Fix docs to explain the new type syntax for QML methods

[ChangeLog][QtQml] It is now possible to specify types for method
parameters and their return value in QML (basic and object types), using
TypeScript-like syntax with a colon separator. The syntax for QML
declared signals supports the same style.

This change also adapts the remaining snippets and docs to the "fresher"
qml signal parameter syntax.

Change-Id: I601781f01f696276951b04785584adab39fedfd9
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

7 files changed, 31 insertions, 28 deletions

diff --git a/src/qml/doc/snippets/qml/events.qml b/src/qml/doc/snippets/qml/events.qml
index 90bf5d7b3d..f437e32890 100644
--- a/src/qml/doc/snippets/qml/events.qml
+++ b/src/qml/doc/snippets/qml/events.qml
@@ -59,8 +59,8 @@ Rectangle {
 
 //! [signal declaration]
     signal trigger
-    signal send (string notice)
-    signal perform (string task, variant object)
+    signal send(notice: string)
+    signal perform(task: string, object: variant)
 //! [signal declaration]
 
 //! [signal handler declaration]
@@ -88,7 +88,7 @@ Rectangle {
 Rectangle {
     id: messenger
 
-    signal send( string person, string notice)
+    signal send(person: string, notice: string)
 
     onSend: {
         console.log("For " + person + ", the notice is: " + notice)
@@ -102,7 +102,7 @@ Rectangle {
 Rectangle {
     id: relay
 
-    signal send( string person, string notice)
+    signal send(person: string, notice: string)
     onSend: console.log("Send signal to: " + person + ", " + notice)
 
     Component.onCompleted: {
diff --git a/src/qml/doc/snippets/qml/qtbinding/functions-qml/MyItem.qml b/src/qml/doc/snippets/qml/qtbinding/functions-qml/MyItem.qml
index 073a5dc361..59907c38e7 100644
--- a/src/qml/doc/snippets/qml/qtbinding/functions-qml/MyItem.qml
+++ b/src/qml/doc/snippets/qml/qtbinding/functions-qml/MyItem.qml
@@ -52,7 +52,7 @@
 import QtQuick 2.0
 
 Item {
-    function myQmlFunction(msg) {
+    function myQmlFunction(msg: string) : string {
         console.log("Got message:", msg)
         return "some return value"
     }
diff --git a/src/qml/doc/snippets/qml/qtbinding/functions-qml/main.cpp b/src/qml/doc/snippets/qml/qtbinding/functions-qml/main.cpp
index c82f71f749..a562eae2b4 100644
--- a/src/qml/doc/snippets/qml/qtbinding/functions-qml/main.cpp
+++ b/src/qml/doc/snippets/qml/qtbinding/functions-qml/main.cpp
@@ -60,13 +60,13 @@ QQmlEngine engine;
 QQmlComponent component(&engine, "MyItem.qml");
 QObject *object = component.create();
 
-QVariant returnedValue;
-QVariant msg = "Hello from C++";
+QString returnedValue;
+QString msg = "Hello from C++";
 QMetaObject::invokeMethod(object, "myQmlFunction",
-        Q_RETURN_ARG(QVariant, returnedValue),
-        Q_ARG(QVariant, msg));
+        Q_RETURN_ARG(QString, returnedValue),
+        Q_ARG(QString, msg));
 
-qDebug() << "QML function returned:" << returnedValue.toString();
+qDebug() << "QML function returned:" << returnedValue;
 delete object;
 //![0]
 }
diff --git a/src/qml/doc/snippets/qml/qtbinding/signals-qml/MyItem.qml b/src/qml/doc/snippets/qml/qtbinding/signals-qml/MyItem.qml
index eebf2db832..aadc89b72c 100644
--- a/src/qml/doc/snippets/qml/qtbinding/signals-qml/MyItem.qml
+++ b/src/qml/doc/snippets/qml/qtbinding/signals-qml/MyItem.qml
@@ -55,7 +55,7 @@ Item {
     id: item
     width: 100; height: 100
 
-    signal qmlSignal(string msg)
+    signal qmlSignal(msg: string)
 
