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now disco debugging the clipping algorithm

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This commit is contained in:
Amy Bowersox 2019-12-10 13:40:23 -07:00
parent a14acdb0ed
commit 3d40bb2943
2 changed files with 26 additions and 0 deletions
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10
src/dc_screen.c
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@ -1,4 +1,5 @@
#include <stdlib.h> #include <stdlib.h>
#include "log.h"
#include "fbinit.h" #include "fbinit.h"
#include "devctxt.h" #include "devctxt.h"
#include "dc_screen.h" #include "dc_screen.h"
@ -78,6 +79,15 @@ static BOOL screen_line(PVOID privdata, INT32 x1, INT32 y1, INT32 x2, INT32 y2,
INT32 tmp; INT32 tmp;
PUINT16 loc; PUINT16 loc;
ASSERT(x1 >= 0);
ASSERT(x1 < Fb_Info->width);
ASSERT(y1 >= 0);
ASSERT(y1 < Fb_Info->height);
ASSERT(x2 >= 0);
ASSERT(x2 < Fb_Info->width);
ASSERT(y2 >= 0);
ASSERT(y2 < Fb_Info->height);
if (ABS(dx) < ABS(dy)) if (ABS(dx) < ABS(dy))
{ {
if (y1 > y2) if (y1 > y2)

16
src/devctxt.c
View File

@ -1,5 +1,6 @@
#include <string.h> #include <string.h>
#include <stdlib.h> #include <stdlib.h>
#include "log.h"
#include "gfxtype.h" #include "gfxtype.h"
#include "gfxobj.h" #include "gfxobj.h"
#include "devctxt.h" #include "devctxt.h"
@ -23,17 +24,27 @@ static BOOL line_clip(PINT32 output, INT32 x1, INT32 y1, INT32 x2, INT32 y2, INT
BYTE outcode1, outcode2, tmpb; BYTE outcode1, outcode2, tmpb;
INT32 tmp; INT32 tmp;
Log(LDEBUG, "clipping line from (%d, %d) to (%d, %d) against bounding box (%d, %d, %d, %d)", x1 >> 16, y1 >> 16, x2 >> 16, y2 >> 16,
xmin >> 16, ymin >> 16, xmax >> 16, ymax >> 16);
/* Cohen-Sutherland line-clipping algorithm (see Foley & Van Dam, pp. 145-149) */ /* Cohen-Sutherland line-clipping algorithm (see Foley & Van Dam, pp. 145-149) */
for (;;) for (;;)
{ {
outcode1 = line_clip_outcode(x1, y1, xmin, ymin, xmax, ymax); outcode1 = line_clip_outcode(x1, y1, xmin, ymin, xmax, ymax);
outcode2 = line_clip_outcode(x2, y2, xmin, ymin, xmax, ymax); outcode2 = line_clip_outcode(x2, y2, xmin, ymin, xmax, ymax);
if ((outcode1 & outcode2) != 0) if ((outcode1 & outcode2) != 0)
{
Log.debug("*REJECT*");
return FALSE; /* trivial rejection */ return FALSE; /* trivial rejection */
}
else if ((outcode1 == 0) && (outcode2 == 0)) else if ((outcode1 == 0) && (outcode2 == 0))
{
Log.debug("*ACCEPT*");
break; /* trivial acceptance */ break; /* trivial acceptance */
}
if (outcode1 == 0) if (outcode1 == 0)
{ {
Log(LDEBUG, "exchange points")
tmp = x1; tmp = x1;
x1 = x2; x1 = x2;
x2 = tmp; x2 = tmp;
@ -48,23 +59,28 @@ static BOOL line_clip(PINT32 output, INT32 x1, INT32 y1, INT32 x2, INT32 y2, INT
{ {
x1 += (x2 - x1) * (ymin - y1) / (y2 - y1); x1 += (x2 - x1) * (ymin - y1) / (y2 - y1);
y1 = ymin; y1 = ymin;
Log.debug("clipped against top to point (%d, %d)", x1 >> 16, y1 >> 16);
} }
else if (outcode1 & 0x4) else if (outcode1 & 0x4)
{ {
x1 += (x2 - x1) * (ymax - y1) / (y2 - y1); x1 += (x2 - x1) * (ymax - y1) / (y2 - y1);
y1 = ymax; y1 = ymax;
Log.debug("clipped against bottom to point (%d, %d)", x1 >> 16, y1 >> 16);
} }
else if (outcode1 & 0x2) else if (outcode1 & 0x2)
{ {
y1 += (y2 - y1) * (xmax - x1) / (x2 - x1); y1 += (y2 - y1) * (xmax - x1) / (x2 - x1);
x1 = xmax; x1 = xmax;
Log.debug("clipped against right to point (%d, %d)", x1 >> 16, y1 >> 16);
} }
else if (outcode1 & 0x1) else if (outcode1 & 0x1)
{ {
y1 += (y2 - y1) * (xmin - x1) / (x2 - x1); y1 += (y2 - y1) * (xmin - x1) / (x2 - x1);
x1 = xmin; x1 = xmin;
Log.debug("clipped against left to point (%d, %d)", x1 >> 16, y1 >> 16);
} }
} }
Log(LDEBUG, "final line is from (%d, %d) to (%d, %d)", x1 >> 16, y1 >> 16, x2 >> 16, y2 >> 16);
output[0] = x1; output[0] = x1;
output[1] = y1; output[1] = y1;
output[2] = x2; output[2] = x2;