| /* |
| * Copyright 2009 The Android Open Source Project |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "include/private/SkMacros.h" |
| #include "src/core/SkEdgeClipper.h" |
| #include "src/core/SkGeometry.h" |
| #include "src/core/SkLineClipper.h" |
| |
| #include <utility> |
| |
| static bool quick_reject(const SkRect& bounds, const SkRect& clip) { |
| return bounds.fTop >= clip.fBottom || bounds.fBottom <= clip.fTop; |
| } |
| |
| static inline void clamp_le(SkScalar& value, SkScalar max) { |
| if (value > max) { |
| value = max; |
| } |
| } |
| |
| static inline void clamp_ge(SkScalar& value, SkScalar min) { |
| if (value < min) { |
| value = min; |
| } |
| } |
| |
| /* src[] must be monotonic in Y. This routine copies src into dst, and sorts |
| it to be increasing in Y. If it had to reverse the order of the points, |
| it returns true, otherwise it returns false |
| */ |
| static bool sort_increasing_Y(SkPoint dst[], const SkPoint src[], int count) { |
| // we need the data to be monotonically increasing in Y |
| if (src[0].fY > src[count - 1].fY) { |
| for (int i = 0; i < count; i++) { |
| dst[i] = src[count - i - 1]; |
| } |
| return true; |
| } else { |
| memcpy(dst, src, count * sizeof(SkPoint)); |
| return false; |
| } |
| } |
| |
| bool SkEdgeClipper::clipLine(SkPoint p0, SkPoint p1, const SkRect& clip) { |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| |
| SkPoint lines[SkLineClipper::kMaxPoints]; |
| const SkPoint pts[] = { p0, p1 }; |
| int lineCount = SkLineClipper::ClipLine(pts, clip, lines, fCanCullToTheRight); |
| for (int i = 0; i < lineCount; i++) { |
| this->appendLine(lines[i], lines[i + 1]); |
| } |
| |
| *fCurrVerb = SkPath::kDone_Verb; |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| return SkPath::kDone_Verb != fVerbs[0]; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| static bool chopMonoQuadAt(SkScalar c0, SkScalar c1, SkScalar c2, |
| SkScalar target, SkScalar* t) { |
| /* Solve F(t) = y where F(t) := [0](1-t)^2 + 2[1]t(1-t) + [2]t^2 |
| * We solve for t, using quadratic equation, hence we have to rearrange |
| * our cooefficents to look like At^2 + Bt + C |
| */ |
| SkScalar A = c0 - c1 - c1 + c2; |
| SkScalar B = 2*(c1 - c0); |
| SkScalar C = c0 - target; |
| |
| SkScalar roots[2]; // we only expect one, but make room for 2 for safety |
| int count = SkFindUnitQuadRoots(A, B, C, roots); |
| if (count) { |
| *t = roots[0]; |
| return true; |
| } |
| return false; |
| } |
| |
| static bool chopMonoQuadAtY(SkPoint pts[3], SkScalar y, SkScalar* t) { |
| return chopMonoQuadAt(pts[0].fY, pts[1].fY, pts[2].fY, y, t); |
| } |
| |
| static bool chopMonoQuadAtX(SkPoint pts[3], SkScalar x, SkScalar* t) { |
| return chopMonoQuadAt(pts[0].fX, pts[1].fX, pts[2].fX, x, t); |
| } |
| |
| // Modify pts[] in place so that it is clipped in Y to the clip rect |
| static void chop_quad_in_Y(SkPoint pts[3], const SkRect& clip) { |
| SkScalar t; |
| SkPoint tmp[5]; // for SkChopQuadAt |
| |
| // are we partially above |
| if (pts[0].fY < clip.fTop) { |
| if (chopMonoQuadAtY(pts, clip.fTop, &t)) { |
| // take the 2nd chopped quad |
| SkChopQuadAt(pts, tmp, t); |
| // clamp to clean up imprecise numerics in the chop |
| tmp[2].fY = clip.fTop; |
| clamp_ge(tmp[3].fY, clip.fTop); |
| |
| pts[0] = tmp[2]; |
