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Diffstat (limited to 'mi/miscanfill.h')
| -rw-r--r-- | mi/miscanfill.h | 144 |
1 files changed, 144 insertions, 0 deletions
diff --git a/mi/miscanfill.h b/mi/miscanfill.h new file mode 100644 index 000000000..06baee399 --- /dev/null +++ b/mi/miscanfill.h @@ -0,0 +1,144 @@ +/* $Xorg: miscanfill.h,v 1.4 2001/02/09 02:05:21 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. + +*/ + + +#ifndef SCANFILLINCLUDED +#define SCANFILLINCLUDED +/* + * scanfill.h + * + * Written by Brian Kelleher; Jan 1985 + * + * 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; /* 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, bres.d, \ + bres.m, bres.m1, bres.incr1, bres.incr2) + +#define BRESINCRPGONSTRUCT(bres) \ + BRESINCRPGON(bres.d, bres.minor, bres.m, bres.m1, bres.incr1, bres.incr2) + + +#endif |