Tree.c

/*
 * $XConsortium: Tree.c,v 1.42 91/02/20 20:06:07 converse Exp $
 *
 * Copyright 1990 Massachusetts Institute of Technology
 * Copyright 1989 Prentice Hall
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose and without fee is hereby granted, provided that the above
 * copyright notice appear in all copies and that both the copyright notice
 * and this permission notice appear in supporting documentation.
 * 
 * M.I.T., Prentice Hall and the authors disclaim all warranties with regard
 * to this software, including all implied warranties of merchantability and
 * fitness.  In no event shall M.I.T., Prentice Hall or the authors be liable
 * for any special, indirect or cosequential 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.
 * 
 * Authors:  Jim Fulton, MIT X Consortium,
 *           based on a version by Douglas Young, Prentice Hall
 * 
 * This widget is based on the Tree widget described on pages 397-419 of
 * Douglas Young's book "The X Window System, Programming and Applications 
 * with Xt OSF/Motif Edition."  The layout code has been rewritten to use
 * additional blank space to make the structure of the graph easier to see
 * as well as to support vertical trees.
 */

#include <X11/Intrinsic.h>
#include <X11/IntrinsicP.h>
#include <X11/StringDefs.h>
#include <X11/CoreP.h>
#include <X11/CompositeP.h>
#include <X11/ConstrainP.h>
#include "TreeP.h"

#define IsHorizontal(tw) ((tw)->tree.gravity == WestGravity || \
			  (tw)->tree.gravity == EastGravity)


					/* widget class method */
static void             ClassInitialize();
static void             Initialize();
static void             ConstraintInitialize();
static void             ConstraintDestroy();
static Boolean          ConstraintSetValues();
static void             Destroy();
static Boolean          SetValues();
static XtGeometryResult GeometryManager();
static void             ChangeManaged();
static void             Redisplay();
static XtGeometryResult	QueryGeometry();

					/* utility routines */
static void             insert_node();
static void             delete_node();
static void             layout_tree();


/*
 * resources of the tree itself
 */
static XtResource resources[] = {
    { XtNautoReconfigure, XtCAutoReconfigure, XtRBoolean, sizeof (Boolean),
	XtOffsetOf(TreeRec, tree.auto_reconfigure), XtRImmediate,
	(XtPointer) FALSE },
    { XtNhSpace, XtCHSpace, XtRDimension, sizeof (Dimension),
	XtOffsetOf(TreeRec, tree.hpad), XtRImmediate, (XtPointer) 0 },
    { XtNvSpace, XtCVSpace, XtRDimension, sizeof (Dimension),
	XtOffsetOf(TreeRec, tree.vpad), XtRImmediate, (XtPointer) 0 },
    { XtNforeground, XtCForeground, XtRPixel, sizeof (Pixel),
	XtOffsetOf(TreeRec, tree.foreground), XtRString,
	XtDefaultForeground},
    { XtNlineWidth, XtCLineWidth, XtRDimension, sizeof (Dimension),
	XtOffsetOf(TreeRec, tree.line_width), XtRImmediate, (XtPointer) 0 },
    { XtNgravity, XtCGravity, XtRGravity, sizeof (XtGravity),
	XtOffsetOf(TreeRec, tree.gravity), XtRImmediate,
	(XtPointer) WestGravity },
};


/*
 * resources that are attached to all children of the tree
 */
static XtResource treeConstraintResources[] = {
    { XtNtreeParent, XtCTreeParent, XtRWidget, sizeof (Widget),
	XtOffsetOf(TreeConstraintsRec, tree.parent), XtRImmediate, NULL },
    { XtNtreeGC, XtCTreeGC, XtRGC, sizeof(GC),
	XtOffsetOf(TreeConstraintsRec, tree.gc), XtRImmediate, NULL },
};


