/*********************************************************** Copyright 1987 by Digital Equipment Corporation, Maynard, Massachusetts, and the Massachusetts Institute of Technology, Cambridge, 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 names of Digital or MIT 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. ******************************************************************/ /* $Header: mfbline.c,v 1.34 87/06/15 02:37:41 sue Exp $ */ #include "X.h" #include "gcstruct.h" #include "windowstr.h" #include "pixmapstr.h" #include "regionstr.h" #include "scrnintstr.h" #include "mistruct.h" #include "mfb.h" #include "maskbits.h" /* single-pixel lines on a monochrome frame buffer NON-SLOPED LINES horizontal lines are always drawn left to right; we have to move the endpoints right by one after they're swapped. horizontal lines will be confined to a single band of a region. the code finds that band (giving up if the lower bound of the band is above the line we're drawing); then it finds the first box in that band that contains part of the line. we clip the line to subsequent boxes in that band. vertical lines are always drawn top to bottom (y-increasing.) this requires adding one to the y-coordinate of each endpoint after swapping. SLOPED LINES when clipping a sloped line, we bring the second point inside the clipping box, rather than one beyond it, and then add 1 to the length of the line before drawing it. this lets us use the same box for finding the outcodes for both endpoints. since the equation for clipping the second endpoint to an edge gives us 1 beyond the edge, we then have to move the point towards the first point by one step on the major axis. eventually, there will be a diagram here to explain what's going on. the method uses Cohen-Sutherland outcodes to determine outsideness, and a method similar to Pike's layers for doing the actual clipping. DIVISION When clipping the lines, we want to round the answer, rather than truncating. We want to avoid floating point; we also want to avoid the special code required when the dividend and divisor have different signs. we work a little to make all the numbers in the division positive. we then use the signs of the major and minor axes decide whether to add or subtract. this takes the special-case code out of the rounding division (making it easier for a compiler or inline to do something clever). CEILING someties, we want the ceiling. ceil(m/n) == floor((m+n-1)/n), for n > 0. in C, integer division results in floor.] MULTIPLICATION when multiplying by signdx or signdy, we KNOW that it will be a multiplication by 1 or -1, but most compilers can't figure this out. if your compiler/hardware combination does better at the ?: operator and 'move negated' instructions that it does at multiplication, you should consider using the alternate macros. OPTIMIZATION there has been no attempt to optimize this code. there are obviously many special cases, at the cost of increased code space. a few inline procedures (e.g. round, SignTimes, ceiling, abs) would be very useful, since the macro expansions are not very intelligent. */ /* NOTE maybe OUTCODES should take box (the one that includes all edges) instead of pbox (the standard no-right-or-lower-edge one)? */ #define OUTCODES(result, x, y, pbox) \ if (x < pbox->x1) \ result |= OUT←LEFT; \ if (y < pbox->y1) \ result |= OUT←ABOVE; \ if (x >= pbox->x2) \ result |= OUT←RIGHT; \ if (y >= pbox->y2) \ result |= OUT←BELOW; #define round(dividend, divisor) \ ( (((dividend)<<1) + (divisor)) / ((divisor)<<1) ) #define