I can think of the following kinds of whitespace (for a single line) in a code file:

1. Leading whitespace:
   Whitespace (spaces, tabs) on a line prior to the first significant character.
   "First significant character" depends on the language, as whitespace/indention
   can be significant in some languages.

2. Trailing whitespace:
   Whitespace on a line after the last significant character.

3. Internal whitespace:
   Whitespace that occurs on a line BETWEEN the first and last
   significant characters.

4. Negative space:
   The physical horizontal area of a line that occurs after the last
   character (of any kind, including whitespace) on that line.


For example, take the following ASCII representation of a line in the editor.
The vertical pipe (|) symbols represent the left and right borders of the
viewable area.  The underscore (_) symbol is used in place of all space characters (\u0020) encoded on the line.

|____public_static_final_String_=_"An_example.";___     |
 1111      3      3     3      3 3   3          22244444

The second line of digits (1-4) mark the positions of each "type" as described above.  The line begins with a sequence of four spaces and ends with a sequence of three spaces.  The first significant character on the line (in this case, for Java) is the 'p' in "public"; the last significant character on the line is the ';' (semicolon).

NetBeans currently treats types 1, 2, and 3 equally, and provides one setting under "Fonts & Colors" for "Whitespace."

Bug 205829 causes the editor to also treat type 4 (negative space) as if it were whitespace actually present on the line (in the file).

This RFE is to allow "trailing whitespace" (type 2) to be configured separately in the editor's "Fonts & Colors" from the other types of whitespace.  There might also be use cases for separate formatting for types 1 and 3 as well, though I suspect trailing whitespace is more important (considering there is an editor action to remove it).

I would like to have a visual indication of "trailing spaces," wherever they occur (including inside comment blocks), without necessarily marking ALL whitespace with the same visual indicator(s).