TreeClassRec treeClassRec = {
  {
					/* core_class fields  */
    (WidgetClass) &constraintClassRec,  /* superclass         */
    "Tree",				/* class_name         */
    sizeof(TreeRec),			/* widget_size        */
    ClassInitialize,			/* class_init         */
    NULL,				/* class_part_init    */
    FALSE,				/* class_inited       */	
    Initialize,				/* initialize         */
    NULL,				/* initialize_hook    */	
    XtInheritRealize,			/* realize            */
    NULL,				/* actions            */
    0,					/* num_actions        */	
    resources,				/* resources          */
    XtNumber(resources),		/* num_resources      */
    NULLQUARK,				/* xrm_class          */
    TRUE,				/* compress_motion    */	
    TRUE,				/* compress_exposure  */	
    TRUE,				/* compress_enterleave*/	
    TRUE,				/* visible_interest   */
    Destroy,				/* destroy            */
    NULL,				/* resize             */
    Redisplay,				/* expose             */
    SetValues,				/* set_values         */
    NULL,				/* set_values_hook    */	
    XtInheritSetValuesAlmost,		/* set_values_almost  */
    NULL,				/* get_values_hook    */	
    NULL,				/* accept_focus       */
    XtVersion,				/* version            */	
    NULL,				/* callback_private   */
    NULL,				/* tm_table           */
    QueryGeometry,			/* query_geometry     */	
    NULL,				/* display_accelerator*/
    NULL,				/* extension          */
  },
  {
					/* composite_class fields */
    GeometryManager,			/* geometry_manager    */
    ChangeManaged,			/* change_managed      */
    XtInheritInsertChild,		/* insert_child        */	
    XtInheritDeleteChild,		/* delete_child        */	
    NULL,				/* extension           */
  },
  { 
					/* constraint_class fields */
   treeConstraintResources,		/* subresources        */
   XtNumber(treeConstraintResources),	/* subresource_count   */
   sizeof(TreeConstraintsRec),		/* constraint_size     */
   ConstraintInitialize,		/* initialize          */
   ConstraintDestroy,			/* destroy             */
   ConstraintSetValues,			/* set_values          */
   NULL,				/* extension           */
   },
  {
					/* Tree class fields */
    0,					/* ignore              */	
  }
};

WidgetClass treeWidgetClass = (WidgetClass) &treeClassRec;


/*****************************************************************************
 *                                                                           *
 *			     tree utility routines                           *
 *                                                                           *
 *****************************************************************************/

static void initialize_dimensions (listp, sizep, n)
    Dimension **listp;
    int *sizep;
    int n;
{
    register int i;
    register Dimension *l;

    if (!*listp) {
	*listp = (Dimension *) XtCalloc ((unsigned int) n,
					 (unsigned int) sizeof(Dimension));
	*sizep = ((*listp) ? n : 0);
	return;
    }
    if (n > *sizep) {
	*listp = (Dimension *) XtRealloc((char *) *listp,
					 (unsigned int) (n*sizeof(Dimension)));
	if (!*listp) {
	    *sizep = 0;
	    return;
	}
	for (i = *sizep, l = (*listp) + i; i < n; i++, l++) *l = 0;
	*sizep = n;
    }
    return;
}

static GC get_tree_gc (w)
    TreeWidget w;
{
    XtGCMask valuemask = GCBackground | GCForeground;
    XGCValues values;

    values.background = w->core.background_pixel;
    values.foreground = w->tree.foreground;
    if (w->tree.line_width != 0) {
	valuemask |= GCLineWidth;
	values.line_width = w->tree.line_width;
    }

    return XtGetGC ((Widget) w, valuemask, &values);
}

static void insert_node (parent, node)
     Widget parent, node;
{
    TreeConstraints pc;
    TreeConstraints nc = TREE_CONSTRAINT(node);
    int nindex;
  
    nc->tree.parent = parent;

    if (parent == NULL) return;

    /*
     * If there isn't more room in the children array, 
     * allocate additional space.
     */  
    pc = TREE_CONSTRAINT(parent);
    nindex = pc->tree.n_children;
  
    if (pc->tree.n_children == pc->tree.max_children) {
	pc->tree.max_children += (pc->tree.max_children / 2) + 2;
	pc->tree.children = (WidgetList) XtRealloc ((char *)pc->tree.children, 
						    (unsigned int)
						    ((pc->tree.max_children) *
						    sizeof(Widget)));
    } 

