Template_widget_source_file.xml   [plain text]

<sect1 id="Widget_Source_File">
<title>Widget Source File</title>
<para>
<!-- .LP -->
The source code file implements the widget class itself.  The unique
part of this file is the declaration and initialization of the
widget class record structure and the declaration of all resources and
action routines added by the widget class.
</para>
<para>
<!-- .LP -->
The contents of the Template implementation file,
<function>&lt; X11/Xaw/Template.c &gt;,</function>
are:
</para>
<!-- .CB -->
<!-- .\".so ../../lib/Xaw/Template.c -->
<literallayout class="monospaced">
/* Copyright (c) X Consortium 1987, 1988
 */

#include &lt;X11/IntrinsicP.h&gt;
#include &lt;X11/StringDefs.h&gt;
#include "TemplateP.h"

static XtResource resources[] = {
#define offset(field) XtOffsetOf(TemplateRec, template.field)
	/* {name, class, type, size, offset, default_type, default_addr}, */
    { XtNtemplateResource, XtCTemplateResource, XtRTemplateResource,
	  sizeof(char*), offset(resource), XtRString, (XtPointer) "default" },
#undef offset
};

static void TemplateAction(/* Widget, XEvent*, String*, Cardinal* */);

static XtActionsRec actions[] =
{
	/* {name,	procedure}, */
	{"template",	TemplateAction},
};

static char translations[] =
"	&lt;Key&gt;:	template(\|) \\n\\
";

TemplateClassRec templateClassRec = {
  { /* core fields */
	/* superclass	*/	(WidgetClass) &amp;widgetClassRec,
	/* class_name	*/	"Template",
	/* widget_size	*/	sizeof(TemplateRec),
	/* class_initialize	*/	NULL,
	/* class_part_initialize	*/	NULL,
	/* class_inited	*/	FALSE,
	/* initialize	*/	NULL,
	/* initialize_hook	*/	NULL,
	/* realize	*/	XtInheritRealize,
	/* actions	*/	actions,
	/* num_actions	*/	XtNumber(actions),
	/* resources	*/	resources,
	/* num_resources	*/	XtNumber(resources),
	/* xrm_class	*/	NULLQUARK,
	/* compress_motion	*/	TRUE,
	/* compress_exposure	*/	TRUE,
	/* compress_enterleave */	TRUE,
	/* visible_interest	*/	FALSE,
	/* destroy	*/	NULL,
	/* resize	*/	NULL,
	/* expose	*/	NULL,
	/* set_values	*/	NULL,
	/* set_values_hook	*/	NULL,
	/* set_values_almost	*/	XtInheritSetValuesAlmost,
	/* get_values_hook	*/	NULL,
	/* accept_focus	*/	NULL,
	/* version	*/	XtVersion,
	/* callback_private	*/	NULL,
	/* tm_table	*/	translations,
	/* query_geometry	*/	XtInheritQueryGeometry,
	/* display_accelerator	*/	XtInheritDisplayAccelerator,
	/* extension	*/	NULL
  },
  { /* template fields */
	/* empty	*/	0
  }
};

WidgetClass templateWidgetClass = (WidgetClass)&amp;templateClassRec;
</literallayout>
<!-- .CE -->
<para>
The resource list for the "WindowWidget" might look like the following:
</para>
<!-- .CB -->
<literallayout class="monospaced">
static XtResource resources[] = {
#define offset(field) XtOffsetOf(WindowWidgetRec, window.field)
	/* {name, class, type, size, offset, default_type, default_addr}, */
	{ XtNdrawingColor1, XtCColor, XtRPixel, sizeof(Pixel),
		  offset(color_1), XtRString, XtDefaultForeground },
	{ XtNdrawingColor2, XtCColor, XtRPixel, sizeof(Pixel),
		  offset(color_2), XtRString, XtDefaultForeground },
	{ XtNfont, XtCFont, XtRFontStruct, sizeof(XFontStruct*),
		  offset(font), XtRString, XtDefaultFont },
	{ XtNexposeCallback, XtCCallback, XtRCallback, sizeof(XtCallbackList),
		  offset(expose_callback), XtRCallback, NULL },
	{ XtNcallback, XtCCallback, XtRCallback, sizeof(XtCallbackList),
		  offset(input_callback), XtRCallback, NULL },
#undef offset
};
</literallayout>
<!-- .CE -->
<para>
<!-- .LP -->
The user input callback will be implemented by an action procedure which
passes the event pointer as call_data.  The action procedure
is declared as:
<!-- .CB -->
</para>
<literallayout class="monospaced">
/* ARGSUSED */
static void InputAction(w, event, params, num_params)
	Widget w;
	XEvent *event;
	String *params;		/* unused */
	Cardinal *num_params;	/* unused */
{
	XtCallCallbacks(w, XtNcallback, (XtPointer)event);
}

static XtActionsRec actions[] =
{
	/* {name,	procedure}, */
	{"input",	InputAction},
};
</literallayout>
<!-- .CE -->
<para>
<!-- .LP -->
and the default input binding will be to execute the input callbacks on
<function>KeyPress</function> and <function>ButtonPress : </function>
</para>
<literallayout class="monospaced">
static char translations[] =
"	&lt;Key&gt;:	input(\|) \\n\\
 	&lt;BtnDown&gt;:	input(\|) \\
";
</literallayout>
<!-- .CE -->
<para>
In the class record declaration and initialization, the only field that
is different from the Template is the expose procedure:
</para>
<!-- .CB -->
<literallayout class="monospaced">
/* ARGSUSED */
static void Redisplay(w, event, region)
	Widget w;
	XEvent *event;	/* unused */
	Region region;
{
	XtCallCallbacks(w, XtNexposeCallback, (XtPointer)region);
}

WindowClassRec windowClassRec = {

	...

	/* expose	*/	Redisplay,
</literallayout>
<!-- .CE -->
<para>
<!-- .LP -->
<!-- .sp -->
The "WindowWidget" will also declare three public procedures to return the
drawing colors and the font id, saving the application the effort of
constructing an argument list for a call to
<function>XtGetValues :</function>
</para>
<!-- .LP -->
<!-- .CB -->
<literallayout class="monospaced">
Pixel WindowColor1(w)
        Widget w;
{
        return ((WindowWidget)w)->window.color_1;
}

Pixel WindowColor2(w)
        Widget w;
{
        return ((WindowWidget)w)->window.color_2;
}

Font WindowFont(w)
        Widget w;
{
        return ((WindowWidget)w)->window.font->fid;
}
</literallayout>

<para>
The "WindowWidget" is now complete.  The application can retrieve the two
drawing colors from the widget instance by calling either
<function>XtGetValues ,</function>
or the <function>WindowColor</function> functions.  The actual window created for the
"WindowWidget" is available by calling the
<function>XtWindow</function> function.
</para>
</sect1>