reactos/reactos/subsys/win32k/objects/path.c

#undef WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <ddk/ntddk.h>
#include <win32k/brush.h>
#include <win32k/dc.h>
#include <win32k/path.h>
#include <win32k/math.h>
#include <win32k/float.h>
#include <win32k/coord.h>
#include <win32k/line.h>

#include <math.h>
#include <float.h>

// #define NDEBUG
#include <internal/debug.h>

#define NUM_ENTRIES_INITIAL 16  /* Initial size of points / flags arrays  */
#define GROW_FACTOR_NUMER    2  /* Numerator of grow factor for the array */
#define GROW_FACTOR_DENOM    1  /* Denominator of grow factor             */


static BOOL PATH_PathToRegion(const GdiPath *pPath, INT nPolyFillMode,
   HRGN *pHrgn);
static void   PATH_EmptyPath(GdiPath *pPath);
static BOOL PATH_AddEntry(GdiPath *pPath, const POINT *pPoint,
   BYTE flags);
static BOOL PATH_ReserveEntries(GdiPath *pPath, INT numEntries);
static BOOL PATH_GetPathFromHDC(HDC hdc, GdiPath **ppPath);
static BOOL PATH_DoArcPart(GdiPath *pPath, FLOAT_POINT corners[],
   double angleStart, double angleEnd, BOOL addMoveTo);
static void PATH_ScaleNormalizedPoint(FLOAT_POINT corners[], double x,
   double y, POINT *pPoint);
static void PATH_NormalizePoint(FLOAT_POINT corners[], const FLOAT_POINT
   *pPoint, double *pX, double *pY);

BOOL
STDCALL
W32kAbortPath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kBeginPath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kCloseFigure(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kEndPath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kFillPath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kFlattenPath(HDC  hDC)
{
  UNIMPLEMENTED;
}


BOOL
STDCALL
W32kGetMiterLimit(HDC  hDC,
                        PFLOAT  Limit)
{
  UNIMPLEMENTED;
}

INT
STDCALL
W32kGetPath(HDC  hDC,
                 LPPOINT  Points,
                 LPBYTE  Types,
                 INT  nSize)
{
  UNIMPLEMENTED;
}

HRGN
STDCALL
W32kPathToRegion(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kSetMiterLimit(HDC  hDC,
                        FLOAT  NewLimit,
                        PFLOAT  OldLimit)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kStrokeAndFillPath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kStrokePath(HDC  hDC)
{
  UNIMPLEMENTED;
}

BOOL
STDCALL
W32kWidenPath(HDC  hDC)
{
   UNIMPLEMENTED;
}

/***********************************************************************
 * Exported functions
 */

/* PATH_InitGdiPath
 *
 * Initializes the GdiPath structure.
 */
void PATH_InitGdiPath(GdiPath *pPath)
{
   assert(pPath!=NULL);

   pPath->state=PATH_Null;
   pPath->pPoints=NULL;
   pPath->pFlags=NULL;
   pPath->numEntriesUsed=0;
   pPath->numEntriesAllocated=0;
}

/* PATH_DestroyGdiPath
 *
 * Destroys a GdiPath structure (frees the memory in the arrays).
 */
void PATH_DestroyGdiPath(GdiPath *pPath)
{
   assert(pPath!=NULL);

   ExFreePool(pPath->pPoints);
   ExFreePool(pPath->pFlags);
}

/* PATH_AssignGdiPath
 *
 * Copies the GdiPath structure "pPathSrc" to "pPathDest". A deep copy is
 * performed, i.e. the contents of the pPoints and pFlags arrays are copied,
 * not just the pointers. Since this means that the arrays in pPathDest may
 * need to be resized, pPathDest should have been initialized using
 * PATH_InitGdiPath (in C++, this function would be an assignment operator,
 * not a copy constructor).
 * Returns TRUE if successful, else FALSE.
 */
BOOL PATH_AssignGdiPath(GdiPath *pPathDest, const GdiPath *pPathSrc)
{
   assert(pPathDest!=NULL && pPathSrc!=NULL);

