path: root/src/bltGrAxisOp.C

/*
 * Smithsonian Astrophysical Observatory, Cambridge, MA, USA
 * This code has been modified under the terms listed below and is made
 * available under the same terms.
 */

/*
 *	Copyright 1993-2004 George A Howlett.
 *
 *	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 AUTHORS OR COPYRIGHT HOLDERS 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.
 */

extern "C" {
#include "bltInt.h"
#include "bltOp.h"
#include "bltBind.h"
};

#include "bltGraph.h"
#include "bltGrAxis.h"
#include "bltGrAxisOp.h"
#include "bltGrMisc.h"

using namespace Blt;

#define EXP10(x)	(pow(10.0,(x)))

static int GetAxisScrollInfo(Tcl_Interp* interp, 
			     int objc, Tcl_Obj* const objv[],
			     double *offsetPtr, double windowSize,
			     double scrollUnits, double scale);

static double Clamp(double x) 
{
  return (x < 0.0) ? 0.0 : (x > 1.0) ? 1.0 : x;
}

int AxisObjConfigure(Tcl_Interp* interp, Axis* axisPtr,
		     int objc, Tcl_Obj* const objv[])
{
  Graph* graphPtr = axisPtr->graphPtr_;
  Tk_SavedOptions savedOptions;
  int mask =0;
  int error;
  Tcl_Obj* errorResult;

  for (error=0; error<=1; error++) {
    if (!error) {
      if (Tk_SetOptions(interp, (char*)axisPtr->ops(), axisPtr->optionTable(), 
			objc, objv, graphPtr->tkwin_, &savedOptions, &mask)
	  != TCL_OK)
	continue;
    }
    else {
      errorResult = Tcl_GetObjResult(interp);
      Tcl_IncrRefCount(errorResult);
      Tk_RestoreSavedOptions(&savedOptions);
    }

    axisPtr->flags |= mask;
    axisPtr->flags |= DIRTY;
    graphPtr->flags |= REDRAW_WORLD | MAP_WORLD | RESET_AXES | CACHE_DIRTY;
    if (axisPtr->configure() != TCL_OK)
      return TCL_ERROR;
    graphPtr->eventuallyRedraw();

    break; 
  }

  if (!error) {
    Tk_FreeSavedOptions(&savedOptions);
    return TCL_OK;
  }
  else {
    Tcl_SetObjResult(interp, errorResult);
    Tcl_DecrRefCount(errorResult);
    return TCL_ERROR;
  }
}

// Common Ops

int AxisCgetOp(Tcl_Interp* interp, Axis* axisPtr, 
	       int objc, Tcl_Obj* const objv[])
{
  Graph* graphPtr = axisPtr->graphPtr_;

  if (objc != 4) {
    Tcl_WrongNumArgs(interp, 2, objv, "cget option");
    return TCL_ERROR;
  }

  Tcl_Obj* objPtr = Tk_GetOptionValue(interp, (char*)axisPtr->ops(),
				      axisPtr->optionTable(),
				      objv[3], graphPtr->tkwin_);
  if (!objPtr)
    return TCL_ERROR;
  else
    Tcl_SetObjResult(interp, objPtr);
  return TCL_OK;
}

int AxisConfigureOp(Tcl_Interp* interp, Axis* axisPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  Graph* graphPtr = axisPtr->graphPtr_;

  if (objc <= 4) {
    Tcl_Obj* objPtr = Tk_GetOptionInfo(interp, (char*)axisPtr->ops(), 
				       axisPtr->optionTable(), 
				       (objc == 4) ? objv[3] : NULL, 
				       graphPtr->tkwin_);
    if (!objPtr)
      return TCL_ERROR;
    else
      Tcl_SetObjResult(interp, objPtr);
    return TCL_OK;
  } 
  else
    return AxisObjConfigure(interp, axisPtr, objc-3, objv+3);
}

int AxisActivateOp(Tcl_Interp* interp, Axis* axisPtr, 
		   int objc, Tcl_Obj* const objv[])
{
  AxisOptions* ops = (AxisOptions*)axisPtr->ops();
  Graph* graphPtr = axisPtr->graphPtr_;
  const char *string;

  string = Tcl_GetString(objv[2]);
  if (string[0] == 'a')
    axisPtr->flags |= ACTIVE;
  else
    axisPtr->flags &= ~ACTIVE;

  if (!ops->hide && axisPtr->use_) {
    graphPtr->flags |= DRAW_MARGINS | CACHE_DIRTY;
    graphPtr->eventuallyRedraw();
  }

  return TCL_OK;
}

int AxisInvTransformOp(Tcl_Interp* interp, Axis* axisPtr, 
		       int objc, Tcl_Obj* const objv[])
{
  Graph* graphPtr = axisPtr->graphPtr_;

  if (graphPtr->flags & RESET_AXES)
    graphPtr->resetAxes();

  int sy;
  if (Tcl_GetIntFromObj(interp, objv[3], &sy) != TCL_OK)
    return TCL_ERROR;