ceiling(m,n) ( ((m) + (n) -1)/(n) ) #define SignTimes(sign, n) ((sign) * (n)) /* #define SignTimes(sign, n) \ ( ((sign)<0) ? -(n) : (n) ) */ #define SWAPPT(p1, p2, pttmp) \ pttmp = p1; \ p1 = p2; \ p2 = pttmp; #define SWAPINT(i, j, t) \ t = i; \ i = j; \ j = t; void mfbLineSS(pDrawable, pGC, mode, npt, pptInit) DrawablePtr pDrawable; GCPtr pGC; int mode; /* Origin or Previous */ int npt; /* number of points */ DDXPointPtr pptInit; { int nboxInit; register int nbox; BoxPtr pboxInit; register BoxPtr pbox; int nptTmp; DDXPointPtr ppt; /* pointer to list of translated points */ DDXPointRec pt1; DDXPointRec pt2; unsigned int oc1; /* outcode of point 1 */ unsigned int oc2; /* outcode of point 2 */ int *addrl; /* address of longword with first point */ int nlwidth; /* width in longwords of destination bitmap */ int xorg, yorg; /* origin of window */ int adx; /* abs values of dx and dy */ int ady; int signdx; /* sign of dx and dy */ int signdy; int e, e1, e2; /* bresenham error and increments */ int len; /* length of segment */ int axis; /* major axis */ int clipDone; /* flag for clipping loop */ DDXPointRec pt1Orig; /* unclipped start point */ DDXPointRec pt2Orig; /* unclipped end point */ int err; /* modified bresenham error term */ int clip1, clip2; /* clippedness of the endpoints */ int clipdx, clipdy; /* difference between clipped and unclipped start point */ /* a bunch of temporaries */ int tmp; int x1, x2, y1, y2; pboxInit = ((mfbPrivGC *)(pGC->devPriv))->pCompositeClip->rects; nboxInit = ((mfbPrivGC *)(pGC->devPriv))->pCompositeClip->numRects; if (pDrawable->type == DRAWABLE←WINDOW) { xorg = ((WindowPtr)pDrawable)->absCorner.x; yorg = ((WindowPtr)pDrawable)->absCorner.y; addrl = (int *) (((PixmapPtr)(pDrawable->pScreen->devPrivate))->devPrivate); nlwidth = (int) (((PixmapPtr)(pDrawable->pScreen->devPrivate))->devKind) >> L2BSP; } else { xorg = 0; yorg = 0; addrl = (int *)(((PixmapPtr)pDrawable)->devPrivate); nlwidth = (int)(((PixmapPtr)pDrawable)->devKind) >> L2BSP; } /* translate the point list */ ppt = pptInit; nptTmp = npt; if (mode == CoordModeOrigin) { while(nptTmp--) { ppt->x += xorg; ppt++->y += yorg; } } else { ppt->x += xorg; ppt->y += yorg; nptTmp--; while(nptTmp--) { ppt++; ppt->x += (ppt-1)->x; ppt->y += (ppt-1)->y; } } ppt = pptInit; while(--npt) { nbox = nboxInit; pbox = pboxInit; pt1 = *ppt++; pt2 = *ppt; if (pt1.x == pt2.x) { /* make the line go top to bottom of screen, keeping endpoint semantics */ if (pt1.y > pt2.y) { tmp = pt2.y; pt2.y = pt1.y + 1; pt1.y = tmp + 1; } /* get to first band that might contain part of line */ while ((nbox) && (pbox->y2 <= pt1.y)) { pbox++; nbox--; } if (nbox) { /* stop when lower edge of box is beyond end of line */ while((nbox) && (pt2.y >= pbox->y1)) { if ((pt1.x >= pbox->x1) && (pt1.x < pbox->x2)) { /* this box has part of the line in it */ y1 = max(pt1.y, pbox->y1); y2 = min(pt2.y, pbox->y2); if (y1 != y2) { mfbVertS( ((mfbPrivGC *)(pGC->devPriv))->rop, addrl, nlwidth, pt1.x, y1, y2-y1); } } nbox--; pbox++; } } } else if (pt1.y == pt2.y) { /* force line from left to right, keeping endpoint semantics */ if (pt1.x > pt2.x) { tmp = pt2.x; pt2.x = pt1.x + 1; pt1.x = tmp + 1; } /* find the correct band */ while( (nbox) && (pbox->y2 <= pt1.y)) { pbox++; nbox--; } /* try to draw the line, if we haven't gone beyond it */ if ((nbox) && (pbox->y1 <= pt1.y)) { /* when we leave this band, we're done */ tmp = pbox->y1; while((nbox) && (pbox->y1 == tmp)) { if (pbox->x2 <= pt1.x) { /* skip boxes until one might contain start