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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
//+-----------------------------------------------------------------------------
//
// class Bezier32
//
// Bezier cracker.
//
// A hybrid cubic Bezier curve flattener based on KirkO's error factor.
// Generates line segments fast without using the stack. Used to flatten a
// path.
//
// For an understanding of the methods used, see:
//
// Kirk Olynyk, "..."
// Goossen and Olynyk, "System and Method of Hybrid Forward
// Differencing to Render Bezier Splines"
// Lien, Shantz and Vaughan Pratt, "Adaptive Forward Differencing for
// Rendering Curves and Surfaces", Computer Graphics, July 1987
// Chang and Shantz, "Rendering Trimmed NURBS with Adaptive Forward
// Differencing", Computer Graphics, August 1988
// Foley and Van Dam, "Fundamentals of Interactive Computer Graphics"
//
// Public Interface:
// bInit(pptfx) - pptfx points to 4 control points of
// Bezier. Current point is set to the first
// point after the start-point.
// Bezier32(pptfx) - Constructor with initialization.
// vGetCurrent(pptfx) - Returns current polyline point.
// bCurrentIsEndPoint() - TRUE if current point is end-point.
// vNext() - Moves to next polyline point.
//
#![allow(unused_parens)]
#![allow(non_upper_case_globals)]
//+-----------------------------------------------------------------------------
//
//
// $TAG ENGR
// $Module: win_mil_graphics_geometry
// $Keywords:
//
// $Description:
// Class for flattening a bezier.
//
// $ENDTAG
//
//------------------------------------------------------------------------------
// First conversion from original 28.4 to 18.14 format
const HFD32_INITIAL_SHIFT: i32 = 10;
// Second conversion to 15.17 format
const HFD32_ADDITIONAL_SHIFT: i32 = 3;
// BEZIER_FLATTEN_GDI_COMPATIBLE:
//
// Don't turn on this switch without testing carefully. It's more for
// documentation's sake - to show the values that GDI used - for an error
// tolerance of 2/3.
// It turns out that 2/3 produces very noticable artifacts on antialiased lines,
// so we want to use 1/4 instead.
/*
#ifdef BEZIER_FLATTEN_GDI_COMPATIBLE
// Flatten to an error of 2/3. During initial phase, use 18.14 format.
#define TEST_MAGNITUDE_INITIAL (6 * 0x00002aa0L)
// Error of 2/3. During normal phase, use 15.17 format.
#define TEST_MAGNITUDE_NORMAL (TEST_MAGNITUDE_INITIAL << 3)
#else
*/
use crate::types::*;
/*
// Flatten to an error of 1/4. During initial phase, use 18.14 format.
const TEST_MAGNITUDE_INITIAL: i32 = (6 * 0x00001000);
// Error of 1/4. During normal phase, use 15.17 format.
const TEST_MAGNITUDE_NORMAL: i32 = (TEST_MAGNITUDE_INITIAL << 3);
*/
// I have modified the constants for HFD32 as part of fixing accuracy errors
// broke so I'd rather not fix it.
// The shift to the steady state 15.17 format
const HFD32_SHIFT: LONG = HFD32_INITIAL_SHIFT + HFD32_ADDITIONAL_SHIFT;
// Added to output numbers before rounding back to original representation
const HFD32_ROUND: LONG = 1 << (HFD32_SHIFT - 1);
// The error is tested on max(|e2|, |e3|), which represent 6 times the actual error.
// The flattening tolerance is hard coded to 1/4 in the original geometry space,
// which translates to 4 in 28.4 format. So 6 times that is:
const HFD32_TOLERANCE: LONGLONG = 24;
// During the initial phase, while working in 18.14 format
const HFD32_INITIAL_TEST_MAGNITUDE: LONGLONG = HFD32_TOLERANCE << HFD32_INITIAL_SHIFT;
// During the steady state, while working in 15.17 format
const HFD32_TEST_MAGNITUDE: LONGLONG = HFD32_INITIAL_TEST_MAGNITUDE << HFD32_ADDITIONAL_SHIFT;
// We will stop halving the segment with basis e1, e2, e3, e4 when max(|e2|, |e3|)
// is less than HFD32_TOLERANCE. The operation e2 = (e2 + e3) >> 3 in vHalveStepSize() may
// eat up 3 bits of accuracy. HfdBasis32 starts off with a pad of HFD32_SHIFT zeros, so
// we can stay exact up to HFD32_SHIFT/3 subdivisions. Since every subdivision is guaranteed
// to shift max(|e2|, |e3|) at least by 2, we will subdivide no more than n times if the
// initial max(|e2|, |e3|) is less than than HFD32_TOLERANCE << 2n. But if the initial
// max(|e2|, |e3|) is greater than HFD32_TOLERANCE >> (HFD32_SHIFT / 3) then we may not be
// able to flatten with the 32 bit hfd, so we need to resort to the 64 bit hfd.