   /* Make sure destination arrays are big enough */
   if(!PATH_ReserveEntries(pPathDest, pPathSrc->numEntriesUsed))
      return FALSE;

   /* Perform the copy operation */
   memcpy(pPathDest->pPoints, pPathSrc->pPoints,
      sizeof(POINT)*pPathSrc->numEntriesUsed);
   memcpy(pPathDest->pFlags, pPathSrc->pFlags,
      sizeof(BYTE)*pPathSrc->numEntriesUsed);

   pPathDest->state=pPathSrc->state;
   pPathDest->numEntriesUsed=pPathSrc->numEntriesUsed;
   pPathDest->newStroke=pPathSrc->newStroke;

   return TRUE;
}

/* PATH_MoveTo
 *
 * Should be called when a MoveTo is performed on a DC that has an
 * open path. This starts a new stroke. Returns TRUE if successful, else
 * FALSE.
 */
BOOL PATH_MoveTo(HDC hdc)
{
   GdiPath *pPath;
   
   /* Get pointer to path */
   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      /* FIXME: Do we have to call SetLastError? */
      return FALSE;

   /* Start a new stroke */
   pPath->newStroke=TRUE;

   return TRUE;
}

/* PATH_LineTo
 *
 * Should be called when a LineTo is performed on a DC that has an
 * open path. This adds a PT_LINETO entry to the path (and possibly
 * a PT_MOVETO entry, if this is the first LineTo in a stroke).
 * Returns TRUE if successful, else FALSE.
 */
BOOL PATH_LineTo(HDC hdc, INT x, INT y)
{
   GdiPath *pPath;
   POINT point, pointCurPos;
   
   /* Get pointer to path */
   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   /* Convert point to device coordinates */
   point.x=x;
   point.y=y;
   if(!W32kLPtoDP(hdc, &point, 1))
      return FALSE;
   
   /* Add a PT_MOVETO if necessary */
   if(pPath->newStroke)
   {
      pPath->newStroke=FALSE;
      if(!W32kGetCurrentPositionEx(hdc, &pointCurPos) ||
         !W32kLPtoDP(hdc, &pointCurPos, 1))
         return FALSE;
      if(!PATH_AddEntry(pPath, &pointCurPos, PT_MOVETO))
         return FALSE;
   }
   
   /* Add a PT_LINETO entry */
   return PATH_AddEntry(pPath, &point, PT_LINETO);
}

/* PATH_Rectangle
 *
 * Should be called when a call to Rectangle is performed on a DC that has
 * an open path. Returns TRUE if successful, else FALSE.
 */
BOOL PATH_Rectangle(HDC hdc, INT x1, INT y1, INT x2, INT y2)
{
   GdiPath *pPath;
   POINT corners[2], pointTemp;
   INT   temp;

   /* Get pointer to path */
   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   /* Convert points to device coordinates */
   corners[0].x=x1;
   corners[0].y=y1;
   corners[1].x=x2;
   corners[1].y=y2;
   if(!W32kLPtoDP(hdc, corners, 2))
      return FALSE;
   
   /* Make sure first corner is top left and second corner is bottom right */
   if(corners[0].x>corners[1].x)
   {
      temp=corners[0].x;
      corners[0].x=corners[1].x;
      corners[1].x=temp;
   }
   if(corners[0].y>corners[1].y)
   {
      temp=corners[0].y;
      corners[0].y=corners[1].y;
      corners[1].y=temp;
   }
   
   /* In GM_COMPATIBLE, don't include bottom and right edges */
   if(W32kGetGraphicsMode(hdc)==GM_COMPATIBLE)
   {
      corners[1].x--;
      corners[1].y--;
   }

   /* Close any previous figure */
   if(!W32kCloseFigure(hdc))
   {
      /* The W32kCloseFigure call shouldn't have failed */
      assert(FALSE);
      return FALSE;
   }

