Scrollers: give control over layouting if parent != flickable

This allows utilizing the convenient attached properties of ScrollBar
and ScrollIndicator, but positioning the scrollers outside of a clipping
Flickable.

Change-Id: I46fe79110658f4797469d042c56f51548eef6c70
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

2 files changed, 60 insertions, 6 deletions

diff --git a/src/quicktemplates2/qquickscrollbar.cpp b/src/quicktemplates2/qquickscrollbar.cpp
index 69cac6ee..d3a2355c 100644
--- a/src/quicktemplates2/qquickscrollbar.cpp
+++ b/src/quicktemplates2/qquickscrollbar.cpp
@@ -65,9 +65,9 @@ QT_BEGIN_NAMESPACE
     }
     \endcode
 
-    \note When ScrollBar is attached \l {ScrollBar::vertical}{vertically} or
-    \l {ScrollBar::horizontal}{horizontally} to a Flickable, its geometry and
-    the following properties are automatically set and updated as appropriate:
+    When ScrollBar is attached \l {ScrollBar::vertical}{vertically} or
+    \l {ScrollBar::horizontal}{horizontally} to a Flickable, the following
+    properties are automatically set and updated as appropriate:
     \list
     \li \l orientation
     \li \l position
@@ -75,6 +75,29 @@ QT_BEGIN_NAMESPACE
     \li \l active
     \endlist
 
+    An attached ScrollBar re-parents itself to the target Flickable. A vertically
+    attached ScrollBar resizes itself to the height of the Flickable, and positions
+    itself to either side of it based on the \l {Control::mirrored}{layout direction}.
+    A horizontally attached ScrollBar resizes itself to the width of the Flickable,
+    and positions itself to the bottom. The automatic geometry management can be disabled
+    by specifying another parent for the attached ScrollBar. This can be useful, for
+    example, if the ScrollBar should be placed outside a clipping Flickable. This is
+    demonstrated by the following example:
+
+    \code
+    Flickable {
+        id: flickable
+        clip: true
+        // ...
+        ScrollBar.vertical: ScrollBar {
+            parent: flickable.parent
+            anchors.top: flickable.top
+            anchors.left: flickable.right
+            anchors.bottom: flickable.bottom
+        }
+    }
+    \endcode
+
     Notice that ScrollBar does not filter key events of the Flickable it is
     attached to. The following example illustrates how to implement scrolling
     with up and down keys:
@@ -465,6 +488,8 @@ void QQuickScrollBarAttachedPrivate::mirrorVertical()
 void QQuickScrollBarAttachedPrivate::layoutHorizontal(bool move)
 {
     Q_ASSERT(horizontal && flickable);
+    if (horizontal->parentItem() != flickable)
+        return;
     horizontal->setWidth(flickable->width());
     if (move)
         horizontal->setY(flickable->height() - horizontal->height());
@@ -473,6 +498,8 @@ void QQuickScrollBarAttachedPrivate::layoutHorizontal(bool move)
 void QQuickScrollBarAttachedPrivate::layoutVertical(bool move)
 {
     Q_ASSERT(vertical && flickable);
+    if (vertical->parentItem() != flickable)
+        return;
     vertical->setHeight(flickable->height());
     if (move)
         vertical->setX(vertical->isMirrored() ? 0 : flickable->width() - vertical->width());
diff --git a/src/quicktemplates2/qquickscrollindicator.cpp b/src/quicktemplates2/qquickscrollindicator.cpp
index 48adda0a..91d03ec9 100644
--- a/src/quicktemplates2/qquickscrollindicator.cpp
+++ b/src/quicktemplates2/qquickscrollindicator.cpp
@@ -65,9 +65,9 @@ QT_BEGIN_NAMESPACE
     }
     \endcode
 
-    \note When ScrollIndicator is attached \l {ScrollIndicator::vertical}{vertically}
-    or \l {ScrollIndicator::horizontal}{horizontally} to a Flickable, its geometry and
-    the following properties are automatically set and updated as appropriate:
+    When ScrollIndicator is attached \l {ScrollIndicator::vertical}{vertically} or
+    \l {ScrollIndicator::horizontal}{horizontally} to a Flickable, the following
+    properties are automatically set and updated as appropriate:
     \list
     \li \l orientation
     \li \l position
@@ -75,6 +75,29 @@ QT_BEGIN_NAMESPACE
     \li \l active
     \endlist
 
+    An attached ScrollIndicator re-parents itself to the target Flickable. A vertically
+    attached ScrollIndicator resizes itself to the height of the Flickable, and positions
+    itself to either side of it based on the \l {Control::mirrored}{layout direction}.
+    A horizontally attached ScrollIndicator resizes itself to the width of the Flickable,
+    and positions itself to the bottom. The automatic geometry management can be disabled
+    by specifying another parent for the attached ScrollIndicator. This can be useful, for
+    example, if the ScrollIndicator should be placed outside a clipping Flickable. This is
+    demonstrated by the following example:
+
+    \code
+    Flickable {
+        id: flickable
+        clip: true
+        // ...
+        ScrollIndicator.vertical: ScrollIndicator {
+            parent: flickable.parent
+            anchors.top: flickable.top
+            anchors.left: flickable.right
+            anchors.bottom: flickable.bottom
+        }
+    }
+    \endcode
+
     Horizontal and vertical scroll indicators do not share the \l active state with
     each other by default. In order to keep both indicators visible whilst scrolling
     to either direction, establish a two-way binding between the active states as
@@ -268,6 +291,8 @@ void QQuickScrollIndicatorAttachedPrivate::activateVertical()
 void QQuickScrollIndicatorAttachedPrivate::layoutHorizontal(bool move)
 {
     Q_ASSERT(horizontal && flickable);
+    if (horizontal->parentItem() != flickable)
+        return;
     horizontal->setWidth(flickable->width());
     if (move)
         horizontal->setY(flickable->height() - horizontal->height());
@@ -276,6 +301,8 @@ void QQuickScrollIndicatorAttachedPrivate::layoutHorizontal(bool move)
 void QQuickScrollIndicatorAttachedPrivate::layoutVertical(bool move)
 {
     Q_ASSERT(vertical && flickable);
+    if (vertical->parentItem() != flickable)
+        return;
     vertical->setHeight(flickable->height());
     if (move && !QQuickItemPrivate::get(vertical)->isMirrored())
         vertical->setX(flickable->width() - vertical->width());