#1404 always indent/dedent to legal level

[YoHell]

Regression (?) of bug 1558460:

https://sourceforge.net/tracker/?func=detail&aid=1558460&group_id=85796&atid=577329

but I couldn't reopen it.

Multiline indent/dedent (tab/shift-tab) does not work as expected, it just shifts the selected block of code four spaces left or right. I expect it to place the start of the selected block at the closest legal indent in the indicated direction, and keep any internal indents or dedents within the block intact.

Single line dedent does not work as expected. As in the multiline case, it just pushes the line of code left by four spaces. Similarly, I expect this to move the line to the closest legal indent to the left.

Example:
Write a class. In a method, indent a few lines to an illegal level, by adding an extra space or two. Attempt to use shift-tab to correct an illegal line, and fail. (Optionally, note that indent works as expected, and a following dedent restores legality, but I don't want to hassle with that). Attempt to restore legality en masse by selecting multiple lines and then trying any combination of tab and shift in any sequence, and notice that you will never succeed, and note that you will have to correct every single line individually to get executable code.