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-rw-r--r--src/core/SkEdgeClipper.cpp508
1 files changed, 508 insertions, 0 deletions
diff --git a/src/core/SkEdgeClipper.cpp b/src/core/SkEdgeClipper.cpp
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+++ b/src/core/SkEdgeClipper.cpp
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+/*
+ * Copyright (C) 2009 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "SkEdgeClipper.h"
+#include "SkGeometry.h"
+
+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;
+ }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+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_ge(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_le(tmp[1].fY, clip.fBottom);
+ clamp_le(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) {
+ SkTSwap<SkPoint>(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
+ 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_ge(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);
+ }
+ }
+
+ // are we partially to the right
+ if (pts[2].fX > clip.fRight) {
+ if (chopMonoQuadAtX(pts, clip.fRight, &t)) {
+ SkChopQuadAt(pts, tmp, t);
+ clamp_le(tmp[1].fX, clip.fRight);
+ clamp_le(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[3].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 eval_cubic_coeff(SkScalar A, SkScalar B, SkScalar C,
+ SkScalar D, SkScalar t) {
+ return SkScalarMulAdd(SkScalarMulAdd(SkScalarMulAdd(A, t, B), t, C), t, D);
+}
+
+/* Given 4 cubic points (either Xs or Ys), and a target X or Y, compute the
+ t value such that cubic(t) = target
+ */
+static bool chopMonoCubicAt(SkScalar c0, SkScalar c1, SkScalar c2, SkScalar c3,
+ SkScalar target, SkScalar* t) {
+ // SkASSERT(c0 <= c1 && c1 <= c2 && c2 <= c3);
+ SkASSERT(c0 < target && target < c3);
+
+ SkScalar D = c0;
+ SkScalar A = c3 + 3*(c1 - c2) - c0;
+ SkScalar B = 3*(c2 - c1 - c1 + c0);
+ SkScalar C = 3*(c1 - c0);
+
+ SkScalar minT = 0;
+ SkScalar maxT = SK_Scalar1;
+ for (int i = 0; i < 8; i++) {
+ SkScalar mid = SkScalarAve(minT, maxT);
+ SkScalar coord = eval_cubic_coeff(A, B, C, D, mid);
+ if (coord < target) {
+ minT = mid;
+ } else {
+ maxT = mid;
+ }
+ }
+ *t = SkScalarAve(minT, maxT);
+ return true;
+}
+
+static bool chopMonoCubicAtY(SkPoint pts[4], SkScalar y, SkScalar* t) {
+ return chopMonoCubicAt(pts[0].fY, pts[1].fY, pts[2].fY, pts[3].fY, y, t);
+}
+
+static bool chopMonoCubicAtX(SkPoint pts[4], SkScalar x, SkScalar* t) {
+ return chopMonoCubicAt(pts[0].fX, pts[1].fX, pts[2].fX, pts[3].fX, x, t);
+}
+
+// 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) {
+ SkScalar t;
+ SkPoint tmp[7]; // for SkChopCubicAt
+
+ // are we partially above
+ if (pts[0].fY < clip.fTop) {
+ if (chopMonoCubicAtY(pts, clip.fTop, &t)) {
+ SkChopCubicAt(pts, tmp, t);
+ clamp_ge(tmp[3].fY, clip.fTop);
+ clamp_ge(tmp[4].fY, clip.fTop);
+ clamp_ge(tmp[5].fY, clip.fTop);
+ pts[0] = tmp[3];
+ pts[1] = tmp[4];
+ pts[2] = tmp[5];
+ } else {
+ // if chopMonoCubicAtY failed, then we may have hit inexact numerics
+ // so we just clamp against the top
