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clipboard.doc
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1992-09-01
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TABLE OF CONTENTS
clipboard.device/CBD_CHANGEHOOK
clipboard.device/CBD_CURRENTREADID
clipboard.device/CBD_CURRENTWRITEID
clipboard.device/CBD_POST
clipboard.device/CMD_READ
clipboard.device/CMD_UPDATE
clipboard.device/CMD_WRITE
clipboard.device/CBD_CHANGEHOOK clipboard.device/CBD_CHANGEHOOK
NAME
CBD_CHANGEHOOK -- Add or remove a clip change hook
FUNCTION
CBD_CHANGEHOOK allows specification of a hook to be called
when the data on the clipboard has changed.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CBD_CHANGEHOOK
io_Length - 0 to remove, 1 to install this hook
io_Data - struct Hook *, the clip change hook
HOOK ENVIRONMENT
hook message - a ClipHookMsg, as defined in devices/clipboard.h
chm_Type - 0, indicating that the message has the
following fields:
chm_ClipID - the clip ID of the clip triggering the change
hook object - io_Unit
clipboard.device/CBD_CURRENTREADID clipboard.device/CBD_CURRENTREADID
NAME
CBD_CURRENTREADID - Determine the current read identifier.
FUNCTION
CBD_CURRENTREADID fills the io_ClipID with a clip identifier that
can be compared with that of a post command: if greater than
the post identifier then the post data held privately by an
application is not valid for its own pasting.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CBD_CURRENTREADID
RESULTS
io_ClipID the ClipID of the current write is set
clipboard.device/CBD_CURRENTWRITEID clipboard.device/CBD_CURRENTWRITEID
NAME
CBD_CURRENTWRITEID -- Determine the current write identifier.
FUNCTION
CBD_CURRENTWRITEID fills the io_ClipID with a clip identifier that
can be compared with that of a post command: if greater than
the post identifier then the post is obsolete and need never
be satisfied.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CBD_CURRENTWRITEID
RESULTS
io_ClipID the ClipID of the current write is set
clipboard.device/CBD_POST clipboard.device/CBD_POST
NAME
CBD_POST -- Post availability of a clip to the clipboard.
FUNCTION
Indicate to the clipboard device that data is available for
use by accessors of the clipboard. This is intended to be
used when a cut is large, in a private data format, and/or
changing frequently, and it thus makes sense to avoid
converting it to an IFF form and writing it to the clipboard
unless another application wants it. The post provides a
message port to which the clipboard device will send a satisfy
message if the data is required.
If the satisfy message is received, the write associated with
the post must be performed. The act of writing the clip
indicates that the message has been received: it may then be
re-used by the clipboard device, and so must actually be
removed from the satisfy message port so that the port is not
corrupted.
If the application wishes to determine if a post it has
performed is still the current clip, it should check the
post's io_ClipID with that returned by the CBD_CURRENTREADID
command. If the current read io_ClipID is greater, the clip
is not still current.
If an application has a pending post and wishes to determine
if it should satisfy it (e.g. before it exits), it should
check the post's io_ClipID with that returned by the
CBD_CURRENTWRITEID command. If the current write io_ClipID is
greater, there is no need to satisfy the post.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CBD_POST
io_Data pointer to satisfy message port
io_ClipID zero
RESULTS
io_Error non-zero if an error occurred
io_ClipID the clip ID assigned to this post, to be used
in the write command if this is satisfied
clipboard.device/CMD_READ clipboard.device/CMD_READ
NAME
CMD_READ -- Read from a clip on the clipboard.
FUNCTION
The read function serves two purposes.
When io_Offset is within the clip, this acts as a normal read
request, and io_Data is filled with data from the clipboard.
The first read request should have a zero io_ClipID, which
will be filled with the ID assigned for this read. Normal
sequential access from the beginning of the clip is achieved
by setting io_Offset to zero for the first read, then leaving
it untouched for subsequent reads. If io_Data is null, then
io_Offset is incremented by io_Actual as if io_Length bytes
had been read: this is useful to skip to the end of file
by using a huge io_Length.
When io_Offset is beyond the end of the clip, this acts as a
signal to the clipboard device that the application is
through reading this clip. Realize that while an application
is in the middle of reading a clip, any attempts to write new
data to the clipboard are held off. This read past the end
of file indicates that those operations may now be initiated.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CMD_READ
io_Length number of bytes to put in data buffer
io_Data pointer to buffer of data to fill, or null to
skip over data
io_Offset byte offset of data to read
io_ClipID zero if this is the initial read
RESULTS
io_Error non-zero if an error occurred
io_Actual filled with the actual number of bytes read
io_Data (the buffer now has io_Actual bytes of data)
io_Offset updated to next read position, which is
beyond EOF if io_Actual != io_Length
io_ClipID the clip ID assigned to this read: do not
alter for subsequent reads
clipboard.device/CMD_UPDATE clipboard.device/CMD_UPDATE
NAME
CMD_UPDATE -- Terminate the writing of a clip to the clipboard.
FUNCTION
Indicate to the clipboard that the previous write commands are
complete and can be used for any pending pastes (reads). This
command cannot be issued while any of the write commands are
pending.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CMD_UPDATE
io_ClipID the ClipID of the write
RESULTS
io_Error non-zero if an error occurred
clipboard.device/CMD_WRITE clipboard.device/CMD_WRITE
NAME
CMD_WRITE -- Write to a clip on the clipboard.
FUNCTION
This command writes data to the clipboard. This data can be
provided sequentially by clearing io_Offset for the initial
write, and using the incremented value unaltered for
subsequent writes. If io_Offset is ever beyond the current
clip size, the clip is padded with zeros.
If this write is in response to a SatisfyMsg for a pending
post, then the io_ClipID returned by the CBD_POST command must
be used. Otherwise, a new ID is obtained by clearing the
io_ClipID for the first write. Subsequent writes must not
alter the io_ClipID.
IO REQUEST
io_Message mn_ReplyPort set up
io_Device preset by OpenDevice
io_Unit preset by OpenDevice
io_Command CMD_WRITE
io_Length number of bytes from io_Data to write
io_Data pointer to block of data to write
io_Offset usually zero if this is the initial write
io_ClipID zero if this is the initial write, ClipID of
the Post if this is to satisfy a post
RESULTS
io_Error non-zero if an error occurred
io_Actual filled with the actual number of bytes written
io_Offset updated to next write position
io_ClipID the clip ID assigned to this write: do not
alter for subsequent writes