window_manager: direction selectors along z axis

require all nodes on paths to lowest common ancestor of current +
prev/next nodes to be z-split nodes.

src/message.c

@@ -1131,6 +1131,28 @@ static struct selector parse_window_selector(FILE *rsp, char **message, struct w
         } else {
             daemon_fail(rsp, "could not locate the selected window.\n");
         }
+    } else if (token_equals(result.token, ARGUMENT_WINDOW_DIR_ABOVE)) {
+        if (acting_window) {
+            struct window *closest_window = window_manager_find_managed_window_above(&g_space_manager, &g_window_manager, acting_window);
+            if (closest_window) {
+                result.window = closest_window;
+            } else {
+                daemon_fail(rsp, "could not locate a managed window above.\n");
+            }
+        } else {
+            daemon_fail(rsp, "could not locate the selected window.\n");
+        }
+    } else if (token_equals(result.token, ARGUMENT_WINDOW_DIR_BELOW)) {
+        if (acting_window) {
+            struct window *closest_window = window_manager_find_managed_window_below(&g_space_manager, &g_window_manager, acting_window);
+            if (closest_window) {
+                result.window = closest_window;
+            } else {
+                daemon_fail(rsp, "could not locate a managed window below.\n");
+            }
+        } else {
+            daemon_fail(rsp, "could not locate the selected window.\n");
+        }
     } else if (token_equals(result.token, ARGUMENT_WINDOW_SEL_MOUSE)) {
         struct window *mouse_window = window_manager_find_window_below_cursor(&g_window_manager);
         if (mouse_window) {

src/view.c

@@ -271,6 +271,29 @@ struct window_node *window_node_find_next_leaf(struct window_node *node)
     return window_node_find_first_leaf(node->parent->right->left);
 }
 
+struct window_node *window_node_find_common_ancestor(struct window_node *node, struct window_node *a, struct window_node *b) {
+    if (!node) return NULL;
+    if (node == a || node == b) return node;
+
+    struct window_node *left = window_node_find_common_ancestor(node->left, a, b);
+    struct window_node *right = window_node_find_common_ancestor(node->right, a, b);
+
+    if (left && right) return node;
+
+    return left ? left : right;
+}
+
+bool window_nodes_are_stacked(struct window_node *ancestor, struct window_node *node) {
+    do {
+        node = node->parent;
+
+        if (node->split != SPLIT_Z)
+            return false;
+    } while (node != ancestor);
+
+    return true;
+}
+
 void window_node_rotate(struct window_node *node, int degrees)
 {
     if ((degrees ==  90 && node->split == SPLIT_Y) ||

src/window_manager.c

@@ -707,6 +707,42 @@ struct window *window_manager_find_closest_window_in_direction(struct window_man
     return result;
 }
 
+struct window *window_manager_find_managed_window_below(struct space_manager *sm, struct window_manager *wm, struct window *window)
+{
+    struct view *view = space_manager_find_view(sm, space_manager_active_space());
+    if (!view) return NULL;
+
+    struct window_node *node = view_find_window_node(view, window->id);
+    if (!node) return NULL;
+
+    struct window_node *prev = window_node_find_prev_leaf(node);
+    if (!prev) return NULL;
+
+    struct window_node *ancestor = window_node_find_common_ancestor(view->root, node, prev);
+    if (!window_nodes_are_stacked(ancestor, node) || !window_nodes_are_stacked(ancestor, prev))
+        return NULL;
+
+    return window_manager_find_window(wm, prev->window_id);
+}
+
+struct window *window_manager_find_managed_window_above(struct space_manager *sm, struct window_manager *wm, struct window *window)
+{
+    struct view *view = space_manager_find_view(sm, space_manager_active_space());
+    if (!view) return NULL;
+
+    struct window_node *node = view_find_window_node(view, window->id);
+    if (!node) return NULL;
+
+    struct window_node *next = window_node_find_next_leaf(node);
+    if (!next) return NULL;
+
+    struct window_node *ancestor = window_node_find_common_ancestor(view->root, node, next);
+    if (!window_nodes_are_stacked(ancestor, node) || !window_nodes_are_stacked(ancestor, next))
+        return NULL;
+
+    return window_manager_find_window(wm, next->window_id);
+}
+
 struct window *window_manager_find_prev_managed_window(struct space_manager *sm, struct window_manager *wm, struct window *window)
 {
     struct view *view = space_manager_find_view(sm, space_manager_active_space());

src/window_manager.h

@@ -95,6 +95,8 @@ struct window *window_manager_find_window_at_point(struct window_manager *wm, CG
 struct window *window_manager_find_window_below_cursor(struct window_manager *wm);
 struct window *window_manager_find_closest_managed_window_in_direction(struct window_manager *wm, struct window *window, int direction);
 struct window *window_manager_find_closest_window_in_direction(struct window_manager *wm, struct window *window, int direction);
+struct window *window_manager_find_managed_window_below(struct space_manager *sm, struct window_manager *wm, struct window *window);
+struct window *window_manager_find_managed_window_above(struct space_manager *sm, struct window_manager *wm, struct window *window);
 struct window *window_manager_find_prev_managed_window(struct space_manager *sm, struct window_manager *wm, struct window *window);
 struct window *window_manager_find_next_managed_window(struct space_manager *sm, struct window_manager *wm, struct window *window);
 struct window *window_manager_find_first_managed_window(struct space_manager *sm, struct window_manager *wm);