Source code of Windows XP (NT5)
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/******************************Module*Header*******************************\
* Module Name: fastfill.c
*
* Fills solid-coloured, unclipped, non-complex rectangles.
*
* Copyright (c) 1993-1994 Microsoft Corporation
\**************************************************************************/
#include "precomp.h"
#define RIGHT 0
#define LEFT 1
#define SWAP(a, b, tmp) { tmp = a; a = b; b = tmp; }
typedef struct _EDGEDATA {
LONG x; // Current x position
LONG dx; // # pixels to advance x on each scan
LONG lError; // Current DDA error
LONG lErrorUp; // DDA error increment on each scan
LONG lErrorDown; // DDA error adjustment
POINTFIX* pptfx; // Points to start of current edge
LONG dptfx; // Delta (in bytes) from pptfx to next point
LONG cy; // Number of scans to go for this edge
} EDGEDATA; /* ed, ped */
/******************************Public*Routine******************************\
* bFastFill
*
* Draws a non-complex, unclipped polygon.
*
* Returns TRUE if the polygon was drawn; FALSE if the polygon was complex.
*
\**************************************************************************/
BOOL bFastFill(
PPDEV ppdev,
LONG cEdges, // Includes close figure edge
POINTFIX* pptfxFirst,
ULONG ulHwMix,
ULONG iSolidColor)
{
LONG yTrapezoid; // Top scan for next trapezoid
LONG cyTrapezoid; // Number of scans in current trapezoid
LONG yStart; // y-position of start point in current edge
LONG dM; // Edge delta in FIX units in x direction
LONG dN; // Edge delta in FIX units in y direction
LONG i;
POINTFIX* pptfxLast; // Points to the last point in the polygon array
POINTFIX* pptfxTop; // Points to the top-most point in the polygon
POINTFIX* pptfxOld; // Start point in current edge
POINTFIX* pptfxScan; // Current edge pointer for finding pptfxTop
LONG cScanEdges; // Number of edges scanned to find pptfxTop
// (doesn't include the closefigure edge)
LONG iEdge;
LONG lQuotient;
LONG lRemainder;
EDGEDATA aed[2]; // DDA terms and stuff
EDGEDATA* ped;
pptfxScan = pptfxFirst;
pptfxTop = pptfxFirst; // Assume for now that the first
// point in path is the topmost
pptfxLast = pptfxFirst + cEdges - 1;
// 'pptfxScan' will always point to the first point in the current
// edge, and 'cScanEdges' will the number of edges remaining, including
// the current one:
cScanEdges = cEdges - 1; // The number of edges, not counting close figure
if ((pptfxScan + 1)->y > pptfxScan->y)
{
// Collect all downs:
do {
if (--cScanEdges == 0)
goto SetUpForFilling;
pptfxScan++;
} while ((pptfxScan + 1)->y >= pptfxScan->y);
// Collect all ups:
do {
if (--cScanEdges == 0)
goto SetUpForFillingCheck;
pptfxScan++;
} while ((pptfxScan + 1)->y <= pptfxScan->y);
// Collect all downs:
pptfxTop = pptfxScan;
do {
if ((pptfxScan + 1)->y > pptfxFirst->y)
break;
if (--cScanEdges == 0)
goto SetUpForFilling;
pptfxScan++;
} while ((pptfxScan + 1)->y >= pptfxScan->y);
return(FALSE);
}
else
{
// Collect all ups:
do {
pptfxTop++; // We increment this now because we
// want it to point to the very last
// point if we early out in the next
// statement...
