pub(crate) unsafe fn install_top_level_focus_restore_hook(hwnd: *mut c_void)Expand description
Subclass a top-level window’s WndProc to handle WM_ACTIVATE: when the
window is being activated (wparam != WA_INACTIVE), look up the last
intentionally-focused child for this root in
LAST_FOCUSED_BY_ROOT and SetFocus it. Closes the
alt-tab-back-and-input-drops bug.
Spec: docs/specs/SPEC_WINDOW_REACTIVATE_FOCUS_RESTORE_2026_05_23.md
§5.1.3.
SAFE on the main CEF Views window: this hook ONLY observes WM_ACTIVATE
and ALWAYS passes the message through to the original WndProc. No
message is short-circuited. That is the crucial difference from
install_frameless_resize_hook, which returns early for
WM_NCCALCSIZE / WM_NCACTIVATE and so MUST NOT be installed on main.
Idempotent: re-calling on an already-hooked HWND is a no-op.