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Horizontal scrolling means shifting all the lines sideways
within a window, so that some of the text near the left margin is not
displayed. When the text in a window is scrolled horizontally, text
lines are truncated rather than continued (see Line Truncation).
If a window shows truncated lines, Emacs performs automatic horizontal
scrolling whenever point moves off the left or right edge of the
screen. By default, all the lines in the window are scrolled
horizontally together, but if you set the variable
auto-hscroll-mode to the special value of
only the line showing the cursor will be scrolled. To disable
automatic horizontal scrolling entirely, set the variable
nil. Note that when the automatic
horizontal scrolling is turned off, if point moves off the edge of the
screen, the cursor disappears to indicate that. (On text terminals,
the cursor is left at the edge instead.)
hscroll-margin controls how close point can get
to the window's left and right edges before automatic scrolling
occurs. It is measured in columns. For example, if the value is 5,
then moving point within 5 columns of an edge causes horizontal
scrolling away from that edge.
hscroll-step determines how many columns to
scroll the window when point gets too close to the edge. Zero, the
default value, means to center point horizontally within the window.
A positive integer value specifies the number of columns to scroll by.
A floating-point number (whose value should be between 0 and 1)
specifies the fraction of the window's width to scroll by.
You can also perform explicit horizontal scrolling with the following commands:
C-x < (
scroll-left) scrolls text in the selected window
to the left by the full width of the window, less two columns. (In
other words, the text in the window moves left relative to the
window.) With a numeric argument n, it scrolls by n
If the text is scrolled to the left, and point moves off the left
edge of the window, the cursor will freeze at the left edge of the
window, until point moves back to the displayed portion of the text.
This is independent of the current setting of
auto-hscroll-mode, which, for text scrolled to the left, only
affects the behavior at the right edge of the window.
C-x > (
scroll-right) scrolls similarly to the right.
The window cannot be scrolled any farther to the right once it is
displayed normally, with each line starting at the window's left
margin; attempting to do so has no effect. This means that you don't
have to calculate the argument precisely for C-x >; any
sufficiently large argument will restore the normal display.
If you use those commands to scroll a window horizontally, that sets
a lower bound for automatic horizontal scrolling. Automatic scrolling
will continue to scroll the window, but never farther to the right
than the amount you previously set by
auto-hscroll-mode is set to
current-line, all the lines
other than the one showing the cursor will be scrolled by that minimal