point */ nbox--; pbox++; continue; } /* stop if left of box is beyond right of line */ if (pbox->x1 >= pt2.x) { nbox = 0; continue; } x1 = max(pt1.x, pbox->x1); x2 = min(pt2.x, pbox->x2); if (x1 != x2) { mfbHorzS( ((mfbPrivGC *)(pGC->devPriv))->rop, addrl, nlwidth, x1, pt1.y, x2-x1); } nbox--; pbox++; } } } else /* sloped line */ { adx = pt2.x - pt1.x; ady = pt2.y - pt1.y; signdx = sign(adx); signdy = sign(ady); adx = abs(adx); ady = abs(ady); if (adx > ady) { axis = X←AXIS; e1 = ady*2; e2 = e1 - 2*adx; e = e1 - adx; } else { axis = Y←AXIS; e1 = adx*2; e2 = e1 - 2*ady; e = e1 - ady; } /* we have bresenham parameters and two points. all we have to do now is clip and draw. */ pt1Orig = pt1; pt2Orig = pt2; while(nbox--) { BoxRec box; pt1 = pt1Orig; pt2 = pt2Orig; clipDone = 0; box.x1 = pbox->x1; box.y1 = pbox->y1; box.x2 = pbox->x2-1; box.y2 = pbox->y2-1; clip1 = 0; clip2 = 0; oc1 = 0; oc2 = 0; OUTCODES(oc1, pt1.x, pt1.y, pbox); OUTCODES(oc2, pt2.x, pt2.y, pbox); if (oc1 & oc2) clipDone = -1; else if ((oc1 | oc2) == 0) clipDone = 1; else /* have to clip */ clipDone = mfbClipLine(pbox, box, &pt1Orig, &pt1, &pt2, adx, ady, signdx, signdy, axis, &clip1, &clip2); if (clipDone == -1) { pbox++; } else { if (axis == X←AXIS) len = abs(pt2.x - pt1.x); else len = abs(pt2.y - pt1.y); len += (clip2 != 0); if (len) { /* unwind bresenham error term to first point */ if (clip1) { clipdx = abs(pt1.x - pt1Orig.x); clipdy = abs(pt1.y - pt1Orig.y); if (axis == X←AXIS) err = e+((clipdy*e2) + ((clipdx-clipdy)*e1)); else err = e+((clipdx*e2) + ((clipdy-clipdx)*e1)); } else err = e; mfbBresS( ((mfbPrivGC *)(pGC->devPriv))->rop, addrl, nlwidth, signdx, signdy, axis, pt1.x, pt1.y, err, e1, e2, len); } /* if segment is unclipped, skip remaining rectangles */ if (!(clip1 || clip2)) break; else pbox++; } } /* while (nbox--) */ } /* sloped line */ } /* while (nline--) */ /* paint the last point if the end style isn't CapNotLast. (Assume that a projecting, butt, or round cap that is one pixel wide is the same as the single pixel of the endpoint.) */ if ((pGC->capStyle != CapNotLast) && ((ppt->x != pptInit->x) || (ppt->y != pptInit->y))) { pt1 = *ppt; nbox = nboxInit; pbox = pboxInit; while (nbox--) { if ((pt1.x >= pbox->x1) && (pt1.y >= pbox->y1) && (pt1.x < pbox->x2) && (pt1.y < pbox->y2)) { addrl += ((long)pt1.y * (long)nlwidth) + (pt1.x >> L2BP); switch( ((mfbPrivGC *)(pGC->devPriv))->rop) { case RROP←BLACK: *addrl &= rmask[pt1.x & BWM]; break; case RROP←WHITE: *addrl |= mask[pt1.x & BWM]; break; case RROP←INVERT: *addrl ↑= mask[pt1.x & BWM]; break; } break; } else pbox++; } } } /* this code does not pretend to be efficient, but it does recycle a lot of the line code and use the miDashLine() code too. a better implementation is to use the solid line code to clip and translate, and then call mfbBresD(), to do the dashes as the line is drawn. a Bres() procedure entry in the devPrivate part of the GC would make this easy to do, as well as possibly speeding up solid lines to (by avoiding the test of rrop for each segment.) to do double dashes we concoct a rop for the (alu, bg) pair. the error term at the start of each dash is computed for us by miDashLine. if the segment we draw is not clipped, we can use this error term; if the first point of the dash is clipped, we have to calculate a new error term based on e at the first point of the line. */ void mfbDashLine( pDrawable, pGC, mode, npt, pptInit) DrawablePtr pDrawable; GCPtr pGC; int mode; /* Origin or Previous */ int npt; /* number of points */ DDXPointPtr