Volume 7A: XView Programming Manual

The selection requestor then requests that the selection owner convert a list of targets.

On the selection owner side, a MULTIPLE request is treated as a stream of single requests.

The package calls the conversion procedure as many times as required to convert all of the

targets requested.

In the special case where a multiple request also involves an incremental target (INCR), the

selection owner calls the application-defined conversion procedure with format set

SEL_MULTIPLE to indicate that the selection request is a incremental request that is part of a

multiple request.

18.6 Additional Transfer Mechanisms (Selection Requestor)

A selection requestor may associate data with the window property being used in the

selection transaction. This property may be used by the selection owner for certain types of

selection transfers. The selection-requestor object attributes: SEL_PROP_DATA, and

SEL_TYPE_INDEX

support bi-directional data transfer for a property associated with a

selection. In addition, the attributes SEL_PROP_FORMAT, SEL_PROP_LENGTH,

SEL_PROP_TYPE, and SEL_PROP_TYPE_NAME, also support this type of selection transfer. A

selection requestor may associate a property with the selection that the requestor is request-

ing. For example, this associated property may be used to support an INSERT_SELECTION or

a INSERT_PROPERTY target. Or properties may be used by the owner for other reasons. A

selection-requestor object may associate data with the property that the selection is request-

ing. This information may be of interest to a selection owner for certain types of selection

transfers.

18.7 Additional Transfer Mechanisms (Selection Owner)

If the selection requestor is sending data to the selection owner, using additional properties,

the attribute SEL_PROP_INFO allows the selection owner to access this property data.

18.8 Sample Selection Owner Program with a Selection Item

Example 18-9 shows a simple panel with two text items and two buttons inside a frame. This

example uses a selection item to return the TARGETS type and a conversion procedure to

return the remaining supported types. The “Selection:” field allows the user to enter the

desired selection rank. The “Contents:” field allows the user to enter a string, the selection

data to be operated on. The “Own Selection” button causes the application to own the

selection. The “Lose Selection” button causes the selection to be lost.

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Example 18-9. Sample program

–

sel_hold.c

/*

* sel_hold.c: Example of how to acquire and hold a selection.

*

*/

#include <stdio.h>

#include <X11/Xlib.h>

#include <xview/xview.h>

#include <xview/frame.h>

#include <xview/panel.h>

#include <xview/textsw.h>

#include <xview/font.h>

#include <xview/sel_pkg.h>

Frame frame;

Xv_Server server;

Panel panel;

Panel_item p_selection,

p_contents,

p_own,

p_lose;

Selection_owner sel;

Selection_item sel_targets;

#define ATOM(server, name) (Atom)xv_get(server, SERVER_ATOM, name)

main(argc, argv)

int argc;

char **argv;

{

Panel_setting NotifyProc();

int SelectionConvertProc();

void SelectionDoneProc(),

SelectionLoseProc();

Xv_Font font;

Atom targets[5];

server = xv_init(XV_INIT_ARGC_PTR_ARGV, &argc, argv, NULL);

frame = xv_create((Window)NULL, FRAME,

XV_X, 520,

XV_Y, 655,

XV_LABEL, "Selection Holder Example",

FRAME_SHOW_FOOTER, True,

NULL);

panel = xv_create(frame, PANEL, NULL);

p_selection = xv_create(panel, PANEL_TEXT,

PANEL_LABEL_STRING, "Selection:",

PANEL_VALUE_DISPLAY_LENGTH, 40,

PANEL_NOTIFY_PROC, NotifyProc,

PANEL_ITEM_X, xv_col(panel,0),

PANEL_ITEM_Y, xv_row(panel,0),

NULL);

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Example 18-9. Sample program

–

sel_hold.c (continued)

p_contents = xv_create(panel, PANEL_TEXT,

PANEL_LABEL_STRING, "Contents:",

PANEL_VALUE_DISPLAY_LENGTH, 40,

PANEL_ITEM_X, xv_col(panel,0),

PANEL_ITEM_Y, xv_row(panel,1),

NULL);

p_own = xv_create(panel, PANEL_BUTTON,

PANEL_LABEL_STRING, "Own Selection",

PANEL_NOTIFY_PROC, NotifyProc,

PANEL_ITEM_X, xv_col(panel,5),

PANEL_ITEM_Y, xv_row(panel,2),

NULL);

p_lose = xv_create(panel, PANEL_BUTTON,

PANEL_LABEL_STRING, "Lose Selection",

PANEL_NOTIFY_PROC, NotifyProc,

PANEL_ITEM_X, xv_col(panel,30),

PANEL_ITEM_Y, xv_row(panel,2),

NULL);

/* Create a selection owner object */

sel = xv_create(panel, SELECTION_OWNER,

SEL_CONVERT_PROC, SelectionConvertProc,

SEL_DONE_PROC, SelectionDoneProc,

SEL_LOSE_PROC, SelectionLoseProc,

NULL);

targets[0] = (Atom)xv_get(server, SERVER_ATOM, "TARGETS");

targets[1] = (Atom)xv_get(server, SERVER_ATOM, "TIMESTAMP");

targets[2] = (Atom)xv_get(server, SERVER_ATOM, "LENGTH");

targets[3] = (Atom)xv_get(server, SERVER_ATOM, "STRING");

targets[4] = (Atom)xv_get(server, SERVER_ATOM, "DELETE");

/* Create a selection item, owned by the selection owner we just

* created. This pre-registers a conversion, in this case a

* conversion for ‘‘TARGETS’’.

