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IABSD.fr/xenocara/app/xterm/scrollbar.c

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  • Author : matthieu
    Date : 2007-06-15 19:29:55
    Hash : 06d70fc7
    Message : import xterm 225

  • app/xterm/scrollbar.c
  • /* $XTermId: scrollbar.c,v 1.132 2007/02/11 14:49:56 tom Exp $ */
    
    /* $XFree86: xc/programs/xterm/scrollbar.c,v 3.48 2006/02/13 01:14:59 dickey Exp $ */
    
    /*
     * Copyright 2000-2006,2007 by Thomas E. Dickey
     *
     *                         All Rights Reserved
     *
     * Permission is hereby granted, free of charge, to any person obtaining a
     * copy of this software and associated documentation files (the
     * "Software"), to deal in the Software without restriction, including
     * without limitation the rights to use, copy, modify, merge, publish,
     * distribute, sublicense, and/or sell copies of the Software, and to
     * permit persons to whom the Software is furnished to do so, subject to
     * the following conditions:
     *
     * The above copyright notice and this permission notice shall be included
     * in all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
     * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
     * IN NO EVENT SHALL THE ABOVE LISTED COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
     * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
     * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
     * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
     *
     * Except as contained in this notice, the name(s) of the above copyright
     * holders shall not be used in advertising or otherwise to promote the
     * sale, use or other dealings in this Software without prior written
     * authorization.
     *
     *
     * Copyright 1987 by Digital Equipment Corporation, Maynard, 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 name of Digital Equipment
     * Corporation 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.
     */
    
    #include <xterm.h>
    
    #include <X11/Xatom.h>
    
    #if defined(HAVE_LIB_XAW)
    #include <X11/Xaw/Scrollbar.h>
    #elif defined(HAVE_LIB_XAW3D)
    #include <X11/Xaw3d/Scrollbar.h>
    #elif defined(HAVE_LIB_NEXTAW)
    #include <X11/neXtaw/Scrollbar.h>
    #elif defined(HAVE_LIB_XAWPLUS)
    #include <X11/XawPlus/Scrollbar.h>
    #endif
    
    #include <data.h>
    #include <error.h>
    #include <menu.h>
    #include <xcharmouse.h>
    
    /*
     * The scrollbar's border overlaps the border of the vt100 window.  If there
     * is no border for the vt100, there can be no border for the scrollbar.
     */
    #define SCROLLBAR_BORDER(xw) ((xw)->screen.scrollBarBorder)
    #if OPT_TOOLBAR
    #define ScrollBarBorder(xw) (BorderWidth(xw) ? SCROLLBAR_BORDER(xw) : 0)
    #else
    #define ScrollBarBorder(xw) SCROLLBAR_BORDER(xw)
    #endif
    
    /* Event handlers */
    
    static void ScrollTextTo PROTO_XT_CALLBACK_ARGS;
    static void ScrollTextUpDownBy PROTO_XT_CALLBACK_ARGS;
    
    /* Resize the text window for a terminal screen, modifying the
     * appropriate WM_SIZE_HINTS and taking advantage of bit gravity.
     */
    void
    DoResizeScreen(XtermWidget xw)
    {
        TScreen *screen = &xw->screen;
    
        int border = 2 * xw->screen.border;
        int min_wide = border + xw->screen.fullVwin.sb_info.width;
        int min_high = border;
        XtGeometryResult geomreqresult;
        Dimension reqWidth, reqHeight, repWidth, repHeight;
    #ifndef NO_ACTIVE_ICON
        VTwin *saveWin = WhichVWin(screen);
    
        /* all units here want to be in the normal font units */
        WhichVWin(screen) = &screen->fullVwin;
    #endif /* NO_ACTIVE_ICON */
    