   /* Add four points to the path */
   pointTemp.x=corners[1].x;
   pointTemp.y=corners[0].y;
   if(!PATH_AddEntry(pPath, &pointTemp, PT_MOVETO))
      return FALSE;
   if(!PATH_AddEntry(pPath, corners, PT_LINETO))
      return FALSE;
   pointTemp.x=corners[0].x;
   pointTemp.y=corners[1].y;
   if(!PATH_AddEntry(pPath, &pointTemp, PT_LINETO))
      return FALSE;
   if(!PATH_AddEntry(pPath, corners+1, PT_LINETO))
      return FALSE;

   /* Close the rectangle figure */
   if(!W32kCloseFigure(hdc))
   {
      /* The W32kCloseFigure call shouldn't have failed */
      assert(FALSE);
      return FALSE;
   }

   return TRUE;
}

/* PATH_Ellipse
 * 
 * Should be called when a call to Ellipse is performed on a DC that has
 * an open path. This adds four Bezier splines representing the ellipse
 * to the path. Returns TRUE if successful, else FALSE.
 */
BOOL PATH_Ellipse(HDC hdc, INT x1, INT y1, INT x2, INT y2)
{
   /* TODO: This should probably be revised to call PATH_AngleArc */
   /* (once it exists) */
   return PATH_Arc(hdc, x1, y1, x2, y2, x1, (y1+y2)/2, x1, (y1+y2)/2);
}

/* PATH_Arc
 *
 * Should be called when a call to Arc is performed on a DC that has
 * an open path. This adds up to five Bezier splines representing the arc
 * to the path. Returns TRUE if successful, else FALSE.
 */
BOOL PATH_Arc(HDC hdc, INT x1, INT y1, INT x2, INT y2,
   INT xStart, INT yStart, INT xEnd, INT yEnd)
{
   GdiPath     *pPath;
   DC          *pDC;
   double      angleStart, angleEnd, angleStartQuadrant, angleEndQuadrant=0.0;
               /* Initialize angleEndQuadrant to silence gcc's warning */
   double      x, y;
   FLOAT_POINT corners[2], pointStart, pointEnd;
   BOOL      start, end;
   INT       temp;

   /* FIXME: This function should check for all possible error returns */
   /* FIXME: Do we have to respect newStroke? */
   
   /* Get pointer to DC */
   pDC=DC_HandleToPtr(hdc);
   if(pDC==NULL)
      return FALSE;

   /* Get pointer to path */
   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   /* FIXME: Do we have to close the current figure? */
   
   /* Check for zero height / width */
   /* FIXME: Only in GM_COMPATIBLE? */
   if(x1==x2 || y1==y2)
      return TRUE;
   
   /* Convert points to device coordinates */
   corners[0].x=(FLOAT)x1;
   corners[0].y=(FLOAT)y1;
   corners[1].x=(FLOAT)x2;
   corners[1].y=(FLOAT)y2;
   pointStart.x=(FLOAT)xStart;
   pointStart.y=(FLOAT)yStart;
   pointEnd.x=(FLOAT)xEnd;
   pointEnd.y=(FLOAT)yEnd;
   INTERNAL_LPTODP_FLOAT(pDC, corners);
   INTERNAL_LPTODP_FLOAT(pDC, corners+1);
   INTERNAL_LPTODP_FLOAT(pDC, &pointStart);
   INTERNAL_LPTODP_FLOAT(pDC, &pointEnd);

   /* Make sure first corner is top left and second corner is bottom right */
   if(corners[0].x>corners[1].x)
   {
      temp=corners[0].x;
      corners[0].x=corners[1].x;
      corners[1].x=temp;
   }
   if(corners[0].y>corners[1].y)
   {
      temp=corners[0].y;
      corners[0].y=corners[1].y;
      corners[1].y=temp;
   }