*/

sel_targets = xv_create(sel, SELECTION_ITEM,

SEL_TYPE_NAME, "TARGETS",

SEL_FORMAT, 32,

SEL_LENGTH, 5,

SEL_DATA, (Xv_opaque)targets,

NULL);

window_fit(panel);

window_fit(frame);

xv_main_loop(frame);

exit(0);

}

The selection-owner object sel specifies the conversion procedure, the done procedure, and

the lose procedure. Next, the targets array is filled with supported atoms. These are the

names for the supported conversions. The selection-item object’s conversion is specified

420 XView Programming Manual

using the attributes: SEL_TYPE_NAME, SEL_FORMAT, and SEL_LENGTH. The attribute

SEL_DATA associates the selection data with the selection item.

18.8.0.1 The notify procedure

Example 18-10 shows how the NotifyProc() routine is used to handle the selection rank

entry, owning the selection, and losing the selection. If a selection rank has been entered, it is

read from the panel text item and then assigned to sel, the selection-owner object. If the

“own” button is pressed, the current selection is acquired by setting SEL_OWN to TRUE and

SEL_TIME to the time of the event. If the “lose” button is pressed, the current selection is

released by setting SEL_OWN to FALSE and SEL_TIME to the time of the event.

Example 18-10. The notify procedure

–

NotifyProc()

Panel_setting

NotifyProc(item, event)

Panel_item item;

Event *event;

{

if (item == p_selection) {

char *rank;

/* Get the rank of the selection */

/* the user would like to use. */

rank = (char *)xv_get(item, PANEL_VALUE);

/* Set the rank to our selection owner object. */

xv_set(sel, SEL_RANK_NAME, rank, NULL);

return(PANEL_NEXT);

} else if (item == p_own) {

/* The user pressed the ‘‘own’’ button, so we */

/* acquire the selection. */

xv_set(sel, SEL_OWN, True,

SEL_TIME, event_time(event),

NULL);

xv_set(frame,

FRAME_LEFT_FOOTER, "Acquired Selection...", NULL);

} else if (item == p_lose) {

/* The user pressed the ‘‘lose’’ button, so we lose ownership

* of the selection.

*/

xv_set(sel, SEL_OWN, False,

SEL_TIME, event_time(event),

NULL);

xv_set(frame, FRAME_LEFT_FOOTER, "Lost Selection...", NULL);

}

return(PANEL_DONE);

}

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18.8.0.2 The conversion procedure

The conversion procedure is specified by the SEL_CONVERT_PROC attribute. This conversion

procedure, SelectionConvertProc, is called whenever an application makes a request

to the selection owned by this application. This procedure is shown in Example 18-11. The

selection owner responds to the requesting application by converting the acquired selection

to the target type requested. A well behaved routine provides for the case of a TARGETS

request by returning a list of valid target types to the requestor. In this case, the selection

owner returns the length of the string selected for LENGTH, a copy of the contents of the string

selected for STRING, and sets the string to NULL and returns NULL for the DELETE target.

Example 18-11. Sample conversion procedure

–

SelectionConvertProc

int

SelectionConvertProc(sel, target, data, length, format)

Selection_owner sel;

Atom *target; /* Input/Output */

Xv_opaque *data; /* Output */

unsigned long *length; /* Output */

int *format; /* Output */

{

/* Request for the length of the selection. */

if (*target == ATOM(server, "LENGTH")) {

static unsigned long len;

char *contents;

contents = (char *)xv_get(p_contents, PANEL_VALUE);

len = strlen(contents);

*target = ATOM(server, "INTEGER");

*format = 32;

*length = 1;

*data = (Xv_opaque)&len;

return(True);

}

/* Request for the string contents of the selection. */

else if (*target == ATOM(server, "STRING")) {

char *contents;

contents = (char *)xv_get(p_contents, PANEL_VALUE);

*target = ATOM(server, "STRING");

*format = 8;

*length = strlen(contents);

*data = (Xv_opaque)strdup(contents);

return(True);

}

/* Request to delete the selection. */

else if (*target == ATOM(server, "DELETE")) {

xv_set(p_contents, PANEL_VALUE, "", NULL);

*target = ATOM(server, "NULL");

*format = 32;

*length = 0;

*data = (Xv_opaque)NULL;

return(True);

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