Here is some detailed explanation I couldn't write earlier. I'm not
surprised by Jon's reaction since I nuked a large portion of the file in
question. This wasn't refactoring though. I replaced a lot of rather weird
and undocumented caching code (it was trying to add each icon as a stock
item, which is not the right thing to do when using named icons) with 1 line
adding builtin icons, because I discovered that doing so fixes the icons in
the eraser toolbar: They are no longer blurred. There is a weird drawing
issue instead where part of the icon is repeated, this may a bug in the
drawing function of SPIcon. I also removed a function that was never
actually executed to reduce the amount of code that needs to be further
scrutinized. I tested this in GDB by setting a breakpoint. I found out why
the named icons were not used on Windows: the index.theme file was missing