QQuickTableView: build the table when the component is finalized

componentComplete() is called on us after all static values
have been assigned, but before bindings to any ancestors
have been evaluated. Especially this means that if our size
is bound to the parents size, it will not be ready at that point.
Since we cannot build the table without knowing our own size, we
waited for the updatePolish() call before we started to build
the table.

The problem with that strategy, is that any asynchronous loaders that
TableView might be inside would already be finished by the time
we received the updatePolish() call. The result would be that we
ended up loading all the delegate items synchronously instead of
asynchronously. (As soon as a loader has finished loading the initial
item, async loading will no longer be used).

This patch will therefore add a componentFinalized function that gets
called after all bindings have been evaluated, but before the loader
has finished. When receiving this call, we load the delegate items (and
build the table).

A nice side effect is that the table will also be ready
by the time Component.onCompeted is emitted to the QML
app. This means that e.g contentWidth/Height has valid values.

Change-Id: Ief92d2fecfaea54f6191da116ed4ba79cc673b01
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

3 files changed, 39 insertions, 0 deletions

diff --git a/src/quick/items/qquicktableview.cpp b/src/quick/items/qquicktableview.cpp
index 67a9a3a7c2..1e2ecf9047 100644
--- a/src/quick/items/qquicktableview.cpp
+++ b/src/quick/items/qquicktableview.cpp
@@ -1946,6 +1946,39 @@ void QQuickTableView::viewportMoved(Qt::Orientations orientation)
         d->updatePolish();
 }
 
+void QQuickTableViewPrivate::_q_componentFinalized()
+{
+    // Now that all bindings are evaluated, and we know
+    // our final geometery, we can build the table.
+    qCDebug(lcTableViewDelegateLifecycle);
+    updatePolish();
+}
+
+void QQuickTableViewPrivate::registerCallbackWhenBindingsAreEvaluated()
+{
+    // componentComplete() is called on us after all static values have been assigned, but
+    // before bindings to any anchestors has been evaluated. Especially this means that
+    // if our size is bound to the parents size, it will still be empty at that point.
+    // And we cannot build the table without knowing our own size. We could wait until we
+    // got the first updatePolish() callback, but at that time, any asynchronous loaders that we
+    // might be inside have already finished loading, which means that we would load all
+    // the delegate items synchronously instead of asynchronously. We therefore add a componentFinalized
+    // function that gets called after all the bindings we rely on has been evaluated.
+    // When receiving this call, we load the delegate items (and build the table).
+    Q_Q(QQuickTableView);
+    QQmlEnginePrivate *engPriv = QQmlEnginePrivate::get(qmlEngine(q));
+    static int finalizedIdx = -1;
+    if (finalizedIdx < 0)
+        finalizedIdx = q->metaObject()->indexOfSlot("_q_componentFinalized()");
+    engPriv->registerFinalizeCallback(q, finalizedIdx);
+}
+
+void QQuickTableView::componentComplete()
+{
+    QQuickFlickable::componentComplete();
+    d_func()->registerCallbackWhenBindingsAreEvaluated();
+}
+
 #include "moc_qquicktableview_p.cpp"
 
 QT_END_NAMESPACE
diff --git a/src/quick/items/qquicktableview_p.h b/src/quick/items/qquicktableview_p.h
index 45e20027ba..9fcd4c6c17 100644
--- a/src/quick/items/qquicktableview_p.h
+++ b/src/quick/items/qquicktableview_p.h
@@ -128,10 +128,13 @@ Q_SIGNALS:
 protected:
     void geometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry) override;
     void viewportMoved(Qt::Orientations orientation) override;
+    void componentComplete() override;
 
 private:
     Q_DISABLE_COPY(QQuickTableView)
     Q_DECLARE_PRIVATE(QQuickTableView)
+
+    Q_PRIVATE_SLOT(d_func(), void _q_componentFinalized())
 };
 
 class Q_QUICK_PRIVATE_EXPORT QQuickTableViewAttached : public QObject
diff --git a/src/quick/items/qquicktableview_p_p.h b/src/quick/items/qquicktableview_p_p.h
index 6bf3de76df..4f5c819887 100644
--- a/src/quick/items/qquicktableview_p_p.h
+++ b/src/quick/items/qquicktableview_p_p.h
@@ -353,6 +353,9 @@ public:
     void columnsRemovedCallback(const QModelIndex &parent, int begin, int end);
     void modelResetCallback();
 
+    void _q_componentFinalized();
+    void registerCallbackWhenBindingsAreEvaluated();
+
     inline QString tableLayoutToString() const;
     void dumpTable() const;
 };