   /* Compute start and end angle */
   PATH_NormalizePoint(corners, &pointStart, &x, &y);
   angleStart=atan2(y, x);
   PATH_NormalizePoint(corners, &pointEnd, &x, &y);
   angleEnd=atan2(y, x);

   /* Make sure the end angle is "on the right side" of the start angle */
   if(W32kGetArcDirection(hdc)==AD_CLOCKWISE)
   {
      if(angleEnd<=angleStart)
      {
         angleEnd+=2*M_PI;
	 assert(angleEnd>=angleStart);
      }
   }
   else
   {
      if(angleEnd>=angleStart)
      {
         angleEnd-=2*M_PI;
	 assert(angleEnd<=angleStart);
      }
   }

   /* In GM_COMPATIBLE, don't include bottom and right edges */
   if(W32kGetGraphicsMode(hdc)==GM_COMPATIBLE)
   {
      corners[1].x--;
      corners[1].y--;
   }
   
   /* Add the arc to the path with one Bezier spline per quadrant that the
    * arc spans */
   start=TRUE;
   end=FALSE;
   do
   {
      /* Determine the start and end angles for this quadrant */
      if(start)
      {
         angleStartQuadrant=angleStart;
	 if(W32kGetArcDirection(hdc)==AD_CLOCKWISE)
	    angleEndQuadrant=(floor(angleStart/M_PI_2)+1.0)*M_PI_2;
	 else
	    angleEndQuadrant=(ceil(angleStart/M_PI_2)-1.0)*M_PI_2;
      }
      else
      {
	 angleStartQuadrant=angleEndQuadrant;
	 if(W32kGetArcDirection(hdc)==AD_CLOCKWISE)
	    angleEndQuadrant+=M_PI_2;
	 else
	    angleEndQuadrant-=M_PI_2;
      }

      /* Have we reached the last part of the arc? */
      if((W32kGetArcDirection(hdc)==AD_CLOCKWISE &&
         angleEnd<angleEndQuadrant) ||
	 (W32kGetArcDirection(hdc)==AD_COUNTERCLOCKWISE &&
	 angleEnd>angleEndQuadrant))
      {
	 /* Adjust the end angle for this quadrant */
         angleEndQuadrant=angleEnd;
	 end=TRUE;
      }

      /* Add the Bezier spline to the path */
      PATH_DoArcPart(pPath, corners, angleStartQuadrant, angleEndQuadrant,
         start);
      start=FALSE;
   }  while(!end);

   return TRUE;
}

BOOL PATH_PolyBezierTo(HDC hdc, const POINT *pts, DWORD cbPoints)
{
   GdiPath     *pPath;
   POINT       pt;
   INT         i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   /* Add a PT_MOVETO if necessary */
   if(pPath->newStroke)
   {
      pPath->newStroke=FALSE;
      if(!W32kGetCurrentPositionEx(hdc, &pt) ||
         !W32kLPtoDP(hdc, &pt, 1))
         return FALSE;
      if(!PATH_AddEntry(pPath, &pt, PT_MOVETO))
         return FALSE;
   }

   for(i = 0; i < cbPoints; i++) {
       pt = pts[i];
       if(!W32kLPtoDP(hdc, &pt, 1))
	   return FALSE;
       PATH_AddEntry(pPath, &pt, PT_BEZIERTO);
   }
   return TRUE;
}
   
BOOL PATH_PolyBezier(HDC hdc, const POINT *pts, DWORD cbPoints)
{
   GdiPath     *pPath;
   POINT       pt;
   INT         i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   for(i = 0; i < cbPoints; i++) {
       pt = pts[i];
       if(!W32kLPtoDP(hdc, &pt, 1))
	   return FALSE;
       PATH_AddEntry(pPath, &pt, (i == 0) ? PT_MOVETO : PT_BEZIERTO);
   }
   return TRUE;
}

