support gradients and stroke+fill

To draw paths that are stroked and filled with a pair of colors,
reduce the fill by the width of the stroke. This is implemented
with path ops subtracting the resolved stroke shape from the
fill shape. This permits rendering the result without requiring
an offscreen bitmap.

The implementation for stroke+fill requires a new entry into
the graphics engine, so a bit was added to device caps for that.

Extract the gradient information out of the axial gradient
function descriptions, and when possible, use Skia to draw
the linear gradient directly. This requires making the function
descriptions non-opaque, and adding a bit to device caps for
another entry into the graphics engine.

BUG=

Review URL: https://codereview.chromium.org/1828283002

10 files changed, 276 insertions, 75 deletions

diff --git a/core/fpdfapi/fpdf_page/fpdf_page_func.cpp b/core/fpdfapi/fpdf_page/fpdf_page_func.cpp
index 96aad6d87f..08eafad6ac 100644
--- a/core/fpdfapi/fpdf_page/fpdf_page_func.cpp
+++ b/core/fpdfapi/fpdf_page/fpdf_page_func.cpp
@@ -520,11 +520,12 @@ class CPDF_SampledFunc : public CPDF_Function {
   CPDF_StreamAcc* m_pSampleStream;
 };
 
-CPDF_SampledFunc::CPDF_SampledFunc() {
+CPDF_SampledFunc::CPDF_SampledFunc() : CPDF_Function(Type::kType0Sampled) {
   m_pSampleStream = NULL;
   m_pEncodeInfo = NULL;
   m_pDecodeInfo = NULL;
 }
+
 CPDF_SampledFunc::~CPDF_SampledFunc() {
   delete m_pSampleStream;
   FX_Free(m_pEncodeInfo);
@@ -665,6 +666,7 @@ FX_BOOL CPDF_SampledFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const {
 class CPDF_PSFunc : public CPDF_Function {
  public:
   // CPDF_Function
+  CPDF_PSFunc() : CPDF_Function(Type::kType4PostScript) {}
   FX_BOOL v_Init(CPDF_Object* pObj) override;
   FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
 
@@ -694,25 +696,14 @@ FX_BOOL CPDF_PSFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const {
   return TRUE;
 }
 
-class CPDF_ExpIntFunc : public CPDF_Function {
- public:
-  CPDF_ExpIntFunc();
-  ~CPDF_ExpIntFunc() override;
-
-  // CPDF_Function
-  FX_BOOL v_Init(CPDF_Object* pObj) override;
-  FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
-
-  FX_FLOAT m_Exponent;
-  FX_FLOAT* m_pBeginValues;
-  FX_FLOAT* m_pEndValues;
-  int m_nOrigOutputs;
-};
+}  // namespace
 
-CPDF_ExpIntFunc::CPDF_ExpIntFunc() {
+CPDF_ExpIntFunc::CPDF_ExpIntFunc()
+    : CPDF_Function(Type::kType2ExpotentialInterpolation) {
   m_pBeginValues = NULL;
   m_pEndValues = NULL;
 }
+
 CPDF_ExpIntFunc::~CPDF_ExpIntFunc() {
   FX_Free(m_pBeginValues);
   FX_Free(m_pEndValues);
@@ -755,26 +746,11 @@ FX_BOOL CPDF_ExpIntFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const {
   return TRUE;
 }
 
-class CPDF_StitchFunc : public CPDF_Function {
- public:
-  CPDF_StitchFunc();
-  ~CPDF_StitchFunc() override;
-
-  // CPDF_Function
-  FX_BOOL v_Init(CPDF_Object* pObj) override;
-  FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
-
-  std::vector<CPDF_Function*> m_pSubFunctions;
-  FX_FLOAT* m_pBounds;
-  FX_FLOAT* m_pEncode;
-
-  static const int kRequiredNumInputs = 1;
-};
-
-CPDF_StitchFunc::CPDF_StitchFunc() {
+CPDF_StitchFunc::CPDF_StitchFunc() : CPDF_Function(Type::kType3Stitching) {
   m_pBounds = NULL;
   m_pEncode = NULL;
 }
+
 CPDF_StitchFunc::~CPDF_StitchFunc() {
   for (auto& sub : m_pSubFunctions) {
     delete sub;
@@ -859,13 +835,10 @@ FX_BOOL CPDF_StitchFunc::v_Call(FX_FLOAT* inputs, FX_FLOAT* outputs) const {
   return TRUE;
 }
 
