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228 lines
7 KiB
C
228 lines
7 KiB
C
/*
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* ReactOS W32 Subsystem
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* Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003 ReactOS Team
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/* $Id$ */
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#include <win32k.h>
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#define NDEBUG
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#include <debug.h>
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/******************************************************************
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*
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* *Very* simple bezier drawing code,
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*
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* It uses a recursive algorithm to divide the curve in a series
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* of straight line segements. Not ideal but for me sufficient.
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* If you are in need for something better look for some incremental
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* algorithm.
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*
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* 7 July 1998 Rein Klazes
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*/
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/*
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* some macro definitions for bezier drawing
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*
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* to avoid trucation errors the coordinates are
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* shifted upwards. When used in drawing they are
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* shifted down again, including correct rounding
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* and avoiding floating point arithmatic
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* 4 bits should allow 27 bits coordinates which I saw
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* somewere in the win32 doc's
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*
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*/
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#define BEZIERSHIFTBITS 4
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#define BEZIERSHIFTUP(x) ((x)<<BEZIERSHIFTBITS)
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#define BEZIERPIXEL BEZIERSHIFTUP(1)
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#define BEZIERSHIFTDOWN(x) (((x)+(1<<(BEZIERSHIFTBITS-1)))>>BEZIERSHIFTBITS)
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/* maximum depth of recursion */
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#define BEZIERMAXDEPTH 8
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/* size of array to store points on */
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/* enough for one curve */
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#define BEZIER_INITBUFSIZE (150)
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/* calculate Bezier average, in this case the middle
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* correctly rounded...
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* */
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#define BEZIERMIDDLE(Mid, P1, P2) \
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(Mid).x=((P1).x+(P2).x + 1) >> 1;\
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(Mid).y=((P1).y+(P2).y + 1) >> 1;
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/**********************************************************
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* BezierCheck helper function to check
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* that recursion can be terminated
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* Points[0] and Points[3] are begin and endpoint
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* Points[1] and Points[2] are control points
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* level is the recursion depth
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* returns true if the recusion can be terminated
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*/
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static BOOL FASTCALL BezierCheck( int level, POINT *Points)
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{
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INT dx, dy;
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dx=Points[3].x-Points[0].x;
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dy=Points[3].y-Points[0].y;
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if ( abs(dy) <= abs(dx) ) /* shallow line */
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{
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/* check that control points are between begin and end */
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if ( Points[1].x < Points[0].x )
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{
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if ( Points[1].x < Points[3].x )
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return FALSE;
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}
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else if ( Points[1].x > Points[3].x )
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return FALSE;
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if ( Points[2].x < Points[0].x)
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{
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if ( Points[2].x < Points[3].x )
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return FALSE;
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}
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else if ( Points[2].x > Points[3].x )
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return FALSE;
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dx = BEZIERSHIFTDOWN(dx);
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if ( !dx )
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return TRUE;
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if ( abs(Points[1].y-Points[0].y-(dy/dx)*
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BEZIERSHIFTDOWN(Points[1].x-Points[0].x)) > BEZIERPIXEL ||
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abs(Points[2].y-Points[0].y-(dy/dx)*
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BEZIERSHIFTDOWN(Points[2].x-Points[0].x)) > BEZIERPIXEL
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)
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return FALSE;
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else
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return TRUE;
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}
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else
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{ /* steep line */
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/* check that control points are between begin and end */
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if(Points[1].y < Points[0].y)
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{
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if(Points[1].y < Points[3].y)
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return FALSE;
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}
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else if(Points[1].y > Points[3].y)
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return FALSE;
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if ( Points[2].y < Points[0].y )
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{
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if ( Points[2].y < Points[3].y )
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return FALSE;
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}
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else if ( Points[2].y > Points[3].y )
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return FALSE;
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dy = BEZIERSHIFTDOWN(dy);
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if ( !dy )
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return TRUE;
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if ( abs(Points[1].x-Points[0].x-(dx/dy)*
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BEZIERSHIFTDOWN(Points[1].y-Points[0].y)) > BEZIERPIXEL ||
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abs(Points[2].x-Points[0].x-(dx/dy)*
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BEZIERSHIFTDOWN(Points[2].y-Points[0].y)) > BEZIERPIXEL
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)
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return FALSE;
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else
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return TRUE;
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}
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}
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/* Helper for GDI_Bezier.
