Improve <use> node resolution process

Since QSvgUse nodes are the only ones that ever get stored in the
m_resolveNodes member, we can avoid extra cast and checks around it.
Also a more descriptive name wouldn't hurt.

Currently, the list is merely cleaned at the end of a parsing process,
but ideally it should not be stored at all, hence I left the comment
for possible future optimizations, if anyone's willing to do it.

Pick-to: 6.2
Change-Id: I86e83a8661679503e532c230e70f6d52092ad58e
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

2 files changed, 15 insertions, 14 deletions

diff --git a/src/svg/qsvghandler.cpp b/src/svg/qsvghandler.cpp
index 778f175..f520c3f 100644
--- a/src/svg/qsvghandler.cpp
+++ b/src/svg/qsvghandler.cpp
@@ -3818,8 +3818,9 @@ bool QSvgHandler::startElement(const QString &localName,
                 } else if (node->type() == QSvgNode::TSPAN) {
                     static_cast<QSvgTspan *>(node)->setWhitespaceMode(m_whitespaceMode.top());
                 } else if (node->type() == QSvgNode::USE) {
-                    if (!static_cast<QSvgUse *>(node)->isResolved())
-                        m_resolveNodes.append(node);
+                    auto useNode = static_cast<QSvgUse *>(node);
+                    if (!useNode->isResolved())
+                        m_toBeResolved.append(useNode);
                 }
             }
         }
@@ -3926,17 +3927,16 @@ void QSvgHandler::resolveGradients(QSvgNode *node, int nestedDepth)
 
 void QSvgHandler::resolveNodes()
 {
-    for (QSvgNode *node : qAsConst(m_resolveNodes)) {
-        if (!node || !node->parent() || node->type() != QSvgNode::USE)
+    for (QSvgUse *useNode : qAsConst(m_toBeResolved)) {
+        const auto parent = useNode->parent();
+        if (!parent)
             continue;
-        QSvgUse *useNode = static_cast<QSvgUse *>(node);
-        if (useNode->isResolved())
-            continue;
-        QSvgNode::Type t = useNode->parent()->type();
-        if (!(t == QSvgNode::DOC || t == QSvgNode::DEFS || t == QSvgNode::G || t == QSvgNode::SWITCH))
+
+        QSvgNode::Type t = parent->type();
+        if (t != QSvgNode::DOC && t != QSvgNode::DEFS && t != QSvgNode::G && t != QSvgNode::SWITCH)
             continue;
 
-        QSvgStructureNode *group = static_cast<QSvgStructureNode *>(useNode->parent());
+        QSvgStructureNode *group = static_cast<QSvgStructureNode *>(parent);
         QSvgNode *link = group->scopeNode(useNode->linkId());
         if (!link) {
             qCWarning(lcSvgHandler, "link #%s is undefined!", qPrintable(useNode->linkId()));
@@ -3948,7 +3948,7 @@ void QSvgHandler::resolveNodes()
 
         useNode->setLink(link);
     }
-    m_resolveNodes.clear();
+    m_toBeResolved.clear();
 }
 
 bool QSvgHandler::characters(const QStringView str)
diff --git a/src/svg/qsvghandler_p.h b/src/svg/qsvghandler_p.h
index 86b9fa4..2c4b158 100644
--- a/src/svg/qsvghandler_p.h
+++ b/src/svg/qsvghandler_p.h
@@ -144,9 +144,10 @@ private:
     void init();
 
     QSvgTinyDocument *m_doc;
-    QStack<QSvgNode*> m_nodes;
-
-    QList<QSvgNode*>  m_resolveNodes;
+    QStack<QSvgNode *> m_nodes;
+    // TODO: This is only needed during parsing, so it unnecessarily takes up space after that.
+    // Temporary container for <use> nodes which haven't been resolved yet.
+    QList<QSvgUse *> m_toBeResolved;
 
     enum CurrentNode
     {