Next: Recentering, Up: Controlling the Display   [Contents][Index]

16.1 Scrolling ¶

If a window is too small to display all the text in its buffer, it displays only a portion of it. Scrolling commands change which portion of the buffer is displayed.

Scrolling forward or up advances the portion of the buffer displayed in the window; equivalently, it moves the buffer text upwards relative to the window. Scrolling backward or down displays an earlier portion of the buffer, and moves the text downwards relative to the window.

In Emacs, scrolling up or down refers to the direction that the text moves in the window, not the direction that the window moves relative to the text. This terminology was adopted by Emacs before the modern meaning of “scrolling up” and “scrolling down” became widespread. Hence, the strange result that PageDown scrolls up in the Emacs sense.

The portion of a buffer displayed in a window always contains point. If you move point past the bottom or top of the window, scrolling occurs automatically to bring it back onscreen (see Automatic Scrolling). You can also scroll explicitly with these commands:

C-v

PageDown

next

Scroll forward by nearly a full window (scroll-up-command).

M-v

PageUp

prior

Scroll backward (scroll-down-command).

C-v (scroll-up-command) scrolls forward by nearly the whole window height. The effect is to take the two lines at the bottom of the window and put them at the top, followed by lines that were not previously visible. If point was in the text that scrolled off the top, it ends up on the window’s new topmost line. The PageDown (or next) key is equivalent to C-v.

M-v (scroll-down-command) scrolls backward in a similar way. The PageUp (or prior) key is equivalent to M-v.

The number of lines of overlap left by these scroll commands is controlled by the variable next-screen-context-lines, whose default value is 2. You can supply the commands with a numeric prefix argument, n, to scroll by n lines; Emacs attempts to leave point unchanged, so that the text and point move up or down together. C-v with a negative argument is like M-v and vice versa.

By default, these commands signal an error (by beeping or flashing the screen) if no more scrolling is possible, because the window has reached the beginning or end of the buffer. If you change the variable scroll-error-top-bottom to t, these commands move point to the farthest possible position. If point is already there, the commands signal an error.

Some users like scroll commands to keep point at the same screen position, so that scrolling back to the same screen conveniently returns point to its original position. You can enable this behavior via the variable scroll-preserve-screen-position. If the value is t, Emacs adjusts point to keep the cursor at the same screen position whenever a scroll command moves it off-window, rather than moving it to the topmost or bottommost line. With any other non-nil value, Emacs adjusts point this way even if the scroll command leaves point in the window. This variable affects all the scroll commands documented in this section, as well as scrolling with the mouse wheel (see Mouse Commands for Editing); in general, it affects any command that has a non-nil scroll-command property. See Property Lists in The Emacs Lisp Reference Manual. The same property also causes Emacs not to exit incremental search when one of these commands is invoked and isearch-allow-scroll is non-nil (see Not Exiting Incremental Search).

Sometimes, particularly when you hold down keys such as C-v and M-v, activating keyboard auto-repeat, Emacs fails to keep up with the rapid rate of scrolling requested; the display doesn’t update and Emacs can become unresponsive to input for quite a long time. You can counter this sluggishness by setting the variable fast-but-imprecise-scrolling to a non-nil value. This instructs the scrolling commands not to fontify (see Font Lock mode) any unfontified text they scroll over, instead to assume it has the default face. This can cause Emacs to scroll to somewhat wrong buffer positions when the faces in use are not all the same size, even with single (i.e., without auto-repeat) scrolling operations.

As an alternative to setting fast-but-imprecise-scrolling you might prefer to enable jit-lock deferred fontification (see Font Lock mode). To do this, customize jit-lock-defer-time to a small positive number such as 0.25, or even 0.1 if you type quickly. This gives you less jerky scrolling when you hold down C-v, but the window contents after any action which scrolls into a fresh portion of the buffer will be momentarily unfontified.

Finally, a third alternative to these variables is redisplay-skip-fontification-on-input. If this variable is non-nil, skip some fontifications if there’s input pending. This usually does not affect the display because redisplay is completely skipped anyway if input was pending, but it can make scrolling smoother by avoiding unnecessary fontification.

The commands M-x scroll-up and M-x scroll-down behave similarly to scroll-up-command and scroll-down-command, except they do not obey scroll-error-top-bottom. Prior to Emacs 24, these were the default commands for scrolling up and down. The commands M-x scroll-up-line and M-x scroll-down-line scroll the current window by one line at a time. If you intend to use any of these commands, you might want to give them key bindings (see Rebinding Keys in Your Init File).

On graphical displays, you can also scroll a window using the scroll bar; see Scroll Bars.

Next: Automatic Scrolling, Previous: Scrolling, Up: Controlling the Display   [Contents][Index]

16.2 Recentering ¶

C-l

Scroll the selected window so the current line is the center-most text line; on subsequent consecutive invocations, make the current line the top line, the bottom line, and so on in cyclic order. Possibly redisplay the screen too (recenter-top-bottom).

C-M-S-l

Scroll the other window; this is equivalent to C-l acting on the other window.

M-x recenter

Scroll the selected window so the current line is the center-most text line. Possibly redisplay the screen too.

C-M-l

Scroll heuristically to bring useful information onto the screen (reposition-window).

The C-l (recenter-top-bottom) command recenters the selected window, scrolling it so that the current screen line is exactly in the center of the window, or as close to the center as possible.

Typing C-l twice in a row (C-l C-l) scrolls the window so that point is on the topmost screen line. Typing a third C-l scrolls the window so that point is on the bottom-most screen line. Each successive C-l cycles through these three positions.

You can change the cycling order by customizing the list variable recenter-positions. Each list element should be the symbol top, middle, or bottom, or a number; an integer means to move the line to the specified screen line, while a floating-point number between 0.0 and 1.0 specifies a percentage of the screen space from the top of the window. The default, (middle top bottom), is the cycling order described above. Furthermore, if you change the variable scroll-margin to a non-zero value n, C-l always leaves at least n screen lines between point and the top or bottom of the window (see Automatic Scrolling).

You can also give C-l a prefix argument. A plain prefix argument, C-u C-l, simply recenters the line showing point. A positive argument n moves line showing point n lines down from the top of the window. An argument of zero moves point’s line to the top of the window. A negative argument −n moves point’s line n lines from the bottom of the window. When given an argument, C-l does not clear the screen or cycle through different screen positions.

If the variable recenter-redisplay has a non-nil value, each invocation of C-l also clears and redisplays the screen; the special value tty (the default) says to do this on text-terminal frames only. Redisplaying is useful in case the screen becomes garbled for any reason (see Garbage on the Screen).

The more primitive command M-x recenter behaves like recenter-top-bottom, but does not cycle among screen positions.

C-M-l (reposition-window) scrolls the current window heuristically in a way designed to get useful information onto the screen. For example, in a Lisp file, this command tries to get the entire current defun onto the screen if possible.

Next: Horizontal Scrolling, Previous: Recentering, Up: Controlling the Display   [Contents][Index]

16.3 Automatic Scrolling ¶

Emacs performs automatic scrolling when point moves out of the visible portion of the text. Normally, automatic scrolling centers point vertically in the window, but there are several ways to alter this behavior.

If you set scroll-conservatively to a small number n, then moving point just a little off the screen (no more than n lines) causes Emacs to scroll just enough to bring point back on screen; if doing so fails to make point visible, Emacs scrolls just far enough to center point in the window. If you set scroll-conservatively to a large number (larger than 100), automatic scrolling never centers point, no matter how far point moves; Emacs always scrolls text just enough to bring point into view, either at the top or bottom of the window depending on the scroll direction. By default, scroll-conservatively is 0, which means to always center point in the window. This said, in minibuffer windows, scrolling is always conservative by default because scroll-minibuffer-conservatively is non-nil, which takes precedence over scroll-conservatively.

Another way to control automatic scrolling is to customize the variable scroll-step. Its value determines the number of lines by which to automatically scroll, when point moves off the screen. If scrolling by that number of lines fails to bring point back into view, point is centered instead. The default value is zero, which (by default) causes point to always be centered after scrolling.

