Text editor capable of viewing invisibles?

Question

A recent problem* left me wondering whether there is a text editor out there that lets you see every single character of the file, even if they are invisible? Specifically, I'm not looking for hex editing capabilities, I am interested in a text editor that'll show me all of the invisible characters (not just the common whitespace / line break characters). The BOM marker is just one example, others are e.g. mathematical invisibles or possibly unsupported characters.

I'm not looking for a text editor that simply supports a large variety of text encoding / translations between encodings. All text editors I've come across treat the invisible characters correctly i.e. leave them invisible (or simply get removed in the translation as in the case of the BOM marker).

I'm asking this mostly out of academic interests, so I'm not particular about any specific OS. I can easily test Linux and OSX solutions, but if you recommend a Windows editor, I would appreciate if you include descriptions of how the editor handles invisibles other than whitespace / line breaks.

EDIT: I'm beginning to be sure that the behavior I want can be implemented in emacs/vim via either custom highlighting or by messing around with the font itself. A solution of this type would also be acceptable.

EDIT2: After looking at several options I found TextMate which at least shows a blank space where an invisible UTF-8 character is in the file. Slightly disappointed with SO's ability to answer my question. Bounty goes to VIM, because that is the direction in which the solution most likely lies.

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*The incident that lead me to this question: I wrote a perl script using TextWrangler and managed to change the encoding to UTF8 BOM, which inserts the BOM marker at the start of the file. Perl (or rather the operating system) promptly misses the #! and mayhem ensues. It then took me the better part of an afternoon to figure this out since most text editors do not show the BOM marker even with various "show invisibles" options turned on. Now I've learned my lesson and will use less immediately :-).

Answer 1

I am not sure as I haven't used it in a while, but I remember that SciTE was a good one that showed me "too much information" for my needs.

Programmer's Notepad on Windows might work.

TextPad (It's nagware, runs on Windows)

I'm not sure which of these will show the hidden characters out of the box, but they're all made for "nerdy" stuff, so I assume that they would work ,at least with a little tweaking. I can verify that Programmer's Notepad does show "hidden" characters.

Answer 2

I've encountered the same limitations — my specific issue is the need to be able to display characters like U+200B, the zero-width space, and U+200C, the zero-width non-joiner. (Used in electronic texts with such languages as Khmer, which otherwise do not separate words with spaces.) Unlike you, instead of "platform doesn't matter," I need an editor with Windows and Linux versions, and Mac too is desirable.

I haven't found any text editors that will let you display them on-screen, although some (many?) will let you enter them and will properly treat them as characters that can be cut and pasted and whose presence is indicated via cursor movement. (That is, if the screen shows "if" and there are three ZWSP's between the "i" and "f," you have to press the arrow key four times to move from "i" to "f.")

TextPad 4.7.3 is otherwise my text editor of choice, but it is very limited in its acceptance of scripts; and TextPad 5 definitely does not show these invisibles.

I have often resorted to opening my files in OpenOffice.org Writer, which will show a gray slash at these characters' location with invisibles turned on, and Microsoft Word, which displays a double-box (box within a box) character for such invisibles. This double-box has width and changes the line-breaks on-screen, which is not trivial and which I haven't seen in any other editor.

Answer 3

I prefer UltraEdit even though it is not free. It is very capable of showing hidden characters, including a robust HEX viewing mode. (I am not affiliated with the publisher, IDM.)