Doc: Make snippets Qt Gui compilable - textdocument-frames

Task-number: QTBUG-81486
Change-Id: Ia027d2f07e61944e8a2cc40a24ee23b2d8e526b0
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>

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

@@ -47,10 +47,8 @@
 ** $QT_END_LICENSE$
 **
 ****************************************************************************/
-
-#include <QtGui>
-
 #include "mainwindow.h"
+#include <QApplication>
 
 int main(int argc, char *argv[])
 {

src/gui/doc/snippets/textdocument-frames/mainwindow.h

@@ -68,7 +68,7 @@ public slots:
 private:
     bool writeXml(const QString &fileName);
 
-    QTextEdit *editor;
+    QTextEdit *editor = nullptr;
 };
 
 #endif

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

@@ -1,3 +1,10 @@
-SOURCES     = main.cpp \
-              mainwindow.cpp
-HEADERS     = mainwindow.h
+TEMPLATE = lib
+TARGET = textdocument-frames_snippets
+QT += core gui widgets
+
+HEADERS = \
+    mainwindow.h
+
+SOURCES = \
+    mainwindow.cpp \
+    main.cpp