View ▸ Split (Ctrl+Alt+S): a second live view of the editor's state, stacked
below the first and editable the same way. The panes share a width, so the
second renders the pagination the first measures — pageBreaks, columnsFlow
and tabStops skip the pass on a split pane rather than run it twice.
Every widget decoration now builds its DOM in a function: two views render
one decoration set, and a shared node is taken back and forth between the
two documents until the tab locks up (measured on a two-page document).
Steffen Becker
41ab0ef06c