        /*
         * I'm going to try to explain, as I understand it, why we
         * have to do XGetWMNormalHints and XSetWMNormalHints here,
         * although I can't guarantee that I've got it right.
         *
         * In a correctly written toolkit program, the Shell widget
         * parses the user supplied geometry argument.  However,
         * because of the way xterm does things, the VT100 widget does
         * the parsing of the geometry option, not the Shell widget.
         * The result of this is that the Shell widget doesn't set the
         * correct window manager hints, and doesn't know that the
         * user has specified a geometry.
         *
         * The XtVaSetValues call below tells the Shell widget to
         * change its hints.  However, since it's confused about the
         * hints to begin with, it doesn't get them all right when it
         * does the SetValues -- it undoes some of what the VT100
         * widget did when it originally set the hints.
         *
         * To fix this, we do the following:
         *
         * 1. Get the sizehints directly from the window, going around
         *    the (confused) shell widget.
         * 2. Call XtVaSetValues to let the shell widget know which
         *    hints have changed.  Note that this may not even be
         *    necessary, since we're going to right ahead after that
         *    and set the hints ourselves, but it's good to put it
         *    here anyway, so that when we finally do fix the code so
         *    that the Shell does the right thing with hints, we
         *    already have the XtVaSetValues in place.
         * 3. We set the sizehints directly, this fixing up whatever
         *    damage was done by the Shell widget during the
         *    XtVaSetValues.
         *
         * Gross, huh?
         *
         * The correct fix is to redo VTRealize, VTInitialize and
         * VTSetValues so that font processing happens early enough to
         * give back responsibility for the size hints to the Shell.
         *
         * Someday, we hope to have time to do this.  Someday, we hope
         * to have time to completely rewrite xterm.
         */
    
        TRACE(("DoResizeScreen\n"));
    
    #if 1				/* ndef nothack */
        /*
         * NOTE: the hints and the XtVaSetValues() must match.
         */
        TRACE(("%s@%d -- ", __FILE__, __LINE__));
        TRACE_WM_HINTS(xw);
        getXtermSizeHints(xw);
    
        xtermSizeHints(xw, ScrollbarWidth(screen));
    
        /* These are obsolete, but old clients may use them */
        xw->hints.width = MaxCols(screen) * FontWidth(screen) + xw->hints.min_width;
        xw->hints.height = MaxRows(screen) * FontHeight(screen) + xw->hints.min_height;
    #endif
    
        XSetWMNormalHints(screen->display, XtWindow(SHELL_OF(xw)), &xw->hints);
    
        reqWidth = MaxCols(screen) * FontWidth(screen) + min_wide;
        reqHeight = MaxRows(screen) * FontHeight(screen) + min_high;
    
        TRACE(("...requesting screensize chars %dx%d, pixels %dx%d\n",
    	   MaxRows(screen),
    	   MaxCols(screen),
    	   reqHeight, reqWidth));
    
        geomreqresult = XtMakeResizeRequest((Widget) xw, reqWidth, reqHeight,
    					&repWidth, &repHeight);
        TRACE(("scrollbar.c XtMakeResizeRequest %dx%d -> %dx%d (status %d)\n",
    	   reqHeight, reqWidth,
    	   repHeight, repWidth,
    	   geomreqresult));
    
        if (geomreqresult == XtGeometryAlmost) {
    	TRACE(("...almost, retry screensize %dx%d\n", repHeight, repWidth));
    	geomreqresult = XtMakeResizeRequest((Widget) xw, repWidth,
    					    repHeight, NULL, NULL);
        }
    #if 1				/* ndef nothack */
        /*
         * XtMakeResizeRequest() has the undesirable side-effect of clearing
         * the window manager's hints, even on a failed request.  This would
         * presumably be fixed if the shell did its own work.
         */
        if (xw->hints.flags
    	&& repHeight
    	&& repWidth) {
    	xw->hints.height = repHeight;
    	xw->hints.width = repWidth;
    	TRACE_HINTS(&xw->hints);
    	XSetWMNormalHints(screen->display, VShellWindow, &xw->hints);
        }
    #endif
        XSync(screen->display, False);	/* synchronize */
        if (XtAppPending(app_con))
    	xevents();
    