const HFD32_MAX_ERROR: INT = (HFD32_TOLERANCE as i32) << ((2 * HFD32_INITIAL_SHIFT) / 3);
// The maximum size of coefficients that can be handled by HfdBasis32.
const HFD32_MAX_SIZE: LONGLONG = 0xffffc000;
// Michka 9/12/03: I found this number in the the body of the code witout any explanation.
// My analysis suggests that we could get away with larger numbers, but if I'm wrong we
// could be in big trouble, so let us stay conservative.
//
// In bInit() we subtract Min(Bezier coeffients) from the original coefficients, so after
// that 0 <= coefficients <= Bound, and the test will be Bound < HFD32_MAX_SIZE. When
// switching to the HFD basis in bInit():
// * e0 is the first Bezier coeffient, so abs(e0) <= Bound.
// * e1 is a difference of non-negative coefficients so abs(e1) <= Bound.
// * e2 and e3 can be written as 12*(p - (q + r)/2) where p,q and r are coefficients.
// 0 <=(q + r)/2 <= Bound, so abs(p - (q + r)/2) <= 2*Bound, hence
// abs(e2), abs(e3) <= 12*Bound.
//
// During vLazyHalveStepSize we add e2 + e3, resulting in absolute value <= 24*Bound.
// Initially HfdBasis32 shifts the numbers by HFD32_INITIAL_SHIFT, so we need to handle
// 24*bounds*(2^HFD32_SHIFT), and that needs to be less than 2^31. So the bounds need to
// be less than 2^(31-HFD32_INITIAL_SHIFT)/24).
//
// For speed, the algorithm uses & rather than < for comparison. To facilitate that we
// replace 24 by 32=2^5, and then the binary representation of the number is of the form
// 0...010...0 with HFD32_SHIFT+5 trailing zeros. By subtracting that from 2^32 = 0xffffffff+1
// we get a number that is 1..110...0 with the same number of trailing zeros, and that can be
// used with an & for comparison. So the number should be:
//
// 0xffffffffL - (1L << (31 - HFD32_INITIAL_SHIFT - 5)) + 1 = (1L << 16) + 1 = 0xffff0000
//
// For the current values of HFD32_INITIAL_SHIFT=10 and HFD32_ADDITIONAL_SHIFT=3, the steady
// state doesn't pose additional requirements, as shown below.
//
// For some reason the current code uses 0xfffc0000 = (1L << 14) + 1.
//
// Here is why the steady state doesn't pose additional requirements:
//
// In vSteadyState we multiply e0 and e1 by 8, so the requirement is Bounds*2^13 < 2^31,
// or Bounds < 2^18, less stringent than the above.
//
// In vLazyHalveStepSize we cut the error down by subdivision, making abs(e2) and abs(e3)
// less than HFD32_TEST_MAGNITUDE = 24*2^13, well below 2^31.
//
// During all the steady-state operations - vTakeStep, vHalveStepSize and vDoubleStepSize,
// e0 is on the curve and e1 is a difference of 2 points on the curve, so
// abs(e0), abs(e1) < Bounds * 2^13, which requires Bound < 2^(31-13) = 2^18. e2 and e3
// are errors, kept below 6*HFD32_TEST_MAGNITUDE = 216*2^13. Details:
//
// In vTakeStep e2 = 2e2 - e3 keeps abs(e2) < 3*HFD32_TEST_MAGNITUDE = 72*2^13,
// well below 2^31
//
// In vHalveStepSize we add e2 + e3 when their absolute is < 3*HFD32_TEST_MAGNITUDE (because
// this comes after a step), so that keeps the result below 6*HFD32_TEST_MAGNITUDE = 216*2^13.
