The Life Pattern Archive
GtkLife comes with the Life Pattern Archive, as amassed by Alan Hensel. By default, a sidebar listing these patterns is displayed to the left of the grid. Click on a pattern name to load it. You can set a different patterns directory, or disable the sidebar, from Preferences. Of course, you can also use the standard File->Open command to load a pattern file from anywhere.
Mouse Operations
Left-click to toggle a cell between alive and dead. Drag the mouse to continue either setting or erasing cells. To recenter the screen around a particular point, right-click on it.
Useful Keybindings
Notes on Speed
Speed is set in generations per second. By default, the program will start to drop frames if it finds itself falling behind---that is, the next generation will be computed, but the screen will not update during that tick. This greatly improves performance, especially if you don't have 2D acceleration on your video card. If you want to temporarily disable frame skipping, deselect the check box in the Speed dialog (accessible from the "Run" menu). Go to Preferences/Run to disable it entirely.
File Format
Pattern files are loaded and saved in the .LIF file format used by the Life Pattern Catalog. This format is recognized by a number of other Life programs, including XLife and the MS Windows Life32. It has one niggly limitation: the pattern description stored in the file is limited to 22 lines by 78 characters. GtkLife will complain if your description goes out of those bounds.