    /*
     * Add the sub_node in the next available slot and 
     * increment the counter.
     */
    pc->tree.children[nindex] = node;
    pc->tree.n_children++;
}

static void delete_node (parent, node)
    Widget parent, node;
{
    TreeConstraints pc;
    int pos, i;

    /*
     * Make sure the parent exists.
     */
    if (!parent) return;  
  
    pc = TREE_CONSTRAINT(parent);

    /*
     * Find the sub_node on its parent's list.
     */
    for (pos = 0; pos < pc->tree.n_children; pos++)
      if (pc->tree.children[pos] == node) break;

    if (pos == pc->tree.n_children) return;

    /*
     * Decrement the number of children
     */  
    pc->tree.n_children--;

    /*
     * Fill in the gap left by the sub_node.
     * Zero the last slot for good luck.
     */
    for (i = pos; i < pc->tree.n_children; i++) 
      pc->tree.children[i] = pc->tree.children[i+1];

    pc->tree.children[pc->tree.n_children]=0;
}

static void check_gravity (tw, grav)
    TreeWidget tw;
    XtGravity grav;
{
    switch (tw->tree.gravity) {
      case WestGravity: case NorthGravity: case EastGravity: case SouthGravity:
	break;
      default:
	tw->tree.gravity = grav;
	break;
    }
}
#define done(address, type) \
        { (*toVal).size = sizeof(type); (*toVal).addr = (caddr_t) address; }

static struct _namepair {
    XrmQuark quark;
    char *name;
    XtGravity gravity;
} names[] = {
    { NULLQUARK, XtEForget, ForgetGravity },
    { NULLQUARK, XtENorthWest, NorthWestGravity },
    { NULLQUARK, XtENorth, NorthGravity },
    { NULLQUARK, XtENorthEast, NorthEastGravity },
    { NULLQUARK, XtEWest, WestGravity },
    { NULLQUARK, XtECenter, CenterGravity },
    { NULLQUARK, XtEEast, EastGravity },
    { NULLQUARK, XtESouthWest, SouthWestGravity },
    { NULLQUARK, XtESouth, SouthGravity },
    { NULLQUARK, XtESouthEast, SouthEastGravity },
    { NULLQUARK, XtEStatic, StaticGravity },
    { NULLQUARK, XtEUnmap, UnmapGravity },
    { NULLQUARK, XtEleft, WestGravity },
    { NULLQUARK, XtEtop, NorthGravity },
    { NULLQUARK, XtEright, EastGravity },
    { NULLQUARK, XtEbottom, SouthGravity },
    { NULLQUARK, NULL, ForgetGravity }
};

void CvtStringToGravity (args, num_args, fromVal, toVal)
    XrmValuePtr args;
    Cardinal    *num_args;
    XrmValuePtr fromVal;
    XrmValuePtr toVal;
{
    static Boolean haveQuarks = FALSE;
    char lowerName[40];
    XrmQuark q;
    char *s, *t;
    struct _namepair *np;

    if (*num_args != 0)
        XtWarningMsg("wrongParameters","cvtStringToGravity","XtToolkitError",
                  "String to Gravity conversion needs no extra arguments",
                  (String *) NULL, (Cardinal *)NULL);

    if (!haveQuarks) {
	for (np = names; np->name; np++) {
	    np->quark = XrmStringToQuark (np->name);
	}
	haveQuarks = TRUE;
    }

    s = (char *) fromVal->addr;
    if (strlen(s) < sizeof lowerName) {
	for (t=lowerName;  (*t++ = tolower(*s++)) != '\0'; );
	q = XrmStringToQuark (lowerName);

	for (np = names; np->name; np++) {
	    if (np->quark == q) {
		done (&np->gravity, XtGravity);
		return;
	    }
	}
    }
    XtStringConversionWarning((char *) fromVal->addr, XtRGravity);
}





/*****************************************************************************
 *                                                                           *
 * 			      tree class methods                             *
 *                                                                           *
 *****************************************************************************/

static void ClassInitialize ()
{
    XtAddConverter (XtRString, XtRGravity, CvtStringToGravity,
		        (XtConvertArgList) NULL, (Cardinal) 0);
}


static void Initialize (grequest, gnew)
    Widget grequest, gnew;
{
    TreeWidget request = (TreeWidget) grequest, new = (TreeWidget) gnew;
    Arg args[2];

