When selecting "Show invisible characters" from the leftmost menu in the text window, the invisible characters are not shown. However, the menu item text changes to "Hide invisible characters", just as on would expect
(and back to "Show..." if selected again).
Weird. I just tried: it works for me. At least, the space characters are marked as ␣ . Do you get them ?
OTOH, I agree that the tabulations and carriage returns are not displayed correctly and this is a bug in Cocoa, not in Alpha. It has already been mentionned in Ticket #60: 60 show invisible.
Oh, I tested this with a tab-separated data file, which had no spaces, just tabs and returns. The spaces do get displayed as ␣. So for the time being, the menu item should perhaps be renamed to "Show/Hide spaces" to avoid confusion.
I overlooked ticket # 60, unfortunately. From a quick search on the web, subclassing the layout manager seems to be the best (and only fully working) way of getting the invisible chars reliably translated to visibles, and also control the glyph and colour used. Perhaps this would be something for a future version of Alpha.
Yes, this is a longstanding bug which was never fixed by Apple and indeed the suggested solution would be to subclass the layout manager and provide our own glyphs. This is the solution I mentionned in Ticket #60. I just don't know if this will result in a performance loss. I have to experiment.
At long last, this is fully implemented now. The following glyphs are used to draw invisible characters:
Changes committed to the repository (rev. 1615 (sourceforge.net)). The core must be rebuilt.