-}  // namespace
-
 CPDF_Function* CPDF_Function::Load(CPDF_Object* pFuncObj) {
   if (!pFuncObj) {
     return NULL;
   }
-  CPDF_Function* pFunc = NULL;
   int type;
   if (CPDF_Stream* pStream = pFuncObj->AsStream()) {
     type = pStream->GetDict()->GetIntegerBy("FunctionType");
@@ -874,14 +847,15 @@ CPDF_Function* CPDF_Function::Load(CPDF_Object* pFuncObj) {
   } else {
     return NULL;
   }
+  CPDF_Function* pFunc = NULL;
   if (type == 0) {
-    pFunc = new CPDF_SampledFunc;
+    pFunc = new CPDF_SampledFunc();
   } else if (type == 2) {
-    pFunc = new CPDF_ExpIntFunc;
+    pFunc = new CPDF_ExpIntFunc();
   } else if (type == 3) {
-    pFunc = new CPDF_StitchFunc;
+    pFunc = new CPDF_StitchFunc();
   } else if (type == 4) {
-    pFunc = new CPDF_PSFunc;
+    pFunc = new CPDF_PSFunc();
   } else {
     return NULL;
   }
@@ -891,10 +865,12 @@ CPDF_Function* CPDF_Function::Load(CPDF_Object* pFuncObj) {
   }
   return pFunc;
 }
-CPDF_Function::CPDF_Function() {
+
+CPDF_Function::CPDF_Function(Type type) : m_Type(type) {
   m_pDomains = NULL;
   m_pRanges = NULL;
 }
+
 CPDF_Function::~CPDF_Function() {
   FX_Free(m_pDomains);
   FX_Free(m_pRanges);
diff --git a/core/fpdfapi/fpdf_page/pageint.h b/core/fpdfapi/fpdf_page/pageint.h
index d254477dc3..297b1e2e77 100644
--- a/core/fpdfapi/fpdf_page/pageint.h
+++ b/core/fpdfapi/fpdf_page/pageint.h
@@ -377,24 +377,68 @@ class CPDF_DocPageData {
 
 class CPDF_Function {
  public:
+  enum class Type {
+    kType0Sampled,
+    kType2ExpotentialInterpolation,
+    kType3Stitching,
+    kType4PostScript,
+  };
+
   static CPDF_Function* Load(CPDF_Object* pFuncObj);
   virtual ~CPDF_Function();
   FX_BOOL Call(FX_FLOAT* inputs,
                int ninputs,
                FX_FLOAT* results,
                int& nresults) const;
-  int CountInputs() { return m_nInputs; }
-  int CountOutputs() { return m_nOutputs; }
+  int CountInputs() const { return m_nInputs; }
+  int CountOutputs() const { return m_nOutputs; }
+  FX_FLOAT GetDomain(int i) const { return m_pDomains[i]; }
+  Type GetType() const { return m_Type; }
 
  protected:
-  CPDF_Function();
-  int m_nInputs, m_nOutputs;
-  FX_FLOAT* m_pDomains;
-  FX_FLOAT* m_pRanges;
+  CPDF_Function(Type type);
   FX_BOOL Init(CPDF_Object* pObj);
   virtual FX_BOOL v_Init(CPDF_Object* pObj) = 0;
   virtual FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const = 0;
+
+  int m_nInputs;
+  int m_nOutputs;
+  FX_FLOAT* m_pDomains;
+  FX_FLOAT* m_pRanges;
+  Type m_Type;
+};
+
+class CPDF_ExpIntFunc : public CPDF_Function {
+ public:
+  CPDF_ExpIntFunc();
+  ~CPDF_ExpIntFunc() override;
+
+  // CPDF_Function
+  FX_BOOL v_Init(CPDF_Object* pObj) override;
+  FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
+
+  int m_nOrigOutputs;
+  FX_FLOAT m_Exponent;
+  FX_FLOAT* m_pBeginValues;
+  FX_FLOAT* m_pEndValues;
+};
+
+class CPDF_StitchFunc : public CPDF_Function {
+ public:
+  CPDF_StitchFunc();
+  ~CPDF_StitchFunc() override;
+
+  // CPDF_Function
+  FX_BOOL v_Init(CPDF_Object* pObj) override;
+  FX_BOOL v_Call(FX_FLOAT* inputs, FX_FLOAT* results) const override;
+
+  std::vector<CPDF_Function*> m_pSubFunctions;
+  FX_FLOAT* m_pBounds;
+  FX_FLOAT* m_pEncode;
+
+  static const int kRequiredNumInputs = 1;
 };
+
 class CPDF_IccProfile {
  public:
   CPDF_IccProfile(const uint8_t* pData, FX_DWORD dwSize);
diff --git a/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp b/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
index d4dd8ec211..94f38c5186 100644
--- a/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
+++ b/core/fpdfapi/fpdf_render/fpdf_render_pattern.cpp
@@ -859,6 +859,11 @@ void CPDF_RenderStatus::DrawShading(CPDF_ShadingPattern* pPattern,
     rect.Transform(pMatrix);
     clip_rect.Intersect(rect.GetOutterRect());
   }
+  if (m_pDevice->GetDeviceCaps(FXDC_RENDER_CAPS) & FXRC_SHADING &&
+      m_pDevice->GetDeviceDriver()->DrawShading(pPattern, pMatrix, alpha,
+                                                bAlphaMode)) {
+    return;
+  }
   CPDF_DeviceBuffer buffer;
   buffer.Initialize(m_pContext, m_pDevice, &clip_rect, m_pCurObj, 150);
   CFX_Matrix FinalMatrix = *pMatrix;
diff --git a/core/fxge/agg/fx_agg_driver.h b/core/fxge/agg/fx_agg_driver.h
index ea4c36059b..2b6b6683f6 100644
--- a/core/fxge/agg/fx_agg_driver.h
+++ b/core/fxge/agg/fx_agg_driver.h
@@ -122,7 +122,7 @@ class CFX_AggDeviceDriver : public IFX_RenderDeviceDriver {
                          FX_DWORD color,
                          int alpha_flag,
                          void* pIccTransform) override;
-  int GetDriverType() override { return 1; }
+  int GetDriverType() const override { return 1; }
 