    #ifndef NO_ACTIVE_ICON
        WhichVWin(screen) = saveWin;
    #endif /* NO_ACTIVE_ICON */
    }
    
    static XtermWidget
    xtermScroller(Widget xw)
    {
        XtermWidget result = 0;
    
        if (xw != 0) {
    	if (IsXtermWidget(xw)) {
    	    result = (XtermWidget) xw;
    	} else {
    	    /*
    	     * This may have been the scrollbar widget.  Try its parent, which
    	     * would be the VT100 widget.
    	     */
    	    result = xtermScroller(XtParent(xw));
    	}
        }
        return result;
    }
    
    static Widget
    CreateScrollBar(XtermWidget xw, int x, int y, int height)
    {
        Widget result;
        Arg args[6];
    
        XtSetArg(args[0], XtNx, x);
        XtSetArg(args[1], XtNy, y);
        XtSetArg(args[2], XtNheight, height);
        XtSetArg(args[3], XtNreverseVideo, xw->misc.re_verse);
        XtSetArg(args[4], XtNorientation, XtorientVertical);
        XtSetArg(args[5], XtNborderWidth, ScrollBarBorder(xw));
    
        result = XtCreateWidget("scrollbar", scrollbarWidgetClass,
    			    (Widget) xw, args, XtNumber(args));
        XtAddCallback(result, XtNscrollProc, ScrollTextUpDownBy, 0);
        XtAddCallback(result, XtNjumpProc, ScrollTextTo, 0);
        return (result);
    }
    
    void
    ScrollBarReverseVideo(Widget scrollWidget)
    {
        XtermWidget xw = xtermScroller(scrollWidget);
    
        if (xw != 0) {
    	SbInfo *sb = &(xw->screen.fullVwin.sb_info);
    	Arg args[4];
    	Cardinal nargs = XtNumber(args);
    
    	/*
    	 * Remember the scrollbar's original colors.
    	 */
    	if (sb->rv_cached == False) {
    	    XtSetArg(args[0], XtNbackground, &(sb->bg));
    	    XtSetArg(args[1], XtNforeground, &(sb->fg));
    	    XtSetArg(args[2], XtNborderColor, &(sb->bdr));
    	    XtSetArg(args[3], XtNborderPixmap, &(sb->bdpix));
    	    XtGetValues(scrollWidget, args, nargs);
    	    sb->rv_cached = True;
    	    sb->rv_active = 0;
    	}
    
    	sb->rv_active = !(sb->rv_active);
    	XtSetArg(args[!(sb->rv_active)], XtNbackground, sb->bg);
    	XtSetArg(args[(sb->rv_active)], XtNforeground, sb->fg);
    	nargs = 2;		/* don't set border_pixmap */
    	if (sb->bdpix == XtUnspecifiedPixmap) {
    	    /* if not pixmap then pixel */
    	    if (sb->rv_active) {
    		/* keep border visible */
    		XtSetArg(args[2], XtNborderColor, args[1].value);
    	    } else {
    		XtSetArg(args[2], XtNborderColor, sb->bdr);
    	    }
    	    nargs = 3;
    	}
    	XtSetValues(scrollWidget, args, nargs);
        }
    }
    
    void
    ScrollBarDrawThumb(Widget scrollWidget)
    {
        XtermWidget xw = xtermScroller(scrollWidget);
    
        if (xw != 0) {
    	TScreen *screen = &xw->screen;
    	int thumbTop, thumbHeight, totalHeight;
    
    	thumbTop = ROW2INX(screen, screen->savedlines);
    	thumbHeight = MaxRows(screen);
    	totalHeight = thumbHeight + screen->savedlines;
    
    	XawScrollbarSetThumb(scrollWidget,
    			     ((float) thumbTop) / totalHeight,
    			     ((float) thumbHeight) / totalHeight);
        }
    }
    
    void
    ResizeScrollBar(XtermWidget xw)
    {
        TScreen *screen = &(xw->screen);
    
        int height = screen->fullVwin.height + screen->border * 2;
        int width = screen->scrollWidget->core.width;
        int ypos = -ScrollBarBorder(xw);
    #ifdef SCROLLBAR_RIGHT
        int xpos = ((xw->misc.useRight)
    		? (screen->fullVwin.fullwidth -
    		   screen->scrollWidget->core.width -
    		   BorderWidth(screen->scrollWidget))
    		: -ScrollBarBorder(xw));
    #else
        int xpos = -ScrollBarBorder(xw);
    #endif
    
