#ifndef lint
static char Xrcsid[] =
    "$XConsortium: Scrollbar.c,v 1.58 89/12/15 11:36:58 kit Exp $";
#endif /* lint */

/***********************************************************
Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
and the Massachusetts Institute of Technology, Cambridge, Massachusetts.

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the names of Digital or MIT not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  

DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/* ScrollBar.c */
/* created by weissman, Mon Jul  7 13:20:03 1986 */
/* converted by swick, Thu Aug 27 1987 */
/* ported to vms by mahan, Wed Oct 30 1991 */

#define XAW_SCROLLBAR_WIDGET

#ifdef vax11c
#include <decw$include/IntrinsicP.h>
#include <decw$include/StringDefs.h>

#include "XawInit.h"
#include "ScrollbarP.h"
#else
#include <X11/IntrinsicP.h>
#include <X11/StringDefs.h>

#include <X11/Xaw/XawInit.h>
#include <X11/Xaw/ScrollbarP.h>
#endif /* vax11c */

/* Private definitions. */

static char defaultTranslations[] =
    "<Btn1Down>:   StartScroll(Forward) \n\
     <Btn2Down>:   StartScroll(Continuous) MoveThumb() NotifyThumb() \n\
     <Btn3Down>:   StartScroll(Backward) \n\
     <Btn2Motion>: MoveThumb() NotifyThumb() \n\
     <BtnUp>:      NotifyScroll(Proportional) EndScroll()";

#ifdef bogusScrollKeys
    /* examples */
    "<KeyPress>f:  StartScroll(Forward) NotifyScroll(FullLength) EndScroll()"
    "<KeyPress>b:  StartScroll(Backward) NotifyScroll(FullLength) EndScroll()"
#endif

static float floatZero = 0.0;

#define Offset(field) XtOffset(ScrollbarWidget, field)

static XtResource resources[] = {
  {XtNlength, XtCLength, XtRDimension, sizeof(Dimension),
       Offset(scrollbar.length), XtRImmediate, (caddr_t) 1},
  {XtNthickness, XtCThickness, XtRDimension, sizeof(Dimension),
       Offset(scrollbar.thickness), XtRImmediate, (caddr_t) 14},
  {XtNorientation, XtCOrientation, XtROrientation, sizeof(XtOrientation),
      Offset(scrollbar.orientation), XtRImmediate, (caddr_t) XtorientVertical},
  {XtNscrollProc, XtCCallback, XtRCallback, sizeof(caddr_t),
       Offset(scrollbar.scrollProc), XtRCallback, NULL},
  {XtNthumbProc, XtCCallback, XtRCallback, sizeof(caddr_t),
       Offset(scrollbar.thumbProc), XtRCallback, NULL},
  {XtNjumpProc, XtCCallback, XtRCallback, sizeof(caddr_t),
       Offset(scrollbar.jumpProc), XtRCallback, NULL},
  {XtNthumb, XtCThumb, XtRPixmap, sizeof(Pixmap),
       Offset(scrollbar.thumb), XtRImmediate, (XtPointer) XtUnspecifiedPixmap},
  {XtNforeground, XtCForeground, XtRPixel, sizeof(Pixel),
       Offset(scrollbar.foreground), XtRString, XtDefaultForeground},
  {XtNshown, XtCShown, XtRFloat, sizeof(float),
       Offset(scrollbar.shown), XtRFloat, (caddr_t)&floatZero},
  {XtNtopOfThumb, XtCTopOfThumb, XtRFloat, sizeof(float),
       Offset(scrollbar.top), XtRFloat, (caddr_t)&floatZero},
  {XtNscrollVCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.verCursor), XtRString, "sb_v_double_arrow"},
  {XtNscrollHCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.horCursor), XtRString, "sb_h_double_arrow"},
  {XtNscrollUCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.upCursor), XtRString, "sb_up_arrow"},
  {XtNscrollDCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.downCursor), XtRString, "sb_down_arrow"},
  {XtNscrollLCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.leftCursor), XtRString, "sb_left_arrow"},
  {XtNscrollRCursor, XtCCursor, XtRCursor, sizeof(Cursor),
       Offset(scrollbar.rightCursor), XtRString, "sb_right_arrow"},
  {XtNminimumThumb, XtCMinimumThumb, XtRDimension, sizeof(Dimension),
       Offset(scrollbar.min_thumb), XtRImmediate, (caddr_t) 7},
};

