1275 lines
44 KiB
C
1275 lines
44 KiB
C
/*************************************************************************\
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* Module Name: Lines.c
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*
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* Contains the code for drawing short fractional endpoint lines and
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* longer lines with strips. There is also a separate x86 Asm version
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* of this code.
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*
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* Copyright (c) 1990-1995 Microsoft Corporation
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* Copyright (c) 1992 Digital Equipment Corporation
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\**************************************************************************/
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#include "precomp.h"
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///////////////////////////////////////////////////////////////////////
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// We have to be careful of arithmetic overflow in a number of places.
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// Fortunately, the compiler is guaranteed to natively support 64-bit
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// signed LONGLONGs and 64-bit unsigned DWORDLONGs.
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//
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// UUInt32x32To64(a, b) is a macro defined in 'winnt.h' that multiplies
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// two 32-bit ULONGs to produce a 64-bit DWORDLONG result.
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//
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// UInt64By32To32 is our own macro to divide a 64-bit DWORDLONG by
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// a 32-bit ULONG to produce a 32-bit ULONG result.
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//
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// UInt64Mod32To32 is our own macro to modulus a 64-bit DWORDLONG by
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// a 32-bit ULONG to produce a 32-bit ULONG result.
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//
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// 64 bit divides are usually very expensive. Since it's very rare
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// that we'll get lines where the upper 32 bits of the 64 bit result
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// are used, we can almost always use 32-bit ULONG divides. We still
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// must correctly handle the larger cases:
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#define UInt64Div32To32(a, b) \
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((((DWORDLONG)(a)) > ULONG_MAX) ? \
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(ULONG)((DWORDLONG)(a) / (ULONG)(b)) : \
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(ULONG)((ULONG)(a) / (ULONG)(b)))
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#define UInt64Mod32To32(a, b) \
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((((DWORDLONG)(a)) > ULONG_MAX) ? \
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(ULONG)((DWORDLONG)(a) % (ULONG)(b)) : \
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(ULONG)((ULONG)(a) % (ULONG)(b)))
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#define SWAPL(x,y,t) {t = x; x = y; y = t;}
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FLONG gaflRound[] = {
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FL_H_ROUND_DOWN | FL_V_ROUND_DOWN, // no flips
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FL_H_ROUND_DOWN | FL_V_ROUND_DOWN, // FL_FLIP_D
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FL_H_ROUND_DOWN, // FL_FLIP_V
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FL_V_ROUND_DOWN, // FL_FLIP_V | FL_FLIP_D
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FL_V_ROUND_DOWN, // FL_FLIP_SLOPE_ONE
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0xbaadf00d, // FL_FLIP_SLOPE_ONE | FL_FLIP_D
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FL_H_ROUND_DOWN, // FL_FLIP_SLOPE_ONE | FL_FLIP_V
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0xbaadf00d // FL_FLIP_SLOPE_ONE | FL_FLIP_V | FL_FLIP_D
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};
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/******************************Public*Routine******************************\
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* BOOL bLines(ppdev, pptfxFirst, pptfxBuf, cptfx, pls,
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* prclClip, apfn[], flStart)
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*
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* Computes the DDA for the line and gets ready to draw it. Puts the
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* pixel data into an array of strips, and calls a strip routine to
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* do the actual drawing.
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*
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* Doing NT Lines Right
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* --------------------
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*
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* In NT, all lines are given to the device driver in fractional
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* coordinates, in a 28.4 fixed point format. The lower 4 bits are
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* fractional for sub-pixel positioning.
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*
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* Note that you CANNOT! just round the coordinates to integers
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* and pass the results to your favorite integer Bresenham routine!!
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* (Unless, of course, you have such a high resolution device that
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* nobody will notice -- not likely for a display device.) The
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* fractions give a more accurate rendering of the line -- this is
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* important for things like our Bezier curves, which would have 'kinks'
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* if the points in its polyline approximation were rounded to integers.
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*
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* Unfortunately, for fractional lines there is more setup work to do
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* a DDA than for integer lines. However, the main loop is exactly
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* the same (and can be done entirely with 32 bit math).
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*
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* If You've Got Hardware That Does Bresenham
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* ------------------------------------------
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*
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* A lot of hardware limits DDA error terms to 'n' bits. With fractional
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* coordinates, 4 bits are given to the fractional part, letting
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* you draw in hardware only those lines that lie entirely in a 2^(n-4)
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* by 2^(n-4) pixel space.
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*
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* And you still have to correctly draw those lines with coordinates
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* outside that space! Remember that the screen is only a viewport
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* onto a 28.4 by 28.4 space -- if any part of the line is visible
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* you MUST render it precisely, regardless of where the end points lie.
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* So even if you do it in software, somewhere you'll have to have a
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* 32 bit DDA routine.
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*
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* Our Implementation
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* ------------------
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*
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* We employ a run length slice algorithm: our DDA calculates the
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* number of pixels that are in each row (or 'strip') of pixels.
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*
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* We've separated the running of the DDA and the drawing of pixels:
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* we run the DDA for several iterations and store the results in
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* a 'strip' buffer (which are the lengths of consecutive pixel rows of
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* the line), then we crank up a 'strip drawer' that will draw all the
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* strips in the buffer.
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*
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* We also employ a 'half-flip' to reduce the number of strip
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* iterations we need to do in the DDA and strip drawing loops: when a
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* (normalized) line's slope is more than 1/2, we do a final flip
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* about the line y = (1/2)x. So now, instead of each strip being
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* consecutive horizontal or vertical pixel rows, each strip is composed
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* of those pixels aligned in 45 degree rows. So a line like (0, 0) to
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* (128, 128) would generate only one strip.
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*
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* We also always draw only left-to-right.
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*
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* Styled lines may have arbitrary style patterns. We specially
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* optimize the default patterns (and call them 'masked' styles).
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*
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* The DDA Derivation
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* ------------------
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*
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* Here is how I like to think of the DDA calculation.
