QQmlAdaptorModel: prepare js list models for recycling support

This patch will enable delegate item recycling for js list models.
So if you e.g set "model: [1, 2, 3, 4]" on a TableView, the delegates
can be recycled.

The patch will override the notify function. This function is called from
QQmlDelegateModel whenever the modelData that the delegate item
depends on, changes. This again is needed to trigger all the modelData
bindings in the item to update.

Note that this function will only be used for recycling items. The model
classes don't listen for changes done to js list models, meaning that
the function will otherwise never be called (which is why it was never
implemented, I guess).

Auto testing this will be included with the patches that implements
delegate recycling for TableView.

Change-Id: I49185bdbaaacc3ccbd94c99cc66d9a1998452f68
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

1 files changed, 19 insertions, 4 deletions

diff --git a/src/qml/util/qqmladaptormodel.cpp b/src/qml/util/qqmladaptormodel.cpp
index 32bf43159a..e460c376da 100644
--- a/src/qml/util/qqmladaptormodel.cpp
+++ b/src/qml/util/qqmladaptormodel.cpp
@@ -566,10 +566,11 @@ public:
 
     void setModelData(const QVariant &data)
     {
-        if (index == -1 && data != cachedData) {
-            cachedData = data;
-            emit modelDataChanged();
-        }
+        if (data == cachedData)
+            return;
+
+        cachedData = data;
+        emit modelDataChanged();
     }
 
     static QV4::ReturnedValue get_modelData(const QV4::FunctionObject *b, const QV4::Value *thisObject, const QV4::Value *, int)
@@ -666,6 +667,20 @@ public:
                 index, row, column,
                 index >= 0 && index < model.list.count() ? model.list.at(index) : QVariant());
     }
+
+    bool notify(const QQmlAdaptorModel &model, const QList<QQmlDelegateModelItem *> &items, int index, int count, const QVector<int> &) const override
+    {
+        for (auto modelItem : items) {
+            const int modelItemIndex = modelItem->index;
+            if (modelItemIndex < index || modelItemIndex >= index + count)
+                continue;
+
+            auto listModelItem = static_cast<QQmlDMListAccessorData *>(modelItem);
+            QVariant updatedModelData = model.list.at(listModelItem->index);
+            listModelItem->setModelData(updatedModelData);
+        }
+        return true;
+    }
 };
 
 //-----------------------------------------------------------------