Context

#GstContext is a container object used to store contexts like a device context, a display server connection and similar concepts that should be shared between multiple elements.

Applications can set a context on a complete pipeline by using gst.element.Element.setContext, which will then be propagated to all child elements. Elements can handle these in #GstElementClass::set_context and merge them with the context information they already have.

When an element needs a context it will do the following actions in this order until one step succeeds:

1. Check if the element already has a context 2. Query downstream with gst.types.QueryType.Context for the context 3. Query upstream with gst.types.QueryType.Context for the context 4. Post a gst.types.MessageType.NeedContext message on the bus with the required context types and afterwards check if a usable context was set now 5. Create a context by itself and post a gst.types.MessageType.HaveContext message on the bus.

Bins will catch gst.types.MessageType.NeedContext messages and will set any previously known context on the element that asks for it if possible. Otherwise the application should provide one if it can.

#GstContext can be persistent. A persistent #GstContext is kept in elements when they reach gst.types.State.Null, non-persistent ones will be removed. Also, a non-persistent context won't override a previous persistent context set to an element.

class Context : Boxed {

this(string contextType, bool persistent);

string getContextType();

gst.structure.Structure getStructure();

bool hasContextType(string contextType);

bool isPersistent();

gst.structure.Structure writableStructure();

}

Constructors

this this(string contextType, bool persistent): Creates a new context.

Members

Functions

getContextType string getContextType(): Gets the type of context.
getStructure gst.structure.Structure getStructure(): Accesses the structure of the context.
hasContextType bool hasContextType(string contextType): Checks if context has context_type.
isPersistent bool isPersistent(): Checks if context is persistent.
writableStructure gst.structure.Structure writableStructure(): Gets a writable version of the structure.

Inherited Members

From Boxed

cInstancePtr void* cInstancePtr;: Pointer to the C boxed value
getType GType getType(): Get the GType of this boxed type.
gType GType gType [@property getter]: Boxed GType property.
self Boxed self(): Convenience method to return this cast to a type. For use in D with statements.
copy_ void* copy_(): Make a copy of the wrapped C boxed data.
boxedCopy void* boxedCopy(void* cBoxed): Copy a C boxed value using g_boxed_copy.
boxedFree void boxedFree(void* cBoxed): Free a C boxed value using g_boxed_free.

gst context classes

Context