A third way to control automatic scrolling is to customize the variables scroll-up-aggressively and scroll-down-aggressively, which directly specify the vertical position of point after scrolling. The value of scroll-up-aggressively should be either nil (the default), or a floating point number f between 0 and 1. The latter means that when point goes below the bottom window edge (i.e., scrolling forward), Emacs scrolls the window so that point is f parts of the window height from the bottom window edge. Thus, larger f means more aggressive scrolling: more new text is brought into view. The default value, nil, is equivalent to 0.5.

Likewise, scroll-down-aggressively is used when point goes above the top window edge (i.e., scrolling backward). The value specifies how far point should be from the top margin of the window after scrolling. Thus, as with scroll-up-aggressively, a larger value is more aggressive.

Note that the variables scroll-conservatively, scroll-step, and scroll-up-aggressively / scroll-down-aggressively control automatic scrolling in contradictory ways. Therefore, you should pick no more than one of these methods to customize automatic scrolling. In case you customize multiple variables, the order of priority is: scroll-conservatively, then scroll-step, and finally scroll-up-aggressively / scroll-down-aggressively.

The variable scroll-margin restricts how close point can come to the top or bottom of a window (even if aggressive scrolling specifies a fraction f that is larger than the window portion between the top and the bottom margins). Its value is a number of screen lines; if point comes within that many lines of the top or bottom of the window, Emacs performs automatic scrolling. By default, scroll-margin is 0. The effective margin size is limited to a quarter of the window height by default, but this limit can be increased up to half (or decreased down to zero) by customizing maximum-scroll-margin.

Next: Narrowing, Previous: Automatic Scrolling, Up: Controlling the Display   [Contents][Index]

16.4 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. 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 current-line, only the line showing the cursor will be scrolled. To disable automatic horizontal scrolling entirely, set the variable auto-hscroll-mode to 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.)

The variable 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.

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

C-x >

Scroll to the right (scroll-right).

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 columns.

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 scroll-left. When auto-hscroll-mode is set to current-line, all the lines other than the one showing the cursor will be scrolled by that minimal amount.

On graphical displays, you can scroll a window horizontally using the horizontal scroll bar, if you turn on the optional horizontal-scroll-bar-mode; see Scroll Bars.

Next: View Mode, Previous: Horizontal Scrolling, Up: Controlling the Display   [Contents][Index]

16.5 Narrowing ¶

Narrowing means focusing in on some portion of the buffer, making the rest temporarily inaccessible. The portion which you can still get to is called the accessible portion. Canceling the narrowing, which makes the entire buffer once again accessible, is called widening. The bounds of narrowing in effect in a buffer are called the buffer’s restriction.

Narrowing can make it easier to concentrate on a single subroutine or paragraph by eliminating clutter. It can also be used to limit the range of operation of a replace command or repeating keyboard macro.

C-x n n

Narrow down to between point and mark (narrow-to-region).

C-x n w

Widen to make the entire buffer accessible again (widen).

C-x n p

Narrow down to the current page (narrow-to-page).

C-x n d

Narrow down to the current defun (narrow-to-defun).

When you have narrowed down to a part of the buffer, that part appears to be all there is. You can’t see the rest, you can’t move into it (motion commands won’t go outside the accessible part), you can’t change it in any way. However, it is not gone, and if you save the file all the inaccessible text will be saved. The word ‘Narrow’ appears in the mode line whenever narrowing is in effect.

The primary narrowing command is C-x n n (narrow-to-region). It sets the current buffer’s restrictions so that the text in the current region remains accessible, but all text before the region or after the region is inaccessible. Point and mark do not change.

Alternatively, use C-x n p (narrow-to-page) to narrow down to the current page. See Pages, for the definition of a page. C-x n d (narrow-to-defun) narrows down to the defun containing point (see Top-Level Definitions, or Defuns).

The way to cancel narrowing is to widen with C-x n w (widen). This makes all text in the buffer accessible again.

You can get information on what part of the buffer you are narrowed down to using the C-x = command. See Cursor Position Information.

Because narrowing can easily confuse users who do not understand it, narrow-to-region is normally a disabled command. Attempting to use this command asks for confirmation and gives you the option of enabling it; if you enable the command, confirmation will no longer be required for it. See Disabling Commands.

Next: Follow Mode, Previous: Narrowing, Up: Controlling the Display   [Contents][Index]

16.6 View Mode ¶

View mode is a minor mode that lets you scan a buffer by sequential screenfuls. It provides commands for scrolling through the buffer conveniently but not for changing it. Apart from the usual Emacs cursor motion commands, you can type SPC to scroll forward one windowful, S-SPC or DEL to scroll backward, and s to start an incremental search.

Typing q (View-quit) disables View mode, and switches back to the buffer and position before View mode was enabled. Typing e (View-exit) disables View mode, keeping the current buffer and position.

M-x view-buffer prompts for an existing Emacs buffer, switches to it, and enables View mode. M-x view-file prompts for a file and visits it with View mode enabled.

Next: Text Faces, Previous: View Mode, Up: Controlling the Display   [Contents][Index]

16.7 Follow Mode ¶

Follow mode is a minor mode that makes two windows, both showing the same buffer, scroll as a single tall virtual window. To use Follow mode, go to a frame with just one window, split it into two side-by-side windows using C-x 3, and then type M-x follow-mode. From then on, you can edit the buffer in either of the two windows, or scroll either one; the other window follows it.

In Follow mode, if you move point outside the portion visible in one window and into the portion visible in the other window, that selects the other window—again, treating the two as if they were parts of one large window.

To turn off Follow mode, type M-x follow-mode a second time.

Next: Colors for Faces, Previous: Follow Mode, Up: Controlling the Display   [Contents][Index]

16.8 Text Faces ¶

Emacs can display text in several different styles, called faces. Each face can specify various face attributes, such as the font, height, weight, slant, foreground and background color, and underlining or overlining. Most major modes assign faces to the text automatically, via Font Lock mode. See Font Lock mode, for more information about how these faces are assigned.

To see what faces are currently defined, and what they look like, type M-x list-faces-display. With a prefix argument, this prompts for a regular expression, and displays only faces with names matching that regular expression (see Syntax of Regular Expressions).

It’s possible for a given face to look different in different frames. For instance, some text terminals do not support all face attributes, particularly font, height, and width, and some support a limited range of colors. In addition, most Emacs faces are defined so that their attributes are different on light and dark frame backgrounds, for reasons of legibility. By default, Emacs automatically chooses which set of face attributes to display on each frame, based on the frame’s current background color. However, you can override this by giving the variable frame-background-mode a non-nil value. A value of dark makes Emacs treat all frames as if they have a dark background, whereas a value of light makes it treat all frames as if they have a light background.

You can customize a face to alter its attributes, and save those customizations for future Emacs sessions. See Customizing Faces, for details.

The default face is the default for displaying text, and all of its attributes are specified. Its background color is also used as the frame’s background color. See Colors for Faces.

Another special face is the cursor face. On graphical displays, the background color of this face is used to draw the text cursor. None of the other attributes of this face have any effect; the foreground color for text under the cursor is taken from the background color of the underlying text. On text terminals, the appearance of the text cursor is determined by the terminal, not by the cursor face.

You can also use X resources to specify attributes of any particular face. See X Resources.

Emacs can display variable-width fonts, but some Emacs commands, particularly indentation commands, do not account for variable character display widths. Therefore, we recommend not using variable-width fonts for most faces, particularly those assigned by Font Lock mode.

Next: Standard Faces, Previous: Text Faces, Up: Controlling the Display   [Contents][Index]

16.9 Colors for Faces ¶

Faces can have various foreground and background colors. When you specify a color for a face—for instance, when customizing the face (see Customizing Faces)—you can use either a color name or an RGB triplet.