if (--cScanEdges == 0)
goto SetUpForFilling;
} while ((pptfxTop + 1)->y <= pptfxTop->y);
// Collect all downs:
pptfxScan = pptfxTop;
do {
if (--cScanEdges == 0)
goto SetUpForFilling;
pptfxScan++;
} while ((pptfxScan + 1)->y >= pptfxScan->y);
// Collect all ups:
do {
if ((pptfxScan + 1)->y < pptfxFirst->y)
break;
if (--cScanEdges == 0)
goto SetUpForFilling;
pptfxScan++;
} while ((pptfxScan + 1)->y <= pptfxScan->y);
return(FALSE);
}
SetUpForFillingCheck:
// We check to see if the end of the current edge is higher
// than the top edge we've found so far:
if ((pptfxScan + 1)->y < pptfxTop->y)
pptfxTop = pptfxScan + 1;
SetUpForFilling:
yTrapezoid = (pptfxTop->y + 15) >> 4;
// We initialize the hardware for the colour, mix, pixel operation,
// rectangle height of one, and the y position for the first scan:
IO_FIFO_WAIT(ppdev, 5);
IO_CUR_Y(ppdev, yTrapezoid);
IO_FRGD_COLOR(ppdev, (INT) iSolidColor);
IO_FRGD_MIX(ppdev, FOREGROUND_COLOR | (WORD) ulHwMix);
IO_PIX_CNTL(ppdev, ALL_ONES);
IO_MIN_AXIS_PCNT(ppdev, 0);
// Make sure we initialize the DDAs appropriately:
aed[LEFT].cy = 0;
aed[RIGHT].cy = 0;
// For now, guess as to which is the left and which is the right edge:
aed[LEFT].dptfx = -(LONG) sizeof(POINTFIX);
aed[RIGHT].dptfx = sizeof(POINTFIX);
aed[LEFT].pptfx = pptfxTop;
aed[RIGHT].pptfx = pptfxTop;
NextEdge:
// We loop through this routine on a per-trapezoid basis.
for (iEdge = 1; iEdge >= 0; iEdge--)
{
ped = &aed[iEdge];
if (ped->cy == 0)
{
// Need a new DDA:
do {
cEdges--;
if (cEdges < 0)
return(TRUE);
// Find the next left edge, accounting for wrapping:
pptfxOld = ped->pptfx;
ped->pptfx = (POINTFIX*) ((BYTE*) ped->pptfx + ped->dptfx);
if (ped->pptfx < pptfxFirst)
ped->pptfx = pptfxLast;
else if (ped->pptfx > pptfxLast)
ped->pptfx = pptfxFirst;
// Have to find the edge that spans yTrapezoid:
ped->cy = ((ped->pptfx->y + 15) >> 4) - yTrapezoid;
// With fractional coordinate end points, we may get edges
// that don't cross any scans, in which case we try the
// next one:
} while (ped->cy <= 0);
// 'pptfx' now points to the end point of the edge spanning
// the scan 'yTrapezoid'.
dN = ped->pptfx->y - pptfxOld->y;
dM = ped->pptfx->x - pptfxOld->x;
ASSERTDD(dN > 0, "Should be going down only");
// Compute the DDA increment terms:
if (dM < 0)
{
dM = -dM;
if (dM < dN) // Can't be '<='
{
ped->dx = -1;
ped->lErrorUp = dN - dM;
}
else
{
QUOTIENT_REMAINDER(dM, dN, lQuotient, lRemainder);
ped->dx = -lQuotient; // - dM / dN
ped->lErrorUp = lRemainder; // dM % dN
if (ped->lErrorUp > 0)
{
ped->dx--;
ped->lErrorUp = dN - ped->lErrorUp;
}
}
}
else
{
if (dM < dN) // Can't be '<='
{
ped->dx = 0;
ped->lErrorUp = dM;
}
else
{
QUOTIENT_REMAINDER(dM, dN, lQuotient, lRemainder);
ped->dx = lQuotient; // dM / dN
ped->lErrorUp = lRemainder; // dM % dN
}
}
ped->lErrorDown = dN; // DDA limit
ped->lError = -1; // Error is initially zero (add dN - 1 for
// the ceiling, but subtract off dN so that
// we can check the sign instead of comparing
// to dN)
ped->x = pptfxOld->x;
yStart = pptfxOld->y;
if ((yStart & 15) != 0)
{
// Advance to the next integer y coordinate
for (i = 16 - (yStart & 15); i != 0; i--)
{
ped->x += ped->dx;
ped->lError += ped->lErrorUp;
if (ped->lError >= 0)
{
ped->lError -= ped->lErrorDown;
ped->x++;
}
}
}
if ((ped->x & 15) != 0)
{
ped->lError -= ped->lErrorDown * (16 - (ped->x & 15));
ped->x += 15; // We'll want the ceiling in just a bit...