  // Is the axis vertical or horizontal?
  // Check the site where the axis was positioned.  If the axis is
  // virtual, all we have to go on is how it was mapped to an
  // element (using either -mapx or -mapy options).  
  double y = axisPtr->isHorizontal() ? 
    axisPtr->invHMap(sy) : axisPtr->invVMap(sy);

  Tcl_SetDoubleObj(Tcl_GetObjResult(interp), y);
  return TCL_OK;
}

int AxisLimitsOp(Tcl_Interp* interp, Axis* axisPtr, 
		 int objc, Tcl_Obj* const objv[])
{
  AxisOptions* ops = (AxisOptions*)axisPtr->ops();
  Graph* graphPtr = axisPtr->graphPtr_;

  if (graphPtr->flags & RESET_AXES)
    graphPtr->resetAxes();

  double min, max;
  if (ops->logScale) {
    min = EXP10(axisPtr->axisRange_.min);
    max = EXP10(axisPtr->axisRange_.max);
  } 
  else {
    min = axisPtr->axisRange_.min;
    max = axisPtr->axisRange_.max;
  }

  Tcl_Obj *listObjPtr = Tcl_NewListObj(0, (Tcl_Obj **)NULL);
  Tcl_ListObjAppendElement(interp, listObjPtr, Tcl_NewDoubleObj(min));
  Tcl_ListObjAppendElement(interp, listObjPtr, Tcl_NewDoubleObj(max));

  Tcl_SetObjResult(interp, listObjPtr);
  return TCL_OK;
}

int AxisMarginOp(Tcl_Interp* interp, Axis* axisPtr, 
		 int objc, Tcl_Obj* const objv[])
{
  const char *marginName = "";
  if (axisPtr->use_)
    marginName = axisNames[axisPtr->margin_].name;

  Tcl_SetStringObj(Tcl_GetObjResult(interp), marginName, -1);
  return TCL_OK;
}

int AxisTransformOp(Tcl_Interp* interp, Axis* axisPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  Graph* graphPtr = axisPtr->graphPtr_;

  if (graphPtr->flags & RESET_AXES)
    graphPtr->resetAxes();

  double x;
  if (Blt_ExprDoubleFromObj(interp, objv[3], &x) != TCL_OK)
    return TCL_ERROR;

  if (axisPtr->isHorizontal())
    x = axisPtr->hMap(x);
  else
    x = axisPtr->vMap(x);

  Tcl_SetIntObj(Tcl_GetObjResult(interp), (int)x);
  return TCL_OK;
}

int AxisTypeOp(Tcl_Interp* interp, Axis* axisPtr, 
	       int objc, Tcl_Obj* const objv[])
{
  const char *typeName;

  typeName = "";
  if (axisPtr->use_) {
    if (axisNames[axisPtr->margin_].classId == CID_AXIS_X)
      typeName = "x";
    else if (axisNames[axisPtr->margin_].classId == CID_AXIS_Y)
      typeName = "y";
  }
  Tcl_SetStringObj(Tcl_GetObjResult(interp), typeName, -1);
  return TCL_OK;
}

int AxisViewOp(Tcl_Interp* interp, Axis* axisPtr, 
	       int objc, Tcl_Obj* const objv[])
{
  AxisOptions* ops = (AxisOptions*)axisPtr->ops();
  Graph* graphPtr = axisPtr->graphPtr_;
  double worldMin = axisPtr->valueRange_.min;
  double worldMax = axisPtr->valueRange_.max;
  /* Override data dimensions with user-selected limits. */
  if (!isnan(axisPtr->scrollMin_))
    worldMin = axisPtr->scrollMin_;

  if (!isnan(axisPtr->scrollMax_))
    worldMax = axisPtr->scrollMax_;

  double viewMin = axisPtr->min_;
  double viewMax = axisPtr->max_;
  /* Bound the view within scroll region. */ 
  if (viewMin < worldMin)
    viewMin = worldMin;

  if (viewMax > worldMax)
    viewMax = worldMax;

  if (ops->logScale) {
    worldMin = log10(worldMin);
    worldMax = log10(worldMax);
    viewMin  = log10(viewMin);
    viewMax  = log10(viewMax);
  }
  double worldWidth = worldMax - worldMin;
  double viewWidth  = viewMax - viewMin;