• Color Names
• RGB Triplets

Next: Icons, Previous: Colors for Faces, Up: Controlling the Display   [Contents][Index]

16.10 Standard Faces ¶

Here are the standard faces for specifying text appearance. You can apply them to specific text when you want the effects they produce.

default

This face is used for ordinary text that doesn’t specify any face. Its background color is used as the frame’s background color.

bold

This face uses a bold variant of the default font.

italic

This face uses an italic variant of the default font.

bold-italic

This face uses a bold italic variant of the default font.

underline

This face underlines text.

fixed-pitch

This face forces use of a fixed-width font. It’s reasonable to customize this face to use a different fixed-width font, if you like, but you should not make it a variable-width font.

fixed-pitch-serif

This face is like fixed-pitch, except the font has serifs and looks more like traditional typewriting.

variable-pitch ¶

This face forces use of a variable-width (i.e., proportional) font. The font size picked for this face matches the font picked for the default (usually fixed-width) font.

variable-pitch-text

This is like the variable-pitch face (from which it inherits), but is slightly larger. A proportional font of the same height as a monospace font usually appears visually smaller, and can therefore be harder to read. When displaying longer texts, this face can be a good choice over the (slightly smaller) variable-pitch face.

shadow ¶

This face is used for making the text less noticeable than the surrounding ordinary text. Usually this can be achieved by using shades of gray in contrast with either black or white default foreground color.

Here’s an incomplete list of faces used to highlight parts of the text temporarily for specific purposes. (Many other modes define their own faces for this purpose.)

highlight

This face is used for text highlighting in various contexts, such as when the mouse cursor is moved over a hyperlink.

isearch

This face is used to highlight the current Isearch match (see Incremental Search).

query-replace

This face is used to highlight the current Query Replace match (see Replacement Commands).

lazy-highlight

This face is used to highlight lazy matches for Isearch and Query Replace (matches other than the current one).

region

This face is used for displaying an active region (see The Mark and the Region). When Emacs is built with GTK+ support, its colors are taken from the current GTK+ theme.

secondary-selection

This face is used for displaying a secondary X selection (see Secondary Selection).

trailing-whitespace

The face for highlighting excess spaces and tabs at the end of a line when show-trailing-whitespace is non-nil (see Useless Whitespace).

escape-glyph

The face for displaying control characters and escape sequences (see How Text Is Displayed).

homoglyph

The face for displaying lookalike characters, i.e., characters that look like but are not the characters being represented (see How Text Is Displayed).

nobreak-space

The face for displaying no-break space characters (see How Text Is Displayed).

nobreak-hyphen

The face for displaying no-break hyphen characters (see How Text Is Displayed).

The following faces control the appearance of parts of the Emacs frame:

mode-line ¶

This is the base face used for the mode lines, as well as header lines and for menu bars when toolkit menus are not used. By default, it’s drawn with shadows for a raised effect on graphical displays, and drawn as the inverse of the default face on text terminals.

The mode-line-active and mode-line-inactive faces (which are the ones used on the mode lines) inherit from this face.

mode-line-active ¶

Like mode-line, but used for the mode line of the currently selected window. This face inherits from mode-line, so changes in that face affect mode lines in all windows.

mode-line-inactive ¶

Like mode-line, but used for mode lines of the windows other than the selected one (if mode-line-in-non-selected-windows is non-nil). This face inherits from mode-line, so changes in that face affect mode lines in all windows.

mode-line-highlight ¶

Like highlight, but used for mouse-sensitive portions of text on mode lines. Such portions of text typically pop up tooltips (see Tooltips) when the mouse pointer hovers above them.

mode-line-buffer-id ¶

This face is used for buffer identification parts in the mode line.

header-line ¶

Similar to mode-line for a window’s header line, which appears at the top of a window just as the mode line appears at the bottom. Most windows do not have a header line—only some special modes, such Info mode, create one.

The header-line-active and header-line-inactive faces (which are the ones actually used on the header lines) inherit from this face.

header-line-active ¶

Like header-line, but used for the header line of the currently selected window. This face inherits from header-line, so changes in that face affect header lines in all windows.

header-line-inactive ¶

Like header-line, but used for header lines of the windows other than the selected one (if those windows have a header line). This face inherits from header-line, so changes in that face affect header lines in all windows.

header-line-highlight ¶

Similar to highlight and mode-line-highlight, but used for mouse-sensitive portions of text on header lines. This is a separate face because the header-line face might be customized in a way that does not interact well with highlight.

tab-line ¶

Similar to mode-line for a window’s tab line, which appears at the top of a window with tabs representing window buffers. See Window Tab Line.

The tab-line-active and tab-line-inactive faces (which are the ones actually used on the tab lines) inherit from this face.

tab-line-active ¶

Like tab-line, but used for the tab line of the currently selected window. This face inherits from tab-line, so changes in that face affect tab lines in all windows.

tab-line-inactive ¶

Like tab-line, but used for tab lines of the windows other than the selected one (if those windows have a tab line). This face inherits from tab-line, so changes in that face affect tab lines in all windows.

vertical-border ¶

This face is used for the vertical divider between windows on text terminals.

minibuffer-prompt ¶

This face is used for the prompt strings displayed in the minibuffer. By default, Emacs automatically adds this face to the value of minibuffer-prompt-properties, which is a list of text properties (see Text Properties in the Emacs Lisp Reference Manual) used to display the prompt text. (This variable takes effect when you enter the minibuffer.)

fringe ¶

The face for the fringes to the left and right of windows on graphic displays. (The fringes are the narrow portions of the Emacs frame between the text area and the window’s right and left borders.) See Window Fringes.

cursor

The :background attribute of this face specifies the color of the text cursor. See Displaying the Cursor.

tooltip

This face is used for tooltip text. By default, if Emacs is built with GTK+ support, tooltips are drawn via GTK+ and this face has no effect. See Tooltips.

mouse

This face determines the color of the mouse pointer.

The following faces likewise control the appearance of parts of the Emacs frame, but only on text terminals, or when Emacs is built on X with no toolkit support. (For all other cases, the appearance of the respective frame elements is determined by system-wide settings.)

scroll-bar

This face determines the visual appearance of the scroll bar. See Scroll Bars.

tool-bar

This face determines the color of tool bar icons. See Tool Bars.

tab-bar

This face determines the color of tab bar icons. See Tab Bars.

menu

This face determines the colors and font of Emacs’s menus. See Menu Bars.

tty-menu-enabled-face

This face is used to display enabled menu items on text-mode terminals.

tty-menu-disabled-face

This face is used to display disabled menu items on text-mode terminals.

tty-menu-selected-face

This face is used to display on text-mode terminals the menu item that would be selected if you click a mouse or press RET.

Next: Text Scale, Previous: Standard Faces, Up: Controlling the Display   [Contents][Index]

16.11 Icons ¶

Emacs sometimes displays clickable buttons (or other informative icons), and you can customize how these look on display.

The main customization point here is the icon-preference user option. By using this, you can tell Emacs your overall preferences for icons. This is a list of icon types, and the first icon type that’s supported will be used. The supported types are:

image

Use an image for the icon.

emoji

Use a colorful emoji for the icon.

symbol

Use a monochrome symbol for the icon.

text

Use a simple text for the icon.

In addition, each individual icon can be customized with M-x customize-icon, and themes can further alter the looks of the icons.

To get a quick description of an icon, use the M-x describe-icon command.

Next: Font Lock mode, Previous: Icons, Up: Controlling the Display   [Contents][Index]

16.12 Text Scale ¶

To increase the font size of the default face in the current buffer, type C-x C-+ or C-x C-=. To decrease it, type C-x C--. To restore the default (global) font size, type C-x C-0. These keys are all bound to the same command, text-scale-adjust, which looks at the last key typed to determine which action to take and adjusts the font size accordingly by changing the height of the default face.

Most faces don’t have an explicit setting of the :height attribute, and thus inherit the height from the default face. Those faces are also scaled by the above commands.

Faces other than default that have an explicit setting of the :height attribute are not affected by these font size changes. The header-line face is an exception: it will be scaled even if it has an explicit setting of the :height attribute.

