Add indexed deleter to sequence wrapper, implement length setter

Previously, elements could not be deleted from sequences directly
without reassignment.  This commit adds an indexed deleter which
allows elements to be deleted by specifying an index.  A deleted
element will be replaced with a default-constructed element in the
sequence (slight departure from ECMA262r3 which specifies that it
should be replaced with Undefined).

This commit also implements the length property setter according
to the requirements on Array [[Put]] by ECMA262r3 which allows
removal of elements from a sequence (required for proper behaviour
of Array.prototype methods such as splice() and pop()).

Task-number: QTBUG-22808
Change-Id: I62511b3edc2ec35f92d2a2bd719278e129c98547
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>

1 files changed, 22 insertions, 1 deletions

diff --git a/doc/src/declarative/extending.qdoc b/doc/src/declarative/extending.qdoc
index c1c7547ec2..385469c29f 100644
--- a/doc/src/declarative/extending.qdoc
+++ b/doc/src/declarative/extending.qdoc
@@ -252,7 +252,7 @@ In particular, QML currently supports:
   \o \c {QList<int>}
   \o \c {QList<qreal>}
   \o \c {QList<bool>}
-  \o \c {QList<QString>}
+  \o \c {QList<QString>} and \c{QStringList}
   \o \c {QList<QUrl>}
 \endlist
 
@@ -274,6 +274,27 @@ modified directly.
 Other sequence types are not supported transparently, and instead an instance of any other
 sequence type will be passed between QML and C++ as an opaque QVariantList.
 
+\bold {Important Note:} There are some minor differences between the semantics of such
+sequence Array types and default JavaScript Array types which result from the use of a
+C++ storage type in the implementation.  In particular, deleting an element from an Array
+will result in a default-constructed value replacing that element, rather than an
+Undefined value.  Similarly, setting the length property of the Array to a value larger
+than its current value will result in the Array being padded out to the specified length
+with default-constructed elements rather than Undefined elements.
+
+The default-constructed values for each sequence type are as follows:
+\table
+\row \o QList<int> \o integer value 0
+\row \o QList<qreal> \o real value 0.0
+\row \o QList<bool> \o boolean value \c {false}
+\row \o QList<QString> and QStringList \o empty QString
+\row \o QList<QUrl> \o empty QUrl
+\endtable
+
+If you wish to remove elements from a sequence rather than simply replace them with default
+constructed values, do not use the indexed delete operator ("delete sequence[i]") but instead
+use the \c {splice} function ("sequence.splice(startIndex, deleteCount)").
+
 \section1 Inheritance and Coercion
 
 \snippet examples/declarative/cppextensions/referenceexamples/coercion/example.qml 0