Change SkMatrix::fixedStepInX to return SkVector (of SkScalar) rather than SkFixed.

All users were immediately converting to SkScalar or SkFixed3232.

This method is not used in Chromium, Android, or Google3.

BUG=skia:4632
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1692013002

Review URL: https://codereview.chromium.org/1692013002

6 files changed, 24 insertions, 43 deletions

diff --git a/src/core/SkMatrix.cpp b/src/core/SkMatrix.cpp
index 7ae4ed21eb..f60ce85a6c 100644
--- a/src/core/SkMatrix.cpp
+++ b/src/core/SkMatrix.cpp
@@ -1150,30 +1150,19 @@ const SkMatrix::MapXYProc SkMatrix::gMapXYProcs[] = {
 // if its nearly zero (just made up 26, perhaps it should be bigger or smaller)
 #define PerspNearlyZero(x)  SkScalarNearlyZero(x, (1.0f / (1 << 26)))
 
-bool SkMatrix::fixedStepInX(SkScalar y, SkFixed* stepX, SkFixed* stepY) const {
-    if (PerspNearlyZero(fMat[kMPersp0])) {
-        if (stepX || stepY) {
-            if (PerspNearlyZero(fMat[kMPersp1]) &&
-                    PerspNearlyZero(fMat[kMPersp2] - 1)) {
-                if (stepX) {
-                    *stepX = SkScalarToFixed(fMat[kMScaleX]);
-                }
-                if (stepY) {
-                    *stepY = SkScalarToFixed(fMat[kMSkewY]);
-                }
-            } else {
-                SkScalar z = y * fMat[kMPersp1] + fMat[kMPersp2];
-                if (stepX) {
-                    *stepX = SkScalarToFixed(fMat[kMScaleX] / z);
-                }
-                if (stepY) {
-                    *stepY = SkScalarToFixed(fMat[kMSkewY] / z);
-                }
-            }
-        }
-        return true;
+bool SkMatrix::isFixedStepInX() const {
+  return PerspNearlyZero(fMat[kMPersp0]);
+}
+
+SkVector SkMatrix::fixedStepInX(SkScalar y) const {
+    SkASSERT(PerspNearlyZero(fMat[kMPersp0]));
+    if (PerspNearlyZero(fMat[kMPersp1]) &&
+        PerspNearlyZero(fMat[kMPersp2] - 1)) {
+        return SkVector::Make(fMat[kMScaleX], fMat[kMSkewY]);
+    } else {
+        SkScalar z = y * fMat[kMPersp1] + fMat[kMPersp2];
+        return SkVector::Make(fMat[kMScaleX] / z, fMat[kMSkewY] / z);
     }
-    return false;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -1800,4 +1789,3 @@ void SkRSXform::toQuad(SkScalar width, SkScalar height, SkPoint quad[4]) const {
     quad[3].set(m01 * height + m02, m11 * height + m12);
 #endif
 }
-
diff --git a/src/core/SkShader.cpp b/src/core/SkShader.cpp
index 4b5dc5dc06..20402a973d 100644
--- a/src/core/SkShader.cpp
+++ b/src/core/SkShader.cpp
@@ -201,7 +201,7 @@ SkShader::Context::MatrixClass SkShader::Context::ComputeMatrixClass(const SkMat
     MatrixClass mc = kLinear_MatrixClass;
 
