Volume 6A: Motif Programming Manual

12.3.6 CheckBoxes

A CheckBox is similar to a RadioBox, except that there is no restriction on how many items may be selected at once.

A word processing program might use a CheckBox for non-exclusive settings, such as whether font smoothing,

bitmap smoothing, or both, should be applied.

Like RadioBoxes, CheckBoxes are implemented using RowColumn widgets and ToggleButton children. To allow

multiple items to be selected, the XmNradioBehavior resource is set to False. The convenience routine

XmVaCreateSimpleCheckBox() works just like the radio box creation routine, except that it turns off the

XmNradioBehavior resource. Rather than using this function, we can simply create a common RowColumn

widget without the aid of convenience functions and add ToggleButton children. With this technique, we have more

direct control over the resources that are set in the RowColumn, since we can specify exactly which ones we want

using the varargs interface for creating the widget.

the source code demonstrates how to create a CheckBox with a regular RowColumn widget.

XtSetLanguageProc() is only available in X11R5; there is no corresponding function in X11R4.

/* toggle_box.c −− demonstrate a homebrew ToggleBox. A static

* list of strings is used as the basis for a list of toggles.

* The callback routine toggled() is set for each toggle item.

* The client data for this routine is set to the enumerated

* value of the item with respect to the entire list. This value

* is treated as a bit which is toggled in "toggles_set" −− a

* mask that contains a complete list of all the selected items.

* This list is printed when the PushButton is selected.

*/

#include <Xm/ToggleBG.h>

#include <Xm/PushBG.h>

#include <Xm/SeparatoG.h>

#include <Xm/RowColumn.h>

unsigned long toggles_set; /* has the bits of which toggles are set */

char *strings[] = {

"One", "Two", "Three", "Four", "Five",

"Six", "Seven", "Eight", "Nine", "Ten",

};

/* A RowColumn is used to manage a ToggleBox (also a RowColumn) and

* a PushButton with a separator gadget in between.

*/

main(argc, argv)

int argc;

char *argv[];

{

Widget toplevel, rowcol, toggle_box, w;

XtAppContext app;

void toggled(), check_bits();

int i;

XtSetLanguageProc (NULL, NULL, NULL);

toplevel = XtVaAppInitialize (&app, "Demos",

NULL, 0, &argc, argv, NULL, NULL);

rowcol = XtVaCreateManagedWidget ("rowcolumn",

xmRowColumnWidgetClass, toplevel,

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NULL);

toggle_box = XtVaCreateWidget ("togglebox",

xmRowColumnWidgetClass, rowcol,

XmNpacking, XmPACK_COLUMN,

XmNnumColumns, 2,

NULL);

/* simply loop thru the strings creating a widget for each one */

for (i = 0; i < XtNumber (strings); i++) {

w = XtVaCreateManagedWidget (strings[i],

xmToggleButtonGadgetClass, toggle_box, NULL);

XtAddCallback (w, XmNvalueChangedCallback, toggled, i);

}

XtVaCreateManagedWidget ("sep",

xmSeparatorGadgetClass, rowcol, NULL);

w = XtVaCreateManagedWidget ("Check Toggles",

xmPushButtonGadgetClass, rowcol, NULL);

XtAddCallback (w, XmNactivateCallback, check_bits, NULL);

XtManageChild (rowcol);

XtManageChild (toggle_box);

XtRealizeWidget (toplevel);

XtAppMainLoop (app);

}

/* callback for all ToggleButtons. */

void

toggled(widget, client_data, call_data)

Widget widget;

XtPointer client_data;

XtPointer call_data;

{

int bit = (int) client_data;

XmToggleButtonCallbackStruct *toggle_data =

(XmToggleButtonCallbackStruct *) call_data;

if (toggle_data−>set) /* if the toggle button is set, flip its bit */

toggles_set |= (1 << bit);

else /* if the toggle is "off", turn off the bit. */

toggles_set &= ~(1 << bit);

}

void

check_bits(widget, client_data, call_data)

Widget widget;

XtPointer client_data;

XtPointer call_data;

{

int i;

printf ("Toggles set:");

for (i = 0; i < XtNumber (strings); i++)

if (toggles_set & (1<<i))

printf (" %s", strings[i]);

putchar ('0);

}

The output of this program is shown in the figure.

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329

Output of toggle_box.c

This example is similar to the previous RadioBox examples, except that since more than one of the buttons may be set

at a time in a CheckBox, we can no longer use toggle_item_set the way we did in the previous examples.

Instead, we are going to change its name to toggles_set and its type to unsigned long. This time we are going

to use the variable as a mask, which means that its individual bits have meaning, rather than the combined value of the

variable. The bits indicate which of the ToggleButtons have been set. Each time a ToggleButton changes its value, the

callback routine flips the corresponding bit in the mask. We can therefore determine at any given time which buttons

are set and which are not. The unsigned long type can only represent up to 32 ToggleButtons. If more buttons are

used within the CheckBox, a new mechanism is needed, although the basic design presented here can still be used.

The PushButton in the program provides a way to check the state of all of the ToggleButtons. The callback routine for

the PushButton prints the strings of those buttons that are selected by looping through the toggles_set variable

and checking for bits that have been set.

One interesting aspect of this program is that it works just as well if the CheckBox is a RadioBox. To test this

statement, we can run the program again with the radioBehavior resource set to True via the −xrm

command−line option:

toggle_box −xrm "*radioBehavior: True"

The result is shown in the figure.

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