static void ClassInitialize();
static void Initialize();
static void Destroy();
static void Realize();
static void Resize();
static void Redisplay();
static Boolean SetValues();

static void StartScroll();
static void MoveThumb();
static void NotifyThumb();
static void NotifyScroll();
static void EndScroll();

static XtActionsRec actions[] = {
	{"StartScroll",		StartScroll},
	{"MoveThumb",		MoveThumb},
	{"NotifyThumb",		NotifyThumb},
	{"NotifyScroll",	NotifyScroll},
	{"EndScroll",		EndScroll},
	{NULL,NULL}
};

#ifdef vax11c
globaldef {"scrollbarclassrec"} noshare
#endif vax11c
ScrollbarClassRec scrollbarClassRec = {
/* core fields */
    /* superclass       */      (WidgetClass) &widgetClassRec,
    /* class_name       */      "Scrollbar",
    /* size             */      sizeof(ScrollbarRec),
    /* class_initialize	*/	ClassInitialize,
    /* class_part_init  */	NULL,
    /* class_inited	*/	FALSE,
    /* initialize       */      Initialize,
    /* initialize_hook  */	NULL,
    /* realize          */      Realize,
    /* 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          */      Destroy,
    /* resize           */      Resize,
    /* expose           */      Redisplay,
    /* set_values       */      SetValues,
    /* set_values_hook  */	NULL,
    /* set_values_almost */	XtInheritSetValuesAlmost,
    /* get_values_hook  */	NULL,
    /* accept_focus     */      NULL,
    /* version          */	XtVersion,
    /* callback_private */      NULL,
    /* tm_table         */      defaultTranslations,
    /* query_geometry	*/	XtInheritQueryGeometry,
    /* display_accelerator*/	XtInheritDisplayAccelerator,
    /* extension        */	NULL
};

#ifdef vax11c
globaldef {"scrollbarwidgetclass"} noshare
#endif /* vax11c */
WidgetClass scrollbarWidgetClass = (WidgetClass)&scrollbarClassRec;

#define NoButton -1
#define PICKLENGTH(widget, x, y) \
    ((widget->scrollbar.orientation == XtorientHorizontal) ? x : y)
#define MIN(x,y)	((x) < (y) ? (x) : (y))
#define MAX(x,y)	((x) > (y) ? (x) : (y))

static void ClassInitialize()
{
    static XtConvertArgRec screenConvertArg[] = {
        {XtWidgetBaseOffset, (caddr_t) XtOffset(Widget, core.screen),
	     sizeof(Screen *)}
    };

    XawInitializeWidgetSet();
    XtAddConverter( XtRString, XtROrientation, XmuCvtStringToOrientation,
		    NULL, (Cardinal)0 );
    XtAddConverter( XtRString, XtRPixmap, XmuCvtStringToBitmap,
		   screenConvertArg, XtNumber(screenConvertArg));
}

/*
 * Make sure the first number is within the range specified by the other
 * two numbers.
 */

static int InRange(num, small, big)
int num, small, big;
{
    return (num < small) ? small : ((num > big) ? big : num);
}

/*
 * Same as above, but for floating numbers. 
 */

static float FloatInRange(num, small, big)
float num, small, big;
{
    return (num < small) ? small : ((num > big) ? big : num);
}


