Add Window attached property on Item

An Item sometimes needs to know a few things about the window
in which it is being displayed; this attached property can expose
them without needing to go up the heirarchy to find the window.
Instead of adding the QQuickWindow pointer as a property on Item
as in 8f49f50a169db85401eb37daf4fe3a0fc3280603, having an attached
property means that it will not be found by introspection; and
it solves the problem that Window is in the QtQuick.Window module:
you must import the module to use the attached property, instead
of having access to a pointer whose type might not be defined
if you didn't import it.  The Window attached property is created
on-demand (so the memory cost adds up if you use it in too many
places); the tradeoff is that it can exist even when the item
is not yet being shown in a window, so bindings at startup work.
The API is purposely incomplete compared to that in QQuickWindow
so that we can introduce what is needed in a controlled fasion
over time.  For now we know of use cases for visibility, active
and activeFocusItem.

[ChangeLog][QtQuick][Window] Added Item.Window attached property

Change-Id: I649404cbd1383326678aa2144f790b2f2542dbbc
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/quick/items/items.pri b/src/quick/items/items.pri
index 042ff80abc..87e2212dd3 100644
--- a/src/quick/items/items.pri
+++ b/src/quick/items/items.pri
@@ -73,6 +73,7 @@ HEADERS += \
     $$PWD/qquickitemview_p_p.h \
     $$PWD/qquickitemviewtransition_p.h \
     $$PWD/qquickscreen_p.h \
+    $$PWD/qquickwindowattached_p.h \
     $$PWD/qquickwindowmodule_p.h \
     $$PWD/qquickframebufferobject.h \
     $$PWD/qquickitemgrabresult.h \
@@ -129,6 +130,7 @@ SOURCES += \
     $$PWD/qquickitemviewtransition.cpp \
     $$PWD/qquickwindowmodule.cpp \
     $$PWD/qquickscreen.cpp \
+    $$PWD/qquickwindowattached.cpp \
     $$PWD/qquickframebufferobject.cpp \
     $$PWD/qquickitemgrabresult.cpp \
     $$PWD/qquickrendercontrol.cpp