Similarly, scrolling the mouse wheel with the Ctrl modifier pressed, when the mouse pointer is above buffer text, will increase or decrease the font size of the affected faces, depending on the direction of the scrolling.

The final key of these commands may be repeated without the leading C-x and without the modifiers. For instance, C-x C-= C-= C-= and C-x C-= = = increase the face height by three steps. Each step scales the text height by a factor of 1.2; to change this factor, customize the variable text-scale-mode-step. A numeric argument of 0 to the text-scale-adjust command restores the default height, the same as typing C-x C-0.

Similarly, to change the sizes of the fonts globally, type C-x C-M-+, C-x C-M-=, C-x C-M-- or C-x C-M-0, or scroll the mouse wheel with both the Ctrl and Meta modifiers pressed. To enable frame resizing when the font size is changed globally, customize the variable global-text-scale-adjust-resizes-frames (see Easy Customization Interface).

The commands text-scale-increase and text-scale-decrease increase or decrease the size of the font in the current buffer, just like C-x C-+ and C-x C-- respectively. You may find it convenient to bind to these commands, rather than text-scale-adjust.

The command text-scale-set scales the size of the font in the current buffer to an absolute level specified by its prefix argument.

The above commands automatically enable the minor mode text-scale-mode if the current font scaling is other than 1, and disable it otherwise.

The command text-scale-pinch increases or decreases the text scale based on the distance between fingers on a touchpad when a pinch gesture is performed by placing two fingers on a touchpad and moving them towards or apart from each other. This is only available on some systems with supported hardware.

The command mouse-wheel-text-scale also changes the text scale. Normally, it is run when you press Ctrl while moving the mouse wheel. The text scale is increased when the wheel is moved downwards, and it is decreased when the wheel is moved upwards.

Next: Interactive Highlighting, Previous: Text Scale, Up: Controlling the Display   [Contents][Index]

16.13 Font Lock mode ¶

Font Lock mode is a minor mode, always local to a particular buffer, which assigns faces to (or fontifies) the text in the buffer. Each buffer’s major mode tells Font Lock mode which text to fontify; for instance, programming language modes fontify syntactically relevant constructs like comments, strings, and function names.

Font Lock mode is enabled by default in major modes that support it. To toggle it in the current buffer, type M-x font-lock-mode. A positive numeric argument unconditionally enables Font Lock mode, and a negative or zero argument disables it.

Type M-x global-font-lock-mode to toggle Font Lock mode in all buffers. To impose this setting for future Emacs sessions, customize the variable global-font-lock-mode (see Easy Customization Interface), or add the following line to your init file:

(global-font-lock-mode 0)

If you have disabled Global Font Lock mode, you can still enable Font Lock for specific major modes by adding the function font-lock-mode to the mode hooks (see Hooks). For example, to enable Font Lock mode for editing C files, you can do this:

(add-hook 'c-mode-hook 'font-lock-mode)

Font Lock mode uses several specifically named faces to do its job, including font-lock-string-face, font-lock-comment-face, and others. The easiest way to find them all is to use M-x customize-group RET font-lock-faces RET. You can then use that customization buffer to customize the appearance of these faces. See Customizing Faces.

Fontifying very large buffers can take a long time. To avoid large delays when a file is visited, Emacs initially fontifies only the visible portion of a buffer. As you scroll through the buffer, each portion that becomes visible is fontified as soon as it is displayed; this type of Font Lock is called Just-In-Time (or JIT) Lock. You can control how JIT Lock behaves, including telling it to perform fontification while idle, by customizing variables in the customization group ‘jit-lock’. See Customizing Specific Items.

The information that major modes use for determining which parts of buffer text to fontify and what faces to use can be based on several different ways of analyzing the text:

• Search for keywords and other textual patterns based on regular expressions (see Regular Expression Search).
• Find syntactically distinct parts of text based on built-in syntax tables (see Syntax Tables in The Emacs Lisp Reference Manual).
• Use syntax tree produced by a full-blown parser, via a special-purpose library, such as the tree-sitter library (see Parsing Program Source in The Emacs Lisp Reference Manual), or an external program.

• Traditional Font Lock
• Parser-based Font Lock
• Semantic Font Lock

'((c-mode . 1) (c++-mode . 1)))

(add-hook 'c-mode-hook
          (lambda ()
           (font-lock-add-keywords nil
            '(("\\<\\(FIXME\\):" 1
               font-lock-warning-face t)))))

Next: Window Fringes, Previous: Font Lock mode, Up: Controlling the Display   [Contents][Index]

16.14 Interactive Highlighting ¶

Highlight Changes mode is a minor mode that highlights the parts of the buffer that were changed most recently, by giving that text a different face. To enable or disable Highlight Changes mode, use M-x highlight-changes-mode.

Hi Lock mode is a minor mode that highlights text that matches regular expressions you specify. For example, you can use it to highlight all the references to a certain variable in a program source file, highlight certain parts in a voluminous output of some program, or highlight certain names in an article. To enable or disable Hi Lock mode, use the command M-x hi-lock-mode. To enable Hi Lock mode for all buffers, use M-x global-hi-lock-mode or place (global-hi-lock-mode 1) in your .emacs file.

Hi Lock mode works like Font Lock mode (see Font Lock mode), except that you specify explicitly the regular expressions to highlight. You can control them with the following commands. (The key bindings below that begin with C-x w are deprecated in favor of the global M-s h bindings, and will be removed in some future Emacs version.)

M-s h r regexp RET face RET ¶

C-x w h regexp RET face RET

Highlight text that matches regexp using face face (highlight-regexp). The highlighting will remain as long as the buffer is loaded. For example, to highlight all occurrences of the word “whim” using the default face (a yellow background), type M-s h r whim RET RET. Any face can be used for highlighting, Hi Lock provides several of its own and these are pre-loaded into a list of default values. While being prompted for a face use M-n and M-p to cycle through them. A prefix numeric argument limits the highlighting to the corresponding subexpression.

Setting the option hi-lock-auto-select-face to a non-nil value causes this command (and other Hi Lock commands that read faces) to automatically choose the next face from the default list without prompting.

You can use this command multiple times, specifying various regular expressions to highlight in different ways.

M-s h u regexp RET ¶

C-x w r regexp RET

Unhighlight regexp (unhighlight-regexp). If you invoke this from the menu, you select the expression to unhighlight from a list. If you invoke this from the keyboard, you use the minibuffer. It will show the most recently added regular expression; use M-n to show the next older expression and M-p to select the next newer expression. (You can also type the expression by hand, with completion.) When the expression you want to unhighlight appears in the minibuffer, press RET to exit the minibuffer and unhighlight it.

M-s h l regexp RET face RET ¶

C-x w l regexp RET face RET

Highlight entire lines containing a match for regexp, using face face (highlight-lines-matching-regexp).

M-s h p phrase RET face RET ¶

C-x w p phrase RET face RET

Highlight matches of phrase, using face face (highlight-phrase). phrase can be any regexp, but spaces will be replaced by matches to whitespace and initial lower-case letters will become case insensitive.

M-s h . ¶

C-x w .

Highlight the symbol found near point, using the next available face (highlight-symbol-at-point).

M-s h w ¶

C-x w b

Insert all the current highlighting regexp/face pairs into the buffer at point, with comment delimiters to prevent them from changing your program. (This key binding runs the hi-lock-write-interactive-patterns command.)

These patterns are extracted from the comments, if appropriate, if you invoke M-x hi-lock-find-patterns, or if you visit the file while Hi Lock mode is enabled (since that runs hi-lock-find-patterns).

M-s h f ¶

C-x w i

Extract regexp/face pairs from comments in the current buffer (hi-lock-find-patterns). Thus, you can enter patterns interactively with highlight-regexp, store them into the file with hi-lock-write-interactive-patterns, edit them (perhaps including different faces for different parenthesized parts of the match), and finally use this command (hi-lock-find-patterns) to have Hi Lock highlight the edited patterns.