  /* Unlike horizontal axes, vertical axis values run opposite of the
   * scrollbar first/last values.  So instead of pushing the axis minimum
   * around, we move the maximum instead. */
  double axisOffset;
  double axisScale;
  if (axisPtr->isHorizontal() != ops->descending) {
    axisOffset  = viewMin - worldMin;
    axisScale = graphPtr->hScale_;
  } else {
    axisOffset  = worldMax - viewMax;
    axisScale = graphPtr->vScale_;
  }
  if (objc == 4) {
    double first = Clamp(axisOffset / worldWidth);
    double last = Clamp((axisOffset + viewWidth) / worldWidth);
    Tcl_Obj *listObjPtr = Tcl_NewListObj(0, NULL);
    Tcl_ListObjAppendElement(interp, listObjPtr, Tcl_NewDoubleObj(first));
    Tcl_ListObjAppendElement(interp, listObjPtr, Tcl_NewDoubleObj(last));
    Tcl_SetObjResult(interp, listObjPtr);
    return TCL_OK;
  }
  double fract = axisOffset / worldWidth;
  if (GetAxisScrollInfo(interp, objc, objv, &fract, viewWidth / worldWidth, 
			ops->scrollUnits, axisScale) != TCL_OK)
    return TCL_ERROR;

  if (axisPtr->isHorizontal() != ops->descending) {
    ops->reqMin = (fract * worldWidth) + worldMin;
    ops->reqMax = ops->reqMin + viewWidth;
  }
  else {
    ops->reqMax = worldMax - (fract * worldWidth);
    ops->reqMin = ops->reqMax - viewWidth;
  }
  if (ops->logScale) {
    ops->reqMin = EXP10(ops->reqMin);
    ops->reqMax = EXP10(ops->reqMax);
  }
  graphPtr->flags |= (GET_AXIS_GEOMETRY | LAYOUT_NEEDED | RESET_AXES);
  graphPtr->eventuallyRedraw();

  return TCL_OK;
}

// Axis

static int CgetOp(Tcl_Interp* interp, Graph* graphPtr, 
		  int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisCgetOp(interp, axisPtr, objc-1, objv+1);
}

static int ConfigureOp(Tcl_Interp* interp, Graph* graphPtr, int objc, 
		       Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisConfigureOp(interp, axisPtr, objc-1, objv+1);
}

static int ActivateOp(Tcl_Interp* interp, Graph* graphPtr, 
		      int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisActivateOp(interp, axisPtr, objc, objv);
}

static int BindOp(Tcl_Interp* interp, Graph* graphPtr, int objc, 
		  Tcl_Obj* const objv[])
{
  if (objc == 3) {
    Tcl_Obj *listObjPtr = Tcl_NewListObj(0, (Tcl_Obj **)NULL);
    Tcl_HashSearch cursor;
    for (Tcl_HashEntry *hPtr = Tcl_FirstHashEntry(&graphPtr->axes_.tagTable, &cursor); hPtr != NULL; hPtr = Tcl_NextHashEntry(&cursor)) {
      const char *tagName = (const char*)
	Tcl_GetHashKey(&graphPtr->axes_.tagTable, hPtr);
      Tcl_Obj *objPtr = Tcl_NewStringObj(tagName, -1);
      Tcl_ListObjAppendElement(interp, listObjPtr, objPtr);
    }
    Tcl_SetObjResult(interp, listObjPtr);
    return TCL_OK;
  }
  else
    return Blt_ConfigureBindingsFromObj(interp, graphPtr->bindTable_, graphPtr->axisTag(Tcl_GetString(objv[3])), objc-4, objv+4);
}

static int CreateOp(Tcl_Interp* interp, Graph* graphPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  if (graphPtr->createAxis(objc, objv) != TCL_OK)
    return TCL_ERROR;
  Tcl_SetObjResult(interp, objv[3]);

  return TCL_OK;
}

static int DeleteOp(Tcl_Interp* interp, Graph* graphPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  if (objc<4)
    return TCL_ERROR;
    
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  if (axisPtr->refCount_ == 0)
    delete axisPtr;

  graphPtr->eventuallyRedraw();

  return TCL_OK;
}

static int FocusOp(Tcl_Interp* interp, Graph* graphPtr, 
		   int objc, Tcl_Obj* const objv[])
{
  graphPtr->focusPtr_ = NULL;
  if (objc == 4) {
    Axis* axisPtr;
    if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
      return TCL_ERROR;

