Add QBlitFramebuffer auto-parenting behavior

As is common with other nodes.

Task-number: QTBUG-65081
Change-Id: I12ccd2fb5344e116f2f5333b73edb4562799543d
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

3 files changed, 62 insertions, 7 deletions

diff --git a/src/render/framegraph/qblitframebuffer.cpp b/src/render/framegraph/qblitframebuffer.cpp
index 505bab96c..629ae04f6 100644
--- a/src/render/framegraph/qblitframebuffer.cpp
+++ b/src/render/framegraph/qblitframebuffer.cpp
@@ -121,7 +121,21 @@ void QBlitFramebuffer::setSource(QRenderTarget *source)
 {
     Q_D(QBlitFramebuffer);
     if (d->m_source != source) {
+        if (d->m_source) {
+            // Remove bookkeeping connection
+            d->unregisterDestructionHelper(d->m_source);
+        }
+
         d->m_source = source;
+
+        if (d->m_source) {
+            // Ensures proper bookkeeping. Calls us back with nullptr in case the rt gets destroyed.
+            d->registerDestructionHelper(d->m_source, &QBlitFramebuffer::setSource, d->m_source);
+
+            if (!d->m_source->parent())
+                d->m_source->setParent(this);
+        }
+
         emit sourceChanged();
     }
 }
@@ -130,7 +144,21 @@ void QBlitFramebuffer::setDestination(QRenderTarget *destination)
 {
     Q_D(QBlitFramebuffer);
     if (d->m_destination != destination) {
+        if (d->m_destination) {
+            // Remove bookkeeping connection
+            d->unregisterDestructionHelper(d->m_destination);
+        }
+
         d->m_destination = destination;
+
+        if (d->m_destination) {
+            // Ensures proper bookkeeping. Calls us back with nullptr in case the rt gets destroyed.
+            d->registerDestructionHelper(d->m_destination, &QBlitFramebuffer::setDestination, d->m_destination);
+
+            if (!d->m_destination->parent())
+                d->m_destination->setParent(this);
+        }
+
         emit destinationChanged();
     }
 }
diff --git a/tests/auto/render/blitframebuffer/tst_blitframebuffer.cpp b/tests/auto/render/blitframebuffer/tst_blitframebuffer.cpp
index 6c70b0e95..26c43b5c2 100644
--- a/tests/auto/render/blitframebuffer/tst_blitframebuffer.cpp
+++ b/tests/auto/render/blitframebuffer/tst_blitframebuffer.cpp
@@ -62,11 +62,11 @@ private Q_SLOTS:
     void checkInitializeFromPeer()
     {
         // GIVEN
-        Qt3DRender::QRenderTarget sourceTarget;
-        Qt3DRender::QRenderTarget destinationTarget;
+        Qt3DRender::QRenderTarget *sourceTarget = new Qt3DRender::QRenderTarget;
+        Qt3DRender::QRenderTarget *destinationTarget = new Qt3DRender::QRenderTarget;
         Qt3DRender::QBlitFramebuffer blitFramebuffer;
-        blitFramebuffer.setSource(&sourceTarget);
-        blitFramebuffer.setDestination(&destinationTarget);
+        blitFramebuffer.setSource(sourceTarget);
+        blitFramebuffer.setDestination(destinationTarget);
         blitFramebuffer.setSourceRect(QRect(0,0,1,1));
         blitFramebuffer.setDestinationRect(QRect(0,0,1,1));
         blitFramebuffer.setSourceAttachmentPoint(Qt3DRender::QRenderTargetOutput::Color1);
@@ -81,8 +81,8 @@ private Q_SLOTS:
             // THEN
             QCOMPARE(backendBlitFramebuffer.isEnabled(), true);
             QCOMPARE(backendBlitFramebuffer.peerId(), blitFramebuffer.id());
-            QCOMPARE(backendBlitFramebuffer.sourceRenderTargetId(), sourceTarget.id());
-            QCOMPARE(backendBlitFramebuffer.destinationRenderTargetId(), destinationTarget.id());
+            QCOMPARE(backendBlitFramebuffer.sourceRenderTargetId(), sourceTarget->id());
+            QCOMPARE(backendBlitFramebuffer.destinationRenderTargetId(), destinationTarget->id());
             QCOMPARE(backendBlitFramebuffer.sourceRect(), QRect(0,0,1,1));
             QCOMPARE(backendBlitFramebuffer.destinationRect(), QRect(0,0,1,1));
             QCOMPARE(backendBlitFramebuffer.sourceAttachmentPoint(), Qt3DRender::QRenderTargetOutput::Color1);
diff --git a/tests/auto/render/qblitframebuffer/tst_qblitframebuffer.cpp b/tests/auto/render/qblitframebuffer/tst_qblitframebuffer.cpp
index 26ef936f6..f6c7e1a8a 100644
--- a/tests/auto/render/qblitframebuffer/tst_qblitframebuffer.cpp
+++ b/tests/auto/render/qblitframebuffer/tst_qblitframebuffer.cpp
@@ -85,7 +85,7 @@ private Q_SLOTS:
         QVector<Qt3DCore::QNodeCreatedChangeBasePtr> creationChanges = creationChangeGenerator.creationChanges();
 
         // THEN
-        QCOMPARE(creationChanges.size(), 1);
+        QCOMPARE(creationChanges.size(), 3); // 3 due to automatic parenting
 
         const Qt3DCore::QNodeCreatedChangePtr<Qt3DRender::QBlitFramebufferData> creationChangeData =
                 qSharedPointerCast<Qt3DCore::QNodeCreatedChange<Qt3DRender::QBlitFramebufferData>>(creationChanges.first());
@@ -331,6 +331,33 @@ private Q_SLOTS:
 
         arbiter.events.clear();
     }
+
+    void checkSourceDestReset()
+    {
+        // GIVEN
+        TestArbiter arbiter;
+        QScopedPointer<Qt3DRender::QBlitFramebuffer> blitFramebuffer(new Qt3DRender::QBlitFramebuffer());
+        arbiter.setArbiterOnNode(blitFramebuffer.data());
+
+        Qt3DRender::QRenderTarget *sourceRenderTarget = new Qt3DRender::QRenderTarget; // no parent
+        Qt3DRender::QRenderTarget *destinationRenderTarget = new Qt3DRender::QRenderTarget(sourceRenderTarget); // have a parent
+
+        // WHEN
+        blitFramebuffer->setSource(sourceRenderTarget);
+        blitFramebuffer->setDestination(destinationRenderTarget);
+        QCoreApplication::processEvents();
+
+        // THEN
+        QCOMPARE(sourceRenderTarget->parent(), blitFramebuffer.data());
+        QCOMPARE(destinationRenderTarget->parent(), sourceRenderTarget); // already set parent must not change
+
+        // WHEN
+        delete sourceRenderTarget;
+
+        // THEN
+        QVERIFY(!blitFramebuffer->source());
+        QVERIFY(!blitFramebuffer->destination()); // gone too since destinationRenderTarget was parented to sourceRenderTarget
+    }
 };
 
 QTEST_MAIN(tst_QBlitFrameBuffer)