/* Fill the area specified by top and bottom with the given pattern. */
static float FractionLoc(w, x, y)
  ScrollbarWidget w;
  int x, y;
{
    float   result;

    result = PICKLENGTH(w, (float) x/w->core.width,
			(float) y/w->core.height);
    return FloatInRange(result, 0.0, 1.0);
}


static FillArea(w, top, bottom, thumb)
  ScrollbarWidget w;
  Position top, bottom;
  int thumb;
{
    Dimension length = bottom-top;

    if (bottom < 0) return;

    switch(thumb) {
	/* Fill the new Thumb location */
      case 1:
	if (w->scrollbar.orientation == XtorientHorizontal) 
	    XFillRectangle(XtDisplay(w), XtWindow(w),
			   w->scrollbar.gc, top, 1, length,
			   w->core.height-2);
	
	else XFillRectangle(XtDisplay(w), XtWindow(w), w->scrollbar.gc,
			    1, top, w->core.width-2, length);

	break;
	/* Clear the old Thumb location */
      case 0:
	if (w->scrollbar.orientation == XtorientHorizontal) 
	    XClearArea(XtDisplay(w), XtWindow(w), top, 1,
		       length, w->core.height-2, FALSE);
	
	else XClearArea(XtDisplay(w), XtWindow(w), 1,
			top, w->core.width-2, length, FALSE);

    }  
}


/* Paint the thumb in the area specified by w->top and
   w->shown.  The old area is erased.  The painting and
   erasing is done cleverly so that no flickering will occur. */

static void PaintThumb( w )
  ScrollbarWidget w;
{
    Position oldtop, oldbot, newtop, newbot;

    oldtop = w->scrollbar.topLoc;
    oldbot = oldtop + w->scrollbar.shownLength;
    newtop = w->scrollbar.length * w->scrollbar.top;
    newbot = newtop + (int)(w->scrollbar.length * w->scrollbar.shown);
    if (newbot < newtop + w->scrollbar.min_thumb) 
      newbot = newtop + w->scrollbar.min_thumb;
    w->scrollbar.topLoc = newtop;
    w->scrollbar.shownLength = newbot - newtop;

    if (XtIsRealized((Widget)w)) {
	if (newtop < oldtop) FillArea(w, newtop, MIN(newbot, oldtop), 1);
	if (newtop > oldtop) FillArea(w, oldtop, MIN(newtop, oldbot), 0);
	if (newbot < oldbot) FillArea(w, MAX(newbot, oldtop), oldbot, 0);
	if (newbot > oldbot) FillArea(w, MAX(newtop, oldbot), newbot, 1);
    }
}


static void SetDimensions(w)
    ScrollbarWidget w;
{
    if (w->scrollbar.orientation == XtorientVertical) {
	w->scrollbar.length = w->core.height;
	w->scrollbar.thickness = w->core.width;
    }
    else {
	w->scrollbar.length = w->core.width;
	w->scrollbar.thickness = w->core.height;
    }
}

/*	Function Name: Destroy
 *	Description: Called as the scrollbar is going away...
 *	Arguments: w - the scrollbar.
 *	Returns: nonw
 */

static void
Destroy(w)
Widget w;
{
    ScrollbarWidget sbw = (ScrollbarWidget) w;
    
    XtReleaseGC(w, sbw->scrollbar.gc);
}

/*	Function Name: CreateGC
 *	Description: Creates the GC.
 *	Arguments: w - the scrollbar widget.
 *	Returns: none. 
 */

static void
CreateGC(w)
Widget w;
{
    ScrollbarWidget sbw = (ScrollbarWidget) w;
    XGCValues gcValues;
    XtGCMask mask;
    unsigned int depth = 1;

    if (sbw->scrollbar.thumb == XtUnspecifiedPixmap) {
        sbw->scrollbar.thumb = XmuCreateStippledPixmap (XtScreen(w), 
							(Pixel) 1, (Pixel) 0,
							depth);
    }
    else if (sbw->scrollbar.thumb != None) {
	Window root;
	int x, y;
	unsigned int width, height, bw;
	if (XGetGeometry(XtDisplay(w), sbw->scrollbar.thumb, &root, &x, &y,
			 &width, &height, &bw, &depth) == 0) {
	    XtAppError(XtWidgetToApplicationContext(w),
	       "Scrollbar Widget: Could not get geometry of thumb pixmap.");
	}
    }