The variable hi-lock-file-patterns-policy controls whether Hi Lock mode should automatically extract and highlight patterns found in a file when it is visited. Its value can be nil (never highlight), ask (query the user), or a function. If it is a function, hi-lock-find-patterns calls it with the patterns as argument; if the function returns non-nil, the patterns are used. The default is ask. Note that patterns are always highlighted if you call hi-lock-find-patterns directly, regardless of the value of this variable.

Also, hi-lock-find-patterns does nothing if the current major mode’s symbol is a member of the list hi-lock-exclude-modes.

Next: Displaying Boundaries, Previous: Interactive Highlighting, Up: Controlling the Display   [Contents][Index]

16.15 Window Fringes ¶

On graphical displays, each Emacs window normally has narrow fringes on the left and right edges. The fringes are used to display symbols that provide information about the text in the window. You can type M-x fringe-mode to toggle display of the fringes or to modify their width. This command affects fringes in all frames; to modify fringes on the selected frame only, use M-x set-fringe-style. You can make your changes to the fringes permanent by customizing the variable fringe-mode.

The most common use of the fringes is to indicate a continuation line (see Continuation Lines). When one line of text is split into multiple screen lines, the left fringe shows a curving arrow for each screen line except the first, indicating that this is not the real beginning. The right fringe shows a curving arrow for each screen line except the last, indicating that this is not the real end. If the line’s direction is right-to-left (see Bidirectional Editing), the meanings of the curving arrows in the fringes are swapped.

The fringes indicate line truncation (see Line Truncation) with short horizontal arrows meaning there’s more text on this line which is scrolled horizontally out of view. Clicking the mouse on one of the arrows scrolls the display horizontally in the direction of the arrow.

The fringes can also indicate other things, such as buffer boundaries (see Displaying Boundaries), unused lines near the end of the window (see indicate-empty-lines), and where a program you are debugging is executing (see Running Debuggers Under Emacs).

The fringe is also used for drawing the cursor, if the current line is exactly as wide as the window and point is at the end of the line. To disable this, change the variable overflow-newline-into-fringe to nil; this causes Emacs to continue or truncate lines that are exactly as wide as the window.

If you customize fringe-mode to remove the fringes on one or both sides of the window display, the features that display on the fringe are not available. Indicators of line continuation and truncation are an exception: when fringes are not available, Emacs uses the leftmost and rightmost character cells to indicate continuation and truncation with special ASCII characters, see Continuation Lines, and Line Truncation. This reduces the width available for displaying text on each line, because the character cells used for truncation and continuation indicators are reserved for that purpose. Since buffer text can include bidirectional text, and thus both left-to-right and right-to-left paragraphs (see Bidirectional Editing), removing only one of the fringes still reserves two character cells, one on each side of the window, for truncation and continuation indicators, because these indicators are displayed on opposite sides of the window in right-to-left paragraphs.

Next: Useless Whitespace, Previous: Window Fringes, Up: Controlling the Display   [Contents][Index]

16.16 Displaying Boundaries ¶

Emacs can display an indication of the fill-column position (see Explicit Fill Commands). The fill-column indicator is a useful functionality especially in prog-mode and its descendants (see Major Modes) to indicate the position of a specific column that has some special meaning for formatting the source code of a program. This assumes the buffer uses a fixed-pitch font, where all the characters (with the possible exception of double-width characters) have the same width on display. If the buffer uses variable-pitch fonts, the fill-column indicators on different lines might appear unaligned.

To activate the fill-column indication display, use the minor modes display-fill-column-indicator-mode and global-display-fill-column-indicator-mode, which enable the indicator locally or globally, respectively.

Alternatively, you can set the two buffer-local variables display-fill-column-indicator and display-fill-column-indicator-character to activate the indicator and control the character used for the indication. Note that both variables must be non-nil for the indication to be displayed. (Turning on the minor mode sets both these variables.)

There are 2 buffer local variables and a face to customize this mode:

display-fill-column-indicator-column ¶

Specifies the column number where the indicator should be set. It can take positive numerical values for the column, or the special value t, which means that the value of the variable fill-column will be used.

Any other value disables the indicator. The default value is t.

display-fill-column-indicator-character ¶

Specifies the character used for the indicator. This character can be any valid character including Unicode ones if the font supports them. The value nil disables the indicator. When the mode is enabled through the functions display-fill-column-indicator-mode or global-display-fill-column-indicator-mode, they will use the character specified by this variable, if it is non-nil; otherwise Emacs will use the character U+2502 BOX DRAWINGS LIGHT VERTICAL, falling back to ‘|’ if U+2502 cannot be displayed.

fill-column-indicator ¶

Specifies the face used to display the indicator. It inherits its default values from the face shadow, but without background color. To change the indicator color, you need only set the foreground color of this face.

On graphical displays, Emacs can indicate the buffer boundaries in the fringes. If you enable this feature, the first line and the last line are marked with angle images in the fringes. This can be combined with up and down arrow images which say whether it is possible to scroll the window.

The buffer-local variable indicate-buffer-boundaries controls how the buffer boundaries and window scrolling is indicated in the fringes. If the value is left or right, both angle and arrow bitmaps are displayed in the left or right fringe, respectively.

If value is an alist (see Association Lists in the Emacs Lisp Reference Manual), each element (indicator . position) specifies the position of one of the indicators. The indicator must be one of top, bottom, up, down, or t which specifies the default position for the indicators not present in the alist. The position is one of left, right, or nil which specifies not to show this indicator.

For example, ((top . left) (t . right)) places the top angle bitmap in left fringe, the bottom angle bitmap in right fringe, and both arrow bitmaps in right fringe. To show just the angle bitmaps in the left fringe, but no arrow bitmaps, use ((top . left) (bottom . left)).

Next: Selective Display, Previous: Displaying Boundaries, Up: Controlling the Display   [Contents][Index]

16.17 Useless Whitespace ¶

It is easy to leave unnecessary spaces at the end of a line, or empty lines at the end of a buffer, without realizing it. In most cases, this trailing whitespace has no effect, but sometimes it can be a nuisance.

You can make trailing whitespace at the end of a line visible by setting the buffer-local variable show-trailing-whitespace to t. Then Emacs displays trailing whitespace, using the face trailing-whitespace.

This feature does not apply when point is at the end of the line containing the whitespace. Strictly speaking, that is trailing whitespace nonetheless, but displaying it specially in that case looks ugly while you are typing in new text. In this special case, the location of point is enough to show you that the spaces are present.

Type M-x delete-trailing-whitespace to delete all trailing whitespace. This command deletes all extra spaces at the end of each line in the buffer, and all empty lines at the end of the buffer; to ignore the latter, change the variable delete-trailing-lines to nil. If the region is active, the command instead deletes extra spaces at the end of each line in the region. If you enable the buffer-local mode delete-trailing-whitespace-mode, Emacs will automatically invoke delete-trailing-whitespace each time you save the buffer.

On graphical displays, Emacs can indicate unused lines at the end of the window with a small image in the left fringe (see Window Fringes). The image appears for screen lines that do not correspond to any buffer text, so blank lines at the end of the buffer stand out because they lack this image. To enable this feature, set the buffer-local variable indicate-empty-lines to a non-nil value. You can enable or disable this feature for all new buffers by setting the default value of this variable, e.g., (setq-default indicate-empty-lines t).

Whitespace mode is a buffer-local minor mode that lets you visualize many kinds of whitespace in the buffer, by either drawing the whitespace characters with a special face or displaying them as special glyphs. To toggle this mode, type M-x whitespace-mode. The kinds of whitespace visualized are determined by the list variable whitespace-style. Individual elements in that list can be toggled on or off in the current buffer by typing M-x whitespace-toggle-options. Here is a partial list of possible elements (see the variable’s documentation for the full list):

face

Enable all visualizations which use special faces. This element has a special meaning: if it is absent from the list, none of the other visualizations take effect except space-mark, tab-mark, and newline-mark.

trailing

Highlight trailing whitespace.

tabs

Highlight tab characters.

spaces

Highlight space and non-breaking space characters.

lines ¶

Highlight lines longer than 80 columns. To change the column limit, customize the variable whitespace-line-column.

newline

Highlight newlines.

missing-newline-at-eof

Highlight the final character if the buffer doesn’t end with a newline character.

empty

Highlight empty lines at the beginning and/or end of the buffer.

big-indent ¶

Highlight too-deep indentation. By default any sequence of at least 4 consecutive tab characters or 32 consecutive space characters is highlighted. To change that, customize the regular expression whitespace-big-indent-regexp.

space-mark

Draw space and non-breaking characters with a special glyph.

tab-mark

Draw tab characters with a special glyph.

newline-mark

Draw newline characters with a special glyph.

