mirror of
https://gitlab.gnome.org/GNOME/gtk.git
synced 2024-11-11 11:20:12 +00:00
292 lines
10 KiB
C
292 lines
10 KiB
C
|
/* $TOG: poly.h /main/5 1998/02/06 17:47:27 kaleb $ */
|
|||
|
|
/************************************************************************
|
|||
|
|
|
|||
|
|
Copyright 1987, 1998 The Open Group
|
|||
|
|
|
|||
|
|
All Rights Reserved.
|
|||
|
|
|
|||
|
|
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; \
|
|||
|
|
} \
|
|||
|
|
}
|