Setting file types in the savepanel

[tvcasualty]

Sorry to drudge up old news, but this is an embarrassingly old issue, be nice to have a filter option in the API by now.
Here was my solution because I didn't like the fact that it could possibly overwrite a file accidentally using TIGs approach (untitled != untitled.txt for example). Anyhow it can be a burden to hit save twice, but I'd rather do that 100x then accidentally save over something important.

Where:

EXT = "txt"
default_dir = "c;\\temp\\"
default_file = "untitled"

The following while loop:

name_valid = false 
while name_valid == false 
 path_to_save_to = UI.savepanel("Save Code File", default_dir, default_file)
 #path_to_save_to = path_to_save_to.tr("\\","/") # This maybe required.
 fileext = File.extname(path_to_save_to) # filename with prefix stripped
 filebase = File.basename(path_to_save_to, ".#{EXT}")
 #puts fileext.inspect
 if fileext == "" || fileext == nil
  default_file = filebase + ".#{EXT}"
  UI.messagebox "Oops! Including the file extension '#{EXT}'\nThis is an embarrassing workaround...\nPlease hit save again."
  #puts default_file.inspect
 else
  filename = filebase + ".#{EXT}"
  path_to_save_to = File.dirname(path_to_save_to) + "\\" + filename
  name_valid = true
 end
end