//
// In vDoubleStepSize we know that abs(e2), abs(e3) < HFD32_TEST_MAGNITUDE/4, otherwise we
// would not have doubled the step.
#[derive(Default)]
struct HfdBasis32
{
e0: LONG,
e1: LONG,
e2: LONG,
e3: LONG,
}
impl HfdBasis32 {
fn lParentErrorDividedBy4(&self) -> LONG {
self.e3.abs().max((self.e2 + self.e2 - self.e3).abs())
}
fn lError(&self) -> LONG
{
self.e2.abs().max(self.e3.abs())
}
fn fxValue(&self) -> INT
{
return((self.e0 + HFD32_ROUND) >> HFD32_SHIFT);
}
fn bInit(&mut self, p1: INT, p2: INT, p3: INT, p4: INT) -> bool
{
// Change basis and convert from 28.4 to 18.14 format:
self.e0 = (p1 ) << HFD32_INITIAL_SHIFT;
self.e1 = (p4 - p1 ) << HFD32_INITIAL_SHIFT;
self.e2 = 6 * (p2 - p3 - p3 + p4);
self.e3 = 6 * (p1 - p2 - p2 + p3);
if (self.lError() >= HFD32_MAX_ERROR)
{
// Large error, will require too many subdivision for this 32 bit hfd
return false;
}
self.e2 <<= HFD32_INITIAL_SHIFT;
self.e3 <<= HFD32_INITIAL_SHIFT;
return true;
}
fn vLazyHalveStepSize(&mut self, cShift: LONG)
{
self.e2 = self.ExactShiftRight(self.e2 + self.e3, 1);
self.e1 = self.ExactShiftRight(self.e1 - self.ExactShiftRight(self.e2, cShift), 1);
}
fn vSteadyState(&mut self, cShift: LONG)
{
// We now convert from 18.14 fixed format to 15.17:
self.e0 <<= HFD32_ADDITIONAL_SHIFT;
self.e1 <<= HFD32_ADDITIONAL_SHIFT;
let mut lShift = cShift - HFD32_ADDITIONAL_SHIFT;
if (lShift < 0)
{
lShift = -lShift;
self.e2 <<= lShift;
self.e3 <<= lShift;
}
else
{
self.e2 >>= lShift;
self.e3 >>= lShift;
}
}
fn vHalveStepSize(&mut self)
{
self.e2 = self.ExactShiftRight(self.e2 + self.e3, 3);
self.e1 = self.ExactShiftRight(self.e1 - self.e2, 1);
self.e3 = self.ExactShiftRight(self.e3, 2);
}
fn vDoubleStepSize(&mut self)
{
self.e1 += self.e1 + self.e2;
self.e3 <<= 2;
self.e2 = (self.e2 << 3) - self.e3;
}
fn vTakeStep(&mut self)
{
self.e0 += self.e1;
let lTemp = self.e2;
self.e1 += lTemp;
self.e2 += lTemp - self.e3;
self.e3 = lTemp;
}
fn ExactShiftRight(&self, num: i32, shift: i32) -> i32
{
// Performs a shift to the right while asserting that we're not
// losing significant bits
assert!(num == (num >> shift) << shift);
return num >> shift;
}
}
fn vBoundBox(
aptfx: &[POINT; 4]) -> RECT
{
let mut left = aptfx[0].x;
let mut right = aptfx[0].x;
let mut top = aptfx[0].y;
let mut bottom = aptfx[0].y;
for i in 1..4
{
left = left.min(aptfx[i].x);
top = top.min(aptfx[i].y);
right = right.max(aptfx[i].x);
bottom = bottom.max(aptfx[i].y);
}
// We make the bounds one pixel loose for the nominal width
// stroke case, which increases the bounds by half a pixel
// in every dimension:
RECT { left: left - 16, top: top - 16, right: right + 16, bottom: bottom + 16}
}
fn bIntersect(
a: &RECT,
b: &RECT) -> bool
{
return((a.left < b.right) &&
(a.top < b.bottom) &&
(a.right > b.left) &&
(a.bottom > b.top));
}
#[derive(Default)]
pub struct Bezier32
{
cSteps: LONG,
x: HfdBasis32,
y: HfdBasis32,
rcfxBound: RECT
}
impl Bezier32 {
fn bInit(&mut self,
aptfxBez: &[POINT; 4],
// Pointer to 4 control points
prcfxClip: Option<&RECT>) -> bool
// Bound box of visible region (optional)
{
let mut aptfx;
let mut cShift = 0; // Keeps track of 'lazy' shifts
self.cSteps = 1; // Number of steps to do before reach end of curve