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*
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* We employ Knuth's "diamond rule": rendering a one-pixel-wide line
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* can be thought of as dragging a one-pixel-wide by one-pixel-high
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* diamond along the true line. Pixel centers lie on the integer
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* coordinates, and so we light any pixel whose center gets covered
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* by the "drag" region (John D. Hobby, Journal of the Association
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* for Computing Machinery, Vol. 36, No. 2, April 1989, pp. 209-229).
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*
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* We must define which pixel gets lit when the true line falls
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* exactly half-way between two pixels. In this case, we follow
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* the rule: when two pels are equidistant, the upper or left pel
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* is illuminated, unless the slope is exactly one, in which case
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* the upper or right pel is illuminated. (So we make the edges
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* of the diamond exclusive, except for the top and left vertices,
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* which are inclusive, unless we have slope one.)
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*
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* This metric decides what pixels should be on any line BEFORE it is
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* flipped around for our calculation. Having a consistent metric
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* this way will let our lines blend nicely with our curves. The
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* metric also dictates that we will never have one pixel turned on
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* directly above another that's turned on. We will also never have
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* a gap; i.e., there will be exactly one pixel turned on for each
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* column between the start and end points. All that remains to be
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* done is to decide how many pixels should be turned on for each row.
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*
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* So lines we draw will consist of varying numbers of pixels on
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* successive rows, for example:
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*
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* ******
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* *****
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* ******
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* *****
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*
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* We'll call each set of pixels on a row a "strip".
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*
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* (Please remember that our coordinate space has the origin as the
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* upper left pixel on the screen; postive y is down and positive x
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* is right.)
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*
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* Device coordinates are specified as fixed point 28.4 numbers,
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* where the first 28 bits are the integer coordinate, and the last
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* 4 bits are the fraction. So coordinates may be thought of as
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* having the form (x, y) = (M/F, N/F) where F is the constant scaling
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* factor F = 2^4 = 16, and M and N are 32 bit integers.
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*
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* Consider the line from (M0/F, N0/F) to (M1/F, N1/F) which runs
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* left-to-right and whose slope is in the first octant, and let
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* dM = M1 - M0 and dN = N1 - N0. Then dM >= 0, dN >= 0 and dM >= dN.
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*
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* Since the slope of the line is less than 1, the edges of the
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* drag region are created by the top and bottom vertices of the
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* diamond. At any given pixel row y of the line, we light those
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* pixels whose centers are between the left and right edges.
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*
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* Let mL(n) denote the line representing the left edge of the drag
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* region. On pixel row j, the column of the first pixel to be
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* lit is
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*
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* iL(j) = ceiling( mL(j * F) / F)
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*
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* Since the line's slope is less than one:
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*
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* iL(j) = ceiling( mL([j + 1/2] F) / F )
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*
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* Recall the formula for our line:
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*
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* n(m) = (dN / dM) (m - M0) + N0
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*
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* m(n) = (dM / dN) (n - N0) + M0
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*
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* Since the line's slope is less than one, the line representing
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* the left edge of the drag region is the original line offset
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* by 1/2 pixel in the y direction:
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*
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* mL(n) = (dM / dN) (n - F/2 - N0) + M0
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*
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* From this we can figure out the column of the first pixel that
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* will be lit on row j, being careful of rounding (if the left
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* edge lands exactly on an integer point, the pixel at that
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* point is not lit because of our rounding convention):
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*
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* iL(j) = floor( mL(j F) / F ) + 1
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*
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* = floor( ((dM / dN) (j F - F/2 - N0) + M0) / F ) + 1
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*
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* = floor( F dM j - F/2 dM - N0 dM + dN M0) / F dN ) + 1
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*
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* F dM j - [ dM (N0 + F/2) - dN M0 ]
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* = floor( ---------------------------------- ) + 1
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* F dN
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*
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* dM j - [ dM (N0 + F/2) - dN M0 ] / F
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* = floor( ------------------------------------ ) + 1 (1)
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* dN
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*
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* = floor( (dM j + alpha) / dN ) + 1
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*
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* where
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*
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* alpha = - [ dM (N0 + F/2) - dN M0 ] / F
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*
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* We use equation (1) to calculate the DDA: there are iL(j+1) - iL(j)
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* pixels in row j. Because we are always calculating iL(j) for
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* integer quantities of j, we note that the only fractional term
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* is constant, and so we can 'throw away' the fractional bits of
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* alpha:
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*
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* beta = floor( - [ dM (N0 + F/2) - dN M0 ] / F ) (2)
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*
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* so
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*
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* iL(j) = floor( (dM j + beta) / dN ) + 1 (3)
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*
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* for integers j.
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*
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* Note if iR(j) is the line's rightmost pixel on row j, that
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* iR(j) = iL(j + 1) - 1.
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*
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* Similarly, rewriting equation (1) as a function of column i,
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* we can determine, given column i, on which pixel row j is the line
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* lit:
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*
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* dN i + [ dM (N0 + F/2) - dN M0 ] / F
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* j(i) = ceiling( ------------------------------------ ) - 1
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* dM
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*
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* Floors are easier to compute, so we can rewrite this:
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*
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* dN i + [ dM (N0 + F/2) - dN M0 ] / F + dM - 1/F
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* j(i) = floor( ----------------------------------------------- ) - 1
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* dM
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*
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* dN i + [ dM (N0 + F/2) - dN M0 ] / F + dM - 1/F - dM
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* = floor( ---------------------------------------------------- )
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* dM
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*
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* dN i + [ dM (N0 + F/2) - dN M0 - 1 ] / F
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* = floor( ---------------------------------------- )
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* dM
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*
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* We can once again wave our hands and throw away the fractional bits
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* of the remainder term:
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*
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* j(i) = floor( (dN i + gamma) / dM ) (4)
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*
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* where
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*
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* gamma = floor( [ dM (N0 + F/2) - dN M0 - 1 ] / F ) (5)
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*
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* We now note that
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*
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* beta = -gamma - 1 = ~gamma (6)
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*
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* To draw the pixels of the line, we could evaluate (3) on every scan
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* line to determine where the strip starts. Of course, we don't want
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* to do that because that would involve a multiply and divide for every
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* scan. So we do everything incrementally.
