Doc: Make snippets Qt Gui compilable - textdocument-blocks

Task-number: QTBUG-81486
Change-Id: I663c53d11e4bd3086c4afee0c994d00ecc0c7cad
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/doc/snippets/snippets.pro

@@ -8,5 +8,6 @@ contains(QT_BUILD_PARTS, tests) {
         code \
         draganddrop \
         qfontdatabase \
+        textdocument-blocks \
         textdocument-end
 }

src/gui/doc/snippets/textdocument-blocks/main.cpp

@@ -51,12 +51,13 @@
 #include <QtGui>
 
 #include "mainwindow.h"
+#include <QApplication>
 
 int main(int argc, char *argv[])
 {
     QApplication app(argc, argv);
-    MainWindow *window = new MainWindow;
-    window->resize(640, 480);
-    window->show();
+    MainWindow window;
+    window.resize(640, 480);
+    window.show();
     return app.exec();
 }

src/gui/doc/snippets/textdocument-blocks/textdocument-blocks.pro

@@ -1,6 +1,10 @@
-QT          += xml
-HEADERS     = mainwindow.h \
-              xmlwriter.h
-SOURCES     = main.cpp \
-              mainwindow.cpp \
-              xmlwriter.cpp
+TEMPLATE = lib
+TARGET = textdocument-blocks_snippets
+QT += core gui widgets
+
+HEADERS = \
+    mainwindow.h
+
+SOURCES = \
+    main.cpp \
+    mainwindow.cpp