BOOL PATH_Polyline(HDC hdc, const POINT *pts, DWORD cbPoints)
{
   GdiPath     *pPath;
   POINT       pt;
   INT         i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   for(i = 0; i < cbPoints; i++) {
       pt = pts[i];
       if(!W32kLPtoDP(hdc, &pt, 1))
	   return FALSE;
       PATH_AddEntry(pPath, &pt, (i == 0) ? PT_MOVETO : PT_LINETO);
   }
   return TRUE;
}
   
BOOL PATH_PolylineTo(HDC hdc, const POINT *pts, DWORD cbPoints)
{
   GdiPath     *pPath;
   POINT       pt;
   INT         i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   /* Add a PT_MOVETO if necessary */
   if(pPath->newStroke)
   {
      pPath->newStroke=FALSE;
      if(!W32kGetCurrentPositionEx(hdc, &pt) ||
         !W32kLPtoDP(hdc, &pt, 1))
         return FALSE;
      if(!PATH_AddEntry(pPath, &pt, PT_MOVETO))
         return FALSE;
   }

   for(i = 0; i < cbPoints; i++) {
       pt = pts[i];
       if(!W32kLPtoDP(hdc, &pt, 1))
	   return FALSE;
       PATH_AddEntry(pPath, &pt, PT_LINETO);
   }

   return TRUE;
}


BOOL PATH_Polygon(HDC hdc, const POINT *pts, DWORD cbPoints)
{
   GdiPath     *pPath;
   POINT       pt;
   INT         i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   for(i = 0; i < cbPoints; i++) {
       pt = pts[i];
       if(!W32kLPtoDP(hdc, &pt, 1))
	   return FALSE;
       PATH_AddEntry(pPath, &pt, (i == 0) ? PT_MOVETO :
		     ((i == cbPoints-1) ? PT_LINETO | PT_CLOSEFIGURE :
		      PT_LINETO));
   }
   return TRUE;
}

BOOL PATH_PolyPolygon( HDC hdc, const POINT* pts, const INT* counts,
		       UINT polygons )
{
   GdiPath     *pPath;
   POINT       pt, startpt;
   INT         poly, point, i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   for(i = 0, poly = 0; poly < polygons; poly++) {
       for(point = 0; point < counts[poly]; point++, i++) {
	   pt = pts[i];
	   if(!W32kLPtoDP(hdc, &pt, 1))
	       return FALSE;
	   if(point == 0) startpt = pt;
	   PATH_AddEntry(pPath, &pt, (point == 0) ? PT_MOVETO : PT_LINETO);
       }
       /* win98 adds an extra line to close the figure for some reason */
       PATH_AddEntry(pPath, &startpt, PT_LINETO | PT_CLOSEFIGURE);
   }
   return TRUE;
}

BOOL PATH_PolyPolyline( HDC hdc, const POINT* pts, const DWORD* counts,
			DWORD polylines )
{
   GdiPath     *pPath;
   POINT       pt;
   INT         poly, point, i;

   if(!PATH_GetPathFromHDC(hdc, &pPath))
      return FALSE;
   
   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;

   for(i = 0, poly = 0; poly < polylines; poly++) {
       for(point = 0; point < counts[poly]; point++, i++) {
	   pt = pts[i];
	   if(!W32kLPtoDP(hdc, &pt, 1))
	       return FALSE;
	   PATH_AddEntry(pPath, &pt, (point == 0) ? PT_MOVETO : PT_LINETO);
       }
   }
   return TRUE;
}
   
/***********************************************************************
 * Internal functions
 */


/* PATH_AddFlatBezier
 *
 */
static BOOL PATH_AddFlatBezier(GdiPath *pPath, POINT *pt, BOOL closed)
{
    POINT *pts;
    INT no, i;

    pts = GDI_Bezier( pt, 4, &no );
    if(!pts) return FALSE;

    for(i = 1; i < no; i++)
        PATH_AddEntry(pPath, &pts[i], 
	    (i == no-1 && closed) ? PT_LINETO | PT_CLOSEFIGURE : PT_LINETO);
    ExFreePool(pts);
    return TRUE;
}

