public ViewportInfo GetRelativeTo(IFrameworkElement_EffectiveViewport element)
{
Rect effective = Effective, clip = Clip;
if (element is UIElement uiElement && Reference is UIElement usuallyTheParentOfElement)
{
var parentToElement = UIElement.GetTransform(uiElement, usuallyTheParentOfElement).Inverse();
if (Effective.IsValid)
{
effective = parentToElement.Transform(Effective);
}
if (Clip.IsValid)
{
clip = parentToElement.Transform(Clip);
}
}
// If the Reference or the element is not a UIElement (native), we don't have any RenderTransform,
// and we assume that the 'element' is stretched in it's parent usually true except for ListView,
// but we won't even try to support that case.
return(new ViewportInfo(element, effective, clip));
}
/// <summary>
/// Used by a parent element to propagate down the viewport change
/// </summary>
void IFrameworkElement_EffectiveViewport.OnParentViewportChanged(
IFrameworkElement_EffectiveViewport parent, // We propagate the parent to avoid costly lookup
Rect viewport, // Be aware tht it might be empty ([+∞,+∞,-∞,-∞]) if not clipped
bool isInitial) // Indicates that this update is only intended to initiate the _parentViewport
{
if (!IsEffectiveViewportEnabled)
{
// We do not keep the _parentViewport up-to-date if not needed.
// It's expected to the root parent to update its children when propagation activated.
return;
}
#if IS_NATIVE_ELEMENT // No RenderTransform on native elements
var viewportInLocalCoordinates = viewport;
#else
var viewportInLocalCoordinates = !viewport.IsEmpty && parent is UIElement parentElt
? GetTransform(this, parentElt).Inverse().Transform(viewport)
: viewport;
#endif
if (!isInitial && viewportInLocalCoordinates == _parentViewport)
{
return;
}
_parentViewport = viewportInLocalCoordinates;
PropagateEffectiveViewportChange(isInitial);
}
/// <summary>
/// Used by a child of this element, in order to subscribe to viewport updates
/// (so the OnParentViewportChanged will be invoked on this given child)
/// </summary>
IDisposable IFrameworkElement_EffectiveViewport.RequestViewportUpdates(IFrameworkElement_EffectiveViewport child)
{
global::System.Diagnostics.Debug.Assert(Uno.UI.Extensions.DependencyObjectExtensions.GetChildren(this).OfType <IFrameworkElement_EffectiveViewport>().Contains(child));
_childrenInterestedInViewportUpdates++;
ReconfigureViewportPropagation(child);
return(Disposable.Create(() =>
{
_childrenInterestedInViewportUpdates--;
ReconfigureViewportPropagation();
}));
}
/// <summary>
/// Make sure to request or disable effective viewport changes from the parent
/// </summary>
private void ReconfigureViewportPropagation(IFrameworkElement_EffectiveViewport child = null)
{
if (IsLoaded && IsEffectiveViewportEnabled)
{
if (_parentViewportUpdatesSubscription == null)
{
TRACE_EFFECTIVE_VIEWPORT("Enabling effective viewport propagation.");
var parent = this.GetVisualTreeParent();
if (parent is IFrameworkElement_EffectiveViewport parentFwElt)
{
_parentViewportUpdatesSubscription = parentFwElt.RequestViewportUpdates(this);
}
else
{
// We are the root of the visual tree (maybe just temporarily),
// we update the effective viewport in order to initialize the _parentViewport of children.
PropagateEffectiveViewportChange(isInitial: true);
}
}
else
{
TRACE_EFFECTIVE_VIEWPORT("New child requested viewport propagation which has already been enabled. Force updating all children.");
// We are already subscribed, the parent won't send any update (and our _parentViewport is expected to be up-to-date).
