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Add an entry for requestable data to the drag-and-drop data
PtRequestables_t *
PtTransportRequestable(
PtTransportCtrl_t *ctrl,
char const * const type,
char const * const desc,
int unsigned const flags,
int unsigned transport,
PtTransportReqDataCB_t *rq_callback,
void *rq_callback_data );
- ctrl
- A pointer to the
PtTransportCtrl_t
control structure for the drag-and-drop operation.
- type
- A descriptive type name, such as image, text,
filename, or files.
This is simply added to the header for the packed data.
- desc
- The specifics of what's in the data.
The extractor uses a regular-expression match against the description to
determine if the data should be unpacked or discarded.
This is simply added to the header for the packed data.
- flags
- Flags that affect the operation:
- Ph_DONT_COPY — refer to the data to be
transported instead of physically copying the data to the transport
control's stream buffers.
|
If this bit is set, any modifications to the data that occur between
packing and actual transport of the data will be reflected in the
data transported.
|
- transport
- The available transport types that can be specified when requesting
data from the source:
- Ph_TRANSPORT_INLINE
- The data being transported is in memory and can be unpacked immediately.
- Ph_TRANSPORT_FILEREF
- The data being transported is in the temporary file(s) named in
the inlined data.
- Ph_TRANSPORT_SHMEM
- The data being transported is in the temporary shared object(s)
named in the inlined data.
- Ph_TRANSPORT_STREAM
- The data being transported will be inlined a small piece at a time.
- Ph_TRANSPORT_NAMED_STREAM
- The data being transported will be inlined a small piece at a time.
The streamed data is named so multiple streams of data can be transferred
serially.
- Ph_TRANSPORT_FILE_STREAM
- The contents of files streamed using extended named streams.
This is like the named stream but with extra information with each data
block, including file information and so on.
The requester of data must choose one of the available request
transport types when requesting delivery of additional data.
- rq_callback
- A pointer (of type PtTransportReqDataCB_t *) to the
callback routine that will provide the data if the
destination of the drag-and-drop operation asks for requestable data.
For more information, see below.
This can be NULL if the source widget calls
PtAddResponseType()
to pack the requestable data before initiating the drag-and-drop operation.
- rq_callback_data
- A pointer to arbitrary data for the rq_callback function.
This pointer is stored in the rq_callback_data member of the
PtRequestables_t structure that's passed to the callback.
ph
This function adds an entry for requestable data to the data being packed
up for a drag-and-drop operation.
It's called by the source widget when it's starting the operation.
The callback function specified by the rq_callback argument
has the following prototype:
int unsigned rq_callback ( int unsigned type,
PtReqResponseHdr_t *req_hdr,
PtRequestables_t *requestables );
The arguments are:
- type
- Currently, this is Pt_DND_REQUEST_DATA, which indicates
that data is being requested.
- req_hdr
- A pointer to a
PtReqResponseHdr_t
structure that provides useful information and tracks streams; see below.
- requestables
- A pointer to a description of the requestable type.
The callback should use this when it calls
PtAddResponseType().
The callback function should return:
- Pt_CONTINUE
- The data has been or will be provided.
- Pt_END
- The source is canceling the destination's request.
The PtReqResponseHdr_t data structure determines how a
data request is responded to.
It's defined as:
typedef struct req_resp_msg_hdr PtReqResponseHdr_t;
struct req_resp_msg_hdr {
int unsigned transport;
int unsigned cmd;
int unsigned chunk_size;
int total_size;
int unsigned byte_offset;
void * source_handle;
void * dest_handle;
int unsigned data_size;
};
This structure's members can be used in the callback function as
described below:
- transport
- If the Ph_TRANSPORT_ENDIAN_OK bit is set in this
member, then the source and destination are of the same endianness.
For example:
if (! (req_hdr->transport &
Ph_TRANSPORT_ENDIAN_OK))
// Destination is a different endian
- cmd
- The action to take.
If the callback's type argument is
Pt_DND_REQUEST_DATA, cmd is
Pt_DND_CMD_PROVIDE_DATA.
- chunk_size
- The size of the data that the client will accept.
If this is too small, return Pt_END from the callback
to make the request fail.
- total_size
- The size of data to be sent to the destination.
This is equal to chunk_size if you're not streaming.
- byte_offset
- The offset into the data from which to start sending data.
This is useful for streams of data.
- source_handle
- An identifier for the source that's passed back in this member if more
than one transmission is required to provide the requested data.
The destination shouldn't modify this member.
- dest_handle
- An identifier for the destination that's passed back in this member
if more than one transmission is required to provide the requested data.
The source shouldn't modify this member.
- data_size
- If you're responding with packed data, this is the packed size, not
the unpacked size.
- 0
- Success.
- -1
- An error occurred; errno is set.
Photon
Safety: | |
Interrupt handler |
No |
Signal handler |
No |
Thread |
No |
PtAddResponseType(),
PtCreateTransportCtrl(),
PtInitDnd(),
PtTransportCtrl_t,
PtTransportType()
Drag and Drop chapter
of the Photon Programmer's Guide
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