QDistanceFieldCache: fix QTextureAtlas dangling pointer

Note: already merged in 5.15

Change-Id: If968714f1ca4869e9c607224b537e355b4a6f0dd
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
(cherry picked from commit b7e398620a5b467e5205722da5314938d1430f8e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/src/extras/text/qdistancefieldglyphcache.cpp b/src/extras/text/qdistancefieldglyphcache.cpp
index 3c0ab4d16..1294cf53a 100644
--- a/src/extras/text/qdistancefieldglyphcache.cpp
+++ b/src/extras/text/qdistancefieldglyphcache.cpp
@@ -162,13 +162,14 @@ StoredGlyph DistanceFieldFont::refGlyph(quint32 glyph)
         // scenarios
         const int size = m_doubleGlyphResolution ? 512 : 256;
 
-        QTextureAtlas *atlas = new QTextureAtlas(m_parentNode);
+        QTextureAtlas *atlas = new QTextureAtlas();
         atlas->setWidth(size);
         atlas->setHeight(size);
         atlas->setFormat(Qt3DRender::QAbstractTexture::R8_UNorm);
         atlas->setPixelFormat(QOpenGLTexture::Red);
         atlas->setMinificationFilter(Qt3DRender::QAbstractTexture::Linear);
         atlas->setMagnificationFilter(Qt3DRender::QAbstractTexture::Linear);
+        atlas->setParent(m_parentNode);
         m_atlasses << atlas;
 
         if (!storedGlyph.addToTextureAtlas(atlas))
@@ -201,7 +202,12 @@ void DistanceFieldFont::derefGlyph(quint32 glyph)
             Q_ASSERT(m_atlasses.contains(atlas));
 
             m_atlasses.removeAll(atlas);
-            delete atlas;
+
+            // This function might have been called as a result of destroying
+            // the scene root which traverses the entire scene tree. Calling
+            // delete on the atlas here could lead to dangling pointers in the
+            // least of children being traversed for destruction.
+            atlas->deleteLater();
         }
 
         m_glyphs.erase(it);
diff --git a/tests/auto/extras/qtext2dentity/tst_qtext2dentity.cpp b/tests/auto/extras/qtext2dentity/tst_qtext2dentity.cpp
index aec1e9315..4bcb39276 100644
--- a/tests/auto/extras/qtext2dentity/tst_qtext2dentity.cpp
+++ b/tests/auto/extras/qtext2dentity/tst_qtext2dentity.cpp
@@ -44,7 +44,7 @@ void tst_qtext2dentity::checkChangeArbiter()
     auto atlases = lookupNodeByClassName(rootEntity.data(), "Qt3DExtras::QTextureAtlas");
     QVERIFY(atlases.size() == 1);
     auto atlas = atlases[0];
-    QTRY_VERIFY(Qt3DCore::QNodePrivate::get(atlas)->m_changeArbiter);
+    QVERIFY(Qt3DCore::QNodePrivate::get(atlas)->m_changeArbiter);
 }
 
 QTEST_MAIN(tst_qtext2dentity)