/tmp/ is not normally writable on linux

[kasbah]

I set the temporary "cache" directory to /tmp/ when the svg hasn't been saved yet. This isn't normally writable by the user so it results in asking for a root password.

[onitake]

That is quite far from the truth.

Most Linux distributions have a user-writable /tmp, and in most cases, the directory has the sticky bit set, so only the user that created a file or directory in /tmp can remove it.

It's a bit unfortunate thate the FHS does not mandate a particular setup for /tmp, but it does recommend its existence as a place for programs to write temporary data: http://refspecs.linuxbase.org/FHS_3.0/fhs/ch03s18.html