The gdefaults file is usually located inside the .crossfire directory.
This file applies to the old gtk-1 client for crossfire,
The newer gtk-2 client uses the gdefaults2 file as configuration file.

At the top of the file one reads :

# This file is generated automatically by gcfclient.
# Manually editing is allowed, however gcfclient may be a bit finicky about
# some of the matching it does.  all comparisons are case sensitive.
# 'True' and 'False' are the proper cases for those two values
# 'True' and 'False' have been replaced with 1 and 0 respectively

Sorted by alphabetical sort:

1. auto_apply_container: < 0 | 1 >
2. cacheimages: < 0 | 1 >
3. command_window: < 1 - 127 >
4. darkness: < 0 | 1 >
5. displaymode: < 0 | 1 | 2 > [ CFG_DM_PIXMAP , CFG_DM_SDL , CFG_DM_OPENGL ]
6. download_all_images: < 0 | 1 >
7. echo_bindings: < 0 | 1 >
8. faceset: < standard | classic >
9. fasttcpsend: < 0 | 1 >
10. fog_of_war: < 0 | 1 >
11. foodbeep: < 0 | 1 >
12. grad_color_bars: < 0 | 1 >
13. iconscale: < 25 - 200 >
14. lighting: < 0 - 3 > [ CFG_LT_NONE , CFG_LT_TILE , CFG_LT_PIXEL , CFG_LT_PIXEL_BEST ]
15. map_height: < 9 - 31 > [ MAP_MAX_SIZE ]
16. map_width: < 9 - 31 > [ MAP_MAX_SIZE ]
17. mapscale: < 25 - 200 >
18. mapscroll: < 0 | 1 >
19. message_timestamping: < 0 | 1 >
20. nosplash: < 0 | 1 >
21. popups: < 0 | 1 >
22. port: 13327 [ EPORT , DEFPORT ]
23. resistances: < 0 | 1 >
24. server: (null)
25. show_grid: < 0 | 1 >
26. showicon: < 0 | 1 >
27. sign_popups: < 0 | 1 >
28. smoothing: < 0 | 1 >
29. sound: < 0 | 1 >
30. sound_server: < cfsndserv | cfsndserv_alsa9 >
31. split: < 0 | 1 >
32. splitinfo: < 0 | 1 >
33. tooltips: < 0 | 1 >
34. trim_info_window: < 0 | 1 >

SDL lighting in pictures: City of Navar around midnight ..

lighting 0 None	lighting 1 Per Tile	lighting 2 Fast per Pixel	lighting 3 Best per Pixel

Values : 0 or 1 – 0 disables popup windows like a separate log-in window, 1 enables them.
Default: 0 ( disabled )

The default is set to 0 inside the source code
in function init_client_vars() in file common/init.c as variable want_config[CONFIG_POPUPS] = FALSE; .

Command-line options : -popups and -nopopups

Behaviour: Most popup-windows might be annoying, while playing the game, but the log-on to a server had been impossible for versions 1.11.0 and below of the GTK-1 client, if that was unset ( 0 ) . To enter a user-name was not possible in the “traditional” Info-Message and Cmd-Line Pane on the right side of the client.
See also

• ChangeLog Popups not the default anymore
• ChangeLog Popups @ v.1.12.0 client GTK1 mixed with GTK2 can not login
• ChangeLog Keyboard input impossible or confusing
• known_client_issues Keyboard input impossible or confusing
• bugs Pressing a keyboard key activates the command-line

This option is only available for the SDL displaymode .
Purpose: It draws a red tile grid-overlay onto the map.
Effect: But this grid vanishes as soon as the player moves.
Implemented: gridline options available under the client config window. MSW 2001-06-17
Client Menu: Client > Configure > Map & Image > Print Grid Overlay (SDL only, slow, useful for debugging, development)

The GTK-2 client does not have such a Menu option to choose anymore; but still has this parameter entry in it's gdefaults2 config file.