Global Whitespace mode is a global minor mode that lets you visualize whitespace in all buffers. To toggle individual features, use M-x global-whitespace-toggle-options.

Next: Optional Mode Line Features, Previous: Useless Whitespace, Up: Controlling the Display   [Contents][Index]

16.18 Selective Display ¶

Emacs has the ability to hide lines indented more than a given number of columns. You can use this to get an overview of a part of a program.

To hide lines in the current buffer, type C-x $ (set-selective-display) with a numeric argument n. Then lines with at least n columns of indentation disappear from the screen. The only indication of their presence is that three dots (‘…’) appear at the end of each visible line that is followed by one or more hidden ones.

The commands C-n and C-p move across the hidden lines as if they were not there.

The hidden lines are still present in the buffer, and most editing commands see them as usual, so you may find point in the middle of the hidden text. When this happens, the cursor appears at the end of the previous line, after the three dots. If point is at the end of the visible line, before the newline that ends it, the cursor appears before the three dots.

To make all lines visible again, type C-x $ with no argument.

If you set the variable selective-display-ellipses to nil, the three dots do not appear at the end of a line that precedes hidden lines. Then there is no visible indication of the hidden lines. This variable becomes local automatically when set.

See also Outline Mode for another way to hide part of the text in a buffer.

Next: How Text Is Displayed, Previous: Selective Display, Up: Controlling the Display   [Contents][Index]

16.19 Optional Mode Line Features ¶

The buffer percentage pos indicates the percentage of the buffer above the top of the window. You can additionally display the size of the buffer by typing M-x size-indication-mode to turn on Size Indication mode. The size will be displayed immediately following the buffer percentage like this:

pos of size

Here size is the human readable representation of the number of characters in the buffer, which means that ‘k’ for 10^3, ‘M’ for 10^6, ‘G’ for 10^9, etc., are used to abbreviate.

The current line number of point appears in the mode line when Line Number mode is enabled. Use the command M-x line-number-mode to turn this mode on and off; normally it is on. The line number appears after the buffer percentage pos, with the letter ‘L’ to indicate what it is.

Similarly, you can display the current column number by turning on Column Number mode with M-x column-number-mode. The column number is indicated by the letter ‘C’. However, when both of these modes are enabled, the line and column numbers are displayed in parentheses, the line number first, rather than with ‘L’ and ‘C’. For example: ‘(561,2)’. See Minor Modes, for more information about minor modes and about how to use these commands.

In Column Number mode, the displayed column number counts from zero starting at the left margin of the window. If you would prefer for the displayed column number to count from one, you may set column-number-indicator-zero-based to nil.

If you have narrowed the buffer (see Narrowing), the displayed line number is relative to the accessible portion of the buffer. Thus, it isn’t suitable as an argument to goto-line. (The command what-line shows the line number relative to the whole file.) You can use goto-line-relative command to move point to the line relative to the accessible portion of the narrowed buffer.

If the buffer is very large (larger than the value of line-number-display-limit), Emacs won’t compute the line number, because that would be too slow; therefore, the line number won’t appear on the mode-line. To remove this limit, set line-number-display-limit to nil.

Line-number computation can also be slow if the lines in the buffer are too long. For this reason, Emacs doesn’t display line numbers if the average width, in characters, of lines near point is larger than the value of line-number-display-limit-width. The default value is 200 characters.

Emacs can optionally display the time and system load in all mode lines. To enable this feature, type M-x display-time or customize the option display-time-mode. The information added to the mode line looks like this:

hh:mmPM l.ll

Here hh and mm are the hour and minute, followed always by ‘AM’ or ‘PM’. l.ll is the average number, collected for the last few minutes, of processes in the whole system that were either running or ready to run (i.e., were waiting for an available processor). (Some fields may be missing if your operating system cannot support them.) If you prefer time display in 24-hour format, set the variable display-time-24hr-format to t.

The word ‘Mail’ appears after the load level if there is mail for you that you have not read yet. On graphical displays, you can use an icon instead of ‘Mail’ by customizing display-time-use-mail-icon; this may save some space on the mode line. You can customize display-time-mail-face to make the mail indicator prominent. Use display-time-mail-file to specify the mail file to check, or set display-time-mail-directory to specify the directory to check for incoming mail (any nonempty regular file in the directory is considered to be newly arrived mail).

When running Emacs on a laptop computer, you can display the battery charge on the mode-line, by using the command display-battery-mode or customizing the variable display-battery-mode. The variable battery-mode-line-format determines the way the battery charge is displayed; the exact mode-line message depends on the operating system, and it usually shows the current battery charge as a percentage of the total charge. The functions in battery-update-functions are run after updating the mode line, and can be used to trigger actions based on the battery status.

On graphical displays, the mode line is drawn as a 3D box. If you don’t like this effect, you can disable it by customizing the mode-line face and setting its box attribute to nil. See Customizing Faces.

By default, the mode line of nonselected windows is displayed in a different face, called mode-line-inactive. Only the selected window is displayed in the mode-line face. This helps show which window is selected. When the minibuffer is selected, since it has no mode line, the window from which you activated the minibuffer has its mode line displayed using mode-line; as a result, ordinary entry to the minibuffer does not change any mode lines.

You can disable use of mode-line-inactive by setting variable mode-line-in-non-selected-windows to nil; then all mode lines are displayed in the mode-line face.

You can customize the mode line display for each of the end-of-line formats by setting each of the variables eol-mnemonic-unix, eol-mnemonic-dos, eol-mnemonic-mac, and eol-mnemonic-undecided to the strings you prefer.

Some modes put a lot of data in the mode line, pushing elements at the end of the mode line off to the right. Emacs can “compress” the mode line if the mode-line-compact variable is non-nil by turning stretches of spaces into a single space. If this variable is long, this is only done when the mode line is wider than the currently selected window. (This computation is approximate, based on the number of characters, and not their displayed width.) This variable can be buffer-local to only compress mode-lines in certain buffers. To further “compress” the mode line, you may customize the mode-line-collapse-minor-modes option to a non-nil value, and Emacs will hide some minor mode indicators on the mode line by collapsing them into a single clickable button.

By default, most buffers display a mode line, but if the mode line is not useful in a buffer, you can use the command M-x mode-line-invisible-mode to hide the mode line in the current buffer, the mode line remains hidden until this command is called again. To always hide the mode line when entering to a major mode, add mode-line-invisible-mode to a hook (see Hooks).

Next: Displaying the Cursor, Previous: Optional Mode Line Features, Up: Controlling the Display   [Contents][Index]

16.20 How Text Is Displayed ¶

Most characters are printing characters: when they appear in a buffer, they are displayed literally on the screen. Printing characters include ASCII numbers, letters, and punctuation characters, as well as many non-ASCII characters.

The ASCII character set contains non-printing control characters. Two of these are displayed specially: the newline character (Unicode code point U+000A) is displayed by starting a new line, while the tab character (U+0009) is displayed as a space that extends to the next tab stop column (normally every 8 columns). The number of spaces per tab is controlled by the buffer-local variable tab-width, which must have an integer value between 1 and 1000, inclusive. Note that the way the tab character in the buffer is displayed has nothing to do with the definition of TAB as a command.

Other ASCII control characters, whose codes are below U+0020 (octal 40, decimal 32), are displayed as a caret (‘^’) followed by the non-control version of the character, with the escape-glyph face. For instance, the ‘control-A’ character, U+0001, is displayed as ‘^A’.

