Prevent badly formed texture nodes in the scene graph.

A texture based node without a valid texture is not allowed,
as the material and the renderer will only tolerate
well-formed nodes. If a node is missing any part of its material
state it should not be in the scene graph in the first place.

Because of an "optimization" in QSGDefaultImageNode::setTexture
and QSGSimpleTextureNode::setTexture, we must temporarily set
the texture to 0 to ensure that it gets updated properly. This
temporarily puts the node into an invalid state which can lead
to crashes when QSGNode::markDirty() reaches the renderer.

Task-number: QTBUG-34062
Change-Id: Ic1735c9b974b90b3684262de9589133c961bac6e
Reviewed-by: Laszlo Agocs <laszlo.agocs@digia.com>

1 files changed, 3 insertions, 5 deletions

diff --git a/src/quick/scenegraph/qsgdefaultimagenode.cpp b/src/quick/scenegraph/qsgdefaultimagenode.cpp
index 349a92ac7f..11d0e5dbeb 100644
--- a/src/quick/scenegraph/qsgdefaultimagenode.cpp
+++ b/src/quick/scenegraph/qsgdefaultimagenode.cpp
@@ -298,15 +298,13 @@ void QSGDefaultImageNode::setHorizontalWrapMode(QSGTexture::WrapMode wrapMode)
 
 void QSGDefaultImageNode::setTexture(QSGTexture *texture)
 {
-    if (texture == m_material.texture())
-        return;
+    Q_ASSERT(texture);
 
     m_material.setTexture(texture);
     m_materialO.setTexture(texture);
     m_smoothMaterial.setTexture(texture);
-    // Texture cleanup
-    if (texture)
-        m_material.setFlag(QSGMaterial::Blending, texture->hasAlphaChannel());
+    m_material.setFlag(QSGMaterial::Blending, texture->hasAlphaChannel());
+
     markDirty(DirtyMaterial);
 
     // Because the texture can be a different part of the atlas, we need to update it...