Theme

Theme

Print the current desktop environment theme

Module type	theme
Default order	24 (only used by --gen-config)
Module source	src/modules/theme/theme.c
Detection source	src/detection/theme/

Prints the theme the desktop is currently using. Two independent parts are collected and joined with , in the default output.

Theme: Breeze (Dark) [Qt], Adwaita [GTK2/3/4]
Theme: Fluent
Theme: Aqua

{theme1} is the window-manager / Qt side, {theme2} the GTK side. Only one of them is filled on most systems — on Windows and macOS the whole answer sits in {theme1}, and a GTK-only desktop fills {theme2} alone.

Platform support

Platform	Implementation	Notes
Linux	theme_linux.c	Qt/Plasma from the Qt detector, GTK2/3/4 from the GTK detector
Android	theme_linux.c	Same file
FreeBSD / NetBSD / OpenBSD / DragonFly	theme_linux.c	Same file
Solaris / illumos	theme_linux.c	Same file
GNU/Hurd	theme_linux.c	Same file
macOS	theme_apple.c	Derived from the reported macOS version
Windows	theme_windows.c	Derived from the reported Windows version and the detected window manager
Haiku	theme_nosupport.c	Stub: always reports Not supported on this platform

Configuration

Key	Type	Default	Description
key	string	Theme	Module key. A single space hides the key and the separator
keyColor	color	–	Overrides display.color.keys
keyIcon	string	built-in glyph	Printed when display.key.type includes the icon bit. Any glyph works; "" prints none.
keyWidth	integer	–	Overrides display.key.width
outputColor	color	–	Overrides display.color.output
format	string	–	Custom output format (see below)
condition	object	–	Show the module only if the conditions match

There are no module-specific options.

Format string

Run fastfetch -h theme-format for the authoritative list.

Variable	Description
{theme1}	Theme part 1 — Qt / window-manager side
{theme2}	Theme part 2 — GTK side

Neither is marked * in the help output, so neither is available in the key format.

Both are empty strings when nothing was found for that side, so a format that prints them unconditionally can produce empty brackets:

{ "type": "theme", "format": "[{theme1}][{theme2}]" }

Theme: [Fluent][]

JSON output

[
    {
        "type": "Theme",
        "result": {
            "theme1": "Fluent",
            "theme2": ""
        }
    }
]

• Both keys are always present. An unfilled side is "", never null or absent.
• On failure the object carries error instead and has no result.
• The key order is theme1, theme2.

Examples

// Only the GTK theme, and hide the module when there is none
{ "type": "theme", "format": "{?theme2}{theme2}{?}" }

// A compact single-value form for a status bar
{ "type": "theme", "format": "{theme1}{?theme2} / {theme2}{?}" }

Pitfalls

• A successful detection can still print nothing. Neither theme_windows.c nor theme_apple.c ever returns an error: they fill what they can and return nullptr. On Windows, if the detected window manager is neither dwm.exe nor explorer.exe, both parts stay empty and the default output is a bare Theme:. On macOS, an OS version that does not start with a digit has the same effect.
• On Windows the theme name is not read from a theme file's contents. It is the file name of HKCU\…\Themes → CurrentTheme with the extension stripped and the first letter capitalised — so a renamed .theme file produces that name, and the built-in themes show up as Fluent, Metro or Aero based on the reported Windows version instead.
• The Windows version mapping has two separate ladders. A version above 1000 is treated as a Windows Server release (>= 2016 → Fluent, >= 2012 → Metro, else Aero); anything else is a client release (>= 10 → Fluent, >= 8 → Metro, else Aero). The version comes from the OS module, so a spoofed or unusual version string changes this answer.
• macOS reports a fixed name per version range, not the actual appearance. > 15 is Liquid Glass, < 10 is Platinum, and everything in between is Aqua. The value says nothing about light or dark mode — that is the WMTheme module's job.
• A TTY reports an error, not an empty theme. On Unix the module returns Theme isn't supported in TTY when the display server is the TTY protocol, and No themes found when Qt, GTK2, GTK3 and GTK4 all came back empty. Both go through ffPrintError() and are therefore invisible unless display.showErrors is true.
• The Linux side merges three GTK versions into one string. ffParseGTK() compares the GTK2, GTK3 and GTK4 themes case-insensitively and collapses the ones that agree, annotating the result as [GTK2/3/4], [GTK2/3], … [GTK4], [GTK2], … [GTK3/4] or [GTK2], … [GTK3], … [GTK4]. {theme2} is therefore not a single theme name.
• The Qt part is annotated too. When a Plasma widget style or colour scheme was found, [Qt] is appended to {theme1}; a colour scheme that starts with the widget style has that prefix removed before it is put in parentheses (Breeze + BreezeDark → Breeze (Dark)).
• The two parts are independent. A machine can report a Qt theme and no GTK theme, or the other way round; {theme1} being empty does not mean detection failed.

Implementation

ffDetectTheme() fills an FFThemeResult — two FFstrbufs, theme1 and theme2 — and returns a const char* error (or nullptr). ffPrintTheme() joins the two with , when both are set, and ffGenerateThemeJsonResult() writes both keys.

Linux

ffConnectDisplayServer() supplies the display-server result; the TTY protocol short-circuits with an error. Then ffDetectQt(), ffDetectGTK2(), ffDetectGTK3() and ffDetectGTK4() are called — if all five values (widget style, colour scheme and the three themes) are empty, the module reports No themes found. Otherwise ffParseGTK() builds theme2 from the GTK themes and theme1 is built from the Plasma widget style and colour scheme, with [Qt] appended when either is present.

macOS

ffDetectTheme() reads the OS module's version and parses its leading integer with strtoul(). When the parse consumed at least one character the version is classified; otherwise nothing is set. There is no plist or API query behind it.

Windows

ffDetectTheme() compares the display server's wmProcessName: dwm.exe selects the version-based name, explorer.exe yields Basic, and anything else leaves both parts empty. The Windows Server / client split is the ver > 1000 test described above.