self.rcfxBound = vBoundBox(aptfxBez);
aptfx = aptfxBez.clone();
{
let mut fxOr;
let mut fxOffset;
// find out if the coordinates minus the bounding box
// exceed 10 bits
fxOffset = self.rcfxBound.left;
fxOr = {aptfx[0].x -= fxOffset; aptfx[0].x};
fxOr |= {aptfx[1].x -= fxOffset; aptfx[1].x};
fxOr |= {aptfx[2].x -= fxOffset; aptfx[2].x};
fxOr |= {aptfx[3].x -= fxOffset; aptfx[3].x};
fxOffset = self.rcfxBound.top;
fxOr |= {aptfx[0].y -= fxOffset; aptfx[0].y};
fxOr |= {aptfx[1].y -= fxOffset; aptfx[1].y};
fxOr |= {aptfx[2].y -= fxOffset; aptfx[2].y};
fxOr |= {aptfx[3].y -= fxOffset; aptfx[3].y};
// This 32 bit cracker can only handle points in a 10 bit space:
if ((fxOr as i64 & HFD32_MAX_SIZE) != 0) {
return false;
}
}
if (!self.x.bInit(aptfx[0].x, aptfx[1].x, aptfx[2].x, aptfx[3].x))
{
return false;
}
if (!self.y.bInit(aptfx[0].y, aptfx[1].y, aptfx[2].y, aptfx[3].y))
{
return false;
}
if (match prcfxClip { None => true, Some(clip) => bIntersect(&self.rcfxBound, clip)})
{
loop {
let lTestMagnitude = (HFD32_INITIAL_TEST_MAGNITUDE << cShift) as LONG;
if (self.x.lError() <= lTestMagnitude && self.y.lError() <= lTestMagnitude) {
break;
}
cShift += 2;
self.x.vLazyHalveStepSize(cShift);
self.y.vLazyHalveStepSize(cShift);
self.cSteps <<= 1;
}
}
self.x.vSteadyState(cShift);
self.y.vSteadyState(cShift);
// Note that this handles the case where the initial error for
// the Bezier is already less than HFD32_TEST_MAGNITUDE:
self.x.vTakeStep();
self.y.vTakeStep();
self.cSteps-=1;
return true;
}
fn cFlatten(&mut self,
mut pptfx: &mut [POINT],
pbMore: &mut bool) -> i32
{
let mut cptfx = pptfx.len();
assert!(cptfx > 0);
let cptfxOriginal = cptfx;
while {
// Return current point:
pptfx[0].x = self.x.fxValue() + self.rcfxBound.left;
pptfx[0].y = self.y.fxValue() + self.rcfxBound.top;
pptfx = &mut pptfx[1..];
// If cSteps == 0, that was the end point in the curve!
if (self.cSteps == 0)
{
*pbMore = false;
// '+1' because we haven't decremented 'cptfx' yet:
return(cptfxOriginal - cptfx + 1) as i32;
}
// Okay, we have to step:
if (self.x.lError().max(self.y.lError()) > HFD32_TEST_MAGNITUDE as LONG)
{
self.x.vHalveStepSize();
self.y.vHalveStepSize();
self.cSteps <<= 1;
}
// We are here after vTakeStep. Before that the error max(|e2|,|e3|) was less
// than HFD32_TEST_MAGNITUDE. vTakeStep changed e2 to 2e2-e3. Since
// |2e2-e3| < max(|e2|,|e3|) << 2 and vHalveStepSize is guaranteed to reduce
// max(|e2|,|e3|) by >> 2, no more than one subdivision should be required to
// bring the new max(|e2|,|e3|) back to within HFD32_TEST_MAGNITUDE, so:
assert!(self.x.lError().max(self.y.lError()) <= HFD32_TEST_MAGNITUDE as LONG);
while (!(self.cSteps & 1 != 0) &&
self.x.lParentErrorDividedBy4() <= (HFD32_TEST_MAGNITUDE as LONG >> 2) &&
self.y.lParentErrorDividedBy4() <= (HFD32_TEST_MAGNITUDE as LONG >> 2))
{
self.x.vDoubleStepSize();
self.y.vDoubleStepSize();
self.cSteps >>= 1;
}
self.cSteps -=1 ;
self.x.vTakeStep();
self.y.vTakeStep();
cptfx -= 1;
cptfx != 0
} {}
*pbMore = true;
return cptfxOriginal as i32;
}
}
///////////////////////////////////////////////////////////////////////////
// Bezier64
//
// All math is done using 64 bit fixed numbers in a 36.28 format.