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*
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* We would like to easily compute c , the number of pixels on scan j:
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* j
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*
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* c = iL(j + 1) - iL(j)
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* j
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*
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* = floor((dM (j + 1) + beta) / dN) - floor((dM j + beta) / dN) (7)
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*
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* This may be rewritten as
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*
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* c = floor(i + r / dN) - floor(i + r / dN) (8)
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* j j+1 j+1 j j
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*
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* where i , i are integers and r < dN, r < dN.
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* j j+1 j j+1
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*
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* Rewriting (7) again:
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*
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* c = floor(i + r / dN + dM / dN) - floor(i + r / dN)
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* j j j j j
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*
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*
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* = floor((r + dM) / dN) - floor(r / dN)
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* j j
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*
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* This may be rewritten as
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*
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* c = dI + floor((r + dR) / dN) - floor(r / dN)
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* j j j
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*
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* where dI + dR / dN = dM / dN, dI is an integer and dR < dN.
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*
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* r is the remainder (or "error") term in the DDA loop: r / dN
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* j j
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* is the exact fraction of a pixel at which the strip ends. To go
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* on to the next scan and compute c we need to know r .
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* j+1 j+1
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*
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* So in the main loop of the DDA:
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*
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* c = dI + floor((r + dR) / dN) and r = (r + dR) % dN
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* j j j+1 j
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*
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* and we know r < dN, r < dN, and dR < dN.
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* j j+1
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*
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* We have derived the DDA only for lines in the first octant; to
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* handle other octants we do the common trick of flipping the line
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* to the first octant by first making the line left-to-right by
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* exchanging the end-points, then flipping about the lines y = 0 and
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* y = x, as necessary. We must record the transformation so we can
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* undo them later.
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*
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* We must also be careful of how the flips affect our rounding. If
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* to get the line to the first octant we flipped about x = 0, we now
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* have to be careful to round a y value of 1/2 up instead of down as
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* we would for a line originally in the first octant (recall that
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* "In the case where two pels are equidistant, the upper or left
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* pel is illuminated...").
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*
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* To account for this rounding when running the DDA, we shift the line
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* (or not) in the y direction by the smallest amount possible. That
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* takes care of rounding for the DDA, but we still have to be careful
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* about the rounding when determining the first and last pixels to be
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* lit in the line.
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*
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* Determining The First And Last Pixels In The Line
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* -------------------------------------------------
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*
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* Fractional coordinates also make it harder to determine which pixels
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* will be the first and last ones in the line. We've already taken
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* the fractional coordinates into account in calculating the DDA, but
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* the DDA cannot tell us which are the end pixels because it is quite
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* happy to calculate pixels on the line from minus infinity to positive
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* infinity.
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*
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* The diamond rule determines the start and end pixels. (Recall that
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* the sides are exclusive except for the left and top vertices.)
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* This convention can be thought of in another way: there are diamonds
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* around the pixels, and wherever the true line crosses a diamond,
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* that pel is illuminated.
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*
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* Consider a line where we've done the flips to the first octant, and the
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* floor of the start coordinates is the origin:
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*
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* +-----------------------> +x
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* |
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* | 0 1
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* | 0123456789abcdef
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* |
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* | 0 00000000?1111111
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* | 1 00000000 1111111
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* | 2 0000000 111111
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* | 3 000000 11111
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* | 4 00000 ** 1111
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* | 5 0000 ****1
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* | 6 000 1***
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* | 7 00 1 ****
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* | 8 ? ***
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* | 9 22 3 ****
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* | a 222 33 ***
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* | b 2222 333 ****
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* | c 22222 3333 **
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* | d 222222 33333
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* | e 2222222 333333
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* | f 22222222 3333333
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* |
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* | 2 3
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* v
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* +y
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*
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* If the start of the line lands on the diamond around pixel 0 (shown by
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* the '0' region here), pixel 0 is the first pel in the line. The same
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* is true for the other pels.
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*
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* A little more work has to be done if the line starts in the
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* 'nether-land' between the diamonds (as illustrated by the '*' line):
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* the first pel lit is the first diamond crossed by the line (pixel 1 in
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* our example). This calculation is determined by the DDA or slope of
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* the line.
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*
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* If the line starts exactly half way between two adjacent pixels
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* (denoted here by the '?' spots), the first pixel is determined by our
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* round-down convention (and is dependent on the flips done to
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* normalize the line).
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*
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* Last Pel Exclusive
|
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* ------------------
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*
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* To eliminate repeatedly lit pels between continuous connected lines,
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* we employ a last-pel exclusive convention: if the line ends exactly on
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* the diamond around a pel, that pel is not lit. (This eliminates the
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* checks we had in the old code to see if we were re-lighting pels.)
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*
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* The Half Flip
|
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* -------------
|
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*
|
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* To make our run length algorithm more efficient, we employ a "half
|
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* flip". If after normalizing to the first octant, the slope is more
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* than 1/2, we subtract the y coordinate from the x coordinate. This
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* has the effect of reflecting the coordinates through the line of slope
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* 1/2. Note that the diagonal gets mapped into the x-axis after a half
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* flip.
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*
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* How Many Bits Do We Need, Anyway?
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* ---------------------------------
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*
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* Note that if the line is visible on your screen, you must light up
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* exactly the correct pixels, no matter where in the 28.4 x 28.4 device
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* space the end points of the line lie (meaning you must handle 32 bit
|
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* DDAs, you can certainly have optimized cases for lesser DDAs).
