HPUX SelHandler[3]
Tk_CreateSelHandler(3) Tk_CreateSelHandler(3)
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NAME
Tk_CreateSelHandler - arrange to handle requests for the primary
selection
SYNOPSIS
#include <tk.h>
Tk_CreateSelHandler(tkwin, target, proc, clientData, format)
ARGUMENTS
Tk_Window tkwin (in) Window for which proc will
provide selection
information.
Atom target (in) Form in which proc can
provide the selection (e.g.
STRING or FILE_NAME).
Corresponds to type
arguments in selection
commands.
Tk_SelectionProc *proc (in) Procedure to invoke whenever
the selection is owned by
tkwin and the selection
contents are requested in
the format given by target.
ClientData clientData (in) Arbitrary one-word value to
pass to proc.
Atom format (in) If the selection requestor
isn't in this process,
format determines the
representation used to
transmit the selection to
its requestor.
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DESCRIPTION
Tk_CreateSelHandler arranges for a particular procedure (proc) to be
called whenever the selection is owned by tkwin and the selection
contents are requested in the form given by target. Target should be
one of the entries defined in the left column of Table 2 of the X
Inter-Client Communication Conventions Manual (ICCCM) or any other
form in which an application is willing to present the selection. The
most common form is STRING.
- 1 - Formatted: August 11, 1996
Tk_CreateSelHandler(3) Tk_CreateSelHandler(3)
Proc should have arguments and result that match the type
Tk_SelectionProc:
typedef int Tk_SelectionProc(
ClientData clientData,
int offset,
char *buffer,
int maxBytes);
The clientData parameter to proc is a copy of the clientData argument
given to Tk_CreateSelHandler. Typically, clientData points to a data
structure containing application-specific information that is needed
to retrieve the selection. Offset specifies an offset position into
the selection, buffer specifies a location at which to copy
information about the selection, and maxBytes specifies the amount of
space available at buffer. Proc should place a NULL-terminated string
at buffer containing maxBytes or fewer characters (not including the
terminating NULL), and it should return a count of the number of non-
NULL characters stored at buffer. If the selection no longer exists
(e.g. it once existed but the user deleted the range of characters
containing it), then proc should return -1.
When transferring large selections, Tk will break them up into smaller
pieces (typically a few thousand bytes each) for more efficient
transmision. It will do this by calling proc one or more times, using
successively higher values of offset to retrieve successive portions
of the selection. If proc returns a count less than maxBytes it means
that the entire remainder of the selection has been returned. If
proc's return value is maxBytes it means there may be additional
information in the selection, so Tk must make another call to proc to
retrieve the next portion.
Proc always returns selection information in the form of a character
string. However, the ICCCM allows for information to be transmitted
from the selection owner to the selection requestor in any of several
formats, such as a string, an array of atoms, an array of integers,
etc. The format argument to Tk_CreateSelHandler indicates what format
should be used to transmit the selection to its requestor (see the
middle column of Table 2 of the ICCCM for examples). If format is not
STRING, then Tk will take the value returned by proc and divided it
into fields separated by white space. If format is ATOM, then Tk will
return the selection as an array of atoms, with each field in proc's
result treated as the name of one atom. For any other value of
format, Tk will return the selection as an array of 32-bit values
where each field of proc's result is treated as a number and
translated to a 32-bit value. In any event, the format atom is
returned to the selection requestor along with the contents of the
selection.
At present there is no way to delete a selection handler except by
deleting the window with which it is associated. However, if
Tk_CreateSelHandler is called when there already exists a handler for
target on tkwin, then the existing handler is replaced with a new one.
- 2 - Formatted: August 11, 1996
Tk_CreateSelHandler(3) Tk_CreateSelHandler(3)
KEYWORDS
format, handler, selection, target
- 3 - Formatted: August 11, 1996