Info Catalog
elisp: Terminal Type
elisp: Editing Types
elisp: Frame Configuration Type
2.4.6 Window Configuration Type
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A “window configuration” stores information about the positions, sizes,
and contents of the windows in a frame, so you can recreate the same
arrangement of windows later.
Window configurations do not have a read syntax; their print syntax
looks like ‘#<window-configuration>’. 
Window Configurations,
for a description of several functions related to window configurations.