24.3 Picture Mode Tabs

Two kinds of tab-like action are provided in Picture mode. Context-based tabbing is done with M-TAB (picture-tab-search). With no argument, it moves to a point underneath the next “interesting” character that follows whitespace in the previous non-blank 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, the 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 the variable picture-tab-chars, which contains a string of characters considered interesting. 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. Without arguments 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 (picture-set-tab-stops.) This command sets the tab stops to the positions which M-TAB would consider significant in the current line. If you use this command with TAB, you can get the effect of context-based tabbing. But M-TAB is more convenient in the cases where it is sufficient.