Public Header File The public header file contains declarations that will be required by any application module that needs to refer to the widget; whether to create an instance of the class, to perform an operation, or to call a public routine implemented by the widget class. The contents of the Template public header file, < X11/Xaw/Template.h >, are: .. /* Copyright (c) X Consortium 1987, 1988 */ #ifndef _Template_h #define _Template_h /**************************************************************** * * Template widget * ****************************************************************/ /* Resources: Name Class RepType Default Value ---- ----- ------- ------------- background Background Pixel XtDefaultBackground border BorderColor Pixel XtDefaultForeground borderWidth BorderWidth Dimension 1 destroyCallback Callback Pointer NULL height Height Dimension 0 mappedWhenManaged MappedWhenManaged Boolean True sensitive Sensitive Boolean True width Width Dimension 0 x Position Position 0 y Position Position 0 */ /* define any special resource names here that are not in <X11/StringDefs.h> */ #define XtNtemplateResource "templateResource" #define XtCTemplateResource "TemplateResource" /* declare specific TemplateWidget class and instance datatypes */ typedef struct _TemplateClassRec* TemplateWidgetClass; typedef struct _TemplateRec* TemplateWidget; /* declare the class constant */ extern WidgetClass templateWidgetClass; #endif /* _Template_h */ You will notice that most of this file is documentation. The crucial parts are the last 8 lines where macros for any private resource names and classes are defined and where the widget class datatypes and class record pointer are declared. For the "WindowWidget", we want 2 drawing colors, a callback list for user input and an exposeCallback callback list, and we will declare three convenience procedures, so we need to add /* Resources: ... callback Callback Callback NULL drawingColor1 Color Pixel XtDefaultForeground drawingColor2 Color Pixel XtDefaultForeground exposeCallback Callback Callback NULL font Font XFontStruct* XtDefaultFont ... */ #define XtNdrawingColor1 "drawingColor1" #define XtNdrawingColor2 "drawingColor2" #define XtNexposeCallback "exposeCallback" extern Pixel WindowColor1(\|/* Widget */\|); extern Pixel WindowColor2(\|/* Widget */\|); extern Font\ \ WindowFont(\|/* Widget */\|); Note that we have chosen to call the input callback list by the generic name, callback, rather than a specific name. If widgets that define a single user-input action all choose the same resource name then there is greater possibility for an application to switch between widgets of different types. Private Header File The private header file contains the complete declaration of the class and instance structures for the widget and any additional private data that will be required by anticipated subclasses of the widget. Information in the private header file is normally hidden from the application and is designed to be accessed only through other public procedures; e.g. XtSetValues . The contents of the Template private header file, < X11/Xaw/TemplateP.h >, are: /* Copyright (c) X Consortium 1987, 1988 */ #ifndef _TemplateP_h #define _TemplateP_h #include <X11/Xaw/Template.h> /* include superclass private header file */ #include <X11/CoreP.h> /* define unique representation types not found in <X11/StringDefs.h> */ #define XtRTemplateResource "TemplateResource" typedef struct { int empty; } TemplateClassPart; typedef struct _TemplateClassRec { CoreClassPart core_class; TemplateClassPart template_class; } TemplateClassRec; extern TemplateClassRec templateClassRec; typedef struct { /* resources */ char* resource; /* private state */ } TemplatePart; typedef struct _TemplateRec { CorePart core; TemplatePart template; } TemplateRec; #endif /* _TemplateP_h */ The private header file includes the private header file of its superclass, thereby exposing the entire internal structure of the widget. It may not always be advantageous to do this; your own project development style will dictate the appropriate level of detail to expose in each module. The "WindowWidget" needs to declare two fields in its instance structure to hold the drawing colors, a resource field for the font and a field for the expose and user input callback lists: typedef struct { /* resources */ Pixel color_1; Pixel color_2; XFontStruct* font; XtCallbackList expose_callback; XtCallbackList input_callback; /* private state */ /* (none) */ } WindowPart; 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.