pptInit; { int nseg; /* number of dashed segments */ miDashPtr pdash; /* list of dashes */ miDashPtr pdashInit; int fgRop; /* reduced rasterop for even dash */ int bgRop; /* reduced rasterop for odd dash */ int rop; int nboxInit; int nbox; BoxPtr pboxInit; BoxPtr pbox; int nptTmp; DDXPointPtr ppt; /* pointer to list of translated points */ DDXPointRec pt1; DDXPointRec pt2; unsigned int oc1; /* outcode of point 1 */ unsigned int oc2; /* outcode of point 2 */ int *addrl; /* address of longword with first point */ int nlwidth; /* width in longwords of destination bitmap */ int xorg, yorg; /* origin of window */ /* these are all per original line */ int adx; /* abs values of dx and dy */ int ady; int signdx; /* sign of dx and dy */ int signdy; int e; /* error term for first point of original line */ int e1, e2; /* i wonder what these are? */ /* these are all per dash */ int err; /* bres error term for first drawn point */ int len; /* length of segment */ int axis; /* major axis */ int clipDone; /* flag for clipping loop */ DDXPointRec pt1Orig; /* unclipped start point */ int clip1, clip2; /* clippedness of the endpoints */ int clipdx, clipdy; /* difference between clipped and unclipped start point */ pboxInit = ((mfbPrivGC *)(pGC->devPriv))->pCompositeClip->rects; nboxInit = ((mfbPrivGC *)(pGC->devPriv))->pCompositeClip->numRects; if (pDrawable->type == DRAWABLE←WINDOW) { xorg = ((WindowPtr)pDrawable)->absCorner.x; yorg = ((WindowPtr)pDrawable)->absCorner.y; addrl = (int *) (((PixmapPtr)(pDrawable->pScreen->devPrivate))->devPrivate); nlwidth = (int) (((PixmapPtr)(pDrawable->pScreen->devPrivate))->devKind) >> L2BSP; } else { xorg = 0; yorg = 0; addrl = (int *)(((PixmapPtr)pDrawable)->devPrivate); nlwidth = (int)(((PixmapPtr)pDrawable)->devKind) >> L2BSP; } /* translate the point list */ ppt = pptInit; nptTmp = npt; if (mode == CoordModeOrigin) { while(nptTmp--) { ppt->x += xorg; ppt++->y += yorg; } } else { ppt->x += xorg; ppt->y += yorg; nptTmp--; while(nptTmp--) { ppt++; ppt->x += (ppt-1)->x; ppt->y += (ppt-1)->y; } } pdash = miDashLine(npt, pptInit, pGC->numInDashList, pGC->dash, pGC->dashOffset, &nseg); pdashInit = pdash; if (pGC->lineStyle == LineOnOffDash) { rop = ((mfbPrivGC *)(pGC->devPriv))->rop; } else { fgRop = ((mfbPrivGC *)(pGC->devPriv))->rop; bgRop = ReduceRop(pGC->alu, pGC->bgPixel); } while(nseg--) { if (pGC->lineStyle == LineOnOffDash) { while ((nseg) && (pdash->which == ODD←DASH)) { if (pdash->newLine) { pt1Orig = pt1 = *pptInit++; pt2 = *pptInit; adx = pt2.x - pt1.x; ady = pt2.y - pt1.y; signdx = sign(adx); signdy = sign(ady); adx = abs(adx); ady = abs(ady); e = pdash->e; e1 = pdash->e1; e2 = pdash->e2; if (adx > ady) axis = X←AXIS; else axis = Y←AXIS; } nseg--; pdash++; } /* ??? is this right ??? */ if (!nseg) break; } else if (pGC->lineStyle == LineDoubleDash) { /* use a different color for odd dashes */ if (pdash->which == EVEN←DASH) rop = fgRop; else rop = bgRop; } if (pdash->newLine) { pt1Orig = pt1 = *pptInit++; pt2 = *pptInit; adx = pt2.x - pt1.x; ady = pt2.y - pt1.y; signdx = sign(adx); signdy = sign(ady); adx = abs(adx); ady = abs(ady); e = pdash->e; e1 = pdash->e1; e2 = pdash->e2; if (adx > ady) axis = X←AXIS; else axis = Y←AXIS; } nbox = nboxInit; pbox = pboxInit; while(nbox--) { BoxRec box; clipDone = 0; pt1 = pdash->pt; pt2 = (pdash+1)->pt; box.x1 = pbox->x1; box.y1 = pbox->y1; box.x2 = pbox->x2-1; box.y2 = pbox->y2-1; clip1 = 0; clip2 = 0; oc1 = 0; oc2 = 0; OUTCODES(oc1, pt1.x, pt1.y, pbox); OUTCODES(oc2, pt2.x, pt2.y, pbox); if (oc1 & oc2) clipDone = -1; else