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*
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* We move the origin to (floor(M0 / F), floor(N0 / F)), so when we
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* calculate gamma from (5), we know that 0 <= M0, N0 < F. And we
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* are in the first octant, so dM >= dN. Then we know that gamma can
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* be in the range [(-1/2)dM, (3/2)dM]. The DDI guarantees us that
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* valid lines will have dM and dN values at most 31 bits (unsigned)
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* of significance. So gamma requires 33 bits of significance (we store
|
|
* this as a 64 bit number for convenience).
|
|
*
|
|
* When running through the DDA loop, r + dR can have a value in the
|
|
* j
|
|
* range 0 <= r < 2 dN; thus the result must be a 32 bit unsigned value.
|
|
* j
|
|
*
|
|
* Testing Lines
|
|
* -------------
|
|
*
|
|
* To be NT compliant, a display driver must exactly adhere to GIQ,
|
|
* which means that for any given line, the driver must light exactly
|
|
* the same pels as does GDI. This can be tested using the Guiman tool
|
|
* provided elsewhere in the DDK, and 'ZTest', which draws random lines
|
|
* on the screen and to a bitmap, and compares the results.
|
|
*
|
|
* If You've Got Line Hardware
|
|
* ---------------------------
|
|
*
|
|
* If your hardware already adheres to GIQ, you're all set. Otherwise
|
|
* you'll want to look at the sample code and read the following:
|
|
*
|
|
* 1) You'll want to special case integer-only lines, since they require
|
|
* less processing time and are more common (CAD programs will probably
|
|
* only ever give integer lines). GDI does not provide a flag saying
|
|
* that all lines in a path are integer lines; consequently, you will
|
|
* have to explicitly check every line.
|
|
*
|
|
* 2) You are required to correctly draw any line in the 28.4 device
|
|
* space that intersects the viewport. If you have less than 32 bits
|
|
* of significance in the hardware for the Bresenham terms, extremely
|
|
* long lines would overflow the hardware. For such (rare) cases, you
|
|
* can fall back to strip-drawing code (or if your display is a frame
|
|
* buffer, fall back to the engine).
|
|
*
|
|
* 3) If you can explicitly set the Bresenham terms in your hardware, you
|
|
* can draw non-integer lines using the hardware. If your hardware has
|
|
* 'n' bits of precision, you can draw GIQ lines that are up to 2^(n-5)
|
|
* pels long (4 bits are required for the fractional part, and one bit is
|
|
* used as a sign bit). Note that integer lines don't require the 4
|
|
* fractional bits, so if you special case them as in 1), you can do
|
|
* integer lines that are up to 2^(n - 1) pels long. See the
|
|
* 'bHardwareLine' routine for an example.
|
|
*
|
|
\**************************************************************************/
|
|
|
|
BOOL bLines(
|
|
PDEV* ppdev,
|
|
POINTFIX* pptfxFirst, // Start of first line
|
|
POINTFIX* pptfxBuf, // Pointer to buffer of all remaining lines
|
|
RUN* prun, // Pointer to runs if doing complex clipping
|
|
ULONG cptfx, // Number of points in pptfxBuf or number of runs
|
|
// in prun
|
|
LINESTATE* pls, // Colour and style info
|
|
RECTL* prclClip, // Pointer to clip rectangle if doing simple clipping
|
|
PFNSTRIP apfn[], // Array of strip functions
|
|
FLONG flStart) // Flags for each line, which is a combination of:
|
|
// FL_SIMPLE_CLIP
|
|
// FL_COMPLEX_CLIP
|
|
// FL_STYLED
|
|
// FL_LAST_PEL_INCLUSIVE
|
|
// - Should be set only for all integer lines,
|
|
// and can't be used with FL_COMPLEX_CLIP
|
|
{
|
|
ULONG M0;
|
|
ULONG dM;
|
|
ULONG N0;
|
|
ULONG dN;
|
|
ULONG dN_Original;
|
|
FLONG fl;
|
|
LONG x;
|
|
LONG y;
|
|
|
|
LONGLONG llBeta;
|
|
LONGLONG llGamma;
|
|
LONGLONG dl;
|
|
LONGLONG ll;
|
|
|
|
ULONG ulDelta;
|
|
|
|
ULONG x0;
|
|
ULONG y0;
|
|
ULONG x1;
|
|
ULONG cStylePels; // Major length of line in pixels for styling
|
|
ULONG xStart;
|
|
POINTL ptlStart;
|
|
STRIP strip;
|
|
PFNSTRIP pfn;
|
|
LONG cPels;
|
|
LONG* plStrip;
|
|
LONG* plStripEnd;
|
|
LONG cStripsInNextRun;
|
|
|
|
POINTFIX* pptfxBufEnd = pptfxBuf + cptfx; // Last point in path record
|
|
STYLEPOS spThis; // Style pos for this line
|
|
|
|
do {
|
|
|
|
/***********************************************************************\
|
|
* Start the DDA calculations. *
|
|
\***********************************************************************/
|
|
|
|
M0 = (LONG) pptfxFirst->x;
|
|
dM = (LONG) pptfxBuf->x;
|
|
|
|
N0 = (LONG) pptfxFirst->y;
|
|
dN = (LONG) pptfxBuf->y;
|
|
|
|
fl = flStart;
|
|
|
|
if ((LONG) M0 > (LONG) dM)
|
|
{
|
|
// Ensure that we run left-to-right:
|
|
|
|
register ULONG ulTmp;
|
|
SWAPL(M0, dM, ulTmp);
|
|
SWAPL(N0, dN, ulTmp);
|
|
fl |= FL_FLIP_H;
|
|
}
|
|
|
|
// Compute the delta dx. The DDI says we can never have a valid delta
|
|
// with a magnitued more than 2^31 - 1, but GDI never actually checks
|
|
// its transforms. So we have to check for this case to avoid overflow:
|
|
|
|
dM -= M0;
|
|
if ((LONG) dM < 0)
|
|
{
|
|
goto Next_Line;
|
|
}
|
|
|
|
if ((LONG) dN < (LONG) N0)
|
|
{
|
|
// Line runs from bottom to top, so flip across y = 0:
|
|
|
|
N0 = -(LONG) N0;
|
|
dN = -(LONG) dN;
|
|
fl |= FL_FLIP_V;
|
|
}
|
|
|
|
dN -= N0;
|
|
|
|
if ((LONG) dN < 0)
|
|
{
|
|
goto Next_Line;
|
|
}
|
|
|
|
// We now have a line running left-to-right, top-to-bottom from (M0, N0)
|
|
// to (M0 + dM, N0 + dN):
|
|
|
|
if (dN >= dM)
|
|
{
|
|
if (dN == dM)
|
|
{
|
|
// Have to special case slopes of one:
|
|
|
|
fl |= FL_FLIP_SLOPE_ONE;
|
|
}
|
|
else
|
|
{
|
|
// Since line has slope greater than 1, flip across x = y:
|
|
|
|
register ULONG ulTmp;
|
|
SWAPL(dM, dN, ulTmp);
|
|
SWAPL(M0, N0, ulTmp);
|
|
fl |= FL_FLIP_D;
|
|
}
|
|
}
|
|
|
|
fl |= gaflRound[(fl & FL_ROUND_MASK) >> FL_ROUND_SHIFT];
|
|
|
|
x = LFLOOR((LONG) M0);
|
|
y = LFLOOR((LONG) N0);
|
|
|
|
M0 = FXFRAC(M0);
|
|
N0 = FXFRAC(N0);
|
|
|
|
// Calculate the remainder term [ dM * (N0 + F/2) - M0 * dN ]:
|
|
|
|
llGamma = UInt32x32To64(dM, N0 + F/2) - UInt32x32To64(M0, dN);
|
|
if (fl & FL_V_ROUND_DOWN) // Adjust so y = 1/2 rounds down
|
|
{
|
|
llGamma--;
|
|
}
|
|
|
|
llGamma >>= FLOG2;
|
|
llBeta = ~llGamma;
|
|
|
|
/***********************************************************************\
|
|
* Figure out which pixels are at the ends of the line. *
|
|
\***********************************************************************/
|
|
|
|
// The toughest part of GIQ is determining the start and end pels.
