Add some additional checks for shadow generation

Change-Id: I4dae4173ad879827e4e1fa3ad12aa0447d1df252
Reviewed-on: https://skia-review.googlesource.com/110360
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>

2 files changed, 16 insertions, 1 deletions

diff --git a/src/utils/SkShadowTessellator.cpp b/src/utils/SkShadowTessellator.cpp
index 11e8f2d5c6..57bf5851fa 100755
--- a/src/utils/SkShadowTessellator.cpp
+++ b/src/utils/SkShadowTessellator.cpp
@@ -177,6 +177,12 @@ void SkBaseShadowTessellator::handleLine(const SkMatrix& m, SkPoint* p) {
 
 void SkBaseShadowTessellator::handleQuad(const SkPoint pts[3]) {
 #if SK_SUPPORT_GPU
+    // check for degeneracy
+    SkVector v0 = pts[1] - pts[0];
+    SkVector v1 = pts[2] - pts[0];
+    if (SkScalarNearlyZero(v0.cross(v1))) {
+        return;
+    }
     // TODO: Pull PathUtils out of Ganesh?
     int maxCount = GrPathUtils::quadraticPointCount(pts, kQuadTolerance);
     fPointBuffer.setReserve(maxCount);
@@ -277,7 +283,7 @@ bool SkBaseShadowTessellator::setTransformedHeightFunc(const SkMatrix& ctm) {
         };
     } else {
         SkMatrix ctmInverse;
-        if (!ctm.invert(&ctmInverse)) {
+        if (!ctm.invert(&ctmInverse) || !ctmInverse.isFinite()) {
             return false;
         }
         // multiply by transpose
diff --git a/src/utils/SkShadowUtils.cpp b/src/utils/SkShadowUtils.cpp
index fcb3432450..b2f50ad40d 100644
--- a/src/utils/SkShadowUtils.cpp
+++ b/src/utils/SkShadowUtils.cpp
@@ -535,6 +535,11 @@ void SkShadowUtils::DrawShadow(SkCanvas* canvas, const SkPath& path, const SkPoi
     canvas->private_draw_shadow_rec(path, rec);
 }
 
+static bool validate_rec(const SkDrawShadowRec& rec) {
+    return rec.fLightPos.isFinite() && rec.fZPlaneParams.isFinite() &&
+           SkScalarIsFinite(rec.fLightRadius);
+}
+
 void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
     auto drawVertsProc = [this](const SkVertices* vertices, SkBlendMode mode, const SkPaint& paint,
                                 SkScalar tx, SkScalar ty) {
@@ -543,6 +548,10 @@ void SkBaseDevice::drawShadow(const SkPath& path, const SkDrawShadowRec& rec) {
         this->drawVertices(vertices, mode, paint);
     };
 
+    if (!validate_rec(rec)) {
+        return;
+    }
+
     SkMatrix viewMatrix = this->ctm();
     SkAutoDeviceCTMRestore adr(this, SkMatrix::I());