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Diffstat (limited to 'libX11/src/poly.h')
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diff --git a/libX11/src/poly.h b/libX11/src/poly.h new file mode 100644 index 000000000..0d82443c9 --- /dev/null +++ b/libX11/src/poly.h @@ -0,0 +1,295 @@ +/* $Xorg: poly.h,v 1.4 2001/02/09 02:03:40 xorgcvs Exp $ */ +/************************************************************************ + +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. + + +Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts. + + All Rights Reserved + +Permission to use, copy, modify, and distribute this software and its +documentation for any purpose and without fee is hereby granted, +provided that the above copyright notice appear in all copies and that +both that copyright notice and this permission notice appear in +supporting documentation, and that the name of Digital not be +used in advertising or publicity pertaining to distribution of the +software without specific, written prior permission. + +DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING +ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL +DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL 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. + +************************************************************************/ + +/* + * This file contains a few macros to help track + * the edge of a filled object. The object is assumed + * to be filled in scanline order, and thus the + * algorithm used is an extension of Bresenham's line + * drawing algorithm which assumes that y is always the + * major axis. + * Since these pieces of code are the same for any filled shape, + * it is more convenient to gather the library in one + * place, but since these pieces of code are also in + * the inner loops of output primitives, procedure call + * overhead is out of the question. + * See the author for a derivation if needed. + */ + + +/* + * In scan converting polygons, we want to choose those pixels + * which are inside the polygon. Thus, we add .5 to the starting + * x coordinate for both left and right edges. Now we choose the + * first pixel which is inside the pgon for the left edge and the + * first pixel which is outside the pgon for the right edge. + * Draw the left pixel, but not the right. + * + * How to add .5 to the starting x coordinate: + * If the edge is moving to the right, then subtract dy from the + * error term from the general form of the algorithm. + * If the edge is moving to the left, then add dy to the error term. + * + * The reason for the difference between edges moving to the left + * and edges moving to the right is simple: If an edge is moving + * to the right, then we want the algorithm to flip immediately. + * If it is moving to the left, then we don't want it to flip until + * we traverse an entire pixel. + */ +#define BRESINITPGON(dy, x1, x2, xStart, d, m, m1, incr1, incr2) { \ + int dx; /* local storage */ \ +\ + /* \ + * if the edge is horizontal, then it is ignored \ + * and assumed not to be processed. Otherwise, do this stuff. \ + */ \ + if ((dy) != 0) { \ + xStart = (x1); \ + dx = (x2) - xStart; \ + if (dx < 0) { \ + m = dx / (dy); \ + m1 = m - 1; \ + incr1 = -2 * dx + 2 * (dy) * m1; \ + incr2 = -2 * dx + 2 * (dy) * m; \ + d = 2 * m * (dy) - 2 * dx - 2 * (dy); \ + } else { \ + m = dx / (dy); \ + m1 = m + 1; \ + incr1 = 2 * dx - 2 * (dy) * m1; \ + incr2 = 2 * dx - 2 * (dy) * m; \ + d = -2 * m * (dy) + 2 * dx; \ + } \ + } \ +} + +#define BRESINCRPGON(d, minval, m, m1, incr1, incr2) { \ + if (m1 > 0) { \ + if (d > 0) { \ + minval += m1; \ + d += incr1; \ + } \ + else { \ + minval += m; \ + d += incr2; \ + } \ + } else {\ + if (d >= 0) { \ + minval += m1; \ + d += incr1; \ + } \ + else { \ + minval += m; \ + d += incr2; \ + } \ + } \ +} + + +/* + * This structure contains all of the information needed + * to run the bresenham algorithm. + * The variables may be hardcoded into the declarations + * instead of using this structure to make use of + * register declarations. + */ +typedef struct { + int minor_axis; /* minor axis */ + int d; /* decision variable */ + int m, m1; /* slope and slope+1 */ + int incr1, incr2; /* error increments */ +} BRESINFO; + + +#define BRESINITPGONSTRUCT(dmaj, min1, min2, bres) \ + BRESINITPGON(dmaj, min1, min2, bres.minor_axis, bres.d, \ + bres.m, bres.m1, bres.incr1, bres.incr2) + +#define BRESINCRPGONSTRUCT(bres) \ + BRESINCRPGON(bres.d, bres.minor_axis, bres.m, bres.m1, bres.incr1, bres.incr2) + + + +/* + * These are the data structures needed to scan + * convert regions. Two different scan conversion + * methods are available -- the even-odd method, and + * the winding number method. + * The even-odd 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 counter-clockwise 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 y-coordinate, 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 even-odd 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 even-odd 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; + + + +/* + * + * 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 even-odd 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; \ + } \ +} |