Doc: Make Qt Gui snippets compilable - draganddrop

Task-number: QTBUG-81486
Change-Id: I0a10e4d353f864e295833ff7d4f47950c5199a21
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/doc/snippets/draganddrop/draganddrop.pro

@@ -1,5 +1,9 @@
-HEADERS     = dragwidget.h \
-              mainwindow.h
-SOURCES     = dragwidget.cpp \
-              main.cpp \
-              mainwindow.cpp
+TEMPLATE = lib
+TARGET = draganddrop_snippets
+QT += core gui widgets
+
+HEADERS = \
+    dragwidget.h
+
+SOURCES = \
+    dragwidget.cpp

src/gui/doc/snippets/draganddrop/dragwidget.cpp

@@ -49,6 +49,9 @@
 ****************************************************************************/
 
 #include <QtGui>
+#include <QLabel>
+#include <QHBoxLayout>
+#include <QApplication>
 
 #include "dragwidget.h"
 

src/gui/doc/snippets/draganddrop/mainwindow.cpp

@@ -66,7 +66,7 @@ MainWindow::MainWindow(QWidget *parent)
 
     connect(dragWidget, &DragWidget::mimeTypes,
             this, &MainWindow::setMimeTypes);
-    connect(dragWidget, &DragWidget:dragResult,
+    connect(dragWidget, &DragWidget::dragResult,
             this, &MainWindow::setDragResult);
 
     QVBoxLayout *mainLayout = new QVBoxLayout(centralWidget);

src/gui/doc/snippets/snippets.pro

@@ -5,6 +5,7 @@ contains(QT_BUILD_PARTS, tests) {
     SUBDIRS += \
         brush \
         code \
+        draganddrop \
         qfontdatabase \
         textdocument-end
 }