|
|
//
|
|
// Our approach here is to calculate x0 and x1 (the inclusive start
|
|
// and end columns of the line respectively, relative to our normalized
|
|
// origin). Then x1 - x0 + 1 is the number of pels in the line. The
|
|
// start point is easily calculated by plugging x0 into our line equation
|
|
// (which takes care of whether y = 1/2 rounds up or down in value)
|
|
// getting y0, and then undoing the normalizing flips to get back
|
|
// into device space.
|
|
//
|
|
// We look at the fractional parts of the coordinates of the start and
|
|
// end points, and call them (M0, N0) and (M1, N1) respectively, where
|
|
// 0 <= M0, N0, M1, N1 < 16. We plot (M0, N0) on the following grid
|
|
// to determine x0:
|
|
//
|
|
// +-----------------------> +x
|
|
// |
|
|
// | 0 1
|
|
// | 0123456789abcdef
|
|
// |
|
|
// | 0 ........?xxxxxxx
|
|
// | 1 ..........xxxxxx
|
|
// | 2 ...........xxxxx
|
|
// | 3 ............xxxx
|
|
// | 4 .............xxx
|
|
// | 5 ..............xx
|
|
// | 6 ...............x
|
|
// | 7 ................
|
|
// | 8 ................
|
|
// | 9 ......**........
|
|
// | a ........****...x
|
|
// | b ............****
|
|
// | c .............xxx****
|
|
// | d ............xxxx ****
|
|
// | e ...........xxxxx ****
|
|
// | f ..........xxxxxx
|
|
// |
|
|
// | 2 3
|
|
// v
|
|
//
|
|
// +y
|
|
//
|
|
// This grid accounts for the appropriate rounding of GIQ and last-pel
|
|
// exclusion. If (M0, N0) lands on an 'x', x0 = 2. If (M0, N0) lands
|
|
// on a '.', x0 = 1. If (M0, N0) lands on a '?', x0 rounds up or down,
|
|
// depending on what flips have been done to normalize the line.
|
|
//
|
|
// For the end point, if (M1, N1) lands on an 'x', x1 =
|
|
// floor((M0 + dM) / 16) + 1. If (M1, N1) lands on a '.', x1 =
|
|
// floor((M0 + dM)). If (M1, N1) lands on a '?', x1 rounds up or down,
|
|
// depending on what flips have been done to normalize the line.
|
|
//
|
|
// Lines of exactly slope one require a special case for both the start
|
|
// and end. For example, if the line ends such that (M1, N1) is (9, 1),
|
|
// the line has gone exactly through (8, 0) -- which may be considered
|
|
// to be part of 'x' because of rounding! So slopes of exactly slope
|
|
// one going through (8, 0) must also be considered as belonging in 'x'.
|
|
//
|
|
// For lines that go left-to-right, we have the following grid:
|
|
//
|
|
// +-----------------------> +x
|
|
// |
|
|
// | 0 1
|
|
// | 0123456789abcdef
|
|
// |
|
|
// | 0 xxxxxxxx?.......
|
|
// | 1 xxxxxxx.........
|
|
// | 2 xxxxxx..........
|
|
// | 3 xxxxx...........
|
|
// | 4 xxxx............
|
|
// | 5 xxx.............
|
|
// | 6 xx..............
|
|
// | 7 x...............
|
|
// | 8 x...............
|
|
// | 9 x.....**........
|
|
// | a xx......****....
|
|
// | b xxx.........****
|
|
// | c xxxx............****
|
|
// | d xxxxx........... ****
|
|
// | e xxxxxx.......... ****
|
|
// | f xxxxxxx.........
|
|
// |
|
|
// | 2 3
|
|
// v
|
|
//
|
|
// +y
|
|
//
|
|
// This grid accounts for the appropriate rounding of GIQ and last-pel
|
|
// exclusion. If (M0, N0) lands on an 'x', x0 = 0. If (M0, N0) lands
|
|
// on a '.', x0 = 1. If (M0, N0) lands on a '?', x0 rounds up or down,
|
|
// depending on what flips have been done to normalize the line.
|
|
//
|
|
// For the end point, if (M1, N1) lands on an 'x', x1 =
|
|
// floor((M0 + dM) / 16) - 1. If (M1, N1) lands on a '.', x1 =
|
|
// floor((M0 + dM)). If (M1, N1) lands on a '?', x1 rounds up or down,
|
|
// depending on what flips have been done to normalize the line.
