processEvent

pub fn processEvent(self: *MenuWidget, e: *Event) void {
    switch (e.evt) {
        .mouse => |me| {
            if (me.action == .position) {
                if (dvui.mouseTotalMotion().nonZero()) {
                    if (dvui.dataGet(null, self.data().id, "_child_popup", ?Rect.Physical) orelse null) |r| {
                        const center = Point.Physical{ .x = r.x + r.w / 2, .y = r.y + r.h / 2 };
                        const cw = dvui.currentWindow();
                        const to_center = center.diff(cw.mouse_pt_prev);
                        const movement = cw.mouse_pt.diff(cw.mouse_pt_prev);
                        const dot_prod = movement.x * to_center.x + movement.y * to_center.y;
                        const cos = dot_prod / (to_center.length() * movement.length());
                        if (std.math.acos(cos) < std.math.pi / 3.0) {
                            // there is an existing submenu and motion is
                            // towards the popup, so eat this event to
                            // prevent any menu items from focusing
                            e.handle(@src(), self.data());
                        }
                    }
                }

                if (self.mouse_mode and !e.handled) {
                    self.mouse_over = true;
                }
            }
        },
        else => {},
    }
}