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Epsilon can help with indenting your program or
other text. The <Tab> key runs the indent-previous
command, which makes the current line start at the same column as the
previous non-blank line. Specifically, if you invoke this command
with point in or adjacent to a line's indentation,
indent-previous replaces that indentation with the
indentation of the previous non-blank line. If point's indentation
exceeds that of the previous non-blank line, or if you invoke this
command with point outside of the line's indentation, this command
simply inserts a <Tab>. See Customizing the Screen for
information on changing the width of a tab.
Epsilon can automatically indent for you when you press <Enter>.
Setting the buffer-specific variable auto-indent nonzero makes
Epsilon do this. The way Epsilon indents depends on the current
mode. For example, C mode knows how to indent for C programs.
In Epsilon's default mode, fundamental mode, Epsilon indents
like indent-previous if you set auto-indent nonzero.
(Auto-indenting removes trailing spaces and tabs too.)
In some modes Epsilon not only indents the newly inserted line, but
also reindents the existing line. Variables named after their modes,
like c-reindent-previous-line, control this. The
default-reindent-previous-line variable controls this for modes
that don't have their own variable.
When Epsilon automatically inserts new lines for you in auto fill
mode, it looks at a different variable to determine whether to indent
these new lines. Epsilon indents in this case only if the
buffer-specific variable auto-fill-indents has a nonzero value.
The Alt-M key moves point to the beginning of the text on the current
line, just past the indentation.
The indent-under command functions like indent-previous,
but each time you invoke it, it indents more, to align with the next
word in the line above. In detail, it goes to the same column in the
previous non-blank line, and looks to the right for the end of the
next region of spaces and tabs. It indents the rest of the current
line to that column after removing spaces and tabs from around point.
With a highlighted region, it indents all lines in the region to that
With a numeric prefix argument, indent-under goes to a
different run of non-spaces. For instance, with an argument of 3, it
goes to the previous line and finds the third word after the original
column, then aligns the original line there.
The indent-rigidly command, bound to Ctrl-X Ctrl-I (or Ctrl-X
<Tab>), changes the indentation of each line between point and
mark by a fixed amount provided as a numeric
argument. For instance, Ctrl-U 8 Ctrl-X Ctrl-I moves all the lines
to the right by eight spaces. With no numeric argument, lines move to
the right by the buffer's tab size (default 8; see Customizing the Screen), and with a negative numeric argument, lines
move to the left. So, for example, Ctrl-U -1000 Ctrl-X Ctrl-I
should remove all the indentation from the lines between point and
If you highlight a region before pressing <Tab> (or any key that
runs one of the commands indent-previous or
do-c-indent), Epsilon indents all lines in the region by one
tab stop, by calling the indent-rigidly command. You can
provide a numeric argument to specify how much indentation you want.
The Shift-<Tab> key moves the cursor back to the previous tab
stop. But if you highlight a region before pressing it, it will
remove one tab stop's worth of indentation. (See the
resize-rectangle-on-tab variable if you want these keys to
instead change the region's shape without moving text.)
The indent-region command, bound to Ctrl-Alt-\,
works similarly. It goes to the start of each line between point and
mark and invokes the command bound to <Tab>. If the resulting
line then contains only spaces and tabs, Epsilon removes them.
You can set up Epsilon to automatically reindent text
when you yank it. Epsilon will indent like indent-region.
By default, Epsilon does this only for C mode (see the
To determine whether to reindent yanked text, the yank
command first looks for a variable whose name is derived from the
buffer's mode as it appears in the mode line:
reindent-after-c-yank for C mode buffers,
reindent-after-html-yank for HTML mode buffers, and so forth. If
there's no variable by that name, Epsilon uses the
reindent-after-yank variable instead. Instead of a variable,
you can write an EEL function with the same name; Epsilon will call
it and use its return value. See the description of
reindent-after-yank for details on what different values do.
The Alt-S command horizontally centers the current line between the
first column and the fill column by padding the left with spaces and
tabs as necessary. Before centering the line, the command removes
spaces and tabs from the beginning and end of the line.
With any of these commands, Epsilon indents by
inserting as many tabs as possible without going past the desired
column, and then inserting spaces as necessary to reach the column.
You can set the size of a tab by setting the tab-size
variable. Set the soft-tab-size variable if you want Epsilon
to use one setting for displaying existing tab characters, and a
different one for indenting.
If you prefer, you can make Epsilon indent using only spaces. The
buffer-specific variable indent-with-tabs controls this
behavior. Set it to 0 using set-variable to make Epsilon use
only spaces when inserting indentation.
If you want <Tab> to simply indent to the next tab stop, you can
bind the indent-to-tab-stop command to it. To disable smart
indenting in a particular language mode, you can bind this command to
<Tab> only in that mode.
The untabify-region command on Ctrl-X Alt-I changes all tab
characters between point and mark to the number of spaces necessary
to make the buffer look the same. The tabify-region command on
Ctrl-X Alt-<Tab> does the reverse. It looks at all runs of spaces and
tabs, and replaces each with tabs and spaces to occupy the same
number of columns. The commands tabify-buffer and
untabify-buffer are similar, but operate on the entire buffer,
instead of just the region.
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