216 lines
7.0 KiB
C
216 lines
7.0 KiB
C
/*




Copyright 1987, 1998 The Open Group




Permission to use, copy, modify, distribute, and sell this software and its


documentation for any purpose is hereby granted without fee, provided that


the above copyright notice appear in all copies and that both that


copyright notice and this permission notice appear in supporting


documentation.




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 OPEN GROUP 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 of The Open Group shall


not be used in advertising or otherwise to promote the sale, use or


other dealings in this Software without prior written authorization


from The Open Group.




*/






/*


* fill.h


*


* Created by Brian Kelleher; Oct 1985


*


* Include file for filled polygon routines.


*


* These are the data structures needed to scan


* convert regions. Two different scan conversion


* methods are available  the evenodd method, and


* the winding number method.


* The evenodd rule states that a point is inside


* the polygon if a ray drawn from that point in any


* direction will pass through an odd number of


* path segments.


* By the winding number rule, a point is decided


* to be inside the polygon if a ray drawn from that


* point in any direction passes through a different


* number of clockwise and counterclockwise path


* segments.


*


* These data structures are adapted somewhat from


* the algorithm in (Foley/Van Dam) for scan converting


* polygons.


* The basic algorithm is to start at the top (smallest y)


* of the polygon, stepping down to the bottom of


* the polygon by incrementing the y coordinate. We


* keep a list of edges which the current scanline crosses,


* sorted by x. This list is called the Active Edge Table (AET)


* As we change the ycoordinate, we update each entry in


* in the active edge table to reflect the edges new xcoord.


* This list must be sorted at each scanline in case


* two edges intersect.


* We also keep a data structure known as the Edge Table (ET),


* which keeps track of all the edges which the current


* scanline has not yet reached. The ET is basically a


* list of ScanLineList structures containing a list of


* edges which are entered at a given scanline. There is one


* ScanLineList per scanline at which an edge is entered.


* When we enter a new edge, we move it from the ET to the AET.


*


* From the AET, we can implement the evenodd rule as in


* (Foley/Van Dam).


* The winding number rule is a little trickier. We also


* keep the EdgeTableEntries in the AET linked by the


* nextWETE (winding EdgeTableEntry) link. This allows


* the edges to be linked just as before for updating


* purposes, but only uses the edges linked by the nextWETE


* link as edges representing spans of the polygon to


* drawn (as with the evenodd rule).


*/




/*


* for the winding number rule


*/


#define CLOCKWISE 1


#define COUNTERCLOCKWISE 1




typedef struct _EdgeTableEntry {


int ymax; /* ycoord at which we exit this edge. */


BRESINFO bres; /* Bresenham info to run the edge */


struct _EdgeTableEntry *next; /* next in the list */


struct _EdgeTableEntry *back; /* for insertion sort */


struct _EdgeTableEntry *nextWETE; /* for winding num rule */


int ClockWise; /* flag for winding number rule */


} EdgeTableEntry;






typedef struct _ScanLineList{


int scanline; /* the scanline represented */


EdgeTableEntry *edgelist; /* header node */


struct _ScanLineList *next; /* next in the list */


} ScanLineList;






typedef struct {


int ymax; /* ymax for the polygon */


int ymin; /* ymin for the polygon */


ScanLineList scanlines; /* header node */


} EdgeTable;






/*


* Here is a struct to help with storage allocation


* so we can allocate a big chunk at a time, and then take


* pieces from this heap when we need to.


*/


#define SLLSPERBLOCK 25




typedef struct _ScanLineListBlock {


ScanLineList SLLs[SLLSPERBLOCK];


struct _ScanLineListBlock *next;


} ScanLineListBlock;




/*


* number of points to buffer before sending them off


* to scanlines() : Must be an even number


*/


#define NUMPTSTOBUFFER 200






/*


*


* a few macros for the inner loops of the fill code where


* performance considerations don't allow a procedure call.


*


* Evaluate the given edge at the given scanline.


* If the edge has expired, then we leave it and fix up


* the active edge table; otherwise, we increment the


* x value to be ready for the next scanline.


* The winding number rule is in effect, so we must notify


* the caller when the edge has been removed so he


* can reorder the Winding Active Edge Table.


*/


#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \


if (pAET>ymax == y) { /* leaving this edge */ \


pPrevAET>next = pAET>next; \


pAET = pPrevAET>next; \


fixWAET = 1; \


if (pAET) \


pAET>back = pPrevAET; \


} \


else { \


BRESINCRPGONSTRUCT(pAET>bres); \


pPrevAET = pAET; \


pAET = pAET>next; \


} \


}






/*


* Evaluate the given edge at the given scanline.


* If the edge has expired, then we leave it and fix up


* the active edge table; otherwise, we increment the


* x value to be ready for the next scanline.


* The evenodd rule is in effect.


*/


#define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \


if (pAET>ymax == y) { /* leaving this edge */ \


pPrevAET>next = pAET>next; \


pAET = pPrevAET>next; \


if (pAET) \


pAET>back = pPrevAET; \


} \


else { \


BRESINCRPGONSTRUCT(pAET>bres); \


pPrevAET = pAET; \


pAET = pAET>next; \


} \


}




/* mipolyutil.c */




extern Bool miInsertEdgeInET(


EdgeTable * /*ET*/,


EdgeTableEntry * /*ETE*/,


int /*scanline*/,


ScanLineListBlock ** /*SLLBlock*/,


int * /*iSLLBlock*/


);




extern Bool miCreateETandAET(


int /*count*/,


DDXPointPtr /*pts*/,


EdgeTable * /*ET*/,


EdgeTableEntry * /*AET*/,


EdgeTableEntry * /*pETEs*/,


ScanLineListBlock * /*pSLLBlock*/


);




extern void miloadAET(


EdgeTableEntry * /*AET*/,


EdgeTableEntry * /*ETEs*/


);




extern void micomputeWAET(


EdgeTableEntry * /*AET*/


);




extern int miInsertionSort(


EdgeTableEntry * /*AET*/


);




extern void miFreeStorage(


ScanLineListBlock * /*pSLLBlock*/


);
