1 files changed, 93 insertions, 0 deletions

diff --git a/sway/layout.c b/sway/layout.c
index 377dad47..5f8da9e6 100644
--- a/sway/layout.c
+++ b/sway/layout.c
@@ -1503,3 +1503,96 @@ enum swayc_layouts default_layout(swayc_t *output) {
 bool is_auto_layout(enum swayc_layouts layout) {
         return (layout >= L_AUTO_FIRST) && (layout <= L_AUTO_LAST);
 }
+
+/**
+ * Return the number of children in the slave groups. This corresponds to the children
+ * that are not members of the master group.
+ */
+static inline size_t auto_slave_count(swayc_t *container) {
+        return container->children->length - container->nb_master;
+}
+
+/**
+ * given the index of a container's child, return the index of the first child of the group
+ * which index is a member of.
+ */
+int auto_group_start_index(swayc_t *container, int index) {
+        if (index < 0 || ! is_auto_layout(container->layout)
+                || (size_t) index < container->nb_master) {
+                return 0;
+        } else {
+                size_t grp_sz = auto_slave_count(container) / container->nb_slave_groups;
+                size_t remainder = auto_slave_count(container) % container->nb_slave_groups;
+                int start_idx;
+                int idx2 = (container->nb_slave_groups - remainder) * grp_sz + container->nb_master;
+                if (index < idx2) {
+                        start_idx = ((index - container->nb_master) / grp_sz) * grp_sz + container->nb_master;
+                } else {
+                        start_idx = idx2 + ((index - idx2) / (grp_sz + 1)) * (grp_sz + 1);
+                }
+                return MIN(start_idx, container->children->length);
+        }
+}
+
+/**
+ * given the index of a container's child, return the index of the first child of the group
+ * that follows the one which index is a member of.
+ * This makes the function usable to walk through the groups in a container.
+ */
+int auto_group_end_index(swayc_t *container, int index) {
+        if (index < 0 || ! is_auto_layout(container->layout)) {
+                return container->children->length;
+        } else {
+                int nxt_idx;
+                if ((size_t)index < container->nb_master) {
+                        nxt_idx = container->nb_master;
+                } else {
+                        size_t grp_sz = auto_slave_count(container) / container->nb_slave_groups;
+                        size_t remainder = auto_slave_count(container) % container->nb_slave_groups;
+                        int idx2 = (container->nb_slave_groups - remainder) * grp_sz + container->nb_master;
+                        if (index < idx2) {
+                                nxt_idx = ((index - container->nb_master) / grp_sz + 1) * grp_sz + container->nb_master;
+                        } else {
+                                nxt_idx = idx2 + ((index - idx2) / (grp_sz + 1) + 1) * (grp_sz + 1);
+                        }
+                }
+                return MIN(nxt_idx, container->children->length);
+        }
+}
+
+/**
+ * Return the combined number of master and slave groups in the container.
+ */
+size_t auto_group_count(swayc_t *container) {
+        return MIN(container->nb_slave_groups, auto_slave_count(container)) + (container->nb_master ? 1 : 0);
+}
+
+/**
+ * return the index of the Group containing <index>th child of <container>.
+ * The index is the order of the group along the container's major axis (starting at 0).
+ */
+size_t auto_group_index(swayc_t *container, int index) {
+        if (index < 0) {
+                return 0;
+        }
+        bool master_first = (container->layout == L_AUTO_LEFT || container->layout == L_AUTO_TOP);
+        int nb_slaves = auto_slave_count(container);
+        if ((size_t) index < container->nb_master) {
+                if (master_first || nb_slaves <= 0) {
+                        return 0;
+                } else {
+                        return MIN(container->nb_slave_groups, nb_slaves);
+                }
+        } else {
+                size_t grp_sz = auto_slave_count(container) / container->nb_slave_groups;
+                size_t remainder = auto_slave_count(container) % container->nb_slave_groups;
+                size_t grp_idx;
+                int idx2 = (container->nb_slave_groups - remainder) * grp_sz + container->nb_master;
+                if (index < idx2) {
+                        grp_idx = (index - container->nb_master) / grp_sz;
+                } else {
+                        grp_idx = (container->nb_slave_groups - remainder) + (index - idx2) / (grp_sz + 1) ;
+                }
+                return grp_idx + (master_first ? 1 : 0);
+        }
+}