/* PATH_FlattenPath
 *
 * Replaces Beziers with line segments
 *
 */
static BOOL PATH_FlattenPath(GdiPath *pPath)
{
    GdiPath newPath;
    INT srcpt;

    memset(&newPath, 0, sizeof(newPath));
    newPath.state = PATH_Open;
    for(srcpt = 0; srcpt < pPath->numEntriesUsed; srcpt++) {
        switch(pPath->pFlags[srcpt] & ~PT_CLOSEFIGURE) {
	case PT_MOVETO:
	case PT_LINETO:
	    PATH_AddEntry(&newPath, &pPath->pPoints[srcpt],
			  pPath->pFlags[srcpt]);
	    break;
	case PT_BEZIERTO:
	  PATH_AddFlatBezier(&newPath, &pPath->pPoints[srcpt-1],
			     pPath->pFlags[srcpt+2] & PT_CLOSEFIGURE);
	    srcpt += 2;
	    break;
	}
    }
    newPath.state = PATH_Closed;
    PATH_AssignGdiPath(pPath, &newPath);
    PATH_EmptyPath(&newPath);
    return TRUE;
}
	  
/* PATH_PathToRegion
 *
 * Creates a region from the specified path using the specified polygon
 * filling mode. The path is left unchanged. A handle to the region that
 * was created is stored in *pHrgn. If successful, TRUE is returned; if an
 * error occurs, SetLastError is called with the appropriate value and
 * FALSE is returned.
 */
static BOOL PATH_PathToRegion(const GdiPath *pPath, INT nPolyFillMode,
   HRGN *pHrgn)
{
   int    numStrokes, iStroke, i;
   INT  *pNumPointsInStroke;
   HRGN hrgn;

   assert(pPath!=NULL);
   assert(pHrgn!=NULL);

      PATH_FlattenPath(pPath);

   /* FIXME: What happens when number of points is zero? */
   
   /* First pass: Find out how many strokes there are in the path */
   /* FIXME: We could eliminate this with some bookkeeping in GdiPath */
   numStrokes=0;
   for(i=0; i<pPath->numEntriesUsed; i++)
      if((pPath->pFlags[i] & ~PT_CLOSEFIGURE) == PT_MOVETO)
         numStrokes++;

   /* Allocate memory for number-of-points-in-stroke array */
   pNumPointsInStroke=(int *)ExAllocatePool(NonPagedPool, sizeof(int) * numStrokes);
   if(!pNumPointsInStroke)
   {
//      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
      return FALSE;
   }
   
   /* Second pass: remember number of points in each polygon */
   iStroke=-1;  /* Will get incremented to 0 at beginning of first stroke */
   for(i=0; i<pPath->numEntriesUsed; i++)
   {
      /* Is this the beginning of a new stroke? */
      if((pPath->pFlags[i] & ~PT_CLOSEFIGURE) == PT_MOVETO)
      {
         iStroke++;
	 pNumPointsInStroke[iStroke]=0;
      }

      pNumPointsInStroke[iStroke]++;
   }

   /* Create a region from the strokes */
/*   hrgn=CreatePolyPolygonRgn(pPath->pPoints, pNumPointsInStroke,
      numStrokes, nPolyFillMode); FIXME: reinclude when region code implemented */
   if(hrgn==(HRGN)0)
   {
//      SetLastError(ERROR_NOT_ENOUGH_MEMORY);
      return FALSE;
   }

   /* Free memory for number-of-points-in-stroke array */
   ExFreePool(pNumPointsInStroke);