The raw bytes with codes U+0080 (octal 200) through U+009F (octal 237) are displayed as octal escape sequences, with the escape-glyph face. For instance, character code U+0098 (octal 230) is displayed as ‘\230’. If you change the buffer-local variable ctl-arrow to nil, the ASCII control characters are also displayed as octal escape sequences instead of caret escape sequences. (You can also request that raw bytes be shown in hex, see display-raw-bytes-as-hex.)

Some non-ASCII characters have the same appearance as an ASCII space or hyphen (minus) character. Such characters can cause problems if they are entered into a buffer without your realization, e.g., by yanking; for instance, source code compilers typically do not treat non-ASCII spaces as whitespace characters. To deal with this problem, Emacs displays such characters specially: it displays U+00A0 NO-BREAK SPACE and other characters from the Unicode horizontal space class with the nobreak-space face, and it displays U+00AD SOFT HYPHEN, U+2010 HYPHEN, and U+2011 NON-BREAKING HYPHEN with the nobreak-hyphen face. To disable this, change the variable nobreak-char-display to nil. If you give this variable a non-nil and non-t value, Emacs instead displays such characters as a highlighted backslash followed by a space or hyphen.

You can customize the way any particular character code is displayed by means of a display table. See Display Tables in The Emacs Lisp Reference Manual.

On graphical displays, some characters may have no glyphs in any of the fonts available to Emacs. These glyphless characters are normally displayed as boxes containing the hexadecimal character code. Similarly, on text terminals, characters that cannot be displayed using the terminal encoding (see Coding Systems for Terminal I/O) are normally displayed as question signs. You can control the display method by customizing the variable glyphless-char-display-control. You can also customize the glyphless-char face to make these characters more prominent on display. See Glyphless Character Display in The Emacs Lisp Reference Manual, for details.

The glyphless-display-mode minor mode can be used to toggle the display of glyphless characters in the current buffer. The glyphless characters will be displayed as boxes with acronyms of their names inside.

Emacs tries to determine if the curved quotes ‘ and ’ can be displayed on the current display. By default, if this seems to be so, then Emacs will translate the ASCII quotes (‘`’ and ‘'’), when they appear in messages and help texts, to these curved quotes. You can influence or inhibit this translation by customizing the user option text-quoting-style (see Keys in Documentation in The Emacs Lisp Reference Manual).

If the curved quotes ‘, ’, “, and ” are known to look just like ASCII characters, they are shown with the homoglyph face. Curved quotes that are known not to be displayable are shown as their ASCII approximations ‘`’, ‘'’, and ‘"’ with the homoglyph face.

Next: Line Truncation, Previous: How Text Is Displayed, Up: Controlling the Display   [Contents][Index]

16.21 Displaying the Cursor ¶

On a text terminal, the cursor’s appearance is controlled by the terminal, largely out of the control of Emacs. Some terminals offer two different cursors: a visible static cursor, and a very visible blinking cursor. By default, Emacs uses the very visible cursor, and switches to it when you start or resume Emacs. If the variable visible-cursor is nil when Emacs starts or resumes, it uses the normal cursor.

On a graphical display and many Xterm-compatible text terminals, the color and shape of the text cursor can be altered. To customize its color, change the :background attribute of the face named cursor (see Customizing Faces). (The other attributes of this face have no effect; the text shown under the cursor is drawn using the frame’s background color.) To change its shape, customize the buffer-local variable cursor-type; possible values are box (the default), (box . size) (box cursor becoming a hollow box under masked images larger than size pixels in either dimension), hollow (a hollow box), bar (a vertical bar), (bar . n) (a vertical bar n pixels wide), hbar (a horizontal bar), (hbar . n) (a horizontal bar n pixels tall), or nil (no cursor at all).

On Xterm-compatible text terminals cursor customization is controlled by the user option xterm-update-cursor. Valid values are t to update the cursor’s color and shape, type to update the cursor’s shape only, color to update the cursor’s color only, and nil to not update the cursor’s appearance. Text terminals can not display a hollow box and instead use a filled box. Similarly, all text terminals ignore the pixel sizes for bar and hbar.

To make the cursor even more visible, you can use HL Line mode, a minor mode that highlights the line containing point. Use M-x hl-line-mode to enable or disable it in the current buffer. M-x global-hl-line-mode enables or disables the same mode globally.

The remaining controls only work on graphical displays where Emacs can fully control the way the cursor appears.

By default, the cursor stops blinking after 10 blinks, if Emacs does not get any input during that time; any input event restarts the count. You can customize the variable blink-cursor-blinks to control that: its value says how many times to blink without input before stopping. Setting that variable to a zero or negative value will make the cursor blink forever. To disable cursor blinking altogether, change the variable blink-cursor-mode to nil (see Easy Customization Interface), or add the line

  (blink-cursor-mode 0)

to your init file. Alternatively, you can change how the cursor looks when it blinks off by customizing the list variable blink-cursor-alist. Each element in the list should have the form (on-type . off-type); this means that if the cursor is displayed as on-type when it blinks on (where on-type is one of the cursor types described above), then it is displayed as off-type when it blinks off.

Some characters, such as tab characters, are extra wide. When the cursor is positioned over such a character, it is normally drawn with the default character width. You can make the cursor stretch to cover wide characters, by changing the variable x-stretch-cursor to a non-nil value.

The cursor normally appears in non-selected windows as a non-blinking hollow box. (For a bar cursor, it instead appears as a thinner bar.) To turn off cursors in non-selected windows, change the variable cursor-in-non-selected-windows to nil.

Next: Visual Line Mode, Previous: Displaying the Cursor, Up: Controlling the Display   [Contents][Index]

16.22 Line Truncation ¶

As an alternative to continuation (see Continuation Lines), Emacs can display long lines by truncation. This means that all the characters that do not fit in the width of the screen or window do not appear at all. On graphical displays, a small straight arrow in the fringe indicates truncation at either end of the line. On text terminals, this is indicated with ‘$’ signs in the rightmost and/or leftmost columns.

Horizontal scrolling automatically causes line truncation (see Horizontal Scrolling). You can explicitly enable line truncation for a particular buffer with the command C-x x t (toggle-truncate-lines). This works by locally changing the variable truncate-lines. If that variable is non-nil, long lines are truncated; if it is nil, they are continued onto multiple screen lines. Setting the variable truncate-lines in any way makes it local to the current buffer; until that time, the default value, which is normally nil, is in effect.

Since line truncation and word wrap (described in the next section) are contradictory, toggle-truncate-lines disables word wrap when it turns on line truncation.

If a split window becomes too narrow, Emacs may automatically enable line truncation. See Splitting Windows, for the variable truncate-partial-width-windows which controls this.

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16.23 Visual Line Mode ¶

Another alternative to ordinary line continuation (see Continuation Lines) is to use word wrap. Here, each long logical line is divided into two or more screen lines, or “visual lines”, like in ordinary line continuation. However, Emacs attempts to wrap the line at word boundaries near the right window edge. (If the line’s direction is right-to-left, it is wrapped at the left window edge instead.) This makes the text easier to read, as wrapping does not occur in the middle of words.

Word wrap is enabled by Visual Line mode, an optional minor mode. To turn on Visual Line mode in the current buffer, type M-x visual-line-mode; repeating this command turns it off. You can also turn on Visual Line mode using the menu bar: in the Options menu, select the ‘Line Wrapping in this Buffer’ submenu, followed by the ‘Word Wrap (Visual Line mode)’ menu item. While Visual Line mode is enabled, the mode line shows the string ‘wrap’ in the mode display. The command M-x global-visual-line-mode toggles Visual Line mode in all buffers.

Since word wrap and line truncation (described in the previous section) are contradictory, turning on visual-line-mode disables line truncation.

In Visual Line mode, some editing commands work on screen lines instead of logical lines: C-a (beginning-of-visual-line) moves to the beginning of the screen line, C-e (end-of-visual-line) moves to the end of the screen line, and C-k (kill-visual-line) kills text to the end of the screen line.