    /*
     * Make sure the widget's width and height are 
     * greater than zero.
     */
    if (request->core.width <= 0) new->core.width = 5;
    if (request->core.height <= 0) new->core.height = 5;

    /*
     * Set the padding according to the orientation
     */
    if (request->tree.hpad == 0 && request->tree.vpad == 0) {
	if (IsHorizontal (request)) {
	    new->tree.hpad = TREE_HORIZONTAL_DEFAULT_SPACING;
	    new->tree.vpad = TREE_VERTICAL_DEFAULT_SPACING;
	} else {
	    new->tree.hpad = TREE_VERTICAL_DEFAULT_SPACING;
	    new->tree.vpad = TREE_HORIZONTAL_DEFAULT_SPACING;
	}
    }

    /*
     * Create a graphics context for the connecting lines.
     */
    new->tree.gc = get_tree_gc (new);

    /*
     * Create the hidden root widget.
     */
    new->tree.tree_root = (Widget) NULL;
    XtSetArg(args[0], XtNwidth, 1);
    XtSetArg(args[1], XtNheight, 1);
    new->tree.tree_root = XtCreateWidget ("root", widgetClass, gnew, args,((Cardinal) 2));
    
    /*
     * Allocate the array used to hold the widest values per depth
     */
    new->tree.largest = NULL;
    new->tree.n_largest = 0;
    initialize_dimensions (&new->tree.largest, &new->tree.n_largest, 
			   TREE_INITIAL_DEPTH);

    /*
     * make sure that our gravity is one of the acceptable values
     */
    check_gravity (new, WestGravity);
} 


/* ARGSUSED */
static void ConstraintInitialize (request, new)
     Widget request, new;
{
    TreeConstraints tc = TREE_CONSTRAINT(new);
    TreeWidget tw = (TreeWidget) new->core.parent;

    /*
     * Initialize the widget to have no sub-nodes.
     */
    tc->tree.n_children = 0;
    tc->tree.max_children = 0;
    tc->tree.children = (Widget *) NULL;
    tc->tree.x = tc->tree.y = 0; 
    tc->tree.bbsubwidth = 0;
    tc->tree.bbsubheight = 0;


    /*
     * If this widget has a super-node, add it to that 
     * widget' sub-nodes list. Otherwise make it a sub-node of 
     * the tree_root widget.
     */
    if (tc->tree.parent)
      insert_node (tc->tree.parent, new);
    else if (tw->tree.tree_root)
      insert_node (tw->tree.tree_root, new);
} 


/* ARGSUSED */
static Boolean SetValues (gcurrent, grequest, gnew)
    Widget gcurrent, grequest, gnew;
{
    TreeWidget current = (TreeWidget) gcurrent, new = (TreeWidget) gnew;
    Boolean redraw = FALSE;

    /*
     * If the foreground color has changed, redo the GC's
     * and indicate a redraw.
     */
    if (new->tree.foreground != current->tree.foreground ||
	new->core.background_pixel != current->core.background_pixel ||
	new->tree.line_width != current->tree.line_width) {
	XtReleaseGC (gnew, new->tree.gc);
	new->tree.gc = get_tree_gc (new);
	redraw = TRUE;     
    }

    /*
     * If the minimum spacing has changed, recalculate the
     * tree layout. layout_tree() does a redraw, so we don't
     * need SetValues to do another one.
     */
    if (new->tree.gravity != current->tree.gravity) {
	check_gravity (new, current->tree.gravity);
    }

    if (IsHorizontal(new) != IsHorizontal(current)) {
	if (new->tree.vpad == current->tree.vpad &&
	    new->tree.hpad == current->tree.hpad) {
	    new->tree.vpad = current->tree.hpad;
	    new->tree.hpad = current->tree.vpad;
	}
    }

    if (new->tree.vpad != current->tree.vpad ||
	new->tree.hpad != current->tree.hpad ||
	new->tree.gravity != current->tree.gravity) {
	layout_tree (new, TRUE);
	redraw = FALSE;
    }
    return redraw;
}


