Module view 

Viewport motions and the jump-back cluster (the vim canon wave): Ctrl-d/u/f/b scroll, zz/zt/zb + H/M/L viewport placement, ZZ write-quit, Ctrl-^ alternate buffer, gv/gi re-entry, g;/g, the change list. Viewport geometry comes from scroll_to_cursor, which the render loop feeds every frame — the pane’s view_rows is the editor’s single source of truth for “how tall is the screen”.