   /* Success! */
   *pHrgn=hrgn;
   return TRUE;
}

/* PATH_EmptyPath
 *
 * Removes all entries from the path and sets the path state to PATH_Null.
 */
static void PATH_EmptyPath(GdiPath *pPath)
{
   assert(pPath!=NULL);

   pPath->state=PATH_Null;
   pPath->numEntriesUsed=0;
}

/* PATH_AddEntry
 *
 * Adds an entry to the path. For "flags", pass either PT_MOVETO, PT_LINETO
 * or PT_BEZIERTO, optionally ORed with PT_CLOSEFIGURE. Returns TRUE if
 * successful, FALSE otherwise (e.g. if not enough memory was available).
 */
BOOL PATH_AddEntry(GdiPath *pPath, const POINT *pPoint, BYTE flags)
{
   assert(pPath!=NULL);
   
   /* FIXME: If newStroke is true, perhaps we want to check that we're
    * getting a PT_MOVETO
    */

   /* Check that path is open */
   if(pPath->state!=PATH_Open)
      return FALSE;
   
   /* Reserve enough memory for an extra path entry */
   if(!PATH_ReserveEntries(pPath, pPath->numEntriesUsed+1))
      return FALSE;

   /* Store information in path entry */
   pPath->pPoints[pPath->numEntriesUsed]=*pPoint;
   pPath->pFlags[pPath->numEntriesUsed]=flags;

   /* If this is PT_CLOSEFIGURE, we have to start a new stroke next time */
   if((flags & PT_CLOSEFIGURE) == PT_CLOSEFIGURE)
      pPath->newStroke=TRUE;

   /* Increment entry count */
   pPath->numEntriesUsed++;

   return TRUE;
}

/* PATH_ReserveEntries
 *
 * Ensures that at least "numEntries" entries (for points and flags) have
 * been allocated; allocates larger arrays and copies the existing entries
 * to those arrays, if necessary. Returns TRUE if successful, else FALSE.
 */
static BOOL PATH_ReserveEntries(GdiPath *pPath, INT numEntries)
{
   INT   numEntriesToAllocate;
   POINT *pPointsNew;
   BYTE    *pFlagsNew;
   
   assert(pPath!=NULL);
   assert(numEntries>=0);

   /* Do we have to allocate more memory? */
   if(numEntries > pPath->numEntriesAllocated)
   {
      /* Find number of entries to allocate. We let the size of the array
       * grow exponentially, since that will guarantee linear time
       * complexity. */
      if(pPath->numEntriesAllocated)
      {
	 numEntriesToAllocate=pPath->numEntriesAllocated;
	 while(numEntriesToAllocate<numEntries)
	    numEntriesToAllocate=numEntriesToAllocate*GROW_FACTOR_NUMER/
	       GROW_FACTOR_DENOM;
      }
      else
         numEntriesToAllocate=numEntries;

      /* Allocate new arrays */
      pPointsNew=(POINT *)ExAllocatePool(NonPagedPool, numEntriesToAllocate * sizeof(POINT));
      if(!pPointsNew)
         return FALSE;
      pFlagsNew=(BYTE *)ExAllocatePool(NonPagedPool, numEntriesToAllocate * sizeof(BYTE));
      if(!pFlagsNew)
      {
         ExFreePool(pPointsNew);
	 return FALSE;
      }

      /* Copy old arrays to new arrays and discard old arrays */
      if(pPath->pPoints)
      {
         assert(pPath->pFlags);

	 memcpy(pPointsNew, pPath->pPoints,
	     sizeof(POINT)*pPath->numEntriesUsed);
	 memcpy(pFlagsNew, pPath->pFlags,
	     sizeof(BYTE)*pPath->numEntriesUsed);

	 ExFreePool(pPath->pPoints);
	 ExFreePool(pPath->pFlags);
      }
      pPath->pPoints=pPointsNew;
      pPath->pFlags=pFlagsNew;
      pPath->numEntriesAllocated=numEntriesToAllocate;
   }

   return TRUE;
}

/* PATH_GetPathFromHDC
 *
 * Retrieves a pointer to the GdiPath structure contained in an HDC and
 * places it in *ppPath. TRUE is returned if successful, FALSE otherwise.
 */
static BOOL PATH_GetPathFromHDC(HDC hdc, GdiPath **ppPath)
{
   DC *pDC;

   pDC=DC_HandleToPtr(hdc);
   if(pDC)
   {
      *ppPath=&pDC->w.path;
      return TRUE;
   }
   else
      return FALSE;
}

