Auto-Detect default indent - determine default indent size from existing file content. If there is not enough data for analysis, default indent value (normally equal to syntax Tab Size) used. Useful, if you do corrections on the code you do not own.
Do on Save
Trim white space at the end of line - remove all white spaces (space, blank, tab character) after the last visible char in a line when saving. The actual text, loaded in the editor is not modified (changes will be only visible after reload).
Check encoding accuracy - Check encoding accuracy during saving. If enabled, the editor would check that all characters can be stored losslessly with a selected code page. This setting influence saving speed.