}
// Chop off those fractional bits:
ped->x >>= 4;
ped->lError >>= 4;
}
}
cyTrapezoid = min(aed[LEFT].cy, aed[RIGHT].cy); // # of scans in this trap
aed[LEFT].cy -= cyTrapezoid;
aed[RIGHT].cy -= cyTrapezoid;
yTrapezoid += cyTrapezoid; // Top scan in next trap
// If the left and right edges are vertical, simply output as
// a rectangle:
if (((aed[LEFT].lErrorUp | aed[RIGHT].lErrorUp) == 0) &&
((aed[LEFT].dx | aed[RIGHT].dx) == 0) &&
(cyTrapezoid > 1))
{
LONG lWidth;
ContinueVertical:
lWidth = aed[RIGHT].x - aed[LEFT].x - 1;
if (lWidth >= 0)
{
IO_FIFO_WAIT(ppdev, 5);
IO_MAJ_AXIS_PCNT(ppdev, lWidth);
IO_MIN_AXIS_PCNT(ppdev, cyTrapezoid - 1);
IO_CUR_X(ppdev, aed[LEFT].x);
IO_CMD(ppdev, RECTANGLE_FILL | DRAWING_DIR_TBLRXM |
DRAW | DIR_TYPE_XY |
LAST_PIXEL_ON | MULTIPLE_PIXELS |
WRITE);
IO_MIN_AXIS_PCNT(ppdev, 0);
}
else if (lWidth == -1)
{
// If the rectangle was too thin to light any pels, we still
// have to advance the y current position:
IO_FIFO_WAIT(ppdev, 1);
IO_CUR_Y(ppdev, yTrapezoid - cyTrapezoid + 1);
}
else
{
LONG lTmp;
POINTFIX* pptfxTmp;
SWAP(aed[LEFT].x, aed[RIGHT].x, lTmp);
SWAP(aed[LEFT].cy, aed[RIGHT].cy, lTmp);
SWAP(aed[LEFT].dptfx, aed[RIGHT].dptfx, lTmp);
SWAP(aed[LEFT].pptfx, aed[RIGHT].pptfx, pptfxTmp);
goto ContinueVertical;
}
goto NextEdge;
}
while (TRUE)
{
LONG lWidth;
// The very first time through, make sure we set x:
lWidth = aed[RIGHT].x - aed[LEFT].x - 1;
if (lWidth >= 0)
{
IO_FIFO_WAIT(ppdev, 3);
IO_MAJ_AXIS_PCNT(ppdev, lWidth);
IO_CUR_X(ppdev, aed[LEFT].x);
IO_CMD(ppdev, RECTANGLE_FILL | DRAWING_DIR_TBLRXM |
DRAW | DIR_TYPE_XY |
LAST_PIXEL_ON | MULTIPLE_PIXELS |
WRITE);
ContinueAfterZero:
// Advance the right wall:
aed[RIGHT].x += aed[RIGHT].dx;
aed[RIGHT].lError += aed[RIGHT].lErrorUp;
if (aed[RIGHT].lError >= 0)
{
aed[RIGHT].lError -= aed[RIGHT].lErrorDown;
aed[RIGHT].x++;
}
// Advance the left wall:
aed[LEFT].x += aed[LEFT].dx;
aed[LEFT].lError += aed[LEFT].lErrorUp;
if (aed[LEFT].lError >= 0)
{
aed[LEFT].lError -= aed[LEFT].lErrorDown;
aed[LEFT].x++;
}
cyTrapezoid--;
if (cyTrapezoid == 0)
goto NextEdge;
}
else if (lWidth == -1)
{
IO_FIFO_WAIT(ppdev, 1);
IO_CUR_Y(ppdev, yTrapezoid - cyTrapezoid + 1);
goto ContinueAfterZero;
}
else
{
// We certainly don't want to optimize for this case because we
// should rarely get self-intersecting polygons (if we're slow,
// the app gets what it deserves):
LONG lTmp;
POINTFIX* pptfxTmp;
SWAP(aed[LEFT].x, aed[RIGHT].x, lTmp);
SWAP(aed[LEFT].dx, aed[RIGHT].dx, lTmp);
SWAP(aed[LEFT].lError, aed[RIGHT].lError, lTmp);
SWAP(aed[LEFT].lErrorUp, aed[RIGHT].lErrorUp, lTmp);
SWAP(aed[LEFT].lErrorDown, aed[RIGHT].lErrorDown, lTmp);
SWAP(aed[LEFT].cy, aed[RIGHT].cy, lTmp);
SWAP(aed[LEFT].dptfx, aed[RIGHT].dptfx, lTmp);
SWAP(aed[LEFT].pptfx, aed[RIGHT].pptfx, pptfxTmp);
continue;
}
}
}