handle clipping large triangles

originally found by fuzzer.

Bug: skia:
Change-Id: I45007a619f13936153c0db8a60b3631a2c9db20c
Reviewed-on: https://skia-review.googlesource.com/101741
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>

1 files changed, 30 insertions, 0 deletions

diff --git a/tests/VerticesTest.cpp b/tests/VerticesTest.cpp
index 399aba2f21..f55adb0ed3 100644
--- a/tests/VerticesTest.cpp
+++ b/tests/VerticesTest.cpp
@@ -5,7 +5,10 @@
  * found in the LICENSE file.
  */
 
+#include "SkCanvas.h"
+#include "SkSurface.h"
 #include "SkVertices.h"
+#include "sk_pixel_iter.h"
 #include "Test.h"
 
 static bool equal(const SkVertices* v0, const SkVertices* v1) {
@@ -86,3 +89,30 @@ DEF_TEST(Vertices, reporter) {
         }
     }
 }
+
+static void fill_triangle(SkCanvas* canvas, const SkPoint pts[], SkColor c) {
+    SkColor colors[] = { c, c, c };
+    auto verts = SkVertices::MakeCopy(SkVertices::kTriangles_VertexMode, 3, pts, nullptr, colors);
+    canvas->drawVertices(verts, SkBlendMode::kSrc, SkPaint());
+}
+
+DEF_TEST(Vertices_clipping, reporter) {
+    // A very large triangle has to be geometrically clipped (since its "fast" clipping is
+    // normally done in after building SkFixed coordinates). Check that we handle this.
+    // (and don't assert).
+    auto surf = SkSurface::MakeRasterN32Premul(3, 3);
+
+    SkPoint pts[] = { { -10, 1 }, { -10, 2 }, { 1e9f, 1.5f } };
+    fill_triangle(surf->getCanvas(), pts, SK_ColorBLACK);
+
+    sk_tool_utils::PixelIter iter(surf.get());
+    SkIPoint loc;
+    while (void* addr = iter.next(&loc)) {
+        SkPMColor c = *(SkPMColor*)addr;
+        if (loc.fY == 1) {
+            REPORTER_ASSERT(reporter, c == 0xFF000000);
+        } else {
+            REPORTER_ASSERT(reporter, c == 0);
+        }
+    }
+}