| pts[1] = tmp[3]; |
| } else { |
| // if chopMonoQuadAtY failed, then we may have hit inexact numerics |
| // so we just clamp against the top |
| for (int i = 0; i < 3; i++) { |
| if (pts[i].fY < clip.fTop) { |
| pts[i].fY = clip.fTop; |
| } |
| } |
| } |
| } |
| |
| // are we partially below |
| if (pts[2].fY > clip.fBottom) { |
| if (chopMonoQuadAtY(pts, clip.fBottom, &t)) { |
| SkChopQuadAt(pts, tmp, t); |
| // clamp to clean up imprecise numerics in the chop |
| clamp_le(tmp[1].fY, clip.fBottom); |
| tmp[2].fY = clip.fBottom; |
| |
| pts[1] = tmp[1]; |
| pts[2] = tmp[2]; |
| } else { |
| // if chopMonoQuadAtY failed, then we may have hit inexact numerics |
| // so we just clamp against the bottom |
| for (int i = 0; i < 3; i++) { |
| if (pts[i].fY > clip.fBottom) { |
| pts[i].fY = clip.fBottom; |
| } |
| } |
| } |
| } |
| } |
| |
| // srcPts[] must be monotonic in X and Y |
| void SkEdgeClipper::clipMonoQuad(const SkPoint srcPts[3], const SkRect& clip) { |
| SkPoint pts[3]; |
| bool reverse = sort_increasing_Y(pts, srcPts, 3); |
| |
| // are we completely above or below |
| if (pts[2].fY <= clip.fTop || pts[0].fY >= clip.fBottom) { |
| return; |
| } |
| |
| // Now chop so that pts is contained within clip in Y |
| chop_quad_in_Y(pts, clip); |
| |
| if (pts[0].fX > pts[2].fX) { |
| using std::swap; |
| swap(pts[0], pts[2]); |
| reverse = !reverse; |
| } |
| SkASSERT(pts[0].fX <= pts[1].fX); |
| SkASSERT(pts[1].fX <= pts[2].fX); |
| |
| // Now chop in X has needed, and record the segments |
| |
| if (pts[2].fX <= clip.fLeft) { // wholly to the left |
| this->appendVLine(clip.fLeft, pts[0].fY, pts[2].fY, reverse); |
| return; |
| } |
| if (pts[0].fX >= clip.fRight) { // wholly to the right |
| if (!this->canCullToTheRight()) { |
| this->appendVLine(clip.fRight, pts[0].fY, pts[2].fY, reverse); |
| } |
| return; |
| } |
| |
| SkScalar t; |
| SkPoint tmp[5]; // for SkChopQuadAt |
| |
| // are we partially to the left |
| if (pts[0].fX < clip.fLeft) { |
| if (chopMonoQuadAtX(pts, clip.fLeft, &t)) { |
| SkChopQuadAt(pts, tmp, t); |
| this->appendVLine(clip.fLeft, tmp[0].fY, tmp[2].fY, reverse); |
| // clamp to clean up imprecise numerics in the chop |
| tmp[2].fX = clip.fLeft; |
| clamp_ge(tmp[3].fX, clip.fLeft); |
| |
| pts[0] = tmp[2]; |
| pts[1] = tmp[3]; |
| } else { |
| // if chopMonoQuadAtY failed, then we may have hit inexact numerics |
| // so we just clamp against the left |
| this->appendVLine(clip.fLeft, pts[0].fY, pts[2].fY, reverse); |
| return; |
| } |
| } |
| |
| // are we partially to the right |
| if (pts[2].fX > clip.fRight) { |
| if (chopMonoQuadAtX(pts, clip.fRight, &t)) { |
| SkChopQuadAt(pts, tmp, t); |
| // clamp to clean up imprecise numerics in the chop |
| clamp_le(tmp[1].fX, clip.fRight); |
| tmp[2].fX = clip.fRight; |
| |
| this->appendQuad(tmp, reverse); |
| this->appendVLine(clip.fRight, tmp[2].fY, tmp[4].fY, reverse); |
| } else { |
| // if chopMonoQuadAtY failed, then we may have hit inexact numerics |
| // so we just clamp against the right |
| this->appendVLine(clip.fRight, pts[0].fY, pts[2].fY, reverse); |
| } |
| } else { // wholly inside the clip |
| this->appendQuad(pts, reverse); |
| } |
| } |
| |
| bool SkEdgeClipper::clipQuad(const SkPoint srcPts[3], const SkRect& clip) { |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| |