|
|
//
|
|
// Lines of exactly slope one must be handled similarly to the right-to-
|
|
// left case.
|
|
|
|
{
|
|
|
|
// Calculate x0, x1
|
|
|
|
ULONG N1 = FXFRAC(N0 + dN);
|
|
ULONG M1 = FXFRAC(M0 + dM);
|
|
|
|
x1 = LFLOOR(M0 + dM);
|
|
|
|
if (fl & FL_LAST_PEL_INCLUSIVE)
|
|
{
|
|
// It sure is easy to compute the first pel when lines have only
|
|
// integer coordinates and are last-pel inclusive:
|
|
|
|
x0 = 0;
|
|
y0 = 0;
|
|
|
|
// Last-pel inclusive lines that are exactly one pixel long
|
|
// have a 'delta-x' and 'delta-y' equal to zero. The problem is
|
|
// that our clip code assumes that 'delta-x' is always non-zero
|
|
// (since it never happens with last-pel exclusive lines). As
|
|
// an inelegant solution, we simply modify 'delta-x' in this
|
|
// case -- because the line is exactly one pixel long, changing
|
|
// the slope will obviously have no effect on rasterization.
|
|
|
|
if (x1 == 0)
|
|
{
|
|
dM = 1;
|
|
llGamma = 0;
|
|
llBeta = ~llGamma;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
if (fl & FL_FLIP_H)
|
|
{
|
|
// ---------------------------------------------------------------
|
|
// Line runs right-to-left: <----
|
|
|
|
// Compute x1:
|
|
|
|
if (N1 == 0)
|
|
{
|
|
if (LROUND(M1, fl & FL_H_ROUND_DOWN))
|
|
{
|
|
x1++;
|
|
}
|
|
}
|
|
else if (abs((LONG) (N1 - F/2)) + M1 > F)
|
|
{
|
|
x1++;
|
|
}
|
|
|
|
if ((fl & (FL_FLIP_SLOPE_ONE | FL_H_ROUND_DOWN))
|
|
== (FL_FLIP_SLOPE_ONE))
|
|
{
|
|
// Have to special-case diagonal lines going through our
|
|
// the point exactly equidistant between two horizontal
|
|
// pixels, if we're supposed to round x=1/2 down:
|
|
|
|
if ((N1 > 0) && (M1 == N1 + 8))
|
|
x1++;
|
|
|
|
// Don't you love special cases? Is this a rhetorical question?
|
|
|
|
if ((N0 > 0) && (M0 == N0 + 8))
|
|
{
|
|
x0 = 2;
|
|
ulDelta = dN;
|
|
goto right_to_left_compute_y0;
|
|
}
|
|
}
|
|
|
|
// Compute x0:
|
|
|
|
x0 = 1;
|
|
ulDelta = 0;
|
|
if (N0 == 0)
|
|
{
|
|
if (LROUND(M0, fl & FL_H_ROUND_DOWN))
|
|
{
|
|
x0 = 2;
|
|
ulDelta = dN;
|
|
}
|
|
}
|
|
else if (abs((LONG) (N0 - F/2)) + M0 > F)
|
|
{
|
|
x0 = 2;
|
|
ulDelta = dN;
|
|
}
|
|
|
|
|
|
// Compute y0:
|
|
|
|
right_to_left_compute_y0:
|
|
|
|
y0 = 0;
|
|
ll = llGamma + (LONGLONG) ulDelta;
|
|
|
|
if (ll >= (LONGLONG) (2 * dM - dN))
|
|
y0 = 2;
|
|
else if (ll >= (LONGLONG) (dM - dN))
|
|
y0 = 1;
|
|
}
|
|
else
|
|
{
|
|
// ---------------------------------------------------------------
|
|
// Line runs left-to-right: ---->
|
|
|
|
// Compute x1:
|
|
|
|
if (!(fl & FL_LAST_PEL_INCLUSIVE))
|
|
x1--;
|
|
|
|
if (M1 > 0)
|
|
{
|
|
if (N1 == 0)
|
|
{
|
|
if (LROUND(M1, fl & FL_H_ROUND_DOWN))
|
|
x1++;
|
|
}
|
|
else if (abs((LONG) (N1 - F/2)) <= (LONG) M1)
|
|
{
|
|
x1++;
|
|
}
|
|
}
|
|
|
|
if ((fl & (FL_FLIP_SLOPE_ONE | FL_H_ROUND_DOWN))
|
|
== (FL_FLIP_SLOPE_ONE | FL_H_ROUND_DOWN))
|
|
{
|
|
// Have to special-case diagonal lines going through our
|
|
// the point exactly equidistant between two horizontal
|
|
// pixels, if we're supposed to round x=1/2 down:
|
|
|
|
if ((M1 > 0) && (N1 == M1 + 8))
|
|
x1--;
|
|
|
|
if ((M0 > 0) && (N0 == M0 + 8))
|
|
{
|
|
x0 = 0;
|
|
goto left_to_right_compute_y0;
|
|
}
|
|
}
|
|
|
|
// Compute x0:
|
|
|
|
x0 = 0;
|
|
if (M0 > 0)
|
|
{
|
|
if (N0 == 0)
|
|
{
|
|
if (LROUND(M0, fl & FL_H_ROUND_DOWN))
|
|
x0 = 1;
|
|
}
|
|
else if (abs((LONG) (N0 - F/2)) <= (LONG) M0)
|
|
{
|
|
x0 = 1;
|
|
}
|
|
}
|
|
|
|
// Compute y0:
|
|
|
|
left_to_right_compute_y0:
|
|
|
|
y0 = 0;
|
|
if (llGamma >= (LONGLONG) (dM - (dN & (-(LONG) x0))))
|
|
{
|
|
y0 = 1;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
cStylePels = x1 - x0 + 1;
|
|
if ((LONG) cStylePels <= 0)
|
|
goto Next_Line;
|
|
|
|
xStart = x0;
|
|
|
|
/***********************************************************************\
|
|
* Complex clipping. *
|
|
\***********************************************************************/
|
|
|
|
if (fl & FL_COMPLEX_CLIP)
|
|
{
|
|
dN_Original = dN;
|
|
|
|
Continue_Complex_Clipping:
|
|
|
|
if (fl & FL_FLIP_H)
|
|
{
|
|
// Line runs right-to-left <-----
|
|
|
|
x0 = xStart + cStylePels - prun->iStop - 1;
|
|
x1 = xStart + cStylePels - prun->iStart - 1;
|
|
}
|
|
else
|
|
{
|
|
// Line runs left-to-right ----->
|
|
|
|
x0 = xStart + prun->iStart;
|
|
x1 = xStart + prun->iStop;
|
|
}
|
|
|
|
prun++;
|
|
|
|
// Reset some variables we'll nuke a little later:
|
|
|
|
dN = dN_Original;
|
|
pls->spNext = pls->spComplex;
|
|
|
|
// No overflow since large integer math is used. Both values
|
|
// will be positive:
|
|
|
|
dl = UInt32x32To64(x0, dN) + llGamma;
|
|
|
|
// y0 = dl / dM:
|
|
|
|
y0 = UInt64Div32To32(dl, dM);
|
|
|
|
ASSERTDD((LONG) y0 >= 0, "y0 weird: Goofed up end pel calc?");
|
|
}
|
|
|
|
/***********************************************************************\
|
|
* Simple rectangular clipping. *
|
|
\***********************************************************************/
|
|
|
|
if (fl & FL_SIMPLE_CLIP)
|
|
{
|
|
ULONG y1;
|
|
LONG xRight;
|
|
LONG xLeft;
|
|
LONG yBottom;
|
|
LONG yTop;
|
|
|
|
// Note that y0 and y1 are actually the lower and upper bounds,
|
|
// respectively, of the y coordinates of the line (the line may
|
|
// have actually shrunk due to first/last pel clipping).