//
// All drawing is done in a 31 bit space, then a 31 bit window offset
// is applied. In the initial transform where we change to the HFD
// basis, e2 and e3 require the most bits precision: e2 = 6(p2 - 2p3 + p4).
// This requires an additional 4 bits precision -- hence we require 36 bits
// for the integer part, and the remaining 28 bits is given to the fraction.
//
// In rendering a Bezier, every 'subdivide' requires an extra 3 bits of
// fractional precision. In order to be reversible, we can allow no
// error to creep in. Since a INT coordinate is 32 bits, and we
// require an additional 4 bits as mentioned above, that leaves us
// 28 bits fractional precision -- meaning we can do a maximum of
// 9 subdivides. Now, the maximum absolute error of a Bezier curve in 27
// bit integer space is 2^29 - 1. But 9 subdivides reduces the error by a
// guaranteed factor of 2^18, meaning we can subdivide down only to an error
// of 2^11 before we overflow, when in fact we want to reduce error to less
// than 1.
//
// So what we do is HFD until we hit an error less than 2^11, reverse our
// basis transform to get the four control points of this smaller curve
// (rounding in the process to 32 bits), then invoke another copy of HFD
// on the reduced Bezier curve. We again have enough precision, but since
// its starting error is less than 2^11, we can reduce error to 2^-7 before
// overflowing! We'll start a low HFD after every step of the high HFD.
////////////////////////////////////////////////////////////////////////////
#[derive(Default)]
struct HfdBasis64
{
e0: LONGLONG,
e1: LONGLONG,
e2: LONGLONG,
e3: LONGLONG,
}
impl HfdBasis64 {
fn vParentError(&self) -> LONGLONG
{
(self.e3 << 2).abs().max(((self.e2 << 3) - (self.e3 << 2)).abs())
}
fn vError(&self) -> LONGLONG
{
self.e2.abs().max(self.e3.abs())
}
fn fxValue(&self) -> INT
{
// Convert from 36.28 and round:
let mut eq = self.e0;
eq += (1 << (BEZIER64_FRACTION - 1));
eq >>= BEZIER64_FRACTION;
return eq as LONG as INT;
}
fn vInit(&mut self, p1: INT, p2: INT, p3: INT, p4: INT)
{
let mut eqTmp;
let eqP2 = p2 as LONGLONG;
let eqP3 = p3 as LONGLONG;
// e0 = p1
// e1 = p4 - p1
// e2 = 6(p2 - 2p3 + p4)
// e3 = 6(p1 - 2p2 + p3)
// Change basis:
self.e0 = p1 as LONGLONG; // e0 = p1
self.e1 = p4 as LONGLONG;
self.e2 = eqP2; self.e2 -= eqP3; self.e2 -= eqP3; self.e2 += self.e1; // e2 = p2 - 2*p3 + p4
self.e3 = self.e0; self.e3 -= eqP2; self.e3 -= eqP2; self.e3 += eqP3; // e3 = p1 - 2*p2 + p3
self.e1 -= self.e0; // e1 = p4 - p1
// Convert to 36.28 format and multiply e2 and e3 by six:
self.e0 <<= BEZIER64_FRACTION;
self.e1 <<= BEZIER64_FRACTION;
eqTmp = self.e2; self.e2 += eqTmp; self.e2 += eqTmp; self.e2 <<= (BEZIER64_FRACTION + 1);
eqTmp = self.e3; self.e3 += eqTmp; self.e3 += eqTmp; self.e3 <<= (BEZIER64_FRACTION + 1);
}
fn vUntransform<F: Fn(&mut POINT) -> &mut LONG>(&self,
afx: &mut [POINT; 4], field: F)
{
// Declare some temps to hold our operations, since we can't modify e0..e3.