/* ARGSUSED */
static Boolean ConstraintSetValues (current, request, new, args, num_args)
    Widget current, request, new;
    ArgList args;
    Cardinal *num_args;
{
    TreeConstraints newc = TREE_CONSTRAINT(new);
    TreeConstraints curc = TREE_CONSTRAINT(current);
    TreeWidget tw = (TreeWidget) new->core.parent;

    /*
     * If the parent field has changed, remove the widget
     * from the old widget's children list and add it to the
     * new one.
     */
    if (curc->tree.parent != newc->tree.parent){
	if (curc->tree.parent)
	  delete_node (curc->tree.parent, new);
	if (newc->tree.parent)
	  insert_node(newc->tree.parent, new);

	/*
	 * If the Tree widget has been realized, 
	 * compute new layout.
	 */
	if (XtIsRealized((Widget)tw))
	  layout_tree (tw, FALSE);
    }
    return False;
}


static void ConstraintDestroy (w) 
    Widget w;
{ 
    TreeConstraints tc = TREE_CONSTRAINT(w);
    TreeWidget tw = (TreeWidget) XtParent(w);
    int i;

    /* 
     * Remove the widget from its parent's sub-nodes list and
     * make all this widget's sub-nodes sub-nodes of the parent.
     */
  
    if (tw->tree.tree_root == w) {
	if (tc->tree.n_children > 0)
	  tw->tree.tree_root = tc->tree.children[0];
	else
	  tw->tree.tree_root = NULL;
    }

    delete_node (tc->tree.parent, (Widget) w);
    for (i = 0; i< tc->tree.n_children; i++)
      insert_node (tc->tree.parent, tc->tree.children[i]);

    layout_tree ((TreeWidget) (w->core.parent), FALSE);
}

/* ARGSUSED */
static XtGeometryResult GeometryManager (w, request, reply)
    Widget w;
    XtWidgetGeometry *request;
    XtWidgetGeometry *reply;
{

    TreeWidget tw = (TreeWidget) w->core.parent;

    /*
     * No position changes allowed!.
     */
    if ((request->request_mode & CWX && request->x!=w->core.x)
	||(request->request_mode & CWY && request->y!=w->core.y))
      return (XtGeometryNo);

    /*
     * Allow all resize requests.
     */

    if (request->request_mode & CWWidth)
      w->core.width = request->width;
    if (request->request_mode & CWHeight)
      w->core.height = request->height;
    if (request->request_mode & CWBorderWidth)
      w->core.border_width = request->border_width;

    if (tw->tree.auto_reconfigure) layout_tree (tw, FALSE);
    return (XtGeometryYes);
}

static void ChangeManaged (gw)
    Widget gw;
{
    layout_tree ((TreeWidget) gw, FALSE);
}


static void Destroy (gw)
    Widget gw;
{
    TreeWidget w = (TreeWidget) gw;

    XtReleaseGC (gw, w->tree.gc);
    if (w->tree.largest) XtFree ((char *) w->tree.largest);
}


/* ARGSUSED */
static void Redisplay (tw, event, region)
     TreeWidget tw;
     XEvent *event;
     Region region;
{
    /*
     * If the Tree widget is visible, visit each managed child.
     */
    if (tw->core.visible) {
	int i, j;
	Display *dpy = XtDisplay (tw);
	Window w = XtWindow (tw);

	for (i = 0; i < tw->composite.num_children; i++) {
	    register Widget child = tw->composite.children[i];
	    TreeConstraints tc = TREE_CONSTRAINT(child);

