private void GenerateFocusedContainer(
ICustomItemContainerGenerator generator,
bool measureInvalidated,
UIElement focusedElement )
{
if( focusedElement == null )
return;
int index = generator.GetRealizedIndexForContainer( focusedElement );
if( index >= 0 )
{
if( measureInvalidated )
{
this.MeasureContainer( focusedElement );
}
m_layoutedContainers.Add( new LayoutedContainerInfo( index, focusedElement ) );
}
else
{
this.RecycleContainer( focusedElement );
}
}
private void GenerateContainers(
ICustomItemContainerGenerator generator,
int pageStartIndex,
int pageEndIndex,
bool measureInvalidated,
ref UIElement focusedElement )
{
HashSet<UIElement> unusedLayoutedContainers = new HashSet<UIElement>( m_layoutedContainers.Select( item => item.Container ) );
m_layoutedContainers.Clear();
ScrollDirection scrollDirection = this.AnimatedScrollInfo.VerticalScrollingDirection;
GeneratorPosition position;
GeneratorDirection direction;
int currentIndex;
int step;
if( ( scrollDirection == ScrollDirection.Forward )
|| ( scrollDirection == ScrollDirection.None ) )
{
position = generator.GeneratorPositionFromIndex( pageStartIndex );
direction = GeneratorDirection.Forward;
currentIndex = pageStartIndex;
step = 1;
}
else
{
position = generator.GeneratorPositionFromIndex( pageEndIndex );
direction = GeneratorDirection.Backward;
currentIndex = pageEndIndex;
step = -1;
}
using( generator.StartAt( position, direction, true ) )
{
while( ( currentIndex >= pageStartIndex ) && ( currentIndex <= pageEndIndex ) )
{
UIElement container = this.GenerateContainer( generator, currentIndex, measureInvalidated, true );
if( container == null )
break;
if( focusedElement == container )
{
focusedElement = null;
}
// The container is now part of the page layout. Add it to the list.
m_layoutedContainers.Add( new LayoutedContainerInfo( currentIndex, container ) );
m_layoutedContainersToRecycle.Remove( container );
unusedLayoutedContainers.Remove( container );
currentIndex += step;
}
}
// A ScrollViewer may measure forever if the containers that are "underneath" the horizontal
// scrollbar are the ones that required the scrollbar in the first place.
if( m_lastVisiblePageIndexes != PageIndexes.Empty )
{
int remainingItemCount = ( m_lastVisiblePageIndexes.EndIndex - m_lastVisiblePageIndexes.StartIndex )
- ( pageEndIndex - pageStartIndex );
if( ( remainingItemCount > 0 ) && ( this.GetMaxDesiredWidth() < this.AnimatedScrollInfo.ExtentWidth ) )
{
int itemCount = generator.ItemCount;
if( ( currentIndex >= 0 ) && ( currentIndex < itemCount ) )
{
position = generator.GeneratorPositionFromIndex( currentIndex );
using( generator.StartAt( position, direction, true ) )
{
while( ( remainingItemCount > 0 ) && ( currentIndex >= 0 ) && ( currentIndex < itemCount ) )
{
UIElement container = this.GenerateContainer( generator, currentIndex, measureInvalidated, true );
if( container == null )
break;
if( focusedElement == container )
{
focusedElement = null;
}
// The container is now part of the page layout. Add it to the list.
m_layoutedContainers.Add( new LayoutedContainerInfo( currentIndex, container ) );
m_layoutedContainersToRecycle.Remove( container );
unusedLayoutedContainers.Remove( container );
currentIndex += step;
remainingItemCount--;
}
}
}
}
}
m_layoutedContainers.Sort();
// Recycle the containers that have not been reused in the current page.
foreach( var container in unusedLayoutedContainers )
{
// We do not recycle the focused element!
if( container.IsKeyboardFocusWithin )
{
Debug.Assert( focusedElement == null );
focusedElement = container;
}
else
{
int index = generator.GetRealizedIndexForContainer( container );
this.RecycleContainer( generator, index, container );
m_layoutedContainersToRecycle.Add( container );
}
}
}
private void RecycleUnusedStickyContainers(
ICustomItemContainerGenerator generator,
StickyContainerInfoList stickyContainers,
StickyContainerInfoList stickyContainersToExclude,
ref UIElement focusedElement )
{
for( int i = stickyContainers.Count - 1; i >= 0; i-- )
{
StickyContainerInfo stickyHeaderInfo = stickyContainers[ i ];
UIElement container = stickyHeaderInfo.Container;
if( m_layoutedContainers.ContainsContainer( container ) )
continue;
if( ( stickyContainersToExclude != null ) && ( stickyContainersToExclude.ContainsContainer( container ) ) )
continue;
if( container.IsKeyboardFocusWithin )
{
Debug.Assert( ( focusedElement == null ) || ( focusedElement == container ) );
focusedElement = container;
continue;
}
int index = generator.GetRealizedIndexForContainer( container );
this.RecycleContainer( generator, index, container );
stickyContainers.RemoveAt( i );
}
}
private UIElement RecycleContainers(
ICustomItemContainerGenerator generator,
int pageStartIndex,
int pageEndIndex )
{
UIElement focusedElement = null;
for( int i = m_layoutedContainers.Count - 1; i >= 0; i-- )
{
var container = m_layoutedContainers[ i ].Container;
int index = generator.GetRealizedIndexForContainer( container );
// If the container's index is now out of view, recycle that container.
if( ( index < pageStartIndex ) || ( index > pageEndIndex ) )
{
// We do not recycle the focused element!
if( container.IsKeyboardFocusWithin )
{
focusedElement = container;
}
else
{
this.RecycleContainer( generator, index, container );
}
m_layoutedContainers.RemoveAt( i );
}
}
return focusedElement;
}
private void RecycleContainers(
HashSet<UIElement> layoutedContainersToRecycle,
ICustomItemContainerGenerator generator )
{
foreach( UIElement containerToRecycle in layoutedContainersToRecycle )
{
this.RecycleContainer( generator, generator.GetRealizedIndexForContainer( containerToRecycle ), containerToRecycle );
}
}
private UIElement RecycleContainers(
ICustomItemContainerGenerator generator,
int pageStartIndex,
int pageEndIndex )
{
UIElement focusedElement = null;
for( int i = 0; i < m_layoutedContainers.Count; i++ )
{
LayoutedContainerInfo layoutedContainerInfo = m_layoutedContainers[ i ];
UIElement container = layoutedContainerInfo.Container;
// We do not recycle the focused element!
if( container.IsKeyboardFocusWithin )
{
focusedElement = container;
continue;
}
int index = generator.GetRealizedIndexForContainer( container );
// If the container's index is now out of view, recycle that container.
if( ( index < pageStartIndex ) || ( index > pageEndIndex ) )
{
this.RecycleContainer( generator, index, container );
m_layoutedContainersToRecycle.Add( container );
}
}
m_layoutedContainers.Clear();
return focusedElement;
}