let mut eqP0;
let mut eqP1;
let mut eqP2;
let mut eqP3;
// p0 = e0
// p1 = e0 + (6e1 - e2 - 2e3)/18
// p2 = e0 + (12e1 - 2e2 - e3)/18
// p3 = e0 + e1
eqP0 = self.e0;
// NOTE PERF: Convert this to a multiply by 6: [andrewgo]
eqP2 = self.e1;
eqP2 += self.e1;
eqP2 += self.e1;
eqP1 = eqP2;
eqP1 += eqP2; // 6e1
eqP1 -= self.e2; // 6e1 - e2
eqP2 = eqP1;
eqP2 += eqP1; // 12e1 - 2e2
eqP2 -= self.e3; // 12e1 - 2e2 - e3
eqP1 -= self.e3;
eqP1 -= self.e3; // 6e1 - e2 - 2e3
// NOTE: May just want to approximate these divides! [andrewgo]
// Or can do a 64 bit divide by 32 bit to get 32 bits right here.
eqP1 /= 18;
eqP2 /= 18;
eqP1 += self.e0;
eqP2 += self.e0;
eqP3 = self.e0;
eqP3 += self.e1;
// Convert from 36.28 format with rounding:
eqP0 += (1 << (BEZIER64_FRACTION - 1)); eqP0 >>= BEZIER64_FRACTION; *field(&mut afx[0]) = eqP0 as LONG;
eqP1 += (1 << (BEZIER64_FRACTION - 1)); eqP1 >>= BEZIER64_FRACTION; *field(&mut afx[1]) = eqP1 as LONG;
eqP2 += (1 << (BEZIER64_FRACTION - 1)); eqP2 >>= BEZIER64_FRACTION; *field(&mut afx[2]) = eqP2 as LONG;
eqP3 += (1 << (BEZIER64_FRACTION - 1)); eqP3 >>= BEZIER64_FRACTION; *field(&mut afx[3]) = eqP3 as LONG;
}
fn vHalveStepSize(&mut self)
{
// e2 = (e2 + e3) >> 3
// e1 = (e1 - e2) >> 1
// e3 >>= 2
self.e2 += self.e3; self.e2 >>= 3;
self.e1 -= self.e2; self.e1 >>= 1;
self.e3 >>= 2;
}
fn vDoubleStepSize(&mut self)
{
// e1 = 2e1 + e2
// e3 = 4e3;
// e2 = 8e2 - e3
self.e1 <<= 1; self.e1 += self.e2;
self.e3 <<= 2;
self.e2 <<= 3; self.e2 -= self.e3;
}
fn vTakeStep(&mut self)
{
self.e0 += self.e1;
let eqTmp = self.e2;
self.e1 += self.e2;
self.e2 += eqTmp; self.e2 -= self.e3;
self.e3 = eqTmp;
}
}
const BEZIER64_FRACTION: LONG = 28;
// The following is our 2^11 target error encoded as a 36.28 number
// (don't forget the additional 4 bits of fractional precision!) and
// the 6 times error multiplier:
const geqErrorHigh: LONGLONG = (6 * (1 << 15) >> (32 - BEZIER64_FRACTION)) << 32;
/*#ifdef BEZIER_FLATTEN_GDI_COMPATIBLE
// The following is the default 2/3 error encoded as a 36.28 number,
// multiplied by 6, and leaving 4 bits for fraction:
const LONGLONG geqErrorLow = (LONGLONG)(4) << 32;
#else*/
// The following is the default 1/4 error encoded as a 36.28 number,
// multiplied by 6, and leaving 4 bits for fraction:
use crate::types::POINT;
const geqErrorLow: LONGLONG = (3) << 31;
//#endif
#[derive(Default)]
pub struct Bezier64
{
xLow: HfdBasis64,
yLow: HfdBasis64,
xHigh: HfdBasis64,
yHigh: HfdBasis64,
eqErrorLow: LONGLONG,
rcfxClip: Option<RECT>,
cStepsHigh: LONG,
cStepsLow: LONG
}
impl Bezier64 {
fn vInit(&mut self,
aptfx: &[POINT; 4],
// Pointer to 4 control points
prcfxVis: Option<&RECT>,
// Pointer to bound box of visible area (may be NULL)
eqError: LONGLONG)
// Fractional maximum error (32.32 format)
{
self.cStepsHigh = 1;
self.cStepsLow = 0;
self.xHigh.vInit(aptfx[0].x, aptfx[1].x, aptfx[2].x, aptfx[3].x);
self.yHigh.vInit(aptfx[0].y, aptfx[1].y, aptfx[2].y, aptfx[3].y);