	    /*
	     * Don't draw lines from the fake tree_root.
	     */
	    if (child != tw->tree.tree_root && tc->tree.n_children) {
		int srcx = child->core.x + child->core.border_width;
		int srcy = child->core.y + child->core.border_width;

		switch (tw->tree.gravity) {
		  case WestGravity:
		    srcx += child->core.width + child->core.border_width;
		    /* fall through */
		  case EastGravity:
		    srcy += child->core.height / 2;
		    break;

		  case NorthGravity:
		    srcy += child->core.height + child->core.border_width;
		    /* fall through */
		  case SouthGravity:
		    srcx += child->core.width / 2;
		    break;
		}

		for (j = 0; j < tc->tree.n_children; j++) {
		    register Widget k = tc->tree.children[j];
		    GC gc = (tc->tree.gc ? tc->tree.gc : tw->tree.gc);

		    switch (tw->tree.gravity) {
		      case WestGravity:
			/*
			 * right center to left center
			 */
			XDrawLine (dpy, w, gc, srcx, srcy,
				   (int) k->core.x,
				   (k->core.y + ((int) k->core.border_width) +
				    ((int) k->core.height) / 2));
			break;

		      case NorthGravity:
			/*
			 * bottom center to top center
			 */
			XDrawLine (dpy, w, gc, srcx, srcy,
				   (k->core.x + ((int) k->core.border_width) +
				    ((int) k->core.width) / 2),
				   (int) k->core.y);
			break;

		      case EastGravity:
			/*
			 * left center to right center
			 */
			XDrawLine (dpy, w, gc, srcx, srcy,
				   (k->core.x +
				    (((int) k->core.border_width) << 1) +
				    (int) k->core.width),
				   (k->core.y + ((int) k->core.border_width) +
				    ((int) k->core.height) / 2));
			break;

		      case SouthGravity:
			/*
			 * top center to bottom center
			 */
			XDrawLine (dpy, w, gc, srcx, srcy,
				   (k->core.x + ((int) k->core.border_width) +
				    ((int) k->core.width) / 2),
				   (k->core.y +
				    (((int) k->core.border_width) << 1) +
				    (int) k->core.height));
			break;
		    }
		}
	    }
	}
    }
}

static XtGeometryResult QueryGeometry (w, intended, preferred)
    Widget w;
    XtWidgetGeometry *intended, *preferred;
{
    register TreeWidget tw = (TreeWidget) w;

    preferred->request_mode = (CWWidth | CWHeight);
    preferred->width = tw->tree.maxwidth;
    preferred->height = tw->tree.maxheight;

    if (((intended->request_mode & (CWWidth | CWHeight)) ==
	 (CWWidth | CWHeight)) &&
	intended->width == preferred->width &&
	intended->height == preferred->height)
      return XtGeometryYes;
    else if (preferred->width == w->core.width &&
             preferred->height == w->core.height)
      return XtGeometryNo;
    else
      return XtGeometryAlmost;
}


/*****************************************************************************
 *                                                                           *
 *			     tree layout algorithm                           *
 *                                                                           *
 * Each node in the tree is "shrink-wrapped" with a minimal bounding         *
 * rectangle, laid next to its siblings (with a small about of padding in    *
 * between) and then wrapped with their parent.  Parents are centered about  *
 * their children (or vice versa if the parent is larger than the children). *
 *                                                                           *
 *****************************************************************************/

static void compute_bounding_box_subtree (tree, w, depth)
    TreeWidget tree;
    Widget w;
    int depth;
{
    TreeConstraints tc = TREE_CONSTRAINT(w);  /* info attached to all kids */
    register int i;
    Bool horiz = IsHorizontal (tree);
    Dimension newwidth, newheight;
    Dimension bw2 = w->core.border_width * 2;

    /*
     * Set the max-size per level.
     */
    if (depth >= tree->tree.n_largest) {
	initialize_dimensions (&tree->tree.largest,
			       &tree->tree.n_largest, depth + 1);
    }
    newwidth = ((horiz ? w->core.width : w->core.height) + bw2);
    if (tree->tree.largest[depth] < newwidth)
      tree->tree.largest[depth] = newwidth;


    /*
     * initialize
     */
    tc->tree.bbwidth = w->core.width + bw2;
    tc->tree.bbheight = w->core.height + bw2;

    if (tc->tree.n_children == 0) return;

