102 lines
2.3 KiB
C
102 lines
2.3 KiB
C
|
/*************************************************************************\
|
||
|
|
* Module Name: intline.c
|
||
|
|
*
|
||
|
|
* Copyright (c) 1993-1994 Microsoft Corporation
|
||
|
|
* Copyright (c) 1992 Digital Equipment Corporation
|
||
|
|
\**************************************************************************/
|
||
|
|
|
||
|
|
#include "precomp.h"
|
||
|
|
|
||
|
|
#define DEFAULT_DRAW_CMD DRAW_LINE | \
|
||
|
|
DRAW | \
|
||
|
|
DIR_TYPE_XY | \
|
||
|
|
MULTIPLE_PIXELS | \
|
||
|
|
WRITE | \
|
||
|
|
LAST_PIXEL_OFF
|
||
|
|
|
||
|
|
/******************************************************************************
|
||
|
|
* bIntegerLine
|
||
|
|
*
|
||
|
|
* This routine attempts to draw a line segment between two points. It
|
||
|
|
* will only draw if both end points are whole integers: it does not support
|
||
|
|
* fractional endpoints.
|
||
|
|
*
|
||
|
|
* Returns:
|
||
|
|
* TRUE if the line segment is drawn
|
||
|
|
* FALSE otherwise
|
||
|
|
*****************************************************************************/
|
||
|
|
|
||
|
|
BOOL
|
||
|
|
bIntegerLine (
|
||
|
|
PDEV* ppdev,
|
||
|
|
ULONG X1,
|
||
|
|
ULONG Y1,
|
||
|
|
ULONG X2,
|
||
|
|
ULONG Y2
|
||
|
|
)
|
||
|
|
{
|
||
|
|
LONG Cmd;
|
||
|
|
LONG DeltaX, DeltaY;
|
||
|
|
LONG ErrorTerm;
|
||
|
|
LONG Major, Minor;
|
||
|
|
|
||
|
|
X1 >>= 4;
|
||
|
|
Y1 >>= 4;
|
||
|
|
X2 >>= 4;
|
||
|
|
Y2 >>= 4;
|
||
|
|
|
||
|
|
Cmd = DEFAULT_DRAW_CMD | PLUS_Y | PLUS_X | MAJOR_Y;
|
||
|
|
|
||
|
|
DeltaX = X2 - X1;
|
||
|
|
if (DeltaX < 0) {
|
||
|
|
DeltaX = -DeltaX;
|
||
|
|
Cmd &= ~PLUS_X;
|
||
|
|
}
|
||
|
|
DeltaY = Y2 - Y1;
|
||
|
|
if (DeltaY < 0) {
|
||
|
|
DeltaY = -DeltaY;
|
||
|
|
Cmd &= ~PLUS_Y;
|
||
|
|
}
|
||
|
|
|
||
|
|
// Compute the major drawing axis
|
||
|
|
|
||
|
|
if (DeltaX > DeltaY) {
|
||
|
|
Cmd &= ~MAJOR_Y;
|
||
|
|
Major = DeltaX;
|
||
|
|
Minor = DeltaY;
|
||
|
|
} else {
|
||
|
|
Major = DeltaY;
|
||
|
|
Minor = DeltaX;
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
// Tell the S3 to draw the line
|
||
|
|
|
||
|
|
IO_FIFO_WAIT (ppdev, 7);
|
||
|
|
IO_CUR_X (ppdev, X1);
|
||
|
|
IO_CUR_Y (ppdev, Y1);
|
||
|
|
IO_MAJ_AXIS_PCNT (ppdev, Major);
|
||
|
|
IO_AXSTP (ppdev, Minor * 2);
|
||
|
|
IO_DIASTP (ppdev, 2 * Minor - 2 * Major);
|
||
|
|
|
||
|
|
// Adjust the error term so that 1/2 always rounds down, to
|
||
|
|
// conform with GIQ.
|
||
|
|
|
||
|
|
ErrorTerm = 2 * Minor - Major;
|
||
|
|
if (Cmd & MAJOR_Y) {
|
||
|
|
if (Cmd & PLUS_X) {
|
||
|
|
ErrorTerm--;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
if (Cmd & PLUS_Y) {
|
||
|
|
ErrorTerm--;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
IO_ERR_TERM (ppdev, ErrorTerm);
|
||
|
|
IO_CMD (ppdev, Cmd);
|
||
|
|
|
||
|
|
return TRUE;
|
||
|
|
|
||
|
|
}
|