mizerline.c

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		utmp = xmin - x1_orig;
		if (utmp <= 32767)		/* clip based on near endpt */
		{
		    if (xmajor)
			eqn = (swapped) ? EQN2 : EQN1;
		    else
			eqn = (swapped) ? EQN4 : EQN3;
		    anchorval = y1_orig;
		}
		else				/* clip based on far endpt */
		{
		    utmp = x2_orig - xmin;
		    if (xmajor)
			eqn = (swapped) ? EQN1B : EQN2B;
		    else
			eqn = (swapped) ? EQN3B : EQN4B;
		    anchorval = y2_orig;
		    negslope = !negslope;
		}
		x1 = xmin;
	    }
	    else if (oc1 & OUT_ABOVE)
	    {
		negslope = IsXDecreasingOctant(octant);
		utmp = ymin - y1_orig;
		if (utmp <= 32767)		/* clip based on near endpt */
		{
		    if (xmajor)
			eqn = (swapped) ? EQN6 : EQN5;
		    else
			eqn = (swapped) ? EQN8 : EQN7;
		    anchorval = x1_orig;
		}
		else				/* clip based on far endpt */
		{
		    utmp = y2_orig - ymin;
		    if (xmajor)
			eqn = (swapped) ? EQN5B : EQN6B;
		    else
			eqn = (swapped) ? EQN7B : EQN8B;
		    anchorval = x2_orig;
		    negslope = !negslope;
		}
		y1 = ymin;
	    }
	    else if (oc1 & OUT_RIGHT)
	    {
		negslope = IsYDecreasingOctant(octant);
		utmp = x1_orig - xmax;
		if (utmp <= 32767)		/* clip based on near endpt */
		{
		    if (xmajor)
			eqn = (swapped) ? EQN2 : EQN1;
		    else
			eqn = (swapped) ? EQN4 : EQN3;
		    anchorval = y1_orig;
		}
		else				/* clip based on far endpt */
		{
		    /*
		     * Technically since the equations can handle
		     * utmp == 32768, this overflow code isn't
		     * needed since X11 protocol can't generate
		     * a line which goes more than 32768 pixels
		     * to the right of a clip rectangle.
		     */
		    utmp = xmax - x2_orig;
		    if (xmajor)
			eqn = (swapped) ? EQN1B : EQN2B;
		    else
			eqn = (swapped) ? EQN3B : EQN4B;
		    anchorval = y2_orig;
		    negslope = !negslope;
		}
		x1 = xmax;
	    }
	    else if (oc1 & OUT_BELOW)
	    {
		negslope = IsXDecreasingOctant(octant);
		utmp = y1_orig - ymax;
		if (utmp <= 32767)		/* clip based on near endpt */
		{
		    if (xmajor)
			eqn = (swapped) ? EQN6 : EQN5;
		    else
			eqn = (swapped) ? EQN8 : EQN7;
		    anchorval = x1_orig;
		}
		else				/* clip based on far endpt */
		{
		    /*
		     * Technically since the equations can handle
		     * utmp == 32768, this overflow code isn't
		     * needed since X11 protocol can't generate
		     * a line which goes more than 32768 pixels
		     * below the bottom of a clip rectangle.
		     */
		    utmp = ymax - y2_orig;
		    if (xmajor)
			eqn = (swapped) ? EQN5B : EQN6B;
		    else
			eqn = (swapped) ? EQN7B : EQN8B;
		    anchorval = x2_orig;
		    negslope = !negslope;
		}
		y1 = ymax;
	    }

	    if (swapped)
		negslope = !negslope;

	    utmp <<= 1;			/* utmp = 2N or 2M */
	    if (eqn & T_2NDX)
		utmp = (utmp * adx);
	    else /* (eqn & T_2MDY) */
		utmp = (utmp * ady);
	    if (eqn & T_DXNOTY)
		if (eqn & T_SUBDXORY)
		    utmp -= adx;
		else
		    utmp += adx;
	    else /* (eqn & T_DYNOTX) */
		if (eqn & T_SUBDXORY)
		    utmp -= ady;
		else
		    utmp += ady;
	    if (eqn & T_BIASSUBONE)
		utmp += bias - 1;
	    else /* (eqn & T_SUBBIAS) */
		utmp -= bias;
	    if (eqn & T_DIV2DX)
		utmp /= (adx << 1);
	    else /* (eqn & T_DIV2DY) */
		utmp /= (ady << 1);
	    if (eqn & T_ADDONE)
		utmp++;

	    if (negslope)
		utmp = -utmp;

	    if (eqn & T_2NDX)	/* We are calculating X steps */
		x1 = anchorval + utmp;
	    else		/* else, Y steps */
		y1 = anchorval + utmp;

	    oc1 = 0;
	    MIOUTCODES(oc1, x1, y1, xmin, ymin, xmax, ymax);
        }
    }

    *new_x1 = x1;
    *new_y1 = y1;
    *new_x2 = x2;
    *new_y2 = y2;
    