    /*
     * Figure the size of the opposite dimension (vertical if tree is 
     * horizontal, else vice versa).  The other dimension will be set 
     * in the second pass once we know the maximum dimensions.
     */
    newwidth = 0;
    newheight = 0;
    for (i = 0; i < tc->tree.n_children; i++) {
	Widget child = tc->tree.children[i];
	TreeConstraints cc = TREE_CONSTRAINT(child);
	    
	compute_bounding_box_subtree (tree, child, depth + 1);

	if (horiz) {
	    if (newwidth < cc->tree.bbwidth) newwidth = cc->tree.bbwidth;
	    newheight += tree->tree.vpad + cc->tree.bbheight;
	} else {
	    if (newheight < cc->tree.bbheight) newheight = cc->tree.bbheight;
	    newwidth += tree->tree.hpad + cc->tree.bbwidth;
	}
    }


    tc->tree.bbsubwidth = newwidth;
    tc->tree.bbsubheight = newheight;

    /*
     * Now fit parent onto side (or top) of bounding box and correct for
     * extra padding.  Be careful of unsigned arithmetic.
     */
    if (horiz) {
	tc->tree.bbwidth += tree->tree.hpad + newwidth;
	newheight -= tree->tree.vpad;
	if (newheight > tc->tree.bbheight) tc->tree.bbheight = newheight;
    } else {
	tc->tree.bbheight += tree->tree.vpad + newheight;
	newwidth -= tree->tree.hpad;
	if (newwidth > tc->tree.bbwidth) tc->tree.bbwidth = newwidth;
    }
}


static void set_positions (tw, w, level)
     TreeWidget tw;
     Widget w;
     int level;
{
    int i;
  
    if (w) {
	TreeConstraints tc = TREE_CONSTRAINT(w);

	if (level > 0) {
	    /*
	     * mirror if necessary
	     */
	    switch (tw->tree.gravity) {
	      case EastGravity:
		tc->tree.x = (((Position) tw->tree.maxwidth) -
			      ((Position) w->core.width) - tc->tree.x);
		break;

	      case SouthGravity:
		tc->tree.y = (((Position) tw->tree.maxheight) -
			      ((Position) w->core.height) - tc->tree.y);
		break;
	    }

	    /*
	     * Move the widget into position.
	     */
	    XtMoveWidget (w, tc->tree.x, tc->tree.y);
	}

	/*
	 * Set the positions of all children.
	 */
	for (i = 0; i < tc->tree.n_children; i++)
	  set_positions (tw, tc->tree.children[i], level + 1);
    }
}


static void arrange_subtree (tree, w, depth, x, y)
    TreeWidget tree;
    Widget w;
    int depth;
    Position x, y;
{
    TreeConstraints tc = TREE_CONSTRAINT(w);  /* info attached to all kids */
    TreeConstraints firstcc, lastcc;
    register int i;
    int newx, newy;
    Bool horiz = IsHorizontal (tree);
    Widget child = NULL;
    Dimension tmp;
    Dimension bw2 = w->core.border_width * 2;
    Bool relayout = True;


    /*
     * If no children, then just lay out where requested.
     */
    tc->tree.x = x;
    tc->tree.y = y;

    if (horiz) {
	int myh = (w->core.height + bw2);

	if (myh > (int)tc->tree.bbsubheight) {
	    y += (myh - (int)tc->tree.bbsubheight) / 2;
	    relayout = False;
	}
    } else {
	int myw = (w->core.width + bw2);

	if (myw > (int)tc->tree.bbsubwidth) {
	    x += (myw - (int)tc->tree.bbsubwidth) / 2;
	    relayout = False;
	}
    }

    if ((tmp = ((Dimension) x) + tc->tree.bbwidth) > tree->tree.maxwidth)
      tree->tree.maxwidth = tmp;
    if ((tmp = ((Dimension) y) + tc->tree.bbheight) > tree->tree.maxheight)
      tree->tree.maxheight = tmp;

    if (tc->tree.n_children == 0) return;


    /*
     * Have children, so walk down tree laying out children, then laying
     * out parents.
     */
    if (horiz) {
	newx = x + tree->tree.largest[depth];
	if (depth > 0) newx += tree->tree.hpad;
	newy = y;
    } else {
	newx = x;
	newy = y + tree->tree.largest[depth];
	if (depth > 0) newy += tree->tree.vpad;
    }

    for (i = 0; i < tc->tree.n_children; i++) {
	TreeConstraints cc;

	child = tc->tree.children[i];	/* last value is used outside loop */
	cc = TREE_CONSTRAINT(child);

	arrange_subtree (tree, child, depth + 1, newx, newy);
	if (horiz) {
	    newy += tree->tree.vpad + cc->tree.bbheight;
	} else {
	    newx += tree->tree.hpad + cc->tree.bbwidth;
	}
    }