     if (mat.hasPerspective()) {
-        if (mat.fixedStepInX(0, nullptr, nullptr)) {
+        if (mat.isFixedStepInX()) {
             mc = kFixedStepInX_MatrixClass;
         } else {
             mc = kPerspective_MatrixClass;
diff --git a/src/effects/gradients/SkLinearGradient.cpp b/src/effects/gradients/SkLinearGradient.cpp
index 4a27a35de4..a1abe543c6 100644
--- a/src/effects/gradients/SkLinearGradient.cpp
+++ b/src/effects/gradients/SkLinearGradient.cpp
@@ -287,10 +287,9 @@ void SkLinearGradient::LinearGradientContext::shadeSpan(int x, int y, SkPMColor*
         SkGradFixed dx, fx = SkScalarToGradFixed(srcPt.fX);
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
-            SkFixed dxStorage[1];
-            (void)fDstToIndex.fixedStepInX(SkIntToScalar(y), dxStorage, nullptr);
+            const auto step = fDstToIndex.fixedStepInX(SkIntToScalar(y));
             // todo: do we need a real/high-precision value for dx here?
-            dx = SkFixedToGradFixed(dxStorage[0]);
+            dx = SkScalarToGradFixed(step.fX);
         } else {
             SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
             dx = SkScalarToGradFixed(fDstToIndex.getScaleX());
@@ -747,4 +746,3 @@ void SkLinearGradient::LinearGradientContext::shade4_clamp(int x, int y, SkPMCol
         }
     }
 }
-
diff --git a/src/effects/gradients/SkRadialGradient.cpp b/src/effects/gradients/SkRadialGradient.cpp
index 7e7ac7a406..020c25ec46 100644
--- a/src/effects/gradients/SkRadialGradient.cpp
+++ b/src/effects/gradients/SkRadialGradient.cpp
@@ -206,11 +206,9 @@ void SkRadialGradient::RadialGradientContext::shadeSpan(int x, int y,
         SkScalar sdy = fDstToIndex.getSkewY();
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
-            SkFixed storage[2];
-            (void)fDstToIndex.fixedStepInX(SkIntToScalar(y),
-                                           &storage[0], &storage[1]);
-            sdx = SkFixedToScalar(storage[0]);
-            sdy = SkFixedToScalar(storage[1]);
+            const auto step = fDstToIndex.fixedStepInX(SkIntToScalar(y));
+            sdx = step.fX;
+            sdy = step.fY;
         } else {
             SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
         }
diff --git a/src/effects/gradients/SkSweepGradient.cpp b/src/effects/gradients/SkSweepGradient.cpp
index ddff882e38..94686524ed 100644
--- a/src/effects/gradients/SkSweepGradient.cpp
+++ b/src/effects/gradients/SkSweepGradient.cpp
@@ -92,11 +92,9 @@ void SkSweepGradient::SweepGradientContext::shadeSpan(int x, int y, SkPMColor* S
         SkScalar dy, fy = srcPt.fY;
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
-            SkFixed storage[2];
-            (void)matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf,
-                                      &storage[0], &storage[1]);
-            dx = SkFixedToScalar(storage[0]);
-            dy = SkFixedToScalar(storage[1]);
+            const auto step = matrix.fixedStepInX(SkIntToScalar(y) + SK_ScalarHalf);
+            dx = step.fX;
+            dy = step.fY;
         } else {
             SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
             dx = matrix.getScaleX();
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.cpp b/src/effects/gradients/SkTwoPointConicalGradient.cpp
index 918f2e06dd..b7c95bc809 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.cpp
+++ b/src/effects/gradients/SkTwoPointConicalGradient.cpp
@@ -261,10 +261,9 @@ void SkTwoPointConicalGradient::TwoPointConicalGradientContext::shadeSpan(
         SkScalar dy, fy = srcPt.fY;
 
         if (fDstToIndexClass == kFixedStepInX_MatrixClass) {
-            SkFixed fixedX, fixedY;
-            (void)fDstToIndex.fixedStepInX(SkIntToScalar(y), &fixedX, &fixedY);
-            dx = SkFixedToScalar(fixedX);
-            dy = SkFixedToScalar(fixedY);
+            const auto step = fDstToIndex.fixedStepInX(SkIntToScalar(y));
+            dx = step.fX;
+            dy = step.fY;
         } else {
             SkASSERT(fDstToIndexClass == kLinear_MatrixClass);
             dx = fDstToIndex.getScaleX();