New util function: BLI_listbases_swaplinks

2 files changed, 29 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_listbase.h b/source/blender/blenlib/BLI_listbase.h
index 96349a7b066..4ec222c073e 100644
--- a/source/blender/blenlib/BLI_listbase.h
+++ b/source/blender/blenlib/BLI_listbase.h
@@ -76,6 +76,7 @@ int  BLI_listbase_count(const struct ListBase *listbase) ATTR_WARN_UNUSED_RESULT
 void BLI_freelinkN(struct ListBase *listbase, void *vlink) ATTR_NONNULL(1);
 
 void BLI_listbase_swaplinks(struct ListBase *listbase, void *vlinka, void *vlinkb) ATTR_NONNULL(1, 2);
+void BLI_listbases_swaplinks(struct ListBase *listbasea, struct ListBase *listbaseb, void *vlinka, void *vlinkb) ATTR_NONNULL(2, 3);
 
 void BLI_movelisttolist(struct ListBase *dst, struct ListBase *src) ATTR_NONNULL(1, 2);
 void BLI_duplicatelist(struct ListBase *dst, const struct ListBase *src) ATTR_NONNULL(1, 2);
diff --git a/source/blender/blenlib/intern/listbase.c b/source/blender/blenlib/intern/listbase.c
index c9bf4976ae8..3bf0dfa09fa 100644
--- a/source/blender/blenlib/intern/listbase.c
+++ b/source/blender/blenlib/intern/listbase.c
@@ -170,6 +170,34 @@ void BLI_listbase_swaplinks(ListBase *listbase, void *vlinka, void *vlinkb)
 }
 
 /**
+ * Swaps \a vlinka and \a vlinkb from their respective lists. Assumes they are both already in their lista!
+ */
+void BLI_listbases_swaplinks(ListBase *listbasea, ListBase *listbaseb, void *vlinka, void *vlinkb)
+{
+	Link *linka = vlinka;
+	Link *linkb = vlinkb;
+	Link linkc = {NULL};
+
+	if (!linka || !linkb) {
+		return;
+	}
+
+	/* Temporary link to use as placeholder of the links positions */
+	BLI_insertlinkafter(listbasea, linka, &linkc);
+
+	/* Bring linka into linkb position */
+	BLI_remlink(listbasea, linka);
+	BLI_insertlinkafter(listbaseb, linkb, linka);
+
+	/* Bring linkb into linka position */
+	BLI_remlink(listbaseb, linkb);
+	BLI_insertlinkafter(listbasea, &linkc, linkb);
+
+	/* Remove temporary link */
+	BLI_remlink(listbasea, &linkc);
+}
+
+/**
  * Removes the head from \a listbase and returns it.
  */
 void *BLI_pophead(ListBase *listbase)