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30.4.3.10 Font and Color Parameters

These frame parameters control the use of fonts and colors.

font-backend

A list of symbols, specifying the font backends to use for drawing characters on the frame, in order of priority. In Emacs built without Cairo drawing on X, there are currently three potentially available font backends: x (the X core font driver), xft (the Xft font driver), and xfthb (the Xft font driver with HarfBuzz text shaping). If built with Cairo drawing, there are also three potentially available font backends on X: x, ftcr (the FreeType font driver on Cairo), and ftcrhb (the FreeType font driver on Cairo with HarfBuzz text shaping). When Emacs is built with HarfBuzz, the default font driver is ftcrhb, although use of the ftcr driver is still possible, but not recommended. On MS-Windows, there are currently three available font backends: gdi (the core MS-Windows font driver), uniscribe (font driver for OTF and TTF fonts with text shaping by the Uniscribe engine), and harfbuzz (font driver for OTF and TTF fonts with HarfBuzz text shaping) (see Windows Fonts in The GNU Emacs Manual). The harfbuzz driver is similarly recommended. On Haiku, there can be several font drivers (see Haiku Fonts in The GNU Emacs Manual).

On other systems, there is only one available font backend, so it does not make sense to modify this frame parameter.

background-mode

This parameter is either dark or light, according to whether the background color is a light one or a dark one.

tty-color-mode ¶

This parameter overrides the terminal’s color support as given by the system’s terminal capabilities database in that this parameter’s value specifies the color mode to use on a text terminal. The value can be either a symbol or a number. A number specifies the number of colors to use (and, indirectly, what commands to issue to produce each color). For example, (tty-color-mode . 8) specifies use of the ANSI escape sequences for 8 standard text colors. A value of −1 turns off color support.

If the parameter’s value is a symbol, it specifies a number through the value of tty-color-mode-alist, and the associated number is used instead.

screen-gamma ¶

If this is a number, Emacs performs gamma correction which adjusts the brightness of all colors. The value should be the screen gamma of your display.

Usual PC monitors have a screen gamma of 2.2, so color values in Emacs, and in X windows generally, are calibrated to display properly on a monitor with that gamma value. If you specify 2.2 for screen-gamma, that means no correction is needed. Other values request correction, designed to make the corrected colors appear on your screen the way they would have appeared without correction on an ordinary monitor with a gamma value of 2.2.

If your monitor displays colors too light, you should specify a screen-gamma value smaller than 2.2. This requests correction that makes colors darker. A screen gamma value of 1.5 may give good results for LCD color displays.

alpha ¶

This parameter specifies the opacity of the frame, on graphical displays that support variable opacity. It should be an integer between 0 and 100, where 0 means completely transparent and 100 means completely opaque. It can also have a nil value, which tells Emacs not to set the frame opacity (leaving it to the window manager).

To prevent the frame from disappearing completely from view, the variable frame-alpha-lower-limit defines a lower opacity limit. If the value of the frame parameter is less than the value of this variable, Emacs uses the latter. By default, frame-alpha-lower-limit is 20.

The alpha frame parameter can also be a cons cell (active . inactive), where active is the opacity of the frame when it is selected, and inactive is the opacity when it is not selected.

Some window systems do not support the alpha parameter for child frames (see Child Frames).

alpha-background ¶

Sets the background transparency of the frame. Unlike the alpha frame parameter, this only controls the transparency of the background while keeping foreground elements such as text fully opaque. It should be an integer between 0 and 100, where 0 means completely transparent and 100 means completely opaque (default).

The following frame parameters are semi-obsolete in that they are automatically equivalent to particular face attributes of particular faces (see Standard Faces in The Emacs Manual):

font

The name of the font for displaying text in the frame. This is a string, either a valid font name for your system or the name of an Emacs fontset (see Fontsets). It is equivalent to the font attribute of the default face.

foreground-color

The color to use for characters. It is equivalent to the :foreground attribute of the default face.

background-color

The color to use for the background of characters. It is equivalent to the :background attribute of the default face.

mouse-color

The color for the mouse pointer. It is equivalent to the :background attribute of the mouse face.

cursor-color

The color for the cursor that shows point. It is equivalent to the :background attribute of the cursor face.

border-color

The color for the border of the frame. It is equivalent to the :background attribute of the border face.

scroll-bar-foreground

If non-nil, the color for the foreground of scroll bars. It is equivalent to the :foreground attribute of the scroll-bar face.

scroll-bar-background

If non-nil, the color for the background of scroll bars. It is equivalent to the :background attribute of the scroll-bar face.