| SkRect bounds; |
| bounds.set(srcPts, 3); |
| |
| if (!quick_reject(bounds, clip)) { |
| SkPoint monoY[5]; |
| int countY = SkChopQuadAtYExtrema(srcPts, monoY); |
| for (int y = 0; y <= countY; y++) { |
| SkPoint monoX[5]; |
| int countX = SkChopQuadAtXExtrema(&monoY[y * 2], monoX); |
| for (int x = 0; x <= countX; x++) { |
| this->clipMonoQuad(&monoX[x * 2], clip); |
| SkASSERT(fCurrVerb - fVerbs < kMaxVerbs); |
| SkASSERT(fCurrPoint - fPoints <= kMaxPoints); |
| } |
| } |
| } |
| |
| *fCurrVerb = SkPath::kDone_Verb; |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| return SkPath::kDone_Verb != fVerbs[0]; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| static SkScalar mono_cubic_closestT(const SkScalar src[], SkScalar x) { |
| SkScalar t = 0.5f; |
| SkScalar lastT; |
| SkScalar bestT SK_INIT_TO_AVOID_WARNING; |
| SkScalar step = 0.25f; |
| SkScalar D = src[0]; |
| SkScalar A = src[6] + 3*(src[2] - src[4]) - D; |
| SkScalar B = 3*(src[4] - src[2] - src[2] + D); |
| SkScalar C = 3*(src[2] - D); |
| x -= D; |
| SkScalar closest = SK_ScalarMax; |
| do { |
| SkScalar loc = ((A * t + B) * t + C) * t; |
| SkScalar dist = SkScalarAbs(loc - x); |
| if (closest > dist) { |
| closest = dist; |
| bestT = t; |
| } |
| lastT = t; |
| t += loc < x ? step : -step; |
| step *= 0.5f; |
| } while (closest > 0.25f && lastT != t); |
| return bestT; |
| } |
| |
| static void chop_mono_cubic_at_y(SkPoint src[4], SkScalar y, SkPoint dst[7]) { |
| if (SkChopMonoCubicAtY(src, y, dst)) { |
| return; |
| } |
| SkChopCubicAt(src, dst, mono_cubic_closestT(&src->fY, y)); |
| } |
| |
| // Modify pts[] in place so that it is clipped in Y to the clip rect |
| static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) { |
| |
| // are we partially above |
| if (pts[0].fY < clip.fTop) { |
| SkPoint tmp[7]; |
| chop_mono_cubic_at_y(pts, clip.fTop, tmp); |
| |
| /* |
| * For a large range in the points, we can do a poor job of chopping, such that the t |
| * we computed resulted in the lower cubic still being partly above the clip. |
| * |
| * If just the first or first 2 Y values are above the fTop, we can just smash them |
| * down. If the first 3 Ys are above fTop, we can't smash all 3, as that can really |
| * distort the cubic. In this case, we take the first output (tmp[3..6] and treat it as |
| * a guess, and re-chop against fTop. Then we fall through to checking if we need to |
| * smash the first 1 or 2 Y values. |
| */ |
| if (tmp[3].fY < clip.fTop && tmp[4].fY < clip.fTop && tmp[5].fY < clip.fTop) { |
| SkPoint tmp2[4]; |
| memcpy(tmp2, &tmp[3].fX, 4 * sizeof(SkPoint)); |
| chop_mono_cubic_at_y(tmp2, clip.fTop, tmp); |
| } |
| |
| // tmp[3, 4].fY should all be to the below clip.fTop. |
| // Since we can't trust the numerics of the chopper, we force those conditions now |
| tmp[3].fY = clip.fTop; |
| clamp_ge(tmp[4].fY, clip.fTop); |
| |
| pts[0] = tmp[3]; |
| pts[1] = tmp[4]; |
| pts[2] = tmp[5]; |
| } |
| |
| // are we partially below |
| if (pts[3].fY > clip.fBottom) { |
| SkPoint tmp[7]; |
| chop_mono_cubic_at_y(pts, clip.fBottom, tmp); |
| tmp[3].fY = clip.fBottom; |
| clamp_le(tmp[2].fY, clip.fBottom); |
| |
| pts[1] = tmp[1]; |
| pts[2] = tmp[2]; |
| pts[3] = tmp[3]; |
| } |
| } |
| |
| static void chop_mono_cubic_at_x(SkPoint src[4], SkScalar x, SkPoint dst[7]) { |
