Function draw_frame 

pub fn draw_frame(
    frame: &mut Frame<'_>,
    app: &App,
    snap: &DocumentSnapshot,
) -> Option<(u32, u32)>

Returns the completion-docs side popup’s inner (rows, cols) when it is shown this frame (PU.5c) — None otherwise. The runtime loop feeds this back via App::set_completion_docs_viewport so build_cells_panes sizes the PaneId::COMPLETION_DOCS matrix. Computed at the exact draw site (with the real chunks[1] buffer area) because the docs popup is cursor-anchored — position-dependent, unlike the floating popup whose geometry the runtime reconstructs (popup_feedback_inner_dims).