Most keys do the same thing in Picture mode that they usually do, but do
it in a quarter-plane style. For example, C-f is rebound to run
picture-forward-column, which moves point one column to
the right, by inserting a space if necessary, so that the actual end of the
line makes no difference. C-b is rebound to run
picture-backward-column, which always moves point left one column,
converting a tab to multiple spaces if necessary. C-n and C-p
are rebound to run
which can either insert spaces or convert tabs as necessary to make sure
that point stays in exactly the same column. C-e runs
picture-end-of-line, which moves to after the last non-blank
character on the line. There was no need to change C-a, as the choice
of screen model does not affect beginnings of lines.
Insertion of text is adapted to the quarter-plane screen model through
the use of Overwrite mode (see Minor Modes). Self-inserting characters
replace existing text, column by column, rather than pushing existing text
to the right. RET runs
picture-newline, which just moves to
the beginning of the following line so that new text will replace that
Text is erased instead of deleted and killed. DEL
picture-backward-clear-column) replaces the preceding character
with a space rather than removing it. C-d
picture-clear-column) does the same in a forward direction.
picture-clear-line) really kills the contents of lines,
but never removes the newlines from a buffer.
To do actual insertion, you must use special commands. C-o
picture-open-line) creates a blank line, but does so after
the current line; it never splits a line. C-M-o,
makes sense in Picture mode, so it remains unchanged. LFD
picture-duplicate-line) inserts another line
with the same contents below the current line.
To actually delete parts of the picture, use C-w, or with
C-c C-d (which is defined as
delete-char, as C-d is
in other modes), or with one of the picture rectangle commands
(see Rectangles in Picture).