    gcValues.foreground = sbw->scrollbar.foreground;
    gcValues.background = sbw->core.background_pixel;
    mask = GCForeground | GCBackground;

    if (sbw->scrollbar.thumb != None) {
	if (depth == 1) {
	    gcValues.fill_style = FillOpaqueStippled;
	    gcValues.stipple = sbw->scrollbar.thumb;
	    mask |= GCFillStyle | GCStipple;
	}
	else {
	    gcValues.fill_style = FillTiled;
	    gcValues.tile = sbw->scrollbar.thumb;
	    mask |= GCFillStyle | GCTile;
	}
    }
    sbw->scrollbar.gc = XtGetGC( w, mask, &gcValues);
}

/* ARGSUSED */
static void Initialize( request, new )
   Widget request;		/* what the client asked for */
   Widget new;			/* what we're going to give him */
{
    ScrollbarWidget w = (ScrollbarWidget) new;

    CreateGC(new);

    if (w->core.width == 0)
	w->core.width = (w->scrollbar.orientation == XtorientVertical)
	    ? w->scrollbar.thickness : w->scrollbar.length;

    if (w->core.height == 0)
	w->core.height = (w->scrollbar.orientation == XtorientHorizontal)
	    ? w->scrollbar.thickness : w->scrollbar.length;

    SetDimensions( w );
    w->scrollbar.direction = 0;
    w->scrollbar.topLoc = 0;
    w->scrollbar.shownLength = w->scrollbar.min_thumb;
}

static void Realize( gw, valueMask, attributes )
   Widget gw;
   Mask *valueMask;
   XSetWindowAttributes *attributes;
{
    ScrollbarWidget w = (ScrollbarWidget) gw;

    w->scrollbar.inactiveCursor =
      (w->scrollbar.orientation == XtorientVertical)
	? w->scrollbar.verCursor
	: w->scrollbar.horCursor;

    attributes->cursor = w->scrollbar.inactiveCursor;
    *valueMask |= CWCursor;
    
    XtCreateWindow( gw, InputOutput, (Visual *)CopyFromParent,
		    *valueMask, attributes );
}

/* ARGSUSED */
static Boolean 
SetValues( current, request, desired )
Widget current,		/* what I am */
       request,		/* what he wants me to be */
       desired;		/* what I will become */
{
    ScrollbarWidget w = (ScrollbarWidget) current;
    ScrollbarWidget dw = (ScrollbarWidget) desired;
    Boolean redraw = FALSE;

/*
 * If these values are outside the acceptable range ignore them...
 */

    if (dw->scrollbar.top < 0.0 || dw->scrollbar.top > 1.0)
        dw->scrollbar.top = w->scrollbar.top;

    if (dw->scrollbar.shown < 0.0 || dw->scrollbar.shown > 1.0)
        dw->scrollbar.shown = w->scrollbar.shown;

/*
 * Change colors and stuff...
 */

    if ( XtIsRealized (desired) ) {
	if ( (w->scrollbar.foreground != dw->scrollbar.foreground) ||
	    (w->core.background_pixel != dw->core.background_pixel) ||
	    (w->scrollbar.thumb != dw->scrollbar.thumb) ) 
	{
	    XtReleaseGC(w, w->scrollbar.thumb);
	    CreateGC( (Widget) dw);
	    redraw = TRUE;
	}
	if (w->scrollbar.top != dw->scrollbar.top ||
	    w->scrollbar.shown != dw->scrollbar.shown)
	    redraw = TRUE;
    }

    return( redraw );
}

static void Resize( gw )
   Widget gw;
{
    /* ForgetGravity has taken care of background, but thumb may
     * have to move as a result of the new size. */
    SetDimensions( (ScrollbarWidget)gw );
    Redisplay( gw, (XEvent*)NULL, (Region)NULL );
}