// Initialize error:
self.eqErrorLow = eqError;
self.rcfxClip = prcfxVis.cloned();
while (((self.xHigh.vError()) > geqErrorHigh) ||
((self.yHigh.vError()) > geqErrorHigh))
{
self.cStepsHigh <<= 1;
self.xHigh.vHalveStepSize();
self.yHigh.vHalveStepSize();
}
}
fn cFlatten(
&mut self,
mut pptfx: &mut [POINT],
pbMore: &mut bool) -> INT
{
let mut aptfx: [POINT; 4] = Default::default();
let mut cptfx = pptfx.len();
let mut rcfxBound: RECT;
let cptfxOriginal = cptfx;
assert!(cptfx > 0);
while {
if (self.cStepsLow == 0)
{
// Optimization that if the bound box of the control points doesn't
// intersect with the bound box of the visible area, render entire
// curve as a single line:
self.xHigh.vUntransform(&mut aptfx, |p| &mut p.x);
self.yHigh.vUntransform(&mut aptfx, |p| &mut p.y);
self.xLow.vInit(aptfx[0].x, aptfx[1].x, aptfx[2].x, aptfx[3].x);
self.yLow.vInit(aptfx[0].y, aptfx[1].y, aptfx[2].y, aptfx[3].y);
self.cStepsLow = 1;
if (match &self.rcfxClip { None => true, Some(clip) => {rcfxBound = vBoundBox(&aptfx); bIntersect(&rcfxBound, &clip)}})
{
while (((self.xLow.vError()) > self.eqErrorLow) ||
((self.yLow.vError()) > self.eqErrorLow))
{
self.cStepsLow <<= 1;
self.xLow.vHalveStepSize();
self.yLow.vHalveStepSize();
}
}
// This 'if' handles the case where the initial error for the Bezier
// is already less than the target error:
if ({self.cStepsHigh -= 1; self.cStepsHigh} != 0)
{
self.xHigh.vTakeStep();
self.yHigh.vTakeStep();
if (((self.xHigh.vError()) > geqErrorHigh) ||
((self.yHigh.vError()) > geqErrorHigh))
{
self.cStepsHigh <<= 1;
self.xHigh.vHalveStepSize();
self.yHigh.vHalveStepSize();
}
while (!(self.cStepsHigh & 1 != 0) &&
((self.xHigh.vParentError()) <= geqErrorHigh) &&
((self.yHigh.vParentError()) <= geqErrorHigh))
{
self.xHigh.vDoubleStepSize();
self.yHigh.vDoubleStepSize();
self.cStepsHigh >>= 1;
}
}
}
self.xLow.vTakeStep();
self.yLow.vTakeStep();
pptfx[0].x = self.xLow.fxValue();
pptfx[0].y = self.yLow.fxValue();
pptfx = &mut pptfx[1..];
self.cStepsLow-=1;
if (self.cStepsLow == 0 && self.cStepsHigh == 0)
{
*pbMore = false;
// '+1' because we haven't decremented 'cptfx' yet:
return(cptfxOriginal - cptfx + 1) as INT;
}
if ((self.xLow.vError() > self.eqErrorLow) ||
(self.yLow.vError() > self.eqErrorLow))
{
self.cStepsLow <<= 1;
self.xLow.vHalveStepSize();
self.yLow.vHalveStepSize();
}
while (!(self.cStepsLow & 1 != 0) &&
((self.xLow.vParentError()) <= self.eqErrorLow) &&
((self.yLow.vParentError()) <= self.eqErrorLow))
{
self.xLow.vDoubleStepSize();
self.yLow.vDoubleStepSize();
self.cStepsLow >>= 1;
}
cptfx -= 1;
cptfx != 0
} {};
*pbMore = true;
return(cptfxOriginal) as INT;
}
}
//+-----------------------------------------------------------------------------
//
// class CMILBezier
//
// Bezier cracker. Flattens any Bezier in our 28.4 device space down to a
// smallest 'error' of 2^-7 = 0.0078. Will use fast 32 bit cracker for small
// curves and slower 64 bit cracker for big curves.
