Two kinds of tab-like action are provided in Picture mode. Use
picture-tab-search) for context-based tabbing.
With no argument, it moves to a point underneath the next
"interesting" character that follows whitespace in the previous
nonblank line. "Next" here means "appearing at a horizontal position
greater than the one point starts out at." With an argument, as in
C-u M-TAB, this command moves to the next such interesting
character in the current line. M-TAB does not change the
text; it only moves point. "Interesting" characters are defined by
picture-tab-chars, which should define a set of
characters. The syntax for this variable is like the syntax used inside
of `[...]' in a regular expression--but without the `['
and the `]'. Its default value is
TAB itself runs
picture-tab, which operates based on the
current tab stop settings; it is the Picture mode equivalent of
tab-to-tab-stop. Normally it just moves point, but with a numeric
argument it clears the text that it moves over.
The context-based and tab-stop-based forms of tabbing are brought
together by the command C-c TAB,
This command sets the tab stops to the positions which M-TAB
would consider significant in the current line. The use of this command,
together with TAB, can get the effect of context-based tabbing. But
M-TAB is more convenient in the cases where it is sufficient.