// But if this "reconfigure" was made for a new child (child != null), we have to initialize its own _parentViewport.
var slot = LayoutInformation.GetLayoutSlot(this); // a.k.a. the implicit viewport to use if none was defined by any parent (usually only few elements at the top of the tree)
var parentViewport = GetParentViewport();
var viewport = GetEffectiveViewport(parentViewport, slot);
child?.OnParentViewportChanged(this, viewport, isInitial: true);
}
}
else
{
if (_parentViewportUpdatesSubscription != null)
{
TRACE_EFFECTIVE_VIEWPORT("Disabling effective viewport propagation.");
_parentViewportUpdatesSubscription.Dispose();
_parentViewportUpdatesSubscription = null;
_parentViewport = Rect.Empty;
}
}
}
void IFrameworkElement_EffectiveViewport.OnParentViewportChanged(
bool isInitial, // Update is intended to initiate the _parentViewport and should be "public" only if not due to a new event listener while tree is live (e.g. load)
bool isInternal, // Indicates that this update is due to a new event handler
IFrameworkElement_EffectiveViewport parent, // We propagate the parent to avoid costly lookup
ViewportInfo viewport) // The viewport of the parent, expressed in parent's coordinates
{
if (!IsEffectiveViewportEnabled)
{
// We do not keep the _parentViewport up-to-date if not needed.
// It's expected to the root parent to update its children when propagation activated.
return;
}
if (!isInitial && viewport == _parentViewport)
{
return;
}
_parentViewport = viewport;
PropagateEffectiveViewportChange(isInitial, isInternal);
}
/// <summary>
/// Used by a parent element to propagate down the viewport change
/// </summary>
void IFrameworkElement_EffectiveViewport.OnParentViewportChanged(
IFrameworkElement_EffectiveViewport parent, // We propagate the parent to avoid costly lookup
Rect viewport, // Be aware tht it might be empty ([+∞,+∞,-∞,-∞]) if not clipped
bool isInitial) // Indicates that this update is only intended to initiate the _parentViewport
{
if (!IsEffectiveViewportEnabled)
{
// We do not keep the _parentViewport up-to-date if not needed.
// It's expected to the root parent to update its children when propagation activated.
return;
}
#if !__IOS__ // cf. GetParentViewport
viewport = ParentToLocalCoordinates(parent, viewport);
#endif
if (!isInitial && viewport == _parentViewport)
{
return;
}
_parentViewport = viewport;
PropagateEffectiveViewportChange(isInitial);
}
/// <summary>
/// Make sure to request or disable effective viewport changes from the parent
/// </summary>
private void ReconfigureViewportPropagation(IFrameworkElement_EffectiveViewport child = null)
{
if (IsLoaded && IsEffectiveViewportEnabled)
{
if (_parentViewportUpdatesSubscription == null)
{
var parent = Parent;
if (parent is IFrameworkElement_EffectiveViewport parentFwElt)
{
_parentViewportUpdatesSubscription = parentFwElt.RequestViewportUpdates(this);
}
else
{
// We are the root of the visual tree (maybe just temporarily),
// we update the effective viewport in order to initialize the _parentViewport of children.
PropagateEffectiveViewportChange(isInitial: true);
}
}
else
{
// We are already subscribed, the parent won't send any update (and our _parentViewport is expected to be up-to-date).
// But if this "reconfigure" was made for a new child (child != null), we have to initialize its own _parentViewport.
child?.OnParentViewportChanged(this, GetEffectiveViewport(), isInitial: true);
}
}
else
{
if (_parentViewportUpdatesSubscription != null)
{
_parentViewportUpdatesSubscription.Dispose();
_parentViewportUpdatesSubscription = null;
_parentViewport = Rect.Empty;
}
}
}
public ViewportInfo(IFrameworkElement_EffectiveViewport reference, Rect effective, Rect clip)
{
Reference = reference;
Effective = effective;
Clip = clip;
}
public ViewportInfo(IFrameworkElement_EffectiveViewport reference, Rect viewport)
{
Reference = reference;
Effective = Clip = viewport;
}
