2.5 UI Themes

UI (colour) themes play a role in two parts: when writing to the console and for the xpce-based development tools such as PceEmacs or the graphical debugger. Coloured console output is based on ansi_format/3. The central message infra structure based on print_message/2 labels message (components) with a Prolog term that specifies the role. This is mapped to concrete colours by means of the hook prolog:console_color/2. Theming the IDE uses xpce class variables that are initialised from Prolog when xpce is loaded.

Themes are implemented as a Prolog file in the file search path library/theme. A theme can be loaded using (for example) the directive below in the user's initialization file (see section 2.2).

:- use_module(library(theme/dark)).

The theme file library(theme/auto) is provided to automatically choose a reasonable theme based on the environment. The current version detects the background color on xterm compatible terminal emulators (found on most Unix systems) and loads the dark theme if the background is‘darkish’.

The following notes apply to the different platforms on which SWI-Prolog is supported:

Unix/Linux

If an xterm compatible terminal emulator is used to run Prolog you may wish to load either an explicit theme or library(theme/auto).

Windows

The swipl-win.exe graphical application can be themed by loading a theme file. The theme file also sets the foreground and background colours for the console.

2.5.1 Status of theme support

Theme support was added in SWI-Prolog 8.1.11. Only part of the IDE tools are covered and the only additional theme (dark) is not net well balanced. The interfaces between the theme file and notably the IDE components is not very well established. Please contribute by improving the dark theme. Once that is complete and properly functioning we can start adding new themes.