    AxisOptions* ops = (AxisOptions*)axisPtr->ops();
    if (axisPtr && !ops->hide && axisPtr->use_)
      graphPtr->focusPtr_ = axisPtr;
  }

  Blt_SetFocusItem(graphPtr->bindTable_, graphPtr->focusPtr_, NULL);

  if (graphPtr->focusPtr_)
    Tcl_SetStringObj(Tcl_GetObjResult(interp), graphPtr->focusPtr_->name_,-1);

  return TCL_OK;
}

static int GetOp(Tcl_Interp* interp, Graph* graphPtr, 
		 int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr = (Axis*)Blt_GetCurrentItem(graphPtr->bindTable_);

  // Report only on axes
  if ((axisPtr) && 
      ((axisPtr->classId_ == CID_AXIS_X) || 
       (axisPtr->classId_ == CID_AXIS_Y) || 
       (axisPtr->classId_ == CID_NONE))) {

    char  *string = Tcl_GetString(objv[3]);
    if (!strcmp(string, "current"))
      Tcl_SetStringObj(Tcl_GetObjResult(interp), axisPtr->name_,-1);
    else if (!strcmp(string, "detail"))
      Tcl_SetStringObj(Tcl_GetObjResult(interp), axisPtr->detail_, -1);
  }

  return TCL_OK;
}

static int InvTransformOp(Tcl_Interp* interp, Graph* graphPtr, 
			  int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisInvTransformOp(interp, axisPtr, objc-1, objv+1);
}

static int LimitsOp(Tcl_Interp* interp, Graph* graphPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisLimitsOp(interp, axisPtr, objc-1, objv+1);
}

static int MarginOp(Tcl_Interp* interp, Graph* graphPtr, 
		    int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisMarginOp(interp, axisPtr, objc-1, objv+1);
}

static int NamesOp(Tcl_Interp* interp, Graph* graphPtr, 
		   int objc, Tcl_Obj* const objv[])
{
  Tcl_Obj *listObjPtr = Tcl_NewListObj(0, (Tcl_Obj **)NULL);
  if (objc == 3) {
    Tcl_HashSearch cursor;
    for (Tcl_HashEntry *hPtr = Tcl_FirstHashEntry(&graphPtr->axes_.table, &cursor); hPtr; hPtr = Tcl_NextHashEntry(&cursor)) {
      Axis* axisPtr = (Axis*)Tcl_GetHashValue(hPtr);
      Tcl_ListObjAppendElement(interp, listObjPtr, Tcl_NewStringObj(axisPtr->name_, -1));
    }
  } 
  else {
    Tcl_HashSearch cursor;
    for (Tcl_HashEntry *hPtr = Tcl_FirstHashEntry(&graphPtr->axes_.table, &cursor); hPtr; hPtr = Tcl_NextHashEntry(&cursor)) {
      Axis* axisPtr = (Axis*)Tcl_GetHashValue(hPtr);
      for (int ii=3; ii<objc; ii++) {
	const char *pattern = (const char*)Tcl_GetString(objv[ii]);
	if (Tcl_StringMatch(axisPtr->name_, pattern)) {
	  Tcl_ListObjAppendElement(interp, listObjPtr, 
				   Tcl_NewStringObj(axisPtr->name_, -1));
	  break;
	}
      }
    }
  }
  Tcl_SetObjResult(interp, listObjPtr);

  return TCL_OK;
}

static int TransformOp(Tcl_Interp* interp, Graph* graphPtr, 
		       int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisTransformOp(interp, axisPtr, objc-1, objv+1);
}

static int TypeOp(Tcl_Interp* interp, Graph* graphPtr, 
		  int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisTypeOp(interp, axisPtr, objc-1, objv+1);
}

static int ViewOp(Tcl_Interp* interp, Graph* graphPtr, 
		  int objc, Tcl_Obj* const objv[])
{
  Axis* axisPtr;
  if (graphPtr->getAxis(objv[3], &axisPtr) != TCL_OK)
    return TCL_ERROR;

