208 lines
6.8 KiB
C
208 lines
6.8 KiB
C
/*
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Copyright 1987, 1998 The Open Group
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Permission to use, copy, modify, distribute, and sell this software and its
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documentation for any purpose is hereby granted without fee, provided that
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the above copyright notice appear in all copies and that both that
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copyright notice and this permission notice appear in supporting
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documentation.
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The above copyright notice and this permission notice shall be included
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in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE OPEN GROUP BE LIABLE FOR ANY CLAIM, DAMAGES OR
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OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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OTHER DEALINGS IN THE SOFTWARE.
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Except as contained in this notice, the name of The Open Group shall
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not be used in advertising or otherwise to promote the sale, use or
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other dealings in this Software without prior written authorization
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from The Open Group.
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*/
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/*
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* fill.h
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*
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* Created by Brian Kelleher; Oct 1985
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*
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* Include file for filled polygon routines.
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*
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* These are the data structures needed to scan
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* convert regions. Two different scan conversion
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* methods are available -- the even-odd method, and
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* the winding number method.
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* The even-odd rule states that a point is inside
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* the polygon if a ray drawn from that point in any
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* direction will pass through an odd number of
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* path segments.
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* By the winding number rule, a point is decided
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* to be inside the polygon if a ray drawn from that
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* point in any direction passes through a different
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* number of clockwise and counter-clockwise path
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* segments.
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*
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* These data structures are adapted somewhat from
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* the algorithm in (Foley/Van Dam) for scan converting
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* polygons.
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* The basic algorithm is to start at the top (smallest y)
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* of the polygon, stepping down to the bottom of
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* the polygon by incrementing the y coordinate. We
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* keep a list of edges which the current scanline crosses,
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* sorted by x. This list is called the Active Edge Table (AET)
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* As we change the y-coordinate, we update each entry in
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* in the active edge table to reflect the edges new xcoord.
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* This list must be sorted at each scanline in case
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* two edges intersect.
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* We also keep a data structure known as the Edge Table (ET),
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* which keeps track of all the edges which the current
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* scanline has not yet reached. The ET is basically a
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* list of ScanLineList structures containing a list of
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* edges which are entered at a given scanline. There is one
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* ScanLineList per scanline at which an edge is entered.
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* When we enter a new edge, we move it from the ET to the AET.
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*
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* From the AET, we can implement the even-odd rule as in
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* (Foley/Van Dam).
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* The winding number rule is a little trickier. We also
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* keep the EdgeTableEntries in the AET linked by the
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* nextWETE (winding EdgeTableEntry) link. This allows
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* the edges to be linked just as before for updating
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* purposes, but only uses the edges linked by the nextWETE
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* link as edges representing spans of the polygon to
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* drawn (as with the even-odd rule).
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*/
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/*
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* for the winding number rule
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*/
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#define CLOCKWISE 1
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#define COUNTERCLOCKWISE -1
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typedef struct _EdgeTableEntry {
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int ymax; /* ycoord at which we exit this edge. */
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BRESINFO bres; /* Bresenham info to run the edge */
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struct _EdgeTableEntry *next; /* next in the list */
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struct _EdgeTableEntry *back; /* for insertion sort */
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struct _EdgeTableEntry *nextWETE; /* for winding num rule */
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int ClockWise; /* flag for winding number rule */
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} EdgeTableEntry;
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typedef struct _ScanLineList{
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int scanline; /* the scanline represented */
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EdgeTableEntry *edgelist; /* header node */
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struct _ScanLineList *next; /* next in the list */
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} ScanLineList;
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typedef struct {
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int ymax; /* ymax for the polygon */
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int ymin; /* ymin for the polygon */
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ScanLineList scanlines; /* header node */
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} EdgeTable;
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/*
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* Here is a struct to help with storage allocation
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* so we can allocate a big chunk at a time, and then take
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* pieces from this heap when we need to.
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*/
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#define SLLSPERBLOCK 25
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typedef struct _ScanLineListBlock {
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ScanLineList SLLs[SLLSPERBLOCK];
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struct _ScanLineListBlock *next;
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} ScanLineListBlock;
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/*
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* number of points to buffer before sending them off
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* to scanlines() : Must be an even number
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*/
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#define NUMPTSTOBUFFER 200
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/*
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*
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* a few macros for the inner loops of the fill code where
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* performance considerations don't allow a procedure call.
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*
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* Evaluate the given edge at the given scanline.
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* If the edge has expired, then we leave it and fix up
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* the active edge table; otherwise, we increment the
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* x value to be ready for the next scanline.
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* The winding number rule is in effect, so we must notify
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* the caller when the edge has been removed so he
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* can reorder the Winding Active Edge Table.
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*/
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#define EVALUATEEDGEWINDING(pAET, pPrevAET, y, fixWAET) { \
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if (pAET->ymax == y) { /* leaving this edge */ \
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pPrevAET->next = pAET->next; \
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pAET = pPrevAET->next; \
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fixWAET = 1; \
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if (pAET) \
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pAET->back = pPrevAET; \
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} \
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else { \
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BRESINCRPGONSTRUCT(pAET->bres); \
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pPrevAET = pAET; \
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pAET = pAET->next; \
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} \
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}
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/*
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* Evaluate the given edge at the given scanline.
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* If the edge has expired, then we leave it and fix up
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* the active edge table; otherwise, we increment the
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* x value to be ready for the next scanline.
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* The even-odd rule is in effect.
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*/
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#define EVALUATEEDGEEVENODD(pAET, pPrevAET, y) { \
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if (pAET->ymax == y) { /* leaving this edge */ \
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pPrevAET->next = pAET->next; \
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pAET = pPrevAET->next; \
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if (pAET) \
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pAET->back = pPrevAET; \
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} \
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else { \
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BRESINCRPGONSTRUCT(pAET->bres); \
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pPrevAET = pAET; \
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pAET = pAET->next; \
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} \
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}
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/* mipolyutil.c */
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extern Bool miCreateETandAET(
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int /*count*/,
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DDXPointPtr /*pts*/,
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EdgeTable * /*ET*/,
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EdgeTableEntry * /*AET*/,
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EdgeTableEntry * /*pETEs*/,
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ScanLineListBlock * /*pSLLBlock*/
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);
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extern void miloadAET(
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EdgeTableEntry * /*AET*/,
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EdgeTableEntry * /*ETEs*/
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);
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extern void micomputeWAET(
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EdgeTableEntry * /*AET*/
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);
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extern int miInsertionSort(
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EdgeTableEntry * /*AET*/
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);
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extern void miFreeStorage(
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ScanLineListBlock * /*pSLLBlock*/
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);
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