Fix Item::suggestedRect() when the parentContainer() wasn't root

src/private/multisplitter/Item.cpp

@@ -1189,9 +1189,16 @@ QRect ItemContainer::suggestedDropRect(QSize minSize, const Item *relativeTo, Lo
     const int count = sizes.count();
 
     if (relativeTo && count == 1) {
-        // If it's the only item then the result is that it's relative to the whole layout
-        // So simplify our code
+
+        // When the container only has one item we can do some simplifications
+
+        if (isRoot()) {
+            // Means the result is relative to the whole window
             relativeTo = nullptr;
+        } else {
+            // Do it relative to this container instead
+            return parentContainer()->suggestedDropRect(minSize, this, loc);
+        }
     }
 
     if (relativeTo) {

src/private/multisplitter/tests/tst_multisplitter.cpp

@@ -185,6 +185,7 @@ private Q_SLOTS:
     void tst_ensureEnoughSize();
     void tst_turnIntoPlaceholder();
     void tst_suggestedRect();
+    void tst_suggestedRect2();
     void tst_insertAnotherRoot();
     void tst_misc1();
     void tst_misc2();
@@ -829,6 +830,23 @@ void TestMultiSplitter::tst_suggestedRect()
     QVERIFY(serializeDeserializeTest(root));
 }
 
+void TestMultiSplitter::tst_suggestedRect2()
+{
+    // Tests a bug where the inner drop locations didn't work when there was a nested container
+    // Like container >> container >> Item
+
+    auto root1 = createRoot();
+    auto root2 = createRoot();
+
+    const QSize minSize(100, 100);
+    Item *item = createItem();
+
+    root2->insertItem(item, Location_OnRight);
+    root1->insertItem(root2.get(), Location_OnRight);
+
+    QVERIFY(item->parentContainer()->suggestedDropRect(minSize, item, Location_OnRight).isValid());
+}
+
 void TestMultiSplitter::tst_insertAnotherRoot()
 {
     {