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* Just handles one Bezier, so Points should point to four POINTs
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*/
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static void APIENTRY GDI_InternalBezier( POINT *Points, POINT **PtsOut, INT *dwOut,
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INT *nPtsOut, INT level )
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{
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if(*nPtsOut == *dwOut) {
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*dwOut *= 2;
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*PtsOut = ExAllocatePoolWithTag(PagedPool, *dwOut * sizeof(POINT), TAG_BEZIER);
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}
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if(!level || BezierCheck(level, Points)) {
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if(*nPtsOut == 0) {
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(*PtsOut)[0].x = BEZIERSHIFTDOWN(Points[0].x);
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(*PtsOut)[0].y = BEZIERSHIFTDOWN(Points[0].y);
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*nPtsOut = 1;
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}
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(*PtsOut)[*nPtsOut].x = BEZIERSHIFTDOWN(Points[3].x);
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(*PtsOut)[*nPtsOut].y = BEZIERSHIFTDOWN(Points[3].y);
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(*nPtsOut) ++;
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} else {
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POINT Points2[4]; /* for the second recursive call */
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Points2[3]=Points[3];
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BEZIERMIDDLE(Points2[2], Points[2], Points[3]);
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BEZIERMIDDLE(Points2[0], Points[1], Points[2]);
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BEZIERMIDDLE(Points2[1],Points2[0],Points2[2]);
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BEZIERMIDDLE(Points[1], Points[0], Points[1]);
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BEZIERMIDDLE(Points[2], Points[1], Points2[0]);
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BEZIERMIDDLE(Points[3], Points[2], Points2[1]);
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Points2[0]=Points[3];
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/* do the two halves */
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GDI_InternalBezier(Points, PtsOut, dwOut, nPtsOut, level-1);
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GDI_InternalBezier(Points2, PtsOut, dwOut, nPtsOut, level-1);
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}
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}
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/***********************************************************************
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* GDI_Bezier [INTERNAL]
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* Calculate line segments that approximate -what microsoft calls- a bezier
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* curve.
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* The routine recursively divides the curve in two parts until a straight
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* line can be drawn
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*
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* PARAMS
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*
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* Points [I] Ptr to count POINTs which are the end and control points
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* of the set of Bezier curves to flatten.
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* count [I] Number of Points. Must be 3n+1.
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* nPtsOut [O] Will contain no of points that have been produced (i.e. no. of
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* lines+1).
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*
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* RETURNS
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*
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* Ptr to an array of POINTs that contain the lines that approximinate the
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* Beziers. The array is allocated on the process heap and it is the caller's
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* responsibility to HeapFree it. [this is not a particularly nice interface
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* but since we can't know in advance how many points will generate, the
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* alternative would be to call the function twice, once to determine the size
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* and a second time to do the work - I decided this was too much of a pain].
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*/
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POINT * FASTCALL GDI_Bezier( const POINT *Points, INT count, INT *nPtsOut )
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{
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POINT *out;
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INT Bezier, dwOut = BEZIER_INITBUFSIZE, i;
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if((count - 1) % 3 != 0) {
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return NULL;
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}
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*nPtsOut = 0;
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out = ExAllocatePoolWithTag(PagedPool, dwOut * sizeof(POINT), TAG_BEZIER);
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for(Bezier = 0; Bezier < (count-1)/3; Bezier++) {
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POINT ptBuf[4];
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memcpy(ptBuf, Points + Bezier * 3, sizeof(POINT) * 4);
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for(i = 0; i < 4; i++) {
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ptBuf[i].x = BEZIERSHIFTUP(ptBuf[i].x);
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ptBuf[i].y = BEZIERSHIFTUP(ptBuf[i].y);
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}
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GDI_InternalBezier( ptBuf, &out, &dwOut, nPtsOut, BEZIERMAXDEPTH );
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}
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return out;
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}
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/* EOF */
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