Comment 2 for bug 238347

Actually after reading the comment above those lines, this may be Invalid:

# The open.filter setting is only used on Windows where the file selector has a menu of filters to apply
# to the types of files seen when opening.
# There is a limit (possibly 256 characters) to the length of a filter,
# so not all source extensions can be in this setting.

I don't know why it says it is only used on Windows as it is used on Linux too (I imagine everywhere), but they seem to knowingly acknowledge that not all file types can be there. However I notice the use of "possibly" when referring to the exact character limit, so maybe it is actually larger and can include more files.

Either way if we are running into a limit maybe more logical choices can be made by popularity. For example I don't know what .hxx or .iface is, while PHP/CSS/JS seem rather popular. If they can't be added due to a limit, maybe they can be swapped for something else.