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1.8.3 Terminal Redisplay

Redisplay is substantially different on a terminal. Hemlock uses different algorithms, and different parameters control redisplay and screen management.

Terminal redisplay uses the Unix termcap database to find out how to use a terminal. Hemlock is useful with terminals that lack capabilities for inserting and deleting lines and characters, and some terminal emulators implement these operations very inefficiently (such as xterm). If you realize poor performance when scrolling, create a termcap entry that excludes these capabilities.

Hemlock Variable: Scroll Redraw Ratio (initial value nil) ¶

This is a ratio of "inserted" lines to the size of a window. When this ratio is exceeded, insert/delete line terminal optimization is aborted, and every altered line is simply redrawn as efficiently as possible. For example, setting this to 1/4 will cause scrolling commands to redraw the entire window instead of moving the bottom two lines of the window to the top (typically 3/4 of the window is being deleted upward and inserted downward, hence a redraw); however, commands like New Line and Open Line will still work efficiently, inserting a line and moving the rest of the window’s text downward.