//
// Public Interface:
// vInit(aptfx, prcfxClip, peqError)
// - pptfx points to 4 control points of Bezier. The first point
// retrieved by bNext() is the the first point in the approximation
// after the start-point.
//
// - prcfxClip is an optional pointer to the bound box of the visible
// region. This is used to optimize clipping of Bezier curves that
// won't be seen. Note that this value should account for the pen's
// width!
//
// - optional maximum error in 32.32 format, corresponding to Kirko's
// error factor.
//
// bNext(pptfx)
// - pptfx points to where next point in approximation will be
// returned. Returns FALSE if the point is the end-point of the
// curve.
//
pub (crate) enum CMILBezier
{
Bezier64(Bezier64),
Bezier32(Bezier32)
}
impl CMILBezier {
// All coordinates must be in 28.4 format:
pub fn new(aptfxBez: &[POINT; 4], prcfxClip: Option<&RECT>) -> Self {
let mut bez32 = Bezier32::default();
let bBez32 = bez32.bInit(aptfxBez, prcfxClip);
if bBez32 {
CMILBezier::Bezier32(bez32)
} else {
let mut bez64 = Bezier64::default();
bez64.vInit(aptfxBez, prcfxClip, geqErrorLow);
CMILBezier::Bezier64(bez64)
}
}
// Returns the number of points filled in. This will never be zero.
//
// The last point returned may not be exactly the last control
// point. The workaround is for calling code to add an extra
// point if this is the case.
pub fn Flatten( &mut self,
pptfx: &mut [POINT],
pbMore: &mut bool) -> INT {
match self {
CMILBezier::Bezier32(bez) => bez.cFlatten(pptfx, pbMore),
CMILBezier::Bezier64(bez) => bez.cFlatten(pptfx, pbMore)
}
}
}
#[test]
fn flatten() {
let curve: [POINT; 4] = [
POINT{x: 1715, y: 6506},
POINT{x: 1692, y: 6506},
POINT{x: 1227, y: 5148},
POINT{x: 647, y: 5211}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 32] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result, &mut more);
assert_eq!(count, 21);
assert_eq!(more, false);
}
#[test]
fn split_flatten32() {
// make sure that flattening a curve into two small buffers matches
// doing it into a large buffer
let curve: [POINT; 4] = [
POINT{x: 1795, y: 8445},
POINT{x: 1795, y: 8445},
POINT{x: 1908, y: 8683},
POINT{x: 2043, y: 8705}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 8] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result[..5], &mut more);
assert_eq!(count, 5);
assert_eq!(more, true);
let count = bez.Flatten(&mut result[5..], &mut more);
assert_eq!(count, 3);
assert_eq!(more, false);
let mut bez = CMILBezier::new(&curve, None);
let mut full_result: [POINT; 8] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut full_result, &mut more);
assert_eq!(count, 8);
assert_eq!(more, false);
assert!(result == full_result);
}
#[test]
fn flatten32() {
let curve: [POINT; 4] = [
POINT{x: 100, y: 100},
POINT{x: 110, y: 100},
POINT{x: 110, y: 110},
POINT{x: 110, y: 100}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 32] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result, &mut more);
assert_eq!(count, 3);
assert_eq!(more, false);
}
#[test]
fn flatten32_double_step_size() {
let curve: [POINT; 4] = [
POINT{x: 1761, y: 8152},
POINT{x: 1761, y: 8152},
POINT{x: 1750, y: 8355},
POINT{x: 1795, y: 8445}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 32] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result, &mut more);
assert_eq!(count, 7);
assert_eq!(more, false);
}
#[test]
fn bezier64_init_high_num_steps() {
let curve: [POINT; 4] = [
POINT{x: 33, y: -1},
POINT{x: -1, y: -1},
POINT{x: -1, y: -16385},
POINT{x: -226, y: 10}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 32] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result, &mut more);
assert_eq!(count, 32);
assert_eq!(more, true);
}
#[test]
fn bezier64_high_error() {
let curve: [POINT; 4] = [
POINT{x: -1, y: -1},
POINT{x: -4097, y: -1},
POINT{x: 65471, y: -256},
POINT{x: -1, y: 0}];
let mut bez = CMILBezier::new(&curve, None);
let mut result: [POINT; 32] = Default::default();
let mut more: bool = false;
let count = bez.Flatten(&mut result, &mut more);
assert_eq!(count, 32);
assert_eq!(more, true);
}