|
|
//
|
|
// Also note that x0, y0 are not necessarily zero.
|
|
|
|
RECTL* prcl = &prclClip[(fl & FL_RECTLCLIP_MASK) >>
|
|
FL_RECTLCLIP_SHIFT];
|
|
|
|
// Normalize to the same point we've normalized for the DDA
|
|
// calculations:
|
|
|
|
xRight = prcl->right - x;
|
|
xLeft = prcl->left - x;
|
|
yBottom = prcl->bottom - y;
|
|
yTop = prcl->top - y;
|
|
|
|
if (yBottom <= (LONG) y0 ||
|
|
xRight <= (LONG) x0 ||
|
|
xLeft > (LONG) x1)
|
|
{
|
|
Totally_Clipped:
|
|
|
|
if (fl & FL_STYLED)
|
|
{
|
|
pls->spNext += cStylePels;
|
|
if (pls->spNext >= pls->spTotal2)
|
|
pls->spNext %= pls->spTotal2;
|
|
}
|
|
|
|
goto Next_Line;
|
|
}
|
|
|
|
if ((LONG) x1 >= xRight)
|
|
x1 = xRight - 1;
|
|
|
|
// We have to know the correct y1, which we haven't bothered to
|
|
// calculate up until now. This multiply and divide is quite
|
|
// expensive; we could replace it with code similar to that which
|
|
// we used for computing y0.
|
|
//
|
|
// The reason why we need the actual value, and not an upper
|
|
// bounds guess like y1 = LFLOOR(dM) + 2 is that we have to be
|
|
// careful when calculating x(y) that y0 <= y <= y1, otherwise
|
|
// we can overflow on the divide (which, needless to say, is very
|
|
// bad).
|
|
|
|
dl = UInt32x32To64(x1, dN) + llGamma;
|
|
|
|
// y1 = dl / dM:
|
|
|
|
y1 = UInt64Div32To32(dl, dM);
|
|
|
|
if (yTop > (LONG) y1)
|
|
goto Totally_Clipped;
|
|
|
|
if (yBottom <= (LONG) y1)
|
|
{
|
|
y1 = yBottom;
|
|
dl = UInt32x32To64(y1, dM) + llBeta;
|
|
|
|
// x1 = dl / dN:
|
|
|
|
x1 = UInt64Div32To32(dl, dN);
|
|
}
|
|
|
|
// At this point, we've taken care of calculating the intercepts
|
|
// with the right and bottom edges. Now we work on the left and
|
|
// top edges:
|
|
|
|
if (xLeft > (LONG) x0)
|
|
{
|
|
x0 = xLeft;
|
|
dl = UInt32x32To64(x0, dN) + llGamma;
|
|
|
|
// y0 = dl / dM;
|
|
|
|
y0 = UInt64Div32To32(dl, dM);
|
|
|
|
if (yBottom <= (LONG) y0)
|
|
goto Totally_Clipped;
|
|
}
|
|
|
|
if (yTop > (LONG) y0)
|
|
{
|
|
y0 = yTop;
|
|
dl = UInt32x32To64(y0, dM) + llBeta;
|
|
|
|
// x0 = dl / dN + 1;
|
|
|
|
x0 = UInt64Div32To32(dl, dN) + 1;
|
|
|
|
if (xRight <= (LONG) x0)
|
|
goto Totally_Clipped;
|
|
}
|
|
|
|
ASSERTDD(x0 <= x1, "Improper rectangle clip");
|
|
}
|
|
|
|
/***********************************************************************\
|
|
* Done clipping. Unflip if necessary. *
|
|
\***********************************************************************/
|
|
|
|
ptlStart.x = x + x0;
|
|
ptlStart.y = y + y0;
|
|
|
|
if (fl & FL_FLIP_D)
|
|
{
|
|
register LONG lTmp;
|
|
SWAPL(ptlStart.x, ptlStart.y, lTmp);
|
|
}
|
|
|
|
|
|
if (fl & FL_FLIP_V)
|
|
{
|
|
ptlStart.y = -ptlStart.y;
|
|
}
|
|
|
|
cPels = x1 - x0 + 1;
|
|
|
|
/***********************************************************************\
|
|
* Style calculations. *
|
|
\***********************************************************************/
|
|
|
|
if (fl & FL_STYLED)
|
|
{
|
|
STYLEPOS sp;
|
|
|
|
spThis = pls->spNext;
|
|
pls->spNext += cStylePels;
|
|
|
|
{
|
|
if (pls->spNext >= pls->spTotal2)
|
|
pls->spNext %= pls->spTotal2;
|
|
|
|
if (fl & FL_FLIP_H)
|
|
sp = pls->spNext - x0 + xStart;
|
|
else
|
|
sp = spThis + x0 - xStart;
|
|
|
|
ASSERTDD(fl & FL_STYLED, "Oops");
|
|
|
|
// Normalize our target style position:
|
|
|
|
if ((sp < 0) || (sp >= pls->spTotal2))
|
|
{
|
|
sp %= pls->spTotal2;
|
|
|
|
// The modulus of a negative number is not well-defined
|
|
// in C -- if it's negative we'll adjust it so that it's
|
|
// back in the range [0, spTotal2):
|
|
|
|
if (sp < 0)
|
|
sp += pls->spTotal2;
|
|
}
|
|
|
|
// Since we always draw the line left-to-right, but styling is
|
|
// always done in the direction of the original line, we have
|
|
// to figure out where we are in the style array for the left
|
|
// edge of this line.
