18.3 Horizontal Scrolling

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. To disable automatic horizontal scrolling, set the variable auto-hscroll-mode to nil.

The variable hscroll-margin controls how close point can get to the window's edges before automatic scrolling occurs. It is measured in columns. If the value is 5, then moving point within 5 columns of an edge causes horizontal scrolling away from that edge.

The variable 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 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 text in current window to the left (scroll-left).

C-x >

Scroll to the right (scroll-right).

C-x < (scroll-left) scrolls 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 columns.

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 scroll-left.