     MouseArea {
         anchors.fill: parent
diff --git a/src/qml/doc/snippets/qml/statemachine/guardcondition.qml b/src/qml/doc/snippets/qml/statemachine/guardcondition.qml
index 8388b96c21..f1ec89b6ba 100644
--- a/src/qml/doc/snippets/qml/statemachine/guardcondition.qml
+++ b/src/qml/doc/snippets/qml/statemachine/guardcondition.qml
@@ -70,7 +70,7 @@ Rectangle {
             }
         }
         // define the signal the SignalTransition is connected with
-        signal mysignal(string mystr)
+        signal mysignal(mystr: string)
         // on clicking the button emit the signal with a single string argument
         onClicked: button.mysignal("test")
     }
diff --git a/src/qml/doc/src/cppintegration/interactqmlfromcpp.qdoc b/src/qml/doc/src/cppintegration/interactqmlfromcpp.qdoc
index 9c33979f40..0a824bb5b5 100644
--- a/src/qml/doc/src/cppintegration/interactqmlfromcpp.qdoc
+++ b/src/qml/doc/src/cppintegration/interactqmlfromcpp.qdoc
@@ -166,9 +166,12 @@ updated, and any \c onButtonTextChanged handlers would not be called.
 
 \section2 Invoking QML Methods
 
-All QML methods are exposed to the meta-object system and can be called from C++
-using QMetaObject::invokeMethod(). Method parameters and return values passed
-from QML are always translated into QVariant values in C++.
+All QML methods are exposed to the meta-object system and can be called from
+C++ using QMetaObject::invokeMethod(). You can specify types for the parameters
+and the return value after the colon character, as shown in the code snippet
+below.  This can be useful, for example, when you want to connect a signal in
+C++ with a certain signature to a QML-defined method. If you omit the types,
+the C++ signature will use QVariant.
 
 Here is a C++ application that calls a QML method using
 QMetaObject::invokeMethod():
@@ -182,9 +185,12 @@ QMetaObject::invokeMethod():
 \li \snippet qml/qtbinding/functions-qml/main.cpp 0
 \endtable
 
-Notice the Q_RETURN_ARG() and Q_ARG() arguments for QMetaObject::invokeMethod()
-must be specified as QVariant types, as this is the generic data type used for
-QML method parameters and return values.
+Notice the parameter and return type specified after the colon. You can use \l
+{QML Basic Types}{basic types} and \l {QML Object Types}{object types} as type
+names.
+
+If the type is omitted in QML, then you must specify QVariant as type with
+Q_RETURN_ARG() and Q_ARG() when calling QMetaObject::invokeMethod.
 
 
 \section2 Connecting to QML Signals
@@ -210,9 +216,8 @@ QObject::connect(), so that the \c cppSlot() method is called whenever the
 \snippet qml/qtbinding/signals-qml/main.cpp 0
 \endtable
 
-When a QML object type is used as a signal parameter, the parameter should
-use \l var as the type, and the value should be received in C++ using the
-QVariant type:
+A QML object type in a signal parameter is translated to a pointer to the class
+in C++:
 
 \table
 \row
@@ -226,7 +231,7 @@ QVariant type:
      id: item
      width: 100; height: 100
 
-     signal qmlSignal(var anObject)
+     signal qmlSignal(anObject: Item)
 
      MouseArea {
          anchors.fill: parent
@@ -241,18 +246,16 @@ QVariant type:
  {
      Q_OBJECT
  public slots:
-     void cppSlot(const QVariant &v) {
-        qDebug() << "Called the C++ slot with value:" << v;
+     void cppSlot(QQuickItem *item) {
+        qDebug() << "Called the C++ slot with item:" << item;
 
-        QQuickItem *item =
-            qobject_cast<QQuickItem*>(v.value<QObject*>());
         qDebug() << "Item dimensions:" << item->width()
                  << item->height();
      }
  };
 
  int main(int argc, char *argv[]) {
-     QApplication app(argc, argv);
+     QGuiApplication app(argc, argv);
 
      QQuickView view(QUrl::fromLocalFile("MyItem.qml"));
      QObject *item = view.rootObject();
diff --git a/src/quick/doc/snippets/qml/qml-extending-types/signals/Button.qml b/src/quick/doc/snippets/qml/qml-extending-types/signals/Button.qml
index b40f517234..96f7fc1c7c 100644
--- a/src/quick/doc/snippets/qml/qml-extending-types/signals/Button.qml
+++ b/src/quick/doc/snippets/qml/qml-extending-types/signals/Button.qml
@@ -55,7 +55,7 @@ Rectangle {
     id: rect
     width: 100; height: 100
 
-    signal buttonClicked(int xPos, int yPos)
+    signal buttonClicked(xPos: int, yPos: int)
 
     MouseArea {
         anchors.fill: parent