Detailed Description

Allows Clients to receive a callback after a specific node has completed execution.

Callbacks are not guaranteed to be called immediately after the Node completes. Callbacks are intended to be used to create simple early exit conditions for Vision graphs using vx_action_e return values. An example of setting up a callback can be seen below:

    vx_graph graph = vxCreateGraph(context);
    status = vxGetStatus((vx_reference)graph);
    if (status == VX_SUCCESS) {
        vx_uint8 lmin = 0, lmax = 0;
        vx_uint32 minCount = 0, maxCount = 0;
        vx_scalar scalars[] = {
            vxCreateScalar(context, VX_TYPE_UINT8, &lmin),
            vxCreateScalar(context, VX_TYPE_UINT8, &lmax),
            vxCreateScalar(context, VX_TYPE_UINT32, &minCount),
            vxCreateScalar(context, VX_TYPE_UINT32, &maxCount),
        };
        vx_array arrays[] = {
            vxCreateArray(context, VX_TYPE_COORDINATES2D, 1),
            vxCreateArray(context, VX_TYPE_COORDINATES2D, 1)
        };
        vx_node nodes[] = {
            vxMinMaxLocNode(graph, input, scalars[0], scalars[1], arrays[0], arrays[1], scalars[2], scalars[3]),
        };
        status = vxAssignNodeCallback(nodes[0], &analyze_brightness);
        // do other
    }

Once the graph has been initialized and the callback has been installed then the callback itself will be called during graph execution.

#define MY_DESIRED_THRESHOLD (10)
vx_action VX_CALLBACK analyze_brightness(vx_node node) {
    // extract the max value
    vx_action action = VX_ACTION_ABANDON;
    vx_parameter pmax = vxGetParameterByIndex(node, 2); // Max Value
    if (pmax) {
        vx_scalar smax = 0;
        vxQueryParameter(pmax, VX_PARAMETER_REF, &smax, sizeof(smax));
        if (smax) {
            vx_uint8 value = 0u;
            vxCopyScalar(smax, &value, VX_READ_ONLY, VX_MEMORY_TYPE_HOST);
            if (value >= MY_DESIRED_THRESHOLD) {
                action = VX_ACTION_CONTINUE;
            }
            vxReleaseScalar(&smax);
        }
        vxReleaseParameter(&pmax);
    }
    return action;
}

Warning: This should be used with extreme caution as it can ruin optimizations in the power/performance efficiency of a graph.

The callback must return a vx_action code indicating how the graph processing should proceed.

If VX_ACTION_CONTINUE is returned, the graph will continue execution with no changes.
If VX_ACTION_ABANDON is returned, execution is unspecified for all nodes for which this node is a dominator. Nodes that are dominators of this node will have executed. Execution of any other node is unspecified.

Node Callback Sequence

Typedefs
typedef vx_enum	vx_action
	The formal typedef of the response from the callback. More...

typedef vx_action(*	vx_nodecomplete_f) (vx_node node)
	A callback to the client after a particular node has completed. More...

Enumerations
enum	vx_action_e { VX_ACTION_CONTINUE = ((( VX_ID_KHRONOS ) << 20) \| ( VX_ENUM_ACTION << 12)) + 0x0, VX_ACTION_ABANDON = ((( VX_ID_KHRONOS ) << 20) \| ( VX_ENUM_ACTION << 12)) + 0x1 }
	A return code enumeration from a `vx_nodecomplete_f` during execution. More...

Functions
vx_status VX_API_CALL	vxAssignNodeCallback (vx_node node, vx_nodecomplete_f callback)
	Assigns a callback to a node. If a callback already exists in this node, this function must return an error and the user may clear the callback by passing a NULL pointer as the callback. More...

vx_nodecomplete_f VX_API_CALL	vxRetrieveNodeCallback (vx_node node)
	Retrieves the current node callback function pointer set on the node. More...

Typedef Documentation

typedef vx_enum vx_action

The formal typedef of the response from the callback.

See also: vx_action_e

Definition at line 451 of file vx_types.h.

typedef vx_action( * vx_nodecomplete_f) (vx_node node)

A callback to the client after a particular node has completed.

See also: vx_action; vxAssignNodeCallback

Parameters

[in] node The node to which the callback was attached.

Returns: An action code from vx_action_e.

Definition at line 460 of file vx_types.h.

Enumeration Type Documentation

enum vx_action_e

A return code enumeration from a vx_nodecomplete_f during execution.

See also: vxAssignNodeCallback

Enumerator
VX_ACTION_CONTINUE	Continue executing the graph with no changes.
VX_ACTION_ABANDON	Stop executing the graph.

Definition at line 601 of file vx_types.h.

Function Documentation

vx_status VX_API_CALL vxAssignNodeCallback	(	vx_node	node,
		vx_nodecomplete_f	callback
	)

Assigns a callback to a node. If a callback already exists in this node, this function must return an error and the user may clear the callback by passing a NULL pointer as the callback.

Parameters

[in]	node	The reference to the node.
[in]	callback	The callback to associate with completion of this specific node.

Warning: This must be used with extreme caution as it can ruin optimizations in the power/performance efficiency of a graph.

Returns: A vx_status_e enumeration.

Return values

VX_SUCCESS	Callback assigned; any other value indicates failure.
VX_ERROR_INVALID_REFERENCE	node is not a valid `vx_node` reference.

vx_nodecomplete_f VX_API_CALL vxRetrieveNodeCallback ( vx_node node )

Retrieves the current node callback function pointer set on the node.

Parameters

[in] node The reference to the vx_node object.

Returns: vx_nodecomplete_f The pointer to the callback function.

Return values

NULL	No callback is set.
*	The node callback function.

Detailed Description

Typedefs

Enumerations

Functions

Typedef Documentation

Enumeration Type Documentation

Function Documentation