Doc: Replace use of \oldcode-\newcode

The command-pair was recently deprecated.

The replacement code should produce an output that is equal to the
previous one.

Task-number: QTBUG-98499
Change-Id: If26e0d85a174ebc3858b638c34d7f43637eab46d
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

src/corelib/doc/src/qt6-changes.qdoc

@@ -604,10 +604,16 @@
     is provided to translate glob patterns into a Perl-compatible regular
     expression that can be used for that purpose.
 
-    \oldcode
+    For example, if you have code like
+
+    \code
         QRegExp wildcard("*.txt");
         wildcard.setPatternSyntax(QRegExp::Wildcard);
-    \newcode
+    \endcode
+
+    you can rewrite it as
+
+    \code
         auto wildcard = QRegularExpression(QRegularExpression::wildcardToRegularExpression("*.txt"));
     \endcode
 
@@ -637,7 +643,9 @@
     \c {QRegExp::indexIn} and a growing offset, but can now be easily implemented
     with \l QRegularExpressionMatchIterator or \l {QString::indexOf}.
 
-    \oldcode
+    For example, if you have code like
+
+    \code
         QString subject("the quick fox");
 
         int offset = 0;
@@ -646,7 +654,11 @@
             offset += re.matchedLength();
             // ...
         }
-    \newcode
+    \endcode
+
+    you can rewrite it as
+
+    \code
         QRegularExpression re("(\\w+)");
         QString subject("the quick fox");
 
@@ -675,7 +687,9 @@
     \note \l QRegularExpressionMatchIterator is not capable of performing a
     backwards search.
 
-    \oldcode
+    For example, if you have code like
+
+    \code
         int offset = -1;
         QString subject("Lorem ipsum dolor sit amet, consetetur sadipscing.");
 
@@ -684,7 +698,11 @@
             --offset;
             // ...
         }
-    \newcode
+    \endcode
+
+    you can rewrite it as
+
+    \code
         qsizetype from = -1;
         QString subject("Lorem ipsum dolor sit amet, consetetur sadipscing.");
 

src/corelib/io/qurl.cpp

@@ -1807,9 +1807,15 @@ inline void QUrlPrivate::validate() const
     help avoid missing QUrl::resolved() calls, and other misuses of
     QString to QUrl conversions.
 
-    \oldcode
+    For example, if you have code like
+
+    \code
         url = filename; // probably not what you want
-    \newcode
+    \endcode
+
+    you can rewrite it as
+
+    \code
         url = QUrl::fromLocalFile(filename);
         url = baseurl.resolved(QUrl(filename));
     \endcode

src/xml/doc/src/qt6-changes.qdoc

@@ -46,7 +46,9 @@
     QXmlStreamReader for reading XML files. Here are some simple steps to
     port your current code to QXmlStreamReader:
 
-    \oldcode
+    For example, if you have code like
+
+    \code
         QFile *file = new QFile(...);
         QXmlInputSource *source = new QXmlInputSource(file);
 
@@ -61,7 +63,11 @@
         } else {
             ... // do error handling
         }
-    \newcode
+    \endcode
+
+    you can rewrite it as
+
+    \code
         QFile file = ...;
         QXmlStreamReader reader(&file);