/* ARGSUSED */
static void Redisplay( gw, event, region )
   Widget gw;
   XEvent *event;
   Region region;
{
    ScrollbarWidget w = (ScrollbarWidget) gw;
    int x, y;
    unsigned int width, height;

    if (w->scrollbar.orientation == XtorientHorizontal) {
	x = w->scrollbar.topLoc;
	y = 1;
	width = w->scrollbar.shownLength;
	height = w->core.height - 2;
    } else {
	x = 1;
	y = w->scrollbar.topLoc;
	width = w->core.width - 2;
	height = w->scrollbar.shownLength;
    }

    if ( (region == NULL) ||
	 (XRectInRegion(region, x, y, width, height) != RectangleOut) ) {
	/* Forces entire thumb to be painted. */
	w->scrollbar.topLoc = -(w->scrollbar.length + 1);
	PaintThumb( w ); 
    }
}


/* ARGSUSED */
static void StartScroll( gw, event, params, num_params )
  Widget gw;
  XEvent *event;
  String *params;		/* direction: Back|Forward|Smooth */
  Cardinal *num_params;		/* we only support 1 */
{
    ScrollbarWidget w = (ScrollbarWidget) gw;
    Cursor cursor;
    char direction;

    if (w->scrollbar.direction != 0) return; /* if we're already scrolling */
    if (*num_params > 0) direction = *params[0];
    else		 direction = 'C';

    w->scrollbar.direction = direction;

    switch( direction ) {
	case 'B':
	case 'b':	cursor = (w->scrollbar.orientation == XtorientVertical)
				   ? w->scrollbar.downCursor
				   : w->scrollbar.rightCursor; break;

	case 'F':
	case 'f':	cursor = (w->scrollbar.orientation == XtorientVertical)
				   ? w->scrollbar.upCursor
				   : w->scrollbar.leftCursor; break;

	case 'C':
	case 'c':	cursor = (w->scrollbar.orientation == XtorientVertical)
				   ? w->scrollbar.rightCursor
				   : w->scrollbar.upCursor; break;

	default:	return; /* invalid invocation */
    }

    XDefineCursor(XtDisplay(w), XtWindow(w), cursor);

    XFlush(XtDisplay(w));
}


static Boolean CompareEvents( oldEvent, newEvent )
    XEvent *oldEvent, *newEvent;
{
#define Check(field) if (newEvent->field != oldEvent->field) return False;

    Check(xany.display);
    Check(xany.type);
    Check(xany.window);

    switch( newEvent->type ) {
      case MotionNotify:
		Check(xmotion.state); break;
      case ButtonPress:
      case ButtonRelease:
		Check(xbutton.state);
		Check(xbutton.button); break;
      case KeyPress:
      case KeyRelease:
		Check(xkey.state);
		Check(xkey.keycode); break;
      case EnterNotify:
      case LeaveNotify:
		Check(xcrossing.mode);
		Check(xcrossing.detail);
		Check(xcrossing.state); break;
    }
#undef Check

    return True;
}

struct EventData {
	XEvent *oldEvent;
	int count;
};

static Bool PeekNotifyEvent( dpy, event, args )
    Display *dpy;
    XEvent *event;
    char *args;
{
    struct EventData *eventData = (struct EventData*)args;

    return ((++eventData->count == QLength(dpy)) /* since PeekIf blocks */
	    || CompareEvents(event, eventData->oldEvent));
}


static Boolean LookAhead( w, event )
    Widget w;
    XEvent *event;
{
    XEvent newEvent;
    struct EventData eventData;

    if (QLength(XtDisplay(w)) == 0) return False;

    eventData.count = 0;
    eventData.oldEvent = event;