| if (SkChopMonoCubicAtX(src, x, dst)) { |
| return; |
| } |
| SkChopCubicAt(src, dst, mono_cubic_closestT(&src->fX, x)); |
| } |
| |
| // srcPts[] must be monotonic in X and Y |
| void SkEdgeClipper::clipMonoCubic(const SkPoint src[4], const SkRect& clip) { |
| SkPoint pts[4]; |
| bool reverse = sort_increasing_Y(pts, src, 4); |
| |
| // are we completely above or below |
| if (pts[3].fY <= clip.fTop || pts[0].fY >= clip.fBottom) { |
| return; |
| } |
| |
| // Now chop so that pts is contained within clip in Y |
| chop_cubic_in_Y(pts, clip); |
| |
| if (pts[0].fX > pts[3].fX) { |
| using std::swap; |
| swap(pts[0], pts[3]); |
| swap(pts[1], pts[2]); |
| reverse = !reverse; |
| } |
| |
| // Now chop in X has needed, and record the segments |
| |
| if (pts[3].fX <= clip.fLeft) { // wholly to the left |
| this->appendVLine(clip.fLeft, pts[0].fY, pts[3].fY, reverse); |
| return; |
| } |
| if (pts[0].fX >= clip.fRight) { // wholly to the right |
| if (!this->canCullToTheRight()) { |
| this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse); |
| } |
| return; |
| } |
| |
| // are we partially to the left |
| if (pts[0].fX < clip.fLeft) { |
| SkPoint tmp[7]; |
| chop_mono_cubic_at_x(pts, clip.fLeft, tmp); |
| this->appendVLine(clip.fLeft, tmp[0].fY, tmp[3].fY, reverse); |
| |
| // tmp[3, 4].fX should all be to the right of clip.fLeft. |
| // Since we can't trust the numerics of |
| // the chopper, we force those conditions now |
| tmp[3].fX = clip.fLeft; |
| clamp_ge(tmp[4].fX, clip.fLeft); |
| |
| pts[0] = tmp[3]; |
| pts[1] = tmp[4]; |
| pts[2] = tmp[5]; |
| } |
| |
| // are we partially to the right |
| if (pts[3].fX > clip.fRight) { |
| SkPoint tmp[7]; |
| chop_mono_cubic_at_x(pts, clip.fRight, tmp); |
| tmp[3].fX = clip.fRight; |
| clamp_le(tmp[2].fX, clip.fRight); |
| |
| this->appendCubic(tmp, reverse); |
| this->appendVLine(clip.fRight, tmp[3].fY, tmp[6].fY, reverse); |
| } else { // wholly inside the clip |
| this->appendCubic(pts, reverse); |
| } |
| } |
| |
| static SkRect compute_cubic_bounds(const SkPoint pts[4]) { |
| SkRect r; |
| r.set(pts, 4); |
| return r; |
| } |
| |
| static bool too_big_for_reliable_float_math(const SkRect& r) { |
| // limit set as the largest float value for which we can still reliably compute things like |
| // - chopping at XY extrema |
| // - chopping at Y or X values for clipping |
| // |
| // Current value chosen just by experiment. Larger (and still succeeds) is always better. |
| // |
| const SkScalar limit = 1 << 22; |
| return r.fLeft < -limit || r.fTop < -limit || r.fRight > limit || r.fBottom > limit; |
| } |
| |
| bool SkEdgeClipper::clipCubic(const SkPoint srcPts[4], const SkRect& clip) { |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| |
| const SkRect bounds = compute_cubic_bounds(srcPts); |
| // check if we're clipped out vertically |
| if (bounds.fBottom > clip.fTop && bounds.fTop < clip.fBottom) { |
| if (too_big_for_reliable_float_math(bounds)) { |
| // can't safely clip the cubic, so we give up and draw a line (which we can safely clip) |
| // |
| // If we rewrote chopcubicat*extrema and chopmonocubic using doubles, we could very |
| // likely always handle the cubic safely, but (it seems) at a big loss in speed, so |