  return AxisViewOp(interp, axisPtr, objc-1, objv+1);
}

static Blt_OpSpec axisOps[] = {
  {"activate",     1, (void*)ActivateOp,     4, 4, "axisName"},
  {"bind",         1, (void*)BindOp,         3, 6, "axisName sequence command"},
  {"cget",         2, (void*)CgetOp,         5, 5, "axisName option"},
  {"configure",    2, (void*)ConfigureOp,    4, 0, "axisName ?axisName?... "
   "?option value?..."},
  {"create",       2, (void*)CreateOp,       4, 0, "axisName ?option value?..."},
  {"deactivate",   3, (void*)ActivateOp,     4, 4, "axisName"},
  {"delete",       3, (void*)DeleteOp,       3, 0, "?axisName?..."},
  {"focus",        1, (void*)FocusOp,        3, 4, "?axisName?"},
  {"get",          1, (void*)GetOp,          4, 4, "name"},
  {"invtransform", 1, (void*)InvTransformOp, 5, 5, "axisName value"},
  {"limits",       1, (void*)LimitsOp,       4, 4, "axisName"},
  {"margin",       1, (void*)MarginOp,       4, 4, "axisName"},
  {"names",        1, (void*)NamesOp,        3, 0, "?pattern?..."},
  {"transform",    2, (void*)TransformOp,    5, 5, "axisName value"},
  {"type",         2, (void*)TypeOp,       4, 4, "axisName"},
  {"view",         1, (void*)ViewOp,         4, 7, "axisName ?moveto fract? "
   "?scroll number what?"},
};
static int nAxisOps = sizeof(axisOps) / sizeof(Blt_OpSpec);

typedef int (GraphAxisProc)(Tcl_Interp* interp, Graph* graphPtr, 
			    int objc, Tcl_Obj* const objv[]);

int Blt_AxisOp(Graph* graphPtr, Tcl_Interp* interp, 
		int objc, Tcl_Obj* const objv[])
{
  GraphAxisProc* proc = (GraphAxisProc*)Blt_GetOpFromObj(interp, nAxisOps, axisOps, BLT_OP_ARG2, objc, objv, 0);
  if (!proc)
    return TCL_ERROR;

  return (*proc)(interp, graphPtr, objc, objv);
}

// Support

Axis *Blt_GetFirstAxis(Blt_Chain chain)
{
  Blt_ChainLink link = Blt_Chain_FirstLink(chain);
  if (!link)
    return NULL;

  return (Axis*)Blt_Chain_GetValue(link);
}

double AdjustViewport(double offset, double windowSize)
{
  // Canvas-style scrolling allows the world to be scrolled within the window.
  if (windowSize > 1.0) {
    if (windowSize < (1.0 - offset))
      offset = 1.0 - windowSize;

    if (offset > 0.0)
      offset = 0.0;
  }
  else {
    if ((offset + windowSize) > 1.0)
      offset = 1.0 - windowSize;

    if (offset < 0.0)
      offset = 0.0;
  }
  return offset;
}

static int GetAxisScrollInfo(Tcl_Interp* interp, 
			     int objc, Tcl_Obj* const objv[],
			     double *offsetPtr, double windowSize,
			     double scrollUnits, double scale)
{
  const char *string;
  char c;
  double offset;
  int length;

  offset = *offsetPtr;
  string = Tcl_GetStringFromObj(objv[0], &length);
  c = string[0];
  scrollUnits *= scale;
  if ((c == 's') && (strncmp(string, "scroll", length) == 0)) {
    int count;
    double fract;

    /* Scroll number unit/page */
    if (Tcl_GetIntFromObj(interp, objv[1], &count) != TCL_OK)
      return TCL_ERROR;

    string = Tcl_GetStringFromObj(objv[2], &length);
    c = string[0];
    if ((c == 'u') && (strncmp(string, "units", length) == 0))
      fract = count * scrollUnits;
    else if ((c == 'p') && (strncmp(string, "pages", length) == 0))
      /* A page is 90% of the view-able window. */
      fract = (int)(count * windowSize * 0.9 + 0.5);
    else if ((c == 'p') && (strncmp(string, "pixels", length) == 0))
      fract = count * scale;
    else {
      Tcl_AppendResult(interp, "unknown \"scroll\" units \"", string,
		       "\"", NULL);
      return TCL_ERROR;
    }
    offset += fract;
  } 
  else if ((c == 'm') && (strncmp(string, "moveto", length) == 0)) {
    double fract;

    /* moveto fraction */
    if (Tcl_GetDoubleFromObj(interp, objv[1], &fract) != TCL_OK) {
      return TCL_ERROR;
    }
    offset = fract;
  } 
  else {
    int count;
    double fract;

    /* Treat like "scroll units" */
    if (Tcl_GetIntFromObj(interp, objv[0], &count) != TCL_OK) {
      return TCL_ERROR;
    }
    fract = (double)count * scrollUnits;
    offset += fract;
    /* CHECK THIS: return TCL_OK; */
  }
  *offsetPtr = AdjustViewport(offset, windowSize);
  return TCL_OK;
}