        TRACE(("ResizeScrollBar at %d,%d %dx%d\n", ypos, xpos, height, width));
    
        XtConfigureWidget(
    			 screen->scrollWidget,
    			 xpos,
    			 ypos,
    			 width,
    			 height,
    			 BorderWidth(screen->scrollWidget));
        ScrollBarDrawThumb(screen->scrollWidget);
    }
    
    void
    WindowScroll(XtermWidget xw, int top)
    {
        TScreen *screen = &(xw->screen);
        int i, lines;
        int scrolltop, scrollheight, refreshtop;
    
        if (top < -screen->savedlines)
    	top = -screen->savedlines;
        else if (top > 0)
    	top = 0;
        if ((i = screen->topline - top) == 0) {
    	ScrollBarDrawThumb(screen->scrollWidget);
    	return;
        }
    
        if (screen->cursor_state)
    	HideCursor();
        lines = i > 0 ? i : -i;
        if (lines > MaxRows(screen))
    	lines = MaxRows(screen);
        scrollheight = screen->max_row - lines + 1;
        if (i > 0)
    	refreshtop = scrolltop = 0;
        else {
    	scrolltop = lines;
    	refreshtop = scrollheight;
        }
        scrolling_copy_area(xw, scrolltop, scrollheight, -i);
        screen->topline = top;
    
        ScrollSelection(screen, i, True);
    
        XClearArea(
    		  screen->display,
    		  VWindow(screen),
    		  OriginX(screen),
    		  OriginY(screen) + refreshtop * FontHeight(screen),
    		  (unsigned) Width(screen),
    		  (unsigned) lines * FontHeight(screen),
    		  False);
        ScrnRefresh(xw, refreshtop, 0, lines, MaxCols(screen), False);
    
        ScrollBarDrawThumb(screen->scrollWidget);
    }
    
    #ifdef SCROLLBAR_RIGHT
    /*
     * Adjust the scrollbar position if we're asked to turn on scrollbars for the
     * first time (or after resizing) after the xterm is already running.  That
     * makes the window grow after we've initially configured the scrollbar's
     * position.  (There must be a better way).
     */
    void
    updateRightScrollbar(XtermWidget xw)
    {
        TScreen *screen = &xw->screen;
    
        if (xw->misc.useRight
    	&& screen->fullVwin.fullwidth < xw->core.width)
    	XtVaSetValues(screen->scrollWidget,
    		      XtNx, screen->fullVwin.fullwidth - BorderWidth(screen->scrollWidget),
    		      (XtPointer) 0);
    }
    #endif
    
    void
    ScrollBarOn(XtermWidget xw, int init, int doalloc)
    {
        TScreen *screen = &xw->screen;
        int i, j, k;
    
        if (screen->fullVwin.sb_info.width || IsIcon(screen))
    	return;
    
        TRACE(("ScrollBarOn\n"));
        if (init) {			/* then create it only */
    	if (screen->scrollWidget == 0) {
    	    /* make it a dummy size and resize later */
    	    screen->scrollWidget = CreateScrollBar(xw,
    						   -ScrollBarBorder(xw),
    						   -ScrollBarBorder(xw),
    						   5);
    	    if (screen->scrollWidget == NULL) {
    		Bell(XkbBI_MinorError, 0);
    	    }
    	}
        } else if (!screen->scrollWidget || !XtIsRealized((Widget) xw)) {
    	Bell(XkbBI_MinorError, 0);
    	Bell(XkbBI_MinorError, 0);
        } else {
    