if ((oc1 | oc2) == 0) clipDone = 1; else /* have to clip */ clipDone = mfbClipLine(pbox, box, &pt1Orig, &pt1, &pt2, adx, ady, signdx, signdy, axis, &clip1, &clip2); if (clipDone == -1) { pbox++; } else { if (axis == X←AXIS) len = abs(pt2.x - pt1.x); else len = abs(pt2.y - pt1.y); len += (clip2 != 0); if (len) { if (clip1) { /* unwind bres error term to first visible point */ clipdx = abs(pt1.x - pt1Orig.x); clipdy = abs(pt1.y - pt1Orig.y); if (axis == X←AXIS) err = e+((clipdy*e2) + ((clipdx-clipdy)*e1)); else err = e+((clipdx*e2) + ((clipdy-clipdx)*e1)); } else { /* use error term calculated with the dash */ err = pdash->e; } mfbBresS( rop, addrl, nlwidth, signdx, signdy, axis, pt1.x, pt1.y, err, e1, e2, len); } /* if segment is unclipped, skip remaining rectangles */ if (!(clip1 || clip2)) break; else pbox++; } } /* while (nbox--) */ pdash++; } /* while --nseg */ Xfree(pdashInit); } /* the clipping code could be cleaned up some; most of its mess derives from originally being inline in the line code, then pulled out to make clipping dashes easier. */ int mfbClipLine(pbox, box, ppt1Orig, ppt1, ppt2, adx, ady, signdx, signdy, axis, pclip1, pclip2) BoxPtr pbox; /* box to clip to */ BoxRec box; /* box to do calculations with */ DDXPointPtr ppt1Orig, ppt1, ppt2; register int adx, ady; register int signdx, signdy; int axis; int *pclip1, *pclip2; { DDXPointRec pt1Orig, pt1, pt2, ptTmp; int swapped = 0; int clipDone = 0; register int tmp; int oc1, oc2; int clip1, clip2; pt1Orig = *ppt1Orig; pt1 = *ppt1; pt2 = *ppt2; clip1 = 0; clip2 = 0; do { oc1 = 0; oc2 = 0; OUTCODES(oc1, pt1.x, pt1.y, pbox); OUTCODES(oc2, pt2.x, pt2.y, pbox); if (oc1 & oc2) clipDone = -1; else if ((oc1 | oc2) == 0) { clipDone = 1; if (swapped) { SWAPPT(pt1, pt2, ptTmp); SWAPINT(oc1, oc2, tmp); SWAPINT(clip1, clip2, tmp); } } else /* have to clip */ { /* only clip one point at a time */ if (!oc1) { SWAPPT(pt1, pt2, ptTmp); SWAPINT(oc1, oc2, tmp); SWAPINT(clip1, clip2, tmp); swapped = !swapped; } clip1 |= oc1; if (oc1 & OUT←LEFT) { pt1.x = box.x1; if(axis==X←AXIS) { pt1.y = pt1Orig.y + SignTimes(signdy, round(abs(box.x1-pt1Orig.x)*ady, adx)); } else { tmp = abs(pt1Orig.x - box.x1); tmp = 2 * tmp * ady; if (swapped) tmp += ady; else tmp -= ady; tmp = abs(tmp); pt1.y = pt1Orig.y + SignTimes(signdy, ceiling(tmp, 2*adx)); if (swapped) pt1.y -= signdy; } } else if (oc1 & OUT←ABOVE) { pt1.y = box.y1; if (axis == Y←AXIS) { pt1.x = pt1Orig.x + SignTimes(signdx, round(abs(box.y1-pt1Orig.y)*adx, ady)); } else { tmp = abs(pt1Orig.y - box.y1); tmp = 2 * tmp * adx; if (swapped) tmp += adx; else tmp -= adx; tmp = abs(tmp); pt1.x = pt1Orig.x + SignTimes(signdx, ceiling(tmp, 2*ady)); if (swapped) pt1.x -= signdx; } } else if (oc1 & OUT←RIGHT) { pt1.x = box.x2; if (axis == X←AXIS) { pt1.y = pt1Orig.y + SignTimes(signdy, round(abs(box.x2-pt1Orig.x)*ady, adx)); } else { tmp = abs(pt1Orig.x - box.x2); tmp = 2 * tmp * ady; if (swapped) tmp += ady; else tmp -= ady; tmp = abs(tmp); pt1.y = pt1Orig.y + SignTimes(signdy, ceiling(tmp, 2*adx)); if (swapped) pt1.y -= signdy; } } else if (oc1 & OUT←BELOW) { pt1.y = box.y2; if (axis == Y←AXIS) { pt1.x = pt1Orig.x + SignTimes(signdx, round(abs(box.y2-pt1Orig.y)*adx, ady)); } else { tmp = abs(pt1Orig.y - box.y2); tmp = 2 * tmp * adx; if (swapped) tmp += adx; else tmp -= adx; tmp = abs(tmp); pt1.x = pt1Orig.x + SignTimes(signdx, ceiling(tmp, 2*ady)); if (swapped) pt1.x -= signdx; } } } /* else have to clip */ } while(!clipDone); *ppt1 = pt1; *ppt2 = pt2; *pclip1 = clip1; *pclip2 = clip2; return clipDone; }