+ for (int i = 0; i < 4; i++) {
+ clamp_ge(pts[i].fY, clip.fTop);
+ }
+ }
+ }
+
+ // are we partially below
+ if (pts[3].fY > clip.fBottom) {
+ if (chopMonoCubicAtY(pts, clip.fBottom, &t)) {
+ SkChopCubicAt(pts, tmp, t);
+ clamp_le(tmp[1].fY, clip.fBottom);
+ clamp_le(tmp[2].fY, clip.fBottom);
+ clamp_le(tmp[3].fY, clip.fBottom);
+ pts[1] = tmp[1];
+ pts[2] = tmp[2];
+ pts[3] = tmp[3];
+ } else {
+ // if chopMonoCubicAtY failed, then we may have hit inexact numerics
+ // so we just clamp against the bottom
+ for (int i = 0; i < 4; i++) {
+ clamp_le(pts[i].fY, clip.fBottom);
+ }
+ }
+ }
+}
+
+// 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) {
+ SkTSwap<SkPoint>(pts[0], pts[3]);
+ SkTSwap<SkPoint>(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
+ this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse);
+ return;
+ }
+
+ SkScalar t;
+ SkPoint tmp[7];
+
+ // are we partially to the left
+ if (pts[0].fX < clip.fLeft) {
+ if (chopMonoCubicAtX(pts, clip.fLeft, &t)) {
+ SkChopCubicAt(pts, tmp, t);
+ this->appendVLine(clip.fLeft, tmp[0].fY, tmp[3].fY, reverse);
+ clamp_ge(tmp[3].fX, clip.fLeft);
+ clamp_ge(tmp[4].fX, clip.fLeft);
+ clamp_ge(tmp[5].fX, clip.fLeft);
+ pts[0] = tmp[3];
+ pts[1] = tmp[4];
+ pts[2] = tmp[5];
+ } else {
+ // if chopMonocubicAtY failed, then we may have hit inexact numerics
+ // so we just clamp against the left
+ this->appendVLine(clip.fLeft, pts[0].fY, pts[3].fY, reverse);
+ }
+ }
+
+ // are we partially to the right
+ if (pts[3].fX > clip.fRight) {
+ if (chopMonoCubicAtX(pts, clip.fRight, &t)) {
+ SkChopCubicAt(pts, tmp, t);
+ clamp_le(tmp[1].fX, clip.fRight);
+ clamp_le(tmp[2].fX, clip.fRight);
+ clamp_le(tmp[3].fX, clip.fRight);
+ this->appendCubic(tmp, reverse);
+ this->appendVLine(clip.fRight, tmp[3].fY, tmp[6].fY, reverse);
+ } else {
+ // if chopMonoCubicAtX failed, then we may have hit inexact numerics
+ // so we just clamp against the right
+ this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse);
+ }
+ } else { // wholly inside the clip
+ this->appendCubic(pts, reverse);
+ }
+}
+
+bool SkEdgeClipper::clipCubic(const SkPoint srcPts[4], const SkRect& clip) {
+ fCurrPoint = fPoints;
+ fCurrVerb = fVerbs;
+
+ SkRect bounds;
+ bounds.set(srcPts, 4);
+
+ if (!quick_reject(bounds, clip)) {
+ SkPoint monoY[10];
+ int countY = SkChopCubicAtYExtrema(srcPts, monoY);
+ for (int y = 0; y <= countY; y++) {
+ // sk_assert_monotonic_y(&monoY[y * 3], 4);
+ SkPoint monoX[10];
+ int countX = SkChopCubicAtXExtrema(&monoY[y * 3], monoX);
+ for (int x = 0; x <= countX; x++) {
+ // sk_assert_monotonic_y(&monoX[x * 3], 4);
+ // sk_assert_monotonic_x(&monoX[x * 3], 4);
+ 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::appendVLine(SkScalar x, SkScalar y0, SkScalar y1,
+ bool reverse) {
+ *fCurrVerb++ = SkPath::kLine_Verb;
+
+ if (reverse) {
+ SkTSwap<SkScalar>(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:
+ SkASSERT(!"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
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