# Widget Source File

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.

The contents of the Template implementation file, `<X11/Xaw/Template.c>`, are:

    /* Copyright (c) X Consortium 1987, 1988
     */

    #include <X11/IntrinsicP.h>
    #include <X11/StringDefs.h>
    #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[] =
    "	<Key>:	template( ) \\n\\
    ";

    TemplateClassRec templateClassRec = {
      { /* core fields */
    	/* superclass		*/	(WidgetClass) &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)&templateClassRec;

The resource list for the "WindowWidget" might look like the following:

    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
    };

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:

    /* 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},
    };

and the default input binding will be to execute the input callbacks on `KeyPress` and `ButtonPress :`

    static char translations[] =
    "	<Key>:	input( ) \\n\\
     	<BtnDown>:	input( ) \\
    ";

In the class record declaration and initialization, the only field that is different from the Template is the expose procedure:

    /* ARGSUSED */
    static void Redisplay(w, event, region)
    	Widget w;
    	XEvent *event;	/* unused */
    	Region region;
    {
    	XtCallCallbacks(w, XtNexposeCallback, (XtPointer)region);
    }

    WindowClassRec windowClassRec = {

    	...

    	/* expose	*/	Redisplay,

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 `XtGetValues :`

    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;
    }

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