From da379fdf722dc5df60caefed012952117a5ce4b4 Mon Sep 17 00:00:00 2001
From: Kaylee Lubick <[email protected]>
Date: Tue, 16 Jun 2026 16:59:17 -0400
Subject: [PATCH] Handle w<=0 conics

SkPath had special logic for degenerate conics [1] and SkGeometry
has an assumption of positive weights [2][3] (possibly other places
too), so this restores that logic to turn it into a lineTo.

[1] https://github.com/google/skia/blob/19936eb1b23fef5187b07fb2e0e67dcf605c0672/src/core/SkPath.cpp#L754-L756
[2] https://github.com/google/skia/blob/d7196b0b493925df3be1e259f41a3c6678732b45/src/core/SkGeometry.h#L350
[3] https://review.skia.org/667436
[4] https://review.skia.org/1225597

Bug: 520506316
Change-Id: I6946e755c5cacade8a487bc882ba0ce5e34531a1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/1267718
Auto-Submit: Kaylee Lubick <[email protected]>
Commit-Queue: Florin Malita <[email protected]>
Reviewed-by: Florin Malita <[email protected]>
---

diff --git a/include/core/SkPathBuilder.h b/include/core/SkPathBuilder.h
index d4b1907..ad6882d 100644
--- a/include/core/SkPathBuilder.h
+++ b/include/core/SkPathBuilder.h
@@ -252,12 +252,14 @@
 
         Appends kMove_Verb to verb array and (0, 0) to SkPoint array, if needed.
 
-        If w is finite and not one, appends kConic_Verb to verb array;
+        If w is finite, positive, and not one, appends kConic_Verb to verb array;
         and pt1, pt2 to SkPoint array; and w to conic weights.
 
         If w is one, appends kQuad_Verb to verb array, and
         pt1, pt2 to SkPoint array.
 
+        If w is zero, this is the same as lineTo(pt2)
+
         If w is not finite, appends kLine_Verb twice to verb array, and
         pt1, pt2 to SkPoint array.
 
diff --git a/src/core/SkPathBuilder.cpp b/src/core/SkPathBuilder.cpp
index 76d418a..833763d 100644
--- a/src/core/SkPathBuilder.cpp
+++ b/src/core/SkPathBuilder.cpp
@@ -202,6 +202,9 @@
 SkPathBuilder& SkPathBuilder::conicTo(SkPoint pt1, SkPoint pt2, SkScalar w) {
     this->ensureMove();
 
+    if (w <= 0) {
+        return this->lineTo(pt2);
+    }
     SkPoint* p = fPts.push_back_n(2);
     p[0] = pt1;
     p[1] = pt2;
diff --git a/tests/PathBuilderTest.cpp b/tests/PathBuilderTest.cpp
index ba22ad3..b152e8d 100644
--- a/tests/PathBuilderTest.cpp
+++ b/tests/PathBuilderTest.cpp
@@ -7,6 +7,7 @@
 
 #include "include/core/SkPath.h"
 #include "include/core/SkPathBuilder.h"
+#include "include/core/SkPathMeasure.h"
 #include "include/core/SkPathTypes.h"
 #include "include/core/SkPoint.h"
 #include "include/core/SkRRect.h"
@@ -1098,11 +1099,73 @@
     {
         // If w is not finite, appends kLine_Verb twice to verb array, and
         // pt1, pt2 to SkPoint array.
-        SkPath p = SkPathBuilder().conicTo({10, 5}, {10, 10}, SK_ScalarInfinity).detach();
+        SkPath p = SkPathBuilder().conicTo({10, 5}, {10, 10}, SK_FloatInfinity).detach();
         REPORTER_ASSERT(reporter, !p.isEmpty());
         REPORTER_ASSERT(reporter, p.verbs().size() == 3u); // moveTo, lineTo, lineTo
         REPORTER_ASSERT(reporter, p.points().size() == 3u);
         REPORTER_ASSERT(reporter, p.conicWeights().empty());
         REPORTER_ASSERT(reporter, p.getSegmentMasks() == SkPath::kLine_SegmentMask);
     }
+
+    {
+        // If w is 0, appends kLine_Verb once to verb array, and
+        // pt2 to SkPoint array.
+        SkPath p = SkPathBuilder().conicTo({10, 5}, {10, 10}, 0).detach();
+        REPORTER_ASSERT(reporter, !p.isEmpty());
+        REPORTER_ASSERT(reporter, p.verbs().size() == 2u); // moveTo, lineTo
+        REPORTER_ASSERT(reporter, p.points().size() == 2u);
+        REPORTER_ASSERT(reporter, p.conicWeights().empty());
+        REPORTER_ASSERT(reporter, p.getSegmentMasks() == SkPath::kLine_SegmentMask);
+    }
+}
+
+DEF_TEST(SkPathBuilder_b520944501, reporter) {
+    SkPath path = SkPathBuilder(SkPathFillType::kInverseEvenOdd)
+                          .moveTo(0, 0)
+                          .cubicTo(8.51330895e-18f,
+                                   4.80215861e+30f,
+                                   4.80215347e+30f,
+                                   4.73888368e-38f,
+                                   2.36942783e-38f,
+                                   7.54830852e-30f)
+                          .moveTo(4.80215831e+30f, 1.03969141e-21f)
+                          .conicTo(4.80215831e+30f,
+                                   4.73888368e-38f,
+                                   2.40107915e+30f,
+                                   4.73888368e-38f,
+                                   0.707106769f)
+                          .conicTo(2.0779294e-21f,
+                                   4.73888368e-38f,
+                                   2.0779294e-21f,
+                                   1.03969141e-21f,
+                                   0.707106769f)
+                          .conicTo(2.0779294e-21f,
+                                   2.07938282e-21f,
+                                   2.40107915e+30f,
+                                   2.07938282e-21f,
+                                   0.707106769f)
+                          .conicTo(4.80215831e+30f,
+                                   2.07938282e-21f,
+                                   4.80215831e+30f,
+                                   1.03969141e-21f,
+                                   0.707106769f)
+                          .close()
+                          .detach();
+
+    SkMatrix m;
+    m.setAll(0.0f,
+             0.0f,
+             0.0f,
+             0.0f,
+             0.0f,
+             10159839284371128320.0f,
+             36261335138304000.0f,
+             0.0f,
+             -0.0f);
+
+    // This previously caused an issue where one of the conic weights turned to
+    // 0, causing an assert later. We should be avoiding that.
+    SkPath transformed = path.makeTransform(m);
+    SkPathMeasure meas(transformed, false);
+    (void)meas.getLength();
 }