    *pt1_clipped = clip1;
    *pt2_clipped = clip2;

    return clipDone;
}


/* Draw lineSolid, fillStyle-independent zero width lines.
 *
 * Must keep X and Y coordinates in "ints" at least until after they're
 * translated and clipped to accomodate CoordModePrevious lines with very
 * large coordinates.
 *
 * Draws the same pixels regardless of sign(dx) or sign(dy).
 *
 * Ken Whaley
 *
 */

/* largest positive value that can fit into a component of a point.
 * Assumes that the point structure is {type x, y;} where type is
 * a signed type.
 */
#define MAX_COORDINATE ((1 << (((sizeof(DDXPointRec) >> 1) << 3) - 1)) - 1)

#define MI_OUTPUT_POINT(xx, yy)\
{\
    if ( !new_span && yy == current_y)\
    {\
        if (xx < spans->x)\
	    spans->x = xx;\
	++*widths;\
    }\
    else\
    {\
        ++Nspans;\
	++spans;\
	++widths;\
	spans->x = xx;\
	spans->y = yy;\
	*widths = 1;\
	current_y = yy;\
        new_span = FALSE;\
    }\
}

void
miZeroLine(pDraw, pGC, mode, npt, pptInit)
    DrawablePtr pDraw;
    GCPtr	pGC;
    int		mode;		/* Origin or Previous */
    int		npt;		/* number of points */
    DDXPointPtr pptInit;
{
    int Nspans, current_y;
    DDXPointPtr ppt; 
    DDXPointPtr pspanInit, spans;
    int *pwidthInit, *widths, list_len;
    int xleft, ytop, xright, ybottom;
    int new_x1, new_y1, new_x2, new_y2;
    int x, y, x1, y1, x2, y2, xstart, ystart;
    int oc1, oc2;
    int result;
    int pt1_clipped, pt2_clipped = 0;
    Bool new_span;
    int signdx, signdy;
    int clipdx, clipdy;
    int width, height;
    int adx, ady;
    int octant;
    unsigned int bias = miGetZeroLineBias(pDraw->pScreen);
    int e, e1, e2, e3;	/* Bresenham error terms */
    int length;		/* length of lines == # of pixels on major axis */

    xleft   = pDraw->x;
    ytop    = pDraw->y;
    xright  = pDraw->x + pDraw->width - 1;
    ybottom = pDraw->y + pDraw->height - 1;

    if (!pGC->miTranslate)
    {
	/* do everything in drawable-relative coordinates */
	xleft    = 0;
	ytop     = 0;
	xright  -= pDraw->x;
	ybottom -= pDraw->y;
    }

    /* it doesn't matter whether we're in drawable or screen coordinates,
     * FillSpans simply cannot take starting coordinates outside of the
     * range of a DDXPointRec component.
     */
    if (xright > MAX_COORDINATE)
	xright = MAX_COORDINATE;
    if (ybottom > MAX_COORDINATE)
	ybottom = MAX_COORDINATE;

    /* since we're clipping to the drawable's boundaries & coordinate
     * space boundaries, we're guaranteed that the larger of width/height
     * is the longest span we'll need to output
     */
    width = xright - xleft + 1;
    height = ybottom - ytop + 1;
    list_len = (height >= width) ? height : width;
    pspanInit = (DDXPointPtr)ALLOCATE_LOCAL(list_len * sizeof(DDXPointRec));
    pwidthInit = (int *)ALLOCATE_LOCAL(list_len * sizeof(int));
    if (!pspanInit || !pwidthInit)
	return;

    Nspans = 0;
    new_span = TRUE;
    spans  = pspanInit - 1;
    widths = pwidthInit - 1;
    ppt = pptInit;

    xstart = ppt->x;
    ystart = ppt->y;
    if (pGC->miTranslate)
    {
	xstart += pDraw->x;
	ystart += pDraw->y;
    }
    
    /* x2, y2, oc2 copied to x1, y1, oc1 at top of loop to simplify
     * iteration logic
     */
    x2 = xstart;
    y2 = ystart;
    oc2 = 0;
    MIOUTCODES(oc2, x2, y2, xleft, ytop, xright, ybottom);

    while (--npt > 0)
    {
	if (Nspans > 0)
	    (*pGC->ops->FillSpans)(pDraw, pGC, Nspans, pspanInit,
				   pwidthInit, FALSE);
	Nspans = 0;
	new_span = TRUE;
	spans  = pspanInit - 1;
	widths = pwidthInit - 1;

	x1  = x2;
	y1  = y2;
	oc1 = oc2;
	++ppt;

	x2 = ppt->x;
	y2 = ppt->y;
	if (pGC->miTranslate && (mode != CoordModePrevious))
	{
	    x2 += pDraw->x;
	    y2 += pDraw->y;
	}
	else if (mode == CoordModePrevious)
	{
	    x2 += x1;
	    y2 += y1;
	}

	oc2 = 0;
	MIOUTCODES(oc2, x2, y2, xleft, ytop, xright, ybottom);