| // we'd only want to take that alternate impl if needed. Perhaps a TODO to try it. |
| // |
| return this->clipLine(srcPts[0], srcPts[3], clip); |
| } else { |
| SkPoint monoY[10]; |
| int countY = SkChopCubicAtYExtrema(srcPts, monoY); |
| for (int y = 0; y <= countY; y++) { |
| SkPoint monoX[10]; |
| int countX = SkChopCubicAtXExtrema(&monoY[y * 3], monoX); |
| for (int x = 0; x <= countX; x++) { |
| this->clipMonoCubic(&monoX[x * 3], clip); |
| SkASSERT(fCurrVerb - fVerbs < kMaxVerbs); |
| SkASSERT(fCurrPoint - fPoints <= kMaxPoints); |
| } |
| } |
| } |
| } |
| |
| *fCurrVerb = SkPath::kDone_Verb; |
| fCurrPoint = fPoints; |
| fCurrVerb = fVerbs; |
| return SkPath::kDone_Verb != fVerbs[0]; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| void SkEdgeClipper::appendLine(SkPoint p0, SkPoint p1) { |
| *fCurrVerb++ = SkPath::kLine_Verb; |
| fCurrPoint[0] = p0; |
| fCurrPoint[1] = p1; |
| fCurrPoint += 2; |
| } |
| |
| void SkEdgeClipper::appendVLine(SkScalar x, SkScalar y0, SkScalar y1, bool reverse) { |
| *fCurrVerb++ = SkPath::kLine_Verb; |
| |
| if (reverse) { |
| using std::swap; |
| swap(y0, y1); |
| } |
| fCurrPoint[0].set(x, y0); |
| fCurrPoint[1].set(x, y1); |
| fCurrPoint += 2; |
| } |
| |
| void SkEdgeClipper::appendQuad(const SkPoint pts[3], bool reverse) { |
| *fCurrVerb++ = SkPath::kQuad_Verb; |
| |
| if (reverse) { |
| fCurrPoint[0] = pts[2]; |
| fCurrPoint[2] = pts[0]; |
| } else { |
| fCurrPoint[0] = pts[0]; |
| fCurrPoint[2] = pts[2]; |
| } |
| fCurrPoint[1] = pts[1]; |
| fCurrPoint += 3; |
| } |
| |
| void SkEdgeClipper::appendCubic(const SkPoint pts[4], bool reverse) { |
| *fCurrVerb++ = SkPath::kCubic_Verb; |
| |
| if (reverse) { |
| for (int i = 0; i < 4; i++) { |
| fCurrPoint[i] = pts[3 - i]; |
| } |
| } else { |
| memcpy(fCurrPoint, pts, 4 * sizeof(SkPoint)); |
| } |
| fCurrPoint += 4; |
| } |
| |
| SkPath::Verb SkEdgeClipper::next(SkPoint pts[]) { |
| SkPath::Verb verb = *fCurrVerb; |
| |
| switch (verb) { |
| case SkPath::kLine_Verb: |
| memcpy(pts, fCurrPoint, 2 * sizeof(SkPoint)); |
| fCurrPoint += 2; |
| fCurrVerb += 1; |
| break; |
| case SkPath::kQuad_Verb: |
| memcpy(pts, fCurrPoint, 3 * sizeof(SkPoint)); |
| fCurrPoint += 3; |
| fCurrVerb += 1; |
| break; |
| case SkPath::kCubic_Verb: |
| memcpy(pts, fCurrPoint, 4 * sizeof(SkPoint)); |
| fCurrPoint += 4; |
| fCurrVerb += 1; |
| break; |
| case SkPath::kDone_Verb: |
| break; |
| default: |
| SkDEBUGFAIL("unexpected verb in quadclippper2 iter"); |
| break; |
| } |
| return verb; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| #ifdef SK_DEBUG |
| static void assert_monotonic(const SkScalar coord[], int count) { |
| if (coord[0] > coord[(count - 1) * 2]) { |
| for (int i = 1; i < count; i++) { |
| SkASSERT(coord[2 * (i - 1)] >= coord[i * 2]); |
| } |
| } else if (coord[0] < coord[(count - 1) * 2]) { |
| for (int i = 1; i < count; i++) { |
| SkASSERT(coord[2 * (i - 1)] <= coord[i * 2]); |
| } |
| } else { |
| for (int i = 1; i < count; i++) { |
| SkASSERT(coord[2 * (i - 1)] == coord[i * 2]); |
| } |
| } |
| } |
| |
| void sk_assert_monotonic_y(const SkPoint pts[], int count) { |
| if (count > 1) { |
| assert_monotonic(&pts[0].fY, count); |
| } |
| } |
| |
| void sk_assert_monotonic_x(const SkPoint pts[], int count) { |
| if (count > 1) { |
| assert_monotonic(&pts[0].fX, count); |
| } |
| } |
| #endif |