/* PATH_DoArcPart
 *
 * Creates a Bezier spline that corresponds to part of an arc and appends the
 * corresponding points to the path. The start and end angles are passed in
 * "angleStart" and "angleEnd"; these angles should span a quarter circle
 * at most. If "addMoveTo" is true, a PT_MOVETO entry for the first control
 * point is added to the path; otherwise, it is assumed that the current
 * position is equal to the first control point.
 */
static BOOL PATH_DoArcPart(GdiPath *pPath, FLOAT_POINT corners[],
   double angleStart, double angleEnd, BOOL addMoveTo)
{
   double  halfAngle, a;
   double  xNorm[4], yNorm[4];
   POINT point;
   int     i;

   assert(fabs(angleEnd-angleStart)<=M_PI_2);

   /* FIXME: Is there an easier way of computing this? */

   /* Compute control points */
   halfAngle=(angleEnd-angleStart)/2.0;
   if(fabs(halfAngle)>1e-8)
   {
      a=4.0/3.0*(1-cos(halfAngle))/sin(halfAngle);
      xNorm[0]=cos(angleStart);
      yNorm[0]=sin(angleStart);
      xNorm[1]=xNorm[0] - a*yNorm[0];
      yNorm[1]=yNorm[0] + a*xNorm[0];
      xNorm[3]=cos(angleEnd);
      yNorm[3]=sin(angleEnd);
      xNorm[2]=xNorm[3] + a*yNorm[3];
      yNorm[2]=yNorm[3] - a*xNorm[3];
   }
   else
      for(i=0; i<4; i++)
      {
	 xNorm[i]=cos(angleStart);
	 yNorm[i]=sin(angleStart);
      }
   
   /* Add starting point to path if desired */
   if(addMoveTo)
   {
      PATH_ScaleNormalizedPoint(corners, xNorm[0], yNorm[0], &point);
      if(!PATH_AddEntry(pPath, &point, PT_MOVETO))
         return FALSE;
   }

   /* Add remaining control points */
   for(i=1; i<4; i++)
   {
      PATH_ScaleNormalizedPoint(corners, xNorm[i], yNorm[i], &point);
      if(!PATH_AddEntry(pPath, &point, PT_BEZIERTO))
         return FALSE;
   }

   return TRUE;
}

/* PATH_ScaleNormalizedPoint
 *
 * Scales a normalized point (x, y) with respect to the box whose corners are
 * passed in "corners". The point is stored in "*pPoint". The normalized
 * coordinates (-1.0, -1.0) correspond to corners[0], the coordinates
 * (1.0, 1.0) correspond to corners[1].
 */
static void PATH_ScaleNormalizedPoint(FLOAT_POINT corners[], double x,
   double y, POINT *pPoint)
{
   pPoint->x=GDI_ROUND( (double)corners[0].x +
      (double)(corners[1].x-corners[0].x)*0.5*(x+1.0) );
   pPoint->y=GDI_ROUND( (double)corners[0].y +
      (double)(corners[1].y-corners[0].y)*0.5*(y+1.0) );
}

/* PATH_NormalizePoint
 *
 * Normalizes a point with respect to the box whose corners are passed in
 * corners. The normalized coordinates are stored in *pX and *pY.
 */
static void PATH_NormalizePoint(FLOAT_POINT corners[],
   const FLOAT_POINT *pPoint,
   double *pX, double *pY)
{
   *pX=(double)(pPoint->x-corners[0].x)/(double)(corners[1].x-corners[0].x) *
      2.0 - 1.0;
   *pY=(double)(pPoint->y-corners[0].y)/(double)(corners[1].y-corners[0].y) *
      2.0 - 1.0;
}