Copyright	Will Thompson and Iñaki García Etxebarria
License	LGPL-2.1
Maintainer	Iñaki García Etxebarria
Safe Haskell	Safe-Inferred
Language	Haskell2010

GI.Gst.Structs.Context

Contents

Exported types
Methods

Description

Context 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 elementSetContext, which will then be propagated to all child elements. Elements can handle these in ElementClass::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:

Check if the element already has a context
Query downstream with QueryTypeContext for the context
Query upstream with QueryTypeContext for the context
Post a MessageTypeNeedContext message on the bus with the required context types and afterwards check if a usable context was set now
Create a context by itself and post a MessageTypeHaveContext message on the bus.

Bins will catch MessageTypeNeedContext 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.

Context can be persistent. A persistent Context is kept in elements when they reach StateNull, non-persistent ones will be removed. Also, a non-persistent context won't override a previous persistent context set to an element.

Since: 1.2

Synopsis

newtype Context = Context (ManagedPtr Context)
contextGetContextType :: (HasCallStack, MonadIO m) => Context -> m Text
contextGetStructure :: (HasCallStack, MonadIO m) => Context -> m Structure
contextHasContextType :: (HasCallStack, MonadIO m) => Context -> Text -> m Bool
contextIsPersistent :: (HasCallStack, MonadIO m) => Context -> m Bool
contextNew :: (HasCallStack, MonadIO m) => Text -> Bool -> m Context
contextWritableStructure :: (HasCallStack, MonadIO m) => Context -> m Structure

Exported types

newtype Context Source #

Memory-managed wrapper type.

Constructors

Context (ManagedPtr Context)

Instances

Instances details

Eq Context Source #
Instance details Defined in GI.Gst.Structs.Context Methods (==) :: Context -> Context -> Bool # (/=) :: Context -> Context -> Bool #
GBoxed Context Source #
Instance details Defined in GI.Gst.Structs.Context
ManagedPtrNewtype Context Source #
Instance details Defined in GI.Gst.Structs.Context Methods toManagedPtr :: Context -> ManagedPtr Context
TypedObject Context Source #
Instance details Defined in GI.Gst.Structs.Context Methods glibType :: IO GType
HasParentTypes Context Source #
Instance details Defined in GI.Gst.Structs.Context
IsGValue (Maybe Context) Source #	Convert `Context` to and from `GValue`. See `toGValue` and `fromGValue`.
Instance details Defined in GI.Gst.Structs.Context Methods gvalueGType_ :: IO GType gvalueSet_ :: Ptr GValue -> Maybe Context -> IO () gvalueGet_ :: Ptr GValue -> IO (Maybe Context)
type ParentTypes Context Source #
Instance details Defined in GI.Gst.Structs.Context type ParentTypes Context = '[] :: [Type]

Methods

Click to display all available methods, including inherited ones

Expand

Methods

hasContextType, isPersistent, writableStructure.

Getters

getContextType, getStructure.

Setters

None.

getContextType

contextGetContextType Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Context	`context`: The `Context`.
-> m Text	Returns: The type of the context.

Gets the type of context.

Since: 1.2

getStructure

contextGetStructure Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Context	`context`: The `Context`.
-> m Structure	Returns: The structure of the context. The structure is still owned by the context, which means that you should not modify it, free it and that the pointer becomes invalid when you free the context.

Accesses the structure of the context.

Since: 1.2

hasContextType

contextHasContextType Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Context	`context`: The `Context`.
-> Text	`contextType`: Context type to check.
-> m Bool	Returns: `True` if `context` has `contextType`.

Checks if context has contextType.

Since: 1.2

isPersistent

contextIsPersistent Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Context	`context`: The `Context`.
-> m Bool	Returns: `True` if the context is persistent.

Checks if context is persistent.

Since: 1.2

new

contextNew Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Text	`contextType`: Context type
-> Bool	`persistent`: Persistent context
-> m Context	Returns: The new context.

Creates a new context.

Since: 1.2

writableStructure

contextWritableStructure Source #

Arguments

:: (HasCallStack, MonadIO m)
=> Context	`context`: The `Context`.
-> m Structure	Returns: The structure of the context. The structure is still owned by the context, which means that you should not free it and that the pointer becomes invalid when you free the context. This function checks if `context` is writable.

Gets a writable version of the structure.

Since: 1.2