    XPeekIfEvent(XtDisplay(w), &newEvent, PeekNotifyEvent, (char*)&eventData);

    if (CompareEvents(event, &newEvent))
	return True;
    else
	return False;
}


static void ExtractPosition( event, x, y )
    XEvent *event;
    Position *x, *y;		/* RETURN */
{
    switch( event->type ) {
      case MotionNotify:
		*x = event->xmotion.x;	 *y = event->xmotion.y;	  break;
      case ButtonPress:
      case ButtonRelease:
		*x = event->xbutton.x;   *y = event->xbutton.y;   break;
      case KeyPress:
      case KeyRelease:
		*x = event->xkey.x;      *y = event->xkey.y;	  break;
      case EnterNotify:
      case LeaveNotify:
		*x = event->xcrossing.x; *y = event->xcrossing.y; break;
      default:
		*x = 0; *y = 0;
    }
}

static void NotifyScroll( gw, event, params, num_params   )
   Widget gw;
   XEvent *event;
   String *params;		/* style: Proportional|FullLength */
   Cardinal *num_params;	/* we only support 1 */
{
    ScrollbarWidget w = (ScrollbarWidget) gw;
    int call_data;
    char style;
    Position x, y;

    if (w->scrollbar.direction == 0) return; /* if no StartScroll */

    if (LookAhead(gw, event)) return;

    if (*num_params > 0) style = *params[0];
    else		 style = 'P';

    switch( style ) {
        case 'P':    /* Proportional */
        case 'p':    ExtractPosition( event, &x, &y );
		     call_data = InRange( PICKLENGTH( w, x, y ),
					  0,
					  (int) w->scrollbar.length); break;

        case 'F':    /* FullLength */
        case 'f':    call_data = w->scrollbar.length; break;
    }

    switch( w->scrollbar.direction ) {
        case 'B':
        case 'b':    call_data = -call_data;
	  	     /* fall through */
        case 'F':
	case 'f':    XtCallCallbacks( gw, XtNscrollProc, (caddr_t)call_data );
	             break;

        case 'C':
	case 'c':    /* NotifyThumb has already called the thumbProc(s) */
		     break;
    }
}

/* ARGSUSED */
static void EndScroll(gw, event, params, num_params )
   Widget gw;
   XEvent *event;		/* unused */
   String *params;		/* unused */
   Cardinal *num_params;	/* unused */
{
    ScrollbarWidget w = (ScrollbarWidget) gw;

    XDefineCursor(XtDisplay(w), XtWindow(w), w->scrollbar.inactiveCursor);
    XFlush(XtDisplay(w));

    w->scrollbar.direction = 0;
}


/* ARGSUSED */
static void MoveThumb( gw, event, params, num_params )
   Widget gw;
   XEvent *event;
   String *params;		/* unused */
   Cardinal *num_params;	/* unused */
{
    ScrollbarWidget w = (ScrollbarWidget) gw;
    Position x, y;

    if (w->scrollbar.direction == 0) return; /* if no StartScroll */

    if (LookAhead(gw, event)) return;

    ExtractPosition( event, &x, &y );
    w->scrollbar.top = FractionLoc(w, x, y);
    PaintThumb(w);
    XFlush(XtDisplay(w));	/* re-draw it before Notifying */
}


/* ARGSUSED */
static void NotifyThumb( gw, event, params, num_params )
   Widget gw;
   XEvent *event;
   String *params;		/* unused */
   Cardinal *num_params;	/* unused */
{
    register ScrollbarWidget w = (ScrollbarWidget) gw;

    if (w->scrollbar.direction == 0) return; /* if no StartScroll */

    if (LookAhead(gw, event)) return;

    XtCallCallbacks( gw, XtNthumbProc, w->scrollbar.top);
    XtCallCallbacks( gw, XtNjumpProc, &w->scrollbar.top);
}



/************************************************************
 *
 *  Public routines. 
 *
 ************************************************************/

/* Set the scroll bar to the given location. */

void 
XawScrollbarSetThumb( gw, top, shown )
Widget gw;
float top, shown;
{
    ScrollbarWidget w = (ScrollbarWidget)gw;

    if (w->scrollbar.direction == 'c') return; /* if still thumbing */

    w->scrollbar.top = (top > 1.0) ? 1.0 :
		       (top >= 0.0) ? top :
			   w->scrollbar.top;

    w->scrollbar.shown = (shown > 1.0) ? 1.0 :
			 (shown >= 0.0) ? shown :
			     w->scrollbar.shown;

    PaintThumb( w );
}
