Fix gradient pattern stroke paint order over solid fills

core/fpdfapi/render/cpdf_renderstatus.cpp

@@ -455,8 +455,21 @@ bool CPDF_RenderStatus::ProcessPath(CPDF_PathObject* path_obj,
                                     const CFX_Matrix& mtObj2Device) {
   CFX_FillRenderOptions::FillType fill_type = path_obj->filltype();
   bool stroke = path_obj->stroke();
+  // EmbedPDF(bug-fix): upstream drew a pattern stroke before the path's solid
+  // fill, so with B and B* the fill covered the stroke's inner half. The
+  // pattern stroke is held back here and drawn after the fill.
+  const CPDF_Color* pattern_stroke =
+      stroke && path_obj->color_state().GetStrokeColor()->IsPattern()
+          ? path_obj->color_state().GetStrokeColor()
+          : nullptr;
+  if (pattern_stroke) {
+    stroke = false;
+  }
   ProcessPathPattern(path_obj, mtObj2Device, &fill_type, &stroke);
   if (fill_type == CFX_FillRenderOptions::FillType::kNoFill && !stroke) {
+    if (pattern_stroke) {
+      DrawPathWithPattern(path_obj, mtObj2Device, pattern_stroke, true);
+    }
     return true;
   }
 
@@ -479,11 +492,18 @@ bool CPDF_RenderStatus::ProcessPath(CPDF_PathObject* path_obj,
     return true;
   }
 
-  return device_->DrawPath(
+  // EmbedPDF(bug-fix): the held-back pattern stroke goes on top of the fill.
+  // When DrawPath() fails, the caller redraws the whole object, stroke
+  // included, so the stroke is skipped here.
+  const bool result = device_->DrawPath(
       *path_obj->path().GetObject(), &path_matrix,
       path_obj->graph_state().GetObject(), fill_argb, stroke_argb,
       GetFillOptionsForDrawPathWithBlend(options, path_obj, fill_type, stroke,
                                          type3_char_));
+  if (result && pattern_stroke) {
+    DrawPathWithPattern(path_obj, mtObj2Device, pattern_stroke, true);
+  }
+  return result;
 }
 
 RetainPtr<CPDF_TransferFunc> CPDF_RenderStatus::GetTransferFunc(

core/fpdfapi/render/fpdf_render_pattern_embeddertest.cpp

@@ -2,13 +2,47 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <cstdint>
+#include <vector>
+
 #include "public/cpp/fpdf_scopers.h"
+#include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/embedder_test_constants.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class FPDFRenderPatternEmbedderTest : public EmbedderTest {};
 
+TEST_F(FPDFRenderPatternEmbedderTest, ShadingStrokePaintsAfterSolidFill) {
+  ASSERT_TRUE(OpenDocument("gradient_pattern_stroke_order.pdf"));
+  ASSERT_EQ(3, FPDF_GetPageCount(document()));
+
+  for (int page_index = 0; page_index < 3; ++page_index) {
+    SCOPED_TRACE(page_index);
+    ScopedPage page = LoadScopedPage(page_index);
+    ASSERT_TRUE(page);
+    for (int scale : {1, 2, 4}) {
+      SCOPED_TRACE(scale);
+      const int size = 100 * scale;
+      const int stride = size * 4;
+      std::vector<uint8_t> pixels(size * stride);
+      ScopedFPDFBitmap bitmap(FPDFBitmap_CreateEx(size, size, FPDFBitmap_BGRA,
+                                                  pixels.data(), stride));
+      ASSERT_TRUE(bitmap);
+      ASSERT_TRUE(FPDFBitmap_FillRect(bitmap.get(), 0, 0, size, size,
+                                      /*color=*/0xFFFFFFFF));
+      FPDF_RenderPageBitmap(bitmap.get(), page.get(), 0, 0, size, size,
+                            /*rotate=*/0, /*flags=*/0);
+
+      // Both halves of the 10-point stroke stay visible for B, B* and S.
+      const int row = 50 * scale * stride;
+      EXPECT_LT(pixels[row + 17 * scale * 4 + 1], 20);
+      EXPECT_LT(pixels[row + 23 * scale * 4 + 1], 20);
+      EXPECT_EQ(pixels[row + 50 * scale * 4 + 1], 255);
+    }
+  }
+}
+
 TEST_F(FPDFRenderPatternEmbedderTest, LoadError547706) {
   // Test shading where object is a dictionary instead of a stream.
   ASSERT_TRUE(OpenDocument("bug_547706.pdf"));

testing/resources/gradient_pattern_stroke_order.in

@@ -0,0 +1,90 @@
+{{header}}
+{{object 1 0}} <<
+  /Type /Catalog
+  /Pages 2 0 R
+>>
+endobj
+{{object 2 0}} <<
+  /Type /Pages
+  /MediaBox [0 0 100 100]
+  /Count 3
+  /Kids [3 0 R 8 0 R 10 0 R]
+  /Resources << /Pattern << /P0 5 0 R >> >>
+>>
+endobj
+{{object 3 0}} <<
+  /Type /Page
+  /Parent 2 0 R
+  /Contents 4 0 R
+>>
+endobj
+{{object 4 0}} <<
+  {{streamlen}}
+>>
+stream
+1 1 1 rg
+/Pattern CS
+/P0 SCN
+10 w
+20 20 60 60 re B
+endstream
+endobj
+{{object 5 0}} <<
+  /Type /Pattern
+  /PatternType 2
+  /Shading 6 0 R
+>>
+endobj
+{{object 6 0}} <<
+  /ShadingType 2
+  /ColorSpace /DeviceRGB
+  /Coords [0 0 100 0]
+  /Extend [true true]
+  /Function 7 0 R
+>>
+endobj
+{{object 7 0}} <<
+  /FunctionType 2
+  /Domain [0 1]
+  /C0 [1 0 0]
+  /C1 [0 0 1]
+  /N 1
+>>
+endobj
+{{object 8 0}} <<
+  /Type /Page
+  /Parent 2 0 R
+  /Contents 9 0 R
+>>
+endobj
+{{object 9 0}} <<
+  {{streamlen}}
+>>
+stream
+1 1 1 rg
+/Pattern CS
+/P0 SCN
+10 w
+20 20 60 60 re B*
+endstream
+endobj
+{{object 10 0}} <<
+  /Type /Page
+  /Parent 2 0 R
+  /Contents 11 0 R
+>>
+endobj
+{{object 11 0}} <<
+  {{streamlen}}
+>>
+stream
+/Pattern CS
+/P0 SCN
+10 w
+20 20 60 60 re S
+endstream
+endobj
+{{xref}}
+{{trailer}}
+{{startxref}}
+%%EOF