Add support for defining properties from member variables.

This associates properties with member variables and
avoids writing getter and setter methods manually.
The metaCall() method directly accesses the member variable,
so additional method calls can be avoided.
The metaCall() setter code also supports NOTIFY signals,
which means the according signal is emitted when the property
gets written.

Task-number: QTBUG-16852

Change-Id: I88a1f237ea53a1e9cf65fc9ef2e207718eb8b6c3
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

1 files changed, 21 insertions, 5 deletions

diff --git a/src/corelib/doc/src/objectmodel/properties.qdoc b/src/corelib/doc/src/objectmodel/properties.qdoc
index 1e88a67a90..e262adf886 100644
--- a/src/corelib/doc/src/objectmodel/properties.qdoc
+++ b/src/corelib/doc/src/objectmodel/properties.qdoc
@@ -53,16 +53,22 @@
 
     \snippet code/doc_src_properties.cpp 1
 
+    Here is an example showing how to export member variables as Qt
+    properties using the \c MEMBER keyword.
+    Note that a \c NOTIFY signal must be specified to allow QML property bindings.
+
+    \snippet code/doc_src_properties.cpp 8
+
     A property behaves like a class data member, but it has additional
     features accessible through the \l {Meta-Object System}.
 
     \list 
 
-    \li A \c READ accessor function is required. It is for reading the
-    property value. Ideally, a const function is used for this purpose,
-    and it must return either the property's type or a pointer or
-    reference to that type. e.g., QWidget::focus is a read-only property
-    with \c READ function, QWidget::hasFocus().
+    \li A \c READ accessor function is required if no \c MEMBER variable was
+    specified. It is for reading the property value. Ideally, a const function
+    is used for this purpose, and it must return either the property's type or a
+    pointer or reference to that type. e.g., QWidget::focus is a read-only
+    property with \c READ function, QWidget::hasFocus().
 
     \li A \c WRITE accessor function is optional. It is for setting the
     property value. It must return void and must take exactly one
@@ -71,6 +77,13 @@
     QWidget::setEnabled().  Read-only properties do not need \c WRITE
     functions. e.g., QWidget::focus has no \c WRITE function.
 
+    \li A \c MEMBER variable association is required if no \c READ accessor
+    function is specified. This makes the given member variable
+    readable and writable without the need of creating \c READ and \c WRITE accessor
+    functions. It's still possible to use \c READ or \c WRITE accessor functions in
+    addition to \c MEMBER variable association (but not both), if you need to
+    control the variable access.
+
     \li A \c RESET function is optional. It is for setting the property
     back to its context specific default value. e.g., QWidget::cursor
     has the typical \c READ and \c WRITE functions, QWidget::cursor()
@@ -82,6 +95,9 @@
     \li A \c NOTIFY signal is optional. If defined, it should specify one
     existing signal in that class that is emitted whenever the value
     of the property changes.
+    \c NOTIFY signals for \c MEMBER variables must take zero or one parameter,
+    which must be of the same type as the property. The parameter will take the
+    new value of the property.
 
     \li A \c REVISION number is optional. If included, it defines
     the property and its notifier signal to be used in a particular