To move by logical lines, use the commands M-x next-logical-line and M-x previous-logical-line. These move point to the next logical line and the previous logical line respectively, regardless of whether Visual Line mode is enabled. If you use these commands frequently, it may be convenient to assign key bindings to them. See Rebinding Keys in Your Init File.

By default, word-wrapped lines do not display fringe indicators. Visual Line mode is often used to edit files that contain many long logical lines, so having a fringe indicator for each wrapped line would be visually distracting. You can change this by customizing the variable visual-line-fringe-indicators.

By default, Emacs only breaks lines after whitespace characters like SPC and TAB, but does not break after whitespace characters like EN QUAD. Emacs provides a minor mode called word-wrap-whitespace-mode that switches on word wrapping in the current mode, and sets up which characters to wrap lines on based on the word-wrap-whitespace-characters user option. There’s also a globalized version of that mode called global-word-wrap-whitespace-mode.

Only breaking after whitespace character produces incorrect results when CJK and Latin text are mixed together (because CJK characters don’t use whitespace to separate words). You can customize the option word-wrap-by-category to allow Emacs to break lines after any character with ‘|’ category (see Categories in the Emacs Lisp Reference Manual), which provides better support for CJK characters. Also, if this variable is set using Customize, Emacs automatically loads kinsoku.el. When kinsoku.el is loaded, Emacs respects kinsoku rules when breaking lines. That means characters with the ‘>’ category don’t appear at the beginning of a line (e.g., U+FF0C FULLWIDTH COMMA), and characters with the ‘<’ category don’t appear at the end of a line (e.g., U+300A LEFT DOUBLE ANGLE BRACKET). You can view the category set of a character using the commands char-category-set and category-set-mnemonics, or by typing C-u C-x = with point on the character and looking at the “category” section in the report. You can add categories to a character using the command modify-category-entry.

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16.24 Customization of Display ¶

This section describes variables that control miscellaneous aspects of the appearance of the Emacs screen. Beginning users can skip it.

If you want to have Emacs display line numbers for every line in the buffer, customize the buffer-local variable display-line-numbers; it is nil by default. This variable can have several different values to support various modes of line-number display:

t

Display (an absolute) line number before each non-continuation screen line that displays buffer text. If the line is a continuation line, or if the entire screen line displays a display or an overlay string, that line will not be numbered.

relative

Display relative line numbers before non-continuation lines which show buffer text. The line numbers are relative to the line showing point, so the numbers grow both up and down as lines become farther from the current line.

visual

This value causes Emacs to count lines visually: only lines actually shown on the display will be counted (disregarding any lines in invisible parts of text), and lines which wrap to consume more than one screen line will be numbered that many times. The displayed numbers are relative, as with relative value above. This is handy in modes that fold text, such as Outline mode (see Outline Mode), and when you need to move by exact number of screen lines.

anything else

Any other non-nil value is treated as t.

The command M-x display-line-numbers-mode provides a convenient way to turn on display of line numbers. This mode has a globalized variant, global-display-line-numbers-mode. The user option display-line-numbers-type controls which sub-mode of line-number display, described above, these modes will activate.

Note that line numbers are not displayed in the minibuffer and in the tooltips, even if you turn on display-line-numbers-mode globally.

When Emacs displays relative line numbers, you can control the number displayed before the current line, the line showing point. By default, Emacs displays the absolute number of the current line there, even though all the other line numbers are relative. If you customize the variable display-line-numbers-current-absolute to a nil value, the number displayed for the current line will be zero. This is handy if you don’t care about the number of the current line, and want to leave more horizontal space for text in large buffers.

In a narrowed buffer (see Narrowing) lines are normally numbered starting at the beginning of the narrowing. However, if you customize the variable display-line-numbers-widen to a non-nil value, line numbers will disregard any narrowing and will start at the first character of the buffer.

If the value of display-line-numbers-offset is non-zero, it is added to each absolute line number, and lines are counted from the beginning of the buffer, as if display-line-numbers-widen were non-nil. It has no effect when set to zero, or when line numbers are not absolute.

In selective display mode (see Selective Display), and other modes that hide many lines from display (such as Outline and Org modes), you may wish to customize the variables display-line-numbers-width-start and display-line-numbers-grow-only, or set display-line-numbers-width to a large enough value, to avoid occasional miscalculations of space reserved for the line numbers.

The line numbers are displayed in a special face line-number. The current line number is displayed in a different face, line-number-current-line, so you can make the current line’s number have a distinct appearance, which will help locating the line showing point. Additional faces line-number-major-tick and line-number-minor-tick can be used to highlight the line numbers of lines which are a multiple of certain numbers. Customize display-line-numbers-major-tick and display-line-numbers-minor-tick respectively to set those numbers.

The variable line-spacing controls the vertical spacing between lines. It can be set to an integer (specifying pixels) or a float (specifying spacing relative to the default frame font height). You can also set this variable to a cons cell of integers or floats, such as (top . bottom). When set to a cons cell, the spacing is distributed above and below the line, allowing for text to be vertically centered within the line height. See also Line Height in The Emacs Lisp Reference Manual.

If the variable visible-bell is non-nil, Emacs attempts to make the whole screen blink when it would normally make an audible bell sound. This variable has no effect if your terminal does not have a way to make the screen blink.

The variable echo-keystrokes controls the echoing of multi-character keys; its value is the number of seconds of pause required to cause echoing to start, or zero, meaning don’t echo at all. The value takes effect when there is something to echo. See The Echo Area.

If the variable echo-keystrokes-help is non-nil (the default), the multi-character key sequence echo shown according to echo-keystrokes will include a short help text about keys which will invoke describe-prefix-bindings (see Other Help Commands) to show the list of commands for the prefix you already typed. For a related help facility, see which-key.

On graphical displays, Emacs displays the mouse pointer as an hourglass if Emacs is busy. To disable this feature, set the variable display-hourglass to nil. The variable hourglass-delay determines the number of seconds of busy time before the hourglass is shown; the default is 1.

If the mouse pointer lies inside an Emacs frame, Emacs makes it invisible each time you type a character to insert text, to prevent it from obscuring the text. (To be precise, the hiding occurs when you type a self-inserting character. See Inserting Text.) Moving the mouse pointer makes it visible again. To disable this feature, set the variable make-pointer-invisible to nil.

On graphical displays, the variable underline-minimum-offset determines the minimum distance between the baseline and underline, in pixels, for underlined text. By default, the value is 1; increasing it may improve the legibility of underlined text for certain fonts. (However, Emacs will never draw the underline below the current line area.) The variable x-underline-at-descent-line determines how to draw underlined text. The default is nil, which means to draw it at the baseline level of the font; if you change it to t, Emacs draws the underline at the same height as the font’s descent line. (If non-default line spacing was specified for the underlined text, see Line Height in The Emacs Lisp Reference Manual, Emacs draws the underline below the additional spacing.)

The variable overline-margin specifies the vertical position of an overline above the text, including the height of the overline itself, in pixels; the default is 2.

On some text terminals, bold face and inverse video together result in text that is hard to read. Call the function tty-suppress-bold-inverse-default-colors with a non-nil argument to suppress the effect of bold-face in this case.

Raw bytes are displayed in octal format by default, for example a byte with a decimal value of 128 is displayed as \200. To change display to the hexadecimal format of \x80, set the variable display-raw-bytes-as-hex to t. Care may be needed when interpreting a raw byte when copying text from a terminal containing an Emacs session, or when a terminal’s escape-glyph face looks like the default face. For example, by default Emacs displays the four characters ‘\’, ‘2’, ‘0’, ‘0’ with the same characters it displays a byte with decimal value 128. The problem can be worse with hex displays, where the raw byte 128 followed by the character ‘7’ is displayed as \x807, which Emacs Lisp reads as the single character U+0807 SAMARITAN LETTER IT; this confusion does not occur with the corresponding octal display \2007 because octal escapes contain at most three digits.