	CalcLineDeltas(x1, y1, x2, y2, adx, ady, signdx, signdy, 1, 1, octant);

	if (adx > ady)
	{
	    e1 = ady << 1;
	    e2 = e1 - (adx << 1);
	    e  = e1 - adx;
	    length  = adx;	/* don't draw endpoint in main loop */

	    FIXUP_ERROR(e, octant, bias);

	    new_x1 = x1;
	    new_y1 = y1;
	    new_x2 = x2;
	    new_y2 = y2;
	    pt1_clipped = 0;
	    pt2_clipped = 0;

	    if ((oc1 | oc2) != 0)
	    {
		result = miZeroClipLine(xleft, ytop, xright, ybottom,
					&new_x1, &new_y1, &new_x2, &new_y2,
					adx, ady,
					&pt1_clipped, &pt2_clipped,
					octant, bias, oc1, oc2);
		if (result == -1)
		    continue;

		length = abs(new_x2 - new_x1);

		/* if we've clipped the endpoint, always draw the full length
		 * of the segment, because then the capstyle doesn't matter 
		 */
		if (pt2_clipped)
		    length++;

		if (pt1_clipped)
		{
		    /* must calculate new error terms */
		    clipdx = abs(new_x1 - x1);
		    clipdy = abs(new_y1 - y1);
		    e += (clipdy * e2) + ((clipdx - clipdy) * e1);
		}
	    }

	    /* draw the segment */

	    x = new_x1;
	    y = new_y1;
	    
	    e3 = e2 - e1;
	    e  = e - e1;

	    while (length--)
	    {
		MI_OUTPUT_POINT(x, y);
		e += e1;
		if (e >= 0)
		{
		    y += signdy;
		    e += e3;
		}
		x += signdx;
	    }
	}
	else    /* Y major line */
	{
	    e1 = adx << 1;
	    e2 = e1 - (ady << 1);
	    e  = e1 - ady;
	    length  = ady;	/* don't draw endpoint in main loop */

	    SetYMajorOctant(octant);
	    FIXUP_ERROR(e, octant, bias);

	    new_x1 = x1;
	    new_y1 = y1;
	    new_x2 = x2;
	    new_y2 = y2;
	    pt1_clipped = 0;
	    pt2_clipped = 0;

	    if ((oc1 | oc2) != 0)
	    {
		result = miZeroClipLine(xleft, ytop, xright, ybottom,
					&new_x1, &new_y1, &new_x2, &new_y2,
					adx, ady,
					&pt1_clipped, &pt2_clipped,
					octant, bias, oc1, oc2);
		if (result == -1)
		    continue;

		length = abs(new_y2 - new_y1);

		/* if we've clipped the endpoint, always draw the full length
		 * of the segment, because then the capstyle doesn't matter 
		 */
		if (pt2_clipped)
		    length++;

		if (pt1_clipped)
		{
		    /* must calculate new error terms */
		    clipdx = abs(new_x1 - x1);
		    clipdy = abs(new_y1 - y1);
		    e += (clipdx * e2) + ((clipdy - clipdx) * e1);
		}
	    }

	    /* draw the segment */

	    x = new_x1;
	    y = new_y1;

	    e3 = e2 - e1;
	    e  = e - e1;

	    while (length--)
	    {
		MI_OUTPUT_POINT(x, y);
		e += e1;
		if (e >= 0)
		{
		    x += signdx;
		    e += e3;
		}
		y += signdy;
	    }
	}
    }

    /* only do the capnotlast check on the last segment
     * and only if the endpoint wasn't clipped.  And then, if the last
     * point is the same as the first point, do not draw it, unless the
     * line is degenerate
     */
    if ( (! pt2_clipped) && (pGC->capStyle != CapNotLast) &&
		(((xstart != x2) || (ystart != y2)) || (ppt == pptInit + 1)))
    {
	MI_OUTPUT_POINT(x, y);
    }    

    if (Nspans > 0)
	(*pGC->ops->FillSpans)(pDraw, pGC, Nspans, pspanInit,
			       pwidthInit, FALSE);

    DEALLOCATE_LOCAL(pwidthInit);
    DEALLOCATE_LOCAL(pspanInit);
}

void
miZeroDashLine(dst, pgc, mode, nptInit, pptInit)
DrawablePtr dst;
GCPtr pgc;
int mode;
int nptInit;		/* number of points in polyline */
DDXPointRec *pptInit;	/* points in the polyline */
{
    /* XXX kludge until real zero-width dash code is written */
    pgc->lineWidth = 1;
    miWideDash (dst, pgc, mode, nptInit, pptInit);
    pgc->lineWidth = 0;
}