class ChildViewWatcher
Defined at line 8918 of file fidling/gen/sdk/fidl/fuchsia.ui.composition/fuchsia.ui.composition/hlcpp/fuchsia/ui/composition/cpp/fidl.h
A protocol that provides information about a particular child View which is attached to the
Viewport owned by the parent client; connections to this protocol are estabished in
[`CreateViewport`]. Since a Flatland instance may contain any number of Viewports, each of
which may or may not be attached to a transform, the client can maintain connections to an
equal number of ChildViewWatcher instances.
Each ChildViewWatcher instance will remain connected as long as the corresponding child View
exists; the connection will also be closed if the child's ViewCreationToken is dropped without
using it to create a View.
Public Methods
void ~ChildViewWatcher ()void GetStatus (GetStatusCallback callback)A hanging get for receiving the status of a View. This provides information to the parent,
such as whether or not the child has successfully presented content through this View.
This hanging get will only fire when the ChildViewStatus is different than the previously
returned ChildViewStatus. This can happen immediately, and even if the creator of the
Viewport hasn't yet called Present() after calling CreateViewport(). This allows the parent
to know that the child has content ready to display before the parent modifies their own
local scene graph to incorporate the child content.
It is invalid to call `GetStatus` while a previous call is still pending. Doing so will
cause both this channel and the Flatland channel that handed out ChildViewWatcher to be
closed.
void GetViewRef (GetViewRefCallback callback)Hanging get to receive the ViewRef of the child View. This will only fire when the View ref
is different from the previously-returned View ref. Note: currently the View ref will not
change after it is first received, but this will change if/when the API changes to allow
relinking of views.
The ViewRef is not returned until the View is included in the View tree, in other words when
there is a chain of ancestor transforms all the way back up to the root of the scene graph,
i.e. the display.
It is invalid to call `GetViewRef` while a previous call is still pending. Doing so will
cause both this channel and the Flatland channel that handed out ChildViewWatcher to be
closed.
A `GetViewRef` call will hang if the View was created using `CreateView`, but returns the
View if the View was created using CreateView2. This is because `CreateView` does not mint
a ViewRef for that View.