    	if (doalloc && screen->allbuf) {
    	    /* FIXME: this is not integrated well with Allocate */
    	    if ((screen->allbuf =
    		 TypeRealloc(ScrnPtr,
    			     MAX_PTRS * (screen->max_row + 2 + screen->savelines),
    			     screen->visbuf)) == NULL) {
    		SysError(ERROR_SBRALLOC);
    	    }
    	    screen->visbuf = &screen->allbuf[MAX_PTRS * screen->savelines];
    	    memmove((char *) screen->visbuf, (char *) screen->allbuf,
    		    MAX_PTRS * (screen->max_row + 2) * sizeof(char *));
    	    for (i = k = 0; i < screen->savelines; i++) {
    		k += BUF_HEAD;
    		for (j = BUF_HEAD; j < MAX_PTRS; j++) {
    		    if ((screen->allbuf[k++] =
    			 TypeCallocN(Char, (unsigned) MaxCols(screen))
    			) == NULL)
    			SysError(ERROR_SBRALLOC2);
    		}
    	    }
    	}
    
    	ResizeScrollBar(xw);
    	xtermAddInput(screen->scrollWidget);
    	XtRealizeWidget(screen->scrollWidget);
    	TRACE_TRANS("scrollbar", screen->scrollWidget);
    
    	screen->fullVwin.sb_info.rv_cached = False;
    
    	screen->fullVwin.sb_info.width = (screen->scrollWidget->core.width
    					  + BorderWidth(screen->scrollWidget));
    
    	TRACE(("setting scrollbar width %d = %d + %d\n",
    	       screen->fullVwin.sb_info.width,
    	       screen->scrollWidget->core.width,
    	       BorderWidth(screen->scrollWidget)));
    
    	ScrollBarDrawThumb(screen->scrollWidget);
    	DoResizeScreen(xw);
    
    #ifdef SCROLLBAR_RIGHT
    	updateRightScrollbar(xw);
    #endif
    
    	XtMapWidget(screen->scrollWidget);
    	update_scrollbar();
    	if (screen->visbuf) {
    	    xtermClear(xw);
    	    Redraw();
    	}
        }
    }
    
    void
    ScrollBarOff(XtermWidget xw)
    {
        TScreen *screen = &xw->screen;
    
        if (!screen->fullVwin.sb_info.width || IsIcon(screen))
    	return;
    
        TRACE(("ScrollBarOff\n"));
        if (XtIsRealized((Widget) xw)) {
    	XtUnmapWidget(screen->scrollWidget);
    	screen->fullVwin.sb_info.width = 0;
    	DoResizeScreen(xw);
    	update_scrollbar();
    	if (screen->visbuf) {
    	    xtermClear(xw);
    	    Redraw();
    	}
        } else {
    	Bell(XkbBI_MinorError, 0);
        }
    }
    
    /*
     * Toggle the visibility of the scrollbars.
     */
    void
    ToggleScrollBar(XtermWidget xw)
    {
        TScreen *screen = &xw->screen;
    
        if (IsIcon(screen)) {
    	Bell(XkbBI_MinorError, 0);
        } else {
    	TRACE(("ToggleScrollBar{{\n"));
    	if (screen->fullVwin.sb_info.width) {
    	    ScrollBarOff(xw);
    	} else {
    	    ScrollBarOn(xw, False, False);
    	}
    	update_scrollbar();
    	TRACE(("...ToggleScrollBar}}\n"));
        }
    }
    
    /*ARGSUSED*/
    static void
    ScrollTextTo(
    		Widget scrollbarWidget,
    		XtPointer client_data GCC_UNUSED,
    		XtPointer call_data)
    {
        XtermWidget xw = xtermScroller(scrollbarWidget);
    
        if (xw != 0) {
    	float *topPercent = (float *) call_data;
    	TScreen *screen = &xw->screen;
    	int thumbTop;		/* relative to first saved line */
    	int newTopLine;
    
    	/*
    	 * screen->savedlines : Number of offscreen text lines,
    	 * MaxRows(screen)    : Number of onscreen  text lines,
    	 */
    	thumbTop = (int) (*topPercent * (screen->savedlines + MaxRows(screen)));
    	newTopLine = thumbTop - screen->savedlines;
    	WindowScroll(xw, newTopLine);
        }
    }
    