    /*
     * now layout parent between first and last children
     */
    if (relayout) {
	Position adjusted;
	firstcc = TREE_CONSTRAINT (tc->tree.children[0]);
	lastcc = TREE_CONSTRAINT (child);

	/* Adjustments are disallowed if they result in a position above
         * or to the left of the originally requested position, because
	 * this could collide with the position of the previous sibling.
	 */
	if (horiz) {
	    tc->tree.x = x;
	    adjusted = firstcc->tree.y +
	      ((lastcc->tree.y + (Position) child->core.height + 
		(Position) child->core.border_width * 2 -
		firstcc->tree.y - (Position) w->core.height - 
		(Position) w->core.border_width * 2 + 1) / 2);
	    if (adjusted > tc->tree.y) tc->tree.y = adjusted;
	} else {
	    adjusted = firstcc->tree.x +
	      ((lastcc->tree.x + (Position) child->core.width +
		(Position) child->core.border_width * 2 -
		firstcc->tree.x - (Position) w->core.width -
		(Position) w->core.border_width * 2 + 1) / 2);
	    if (adjusted > tc->tree.x) tc->tree.x = adjusted;
	    tc->tree.y = y;
	}
    }
}

static void set_tree_size (tw, insetvalues, width, height)
    TreeWidget tw;
    Boolean insetvalues;
    Dimension width, height;
{
    if (insetvalues) {
	tw->core.width = width;
	tw->core.height = height;
    } else {
	Dimension replyWidth = 0, replyHeight = 0;
	XtGeometryResult result = XtMakeResizeRequest ((Widget) tw,
						       width, height,
						       &replyWidth,
						       &replyHeight);
	/*
	 * Accept any compromise.
	 */
	if (result == XtGeometryAlmost)
	  XtMakeResizeRequest ((Widget) tw, replyWidth, replyHeight,
			       (Dimension *) NULL, (Dimension *) NULL);
    }
    return;
}

static void layout_tree (tw, insetvalues)
    TreeWidget tw;
    Boolean insetvalues;
{
    int i;
    Dimension *dp;

    /*
     * Do a depth-first search computing the width and height of the bounding
     * box for the tree at that position (and below).  Then, walk again using
     * this information to layout the children at each level.
     */

    if (tw->tree.tree_root == NULL)
	return;

    tw->tree.maxwidth = tw->tree.maxheight = 0;
    for (i = 0, dp = tw->tree.largest; i < tw->tree.n_largest; i++, dp++)
      *dp = 0;
    initialize_dimensions (&tw->tree.largest, &tw->tree.n_largest, 
			   tw->tree.n_largest);
    compute_bounding_box_subtree (tw, tw->tree.tree_root, 0);

   /*
    * Second pass to do final layout.  Each child's bounding box is stacked
    * on top of (if horizontal, else next to) on top of its siblings.  The
    * parent is centered between the first and last children.
    */
    arrange_subtree (tw, tw->tree.tree_root, 0, 0, 0);

    /*
     * Move each widget into place.
     */
    set_tree_size (tw, insetvalues, tw->tree.maxwidth, tw->tree.maxheight);
    set_positions (tw, tw->tree.tree_root, 0);

    /*
     * And redisplay.
     */
    if (XtIsRealized ((Widget) tw)) {
	XClearArea (XtDisplay(tw), XtWindow((Widget)tw), 0, 0, 0, 0, True);
    }
}



/*****************************************************************************
 *                                                                           *
 * 				Public Routines                              *
 *                                                                           *
 *****************************************************************************/

void
#if NeedFunctionPrototypes
TreeForceLayout (Widget tree)
#else
TreeForceLayout (tree)
    Widget tree;
#endif
{
    layout_tree ((TreeWidget) tree, FALSE);
}