mirror of
https://gitlab.gnome.org/GNOME/gtk.git
synced 2024-11-17 14:30:15 +00:00
140 lines
4.5 KiB
C
140 lines
4.5 KiB
C
/* $TOG: miscanfill.h /main/6 1998/02/09 14:48:35 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.
|
||
|
||
*/
|
||
|
||
#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
|