/**
* inf_adopted_request_mirror:
* @request: A #InfAdoptedRequest.
* @by: The number of requests between the original and the mirrored
* operation.
*
* Mirrors @request as described in "Reducing the Problems of Group Undo" by
* Matthias Ressel and Rul Gunzenhäuser
* (http://portal.acm.org/citation.cfm?doid=320297.320312).
*
* Note that @by is the total amount of requests between the original and
* mirrored request, and thus equivalent to 2j-1 in the paper's definition.
*
* @request must be of type %INF_ADOPTED_REQUEST_DO and its operation must
* be reversible.
*
* Returns: The mirrored request as a new #InfAdoptedRequest.
**/
InfAdoptedRequest*
inf_adopted_request_mirror(InfAdoptedRequest* request,
guint by)
{
InfAdoptedRequestPrivate* priv;
InfAdoptedOperation* new_operation;
InfAdoptedStateVector* new_vector;
InfAdoptedRequest* new_request;
g_return_val_if_fail(INF_ADOPTED_IS_REQUEST(request), NULL);
g_return_val_if_fail(by % 2 == 1, NULL);
priv = INF_ADOPTED_REQUEST_PRIVATE(request);
g_return_val_if_fail(priv->type == INF_ADOPTED_REQUEST_DO, NULL);
g_return_val_if_fail(
inf_adopted_operation_is_reversible(priv->operation),
NULL
);
new_operation = inf_adopted_operation_revert(priv->operation);
new_vector = inf_adopted_state_vector_copy(priv->vector);
inf_adopted_state_vector_add(new_vector, priv->user_id, by);
new_request = inf_adopted_request_new_do(
new_vector,
priv->user_id,
new_operation
);
g_object_unref(new_operation);
inf_adopted_state_vector_free(new_vector);
return new_request;
}
/**
* inf_adopted_operation_revert:
* @operation: A #InfAdoptedOperation.
*
* Returns a new #InfAdoptedOperation that undoes the effect of @operation. If
* @operation and then its reverse operation are applied to a buffer (in that
* order), the buffer remains unchanged.
*
* @operation must be reversible for this function to be called (i.e.
* inf_adopted_operation_is_reversible() must return TRUE).
*
* Return Value: The reverse operation of @operation.
**/
InfAdoptedOperation*
inf_adopted_operation_revert(InfAdoptedOperation* operation)
{
InfAdoptedOperationIface* iface;
g_return_val_if_fail(INF_ADOPTED_IS_OPERATION(operation), NULL);
g_assert(inf_adopted_operation_is_reversible(operation) == TRUE);
iface = INF_ADOPTED_OPERATION_GET_IFACE(operation);
/* When inf_adopted_operation_is_reversible() returns TRUE for an operation
* it must implement revert. */
g_assert(iface->revert != NULL);
return (*iface->revert)(operation);
}
/**
* inf_adopted_operation_make_reversible:
* @operation: A #InfAdoptedOperation.
* @with: Another #InfAdoptedOperation that emerged from @operation by
* transforming it.
* @buffer: A #InfBuffer.
*
* Some operations may not be reversible, but can be made reversible with
* some extra information such as another operation that collected
* enough information while being transformed, and the current buffer.
*
* This function can only be called when @operation is not yet reversible
* and returns a new operation that has the same effect as @operation, but is
* reversible.
*
* For example, an operation that deletes some range of text in a text editor
* is not reversible if it only stores the position and length of the range,
* but can be made reversible when it looks up what there is at that position
* in the buffer.
*
* Return Value: A reversible #InfAdoptedOperation, or %NULL if @operation
* cannot be made reversible with the given transformed operation @with and
* @buffer.
**/
InfAdoptedOperation*
inf_adopted_operation_make_reversible(InfAdoptedOperation* operation,
InfAdoptedOperation* with,
InfBuffer* buffer)
{
InfAdoptedOperationIface* iface;
g_return_val_if_fail(INF_ADOPTED_IS_OPERATION(operation), NULL);
g_return_val_if_fail(INF_ADOPTED_IS_OPERATION(with), NULL);
g_return_val_if_fail(INF_IS_BUFFER(buffer), NULL);
g_assert(inf_adopted_operation_is_reversible(operation) == FALSE);
iface = INF_ADOPTED_OPERATION_GET_IFACE(operation);
if(iface->make_reversible != NULL)
return (*iface->make_reversible)(operation, with, buffer);
else
return NULL;
}
