of various other distros and none of them displayed the problem. It is new with Mint 18.3 and exists from the time I get it loaded and configured. Here are some screenshots of what the icons should look like:

Older version of Mint KDE:

Current openSUSE (ignore sizing):

Mint 18.3 Cinnamon and KDE look like this:

It's a tiny LibreOffice icon on a strange background image. In Cinnamon, the icons in the main menu are correct. But in KDE, the LibreOffice menu icons are also corrupted:

If you edit the menu, the icons are correct in the application settings:

I installed Mint 18.3 a few months ago and this has been a minor annoyance. I've dabbled with it on and off and was going to ask here for advice on where to focus to find the problem. However, I just discovered what the problem was. I'll post an answer in case it will be useful to anyone else.

Answer 1

I discovered the issue by reloading the live session / installation DVD. The icons were normal there, suggesting that it was something in the customization.

Each distro comes with a collection of themes. I didn't like the default icon theme in Mint 18.3, so I changed it to another included choice. That has never been an issue with previous versions of Mint, or any of the other distros I've installed.

However, there appears to be some kind of incompatibility in v18.3 between the Gnome icon theme and LibreOffice. The other icon themes don't have a problem (and the Gnome theme wasn't a problem on earlier versions of Mint).

I did further testing and discovered that Manjaro KDE came with a default icon theme that was fine, so I didn't change it. However, it also includes the Gnome icon theme, and that corrupts the LibreOffice icons in the same way.

So it appears that, at least in the Cinnamon and KDE desktops on recent Linux releases, the Gnome icon theme does strange things to the LibreOffice icons. Pick another icon theme to solve the problem.

Mint v18.3 KDE with the Breeze icon theme (default for Plasma 5):

Answer 2

Themes that change the standard icons of icons too significantly are a nuisance, they break the visual identity. My opinion is that each application (and version if needed) has its own visual identity. A theme for an OS should only change the icons of core builtin apps directly supported in the distribution, but NEVER the icons of optional installable packages (unless these packages are directly supported by the distrib).

I don't understand the need of so many themes to change so many icons, they are just a nuisance, polluting, using lot of space (even for apps that we don't even need to install). Themes should only be reduced to the design and colors of the UI decorations, bars, buttons, windows, notifications and layout of menus/panels; background desktop images should be also removed (placed in separate packages if we wan them, there are lot of many other sources of good images without needing them in any theme).

Each app will maintain their own sets of icons (including legacy icons if they have supporters). I really hate themes and prefer keeping only a single one and avoid those that are too much intensive in graphics, transparencies, shadows, and unnecessary animations. This is even worse when they also want to enforce sounds for basic clicks on common buttons!