    /*ARGSUSED*/
    static void
    ScrollTextUpDownBy(
    		      Widget scrollbarWidget,
    		      XtPointer client_data GCC_UNUSED,
    		      XtPointer call_data)
    {
        XtermWidget xw = xtermScroller(scrollbarWidget);
    
        if (xw != 0) {
    	long pixels = (long) call_data;
    
    	TScreen *screen = &xw->screen;
    	int rowOnScreen, newTopLine;
    
    	rowOnScreen = pixels / FontHeight(screen);
    	if (rowOnScreen == 0) {
    	    if (pixels < 0)
    		rowOnScreen = -1;
    	    else if (pixels > 0)
    		rowOnScreen = 1;
    	}
    	newTopLine = ROW2INX(screen, rowOnScreen);
    	WindowScroll(xw, newTopLine);
        }
    }
    
    /*
     * assume that b is lower case and allow plural
     */
    static int
    specialcmplowerwiths(char *a, char *b, int *modifier)
    {
        char ca, cb;
    
        *modifier = 0;
        if (!a || !b)
    	return 0;
    
        while (1) {
    	ca = char2lower(*a);
    	cb = *b;
    	if (ca != cb || ca == '\0')
    	    break;		/* if not eq else both nul */
    	a++, b++;
        }
        if (cb != '\0')
    	return 0;
    
        if (ca == 's')
    	ca = *++a;
    
        switch (ca) {
        case '+':
        case '-':
    	*modifier = (ca == '-' ? -1 : 1) * atoi(a + 1);
    	return 1;
    
        case '\0':
    	return 1;
    
        default:
    	return 0;
        }
    }
    
    static long
    params_to_pixels(TScreen * screen, String * params, Cardinal n)
    {
        int mult = 1;
        char *s;
        int modifier;
    
        switch (n > 2 ? 2 : n) {
        case 2:
    	s = params[1];
    	if (specialcmplowerwiths(s, "page", &modifier)) {
    	    mult = (MaxRows(screen) + modifier) * FontHeight(screen);
    	} else if (specialcmplowerwiths(s, "halfpage", &modifier)) {
    	    mult = ((MaxRows(screen) + modifier) * FontHeight(screen)) / 2;
    	} else if (specialcmplowerwiths(s, "pixel", &modifier)) {
    	    mult = 1;
    	} else {
    	    /* else assume that it is Line */
    	    mult = FontHeight(screen);
    	}
    	mult *= atoi(params[0]);
    	break;
        case 1:
    	mult = atoi(params[0]) * FontHeight(screen);	/* lines */
    	break;
        default:
    	mult = screen->scrolllines * FontHeight(screen);
    	break;
        }
        return mult;
    }
    
    static long
    AmountToScroll(Widget xw, String * params, Cardinal nparams)
    {
        if (xw != 0) {
    	if (IsXtermWidget(xw)) {
    	    TScreen *screen = TScreenOf((XtermWidget) xw);
    	    if (nparams > 2
    		&& screen->send_mouse_pos != MOUSE_OFF)
    		return 0;
    	    return params_to_pixels(screen, params, nparams);
    	} else {
    	    /*
    	     * This may have been the scrollbar widget.  Try its parent, which
    	     * would be the VT100 widget.
    	     */
    	    return AmountToScroll(XtParent(xw), params, nparams);
    	}
        }
        return 0;
    }
    
    /*ARGSUSED*/
    void
    HandleScrollForward(
    		       Widget xw,
    		       XEvent * event GCC_UNUSED,
    		       String * params,
    		       Cardinal *nparams)
    {
        long amount;
    
        if ((amount = AmountToScroll(xw, params, *nparams)) != 0) {
    	ScrollTextUpDownBy(xw, (XtPointer) 0, (XtPointer) amount);
        }
    }
    
    /*ARGSUSED*/
    void
    HandleScrollBack(
    		    Widget xw,
    		    XEvent * event GCC_UNUSED,
    		    String * params,
    		    Cardinal *nparams)
    {
        long amount;
    
        if ((amount = -AmountToScroll(xw, params, *nparams)) != 0) {
    	ScrollTextUpDownBy(xw, (XtPointer) 0, (XtPointer) amount);
        }
    }