|
|
|
|
if (fl & FL_FLIP_H)
|
|
{
|
|
// Line originally ran right-to-left:
|
|
|
|
sp = -sp;
|
|
if (sp < 0)
|
|
sp += pls->spTotal2;
|
|
|
|
pls->ulStyleMask = ~pls->ulStartMask;
|
|
pls->pspStart = &pls->aspRtoL[0];
|
|
pls->pspEnd = &pls->aspRtoL[pls->cStyle - 1];
|
|
}
|
|
else
|
|
{
|
|
// Line originally ran left-to-right:
|
|
|
|
pls->ulStyleMask = pls->ulStartMask;
|
|
pls->pspStart = &pls->aspLtoR[0];
|
|
pls->pspEnd = &pls->aspLtoR[pls->cStyle - 1];
|
|
}
|
|
|
|
if (sp >= pls->spTotal)
|
|
{
|
|
sp -= pls->spTotal;
|
|
if (pls->cStyle & 1)
|
|
pls->ulStyleMask = ~pls->ulStyleMask;
|
|
}
|
|
|
|
pls->psp = pls->pspStart;
|
|
while (sp >= *pls->psp)
|
|
sp -= *pls->psp++;
|
|
|
|
ASSERTDD(pls->psp <= pls->pspEnd,
|
|
"Flew off into NeverNeverLand");
|
|
|
|
pls->spRemaining = *pls->psp - sp;
|
|
if ((pls->psp - pls->pspStart) & 1)
|
|
pls->ulStyleMask = ~pls->ulStyleMask;
|
|
}
|
|
}
|
|
|
|
plStrip = &strip.alStrips[0];
|
|
plStripEnd = &strip.alStrips[STRIP_MAX]; // Is exclusive
|
|
cStripsInNextRun = 0x7fffffff;
|
|
|
|
strip.ptlStart = ptlStart;
|
|
|
|
// Now, run the DDA starting at (ptlStart.x, ptlStart.y)!
|
|
|
|
strip.flFlips = fl;
|
|
pfn = apfn[(fl & FL_STRIP_MASK) >> FL_STRIP_SHIFT];
|
|
|
|
// Now calculate the DDA variables needed to figure out how many pixels
|
|
// go in the very first strip:
|
|
|
|
{
|
|
register LONG i;
|
|
register ULONG dI;
|
|
register ULONG dR;
|
|
ULONG r;
|
|
|
|
if (dN == 0)
|
|
i = 0x7fffffff;
|
|
else
|
|
{
|
|
dl = UInt32x32To64(y0 + 1, dM) + llBeta;
|
|
|
|
ASSERTDD(dl >= 0, "Oops!");
|
|
|
|
// i = (dl / dN) - x0 + 1;
|
|
// r = (dl % dN);
|
|
|
|
i = UInt64Div32To32(dl, dN);
|
|
r = UInt64Mod32To32(dl, dN);
|
|
i = i - x0 + 1;
|
|
|
|
dI = dM / dN;
|
|
dR = dM % dN; // 0 <= dR < dN
|
|
|
|
ASSERTDD(dI > 0, "Weird dI");
|
|
}
|
|
|
|
ASSERTDD(i > 0 && i <= 0x7fffffff, "Weird initial strip length");
|
|
ASSERTDD(cPels > 0, "Zero pel line");
|
|
|
|
/***********************************************************************\
|
|
* Run the DDA! *
|
|
\***********************************************************************/
|
|
|
|
while(TRUE)
|
|
{
|
|
cPels -= i;
|
|
if (cPels <= 0)
|
|
break;
|
|
|
|
*plStrip++ = i;
|
|
|
|
if (plStrip == plStripEnd)
|
|
{
|
|
strip.cStrips = (LONG)(plStrip - &strip.alStrips[0]);
|
|
(*pfn)(ppdev, &strip, pls);
|
|
plStrip = &strip.alStrips[0];
|
|
}
|
|
|
|
i = dI;
|
|
r += dR;
|
|
|
|
if (r >= dN)
|
|
{
|
|
r -= dN;
|
|
i++;
|
|
}
|
|
}
|
|
|
|
*plStrip++ = cPels + i;
|
|
|
|
strip.cStrips = (LONG)(plStrip - &strip.alStrips[0]);
|
|
(*pfn)(ppdev, &strip, pls);
|
|
|
|
|
|
}
|
|
|
|
Next_Line:
|
|
|
|
if (fl & FL_COMPLEX_CLIP)
|
|
{
|
|
cptfx--;
|
|
if (cptfx != 0)
|
|
goto Continue_Complex_Clipping;
|
|
|
|
break;
|
|
}
|
|
else
|
|
{
|
|
pptfxFirst = pptfxBuf;
|
|
pptfxBuf++;
|
|
}
|
|
|
|
} while (pptfxBuf < pptfxBufEnd);
|
|
|
|
return(TRUE);
|
|
|
|
}
|