   FX_BOOL RenderRasterizer(agg::rasterizer_scanline_aa& rasterizer,
                            FX_DWORD color,
diff --git a/core/fxge/apple/apple_int.h b/core/fxge/apple/apple_int.h
index 037eca767f..c4f95d6d26 100644
--- a/core/fxge/apple/apple_int.h
+++ b/core/fxge/apple/apple_int.h
@@ -173,7 +173,7 @@ class CFX_QuartzDeviceDriver : public IFX_RenderDeviceDriver {
                          FX_DWORD color,
                          int alpha_flag = 0,
                          void* pIccTransform = NULL) override;
-  void* GetPlatformSurface() override { return NULL; }
+  void* GetPlatformSurface() const override { return NULL; }
   void ClearDriver() override;
 
  protected:
diff --git a/core/fxge/ge/fx_ge_device.cpp b/core/fxge/ge/fx_ge_device.cpp
index b8ddfec841..eefac5c033 100644
--- a/core/fxge/ge/fx_ge_device.cpp
+++ b/core/fxge/ge/fx_ge_device.cpp
@@ -109,6 +109,7 @@ void CFX_RenderDevice::UpdateClipBox() {
   m_ClipBox.right = m_Width;
   m_ClipBox.bottom = m_Height;
 }
+
 FX_BOOL CFX_RenderDevice::DrawPath(const CFX_PathData* pPathData,
                                    const CFX_Matrix* pObject2Device,
                                    const CFX_GraphStateData* pGraphState,
@@ -224,6 +225,31 @@ FX_BOOL CFX_RenderDevice::DrawPath(const CFX_PathData* pPathData,
   }
   if ((fill_mode & 3) && fill_alpha && stroke_alpha < 0xff &&
       (fill_mode & FX_FILL_STROKE)) {
+    if (m_RenderCaps & FXRC_FILLSTROKE_PATH) {
+      return m_pDeviceDriver->DrawPath(pPathData, pObject2Device, pGraphState,
+                                       fill_color, stroke_color, fill_mode,
+                                       alpha_flag, pIccTransform, blend_type);
+    }
+    return DrawFillStrokePath(pPathData, pObject2Device, pGraphState,
+                              fill_color, stroke_color, fill_mode, alpha_flag,
+                              pIccTransform, blend_type);
+  }
+  return m_pDeviceDriver->DrawPath(pPathData, pObject2Device, pGraphState,
+                                   fill_color, stroke_color, fill_mode,
+                                   alpha_flag, pIccTransform, blend_type);
+}
+
+// This can be removed once PDFium entirely relies on Skia
+FX_BOOL CFX_RenderDevice::DrawFillStrokePath(
+    const CFX_PathData* pPathData,
+    const CFX_Matrix* pObject2Device,
+    const CFX_GraphStateData* pGraphState,
+    FX_DWORD fill_color,
+    FX_DWORD stroke_color,
+    int fill_mode,
+    int alpha_flag,
+    void* pIccTransform,
+    int blend_type) {
     if (!(m_RenderCaps & FXRC_GET_BITS)) {
       return FALSE;
     }
@@ -272,11 +298,8 @@ FX_BOOL CFX_RenderDevice::DrawPath(const CFX_PathData* pPathData,
                      FXSYS_round(rect.Height() * fScaleY));
     return m_pDeviceDriver->SetDIBits(&bitmap, 0, &src_rect, rect.left,
                                       rect.top, FXDIB_BLEND_NORMAL);
-  }
-  return m_pDeviceDriver->DrawPath(pPathData, pObject2Device, pGraphState,
-                                   fill_color, stroke_color, fill_mode,
-                                   alpha_flag, pIccTransform, blend_type);
 }
+
 FX_BOOL CFX_RenderDevice::SetPixel(int x,
                                    int y,
                                    FX_DWORD color,
diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index f0c7d4e442..ed6ff82fd0 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -7,6 +7,10 @@
 #if defined(_SKIA_SUPPORT_)
 #include "core/include/fxcodec/fx_codec.h"
 
+#include "core/fpdfapi/fpdf_page/cpdf_shadingpattern.h"
+#include "core/fpdfapi/fpdf_page/pageint.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_array.h"
+#include "core/fpdfapi/fpdf_parser/include/cpdf_dictionary.h"
 #include "core/fxge/agg/fx_agg_driver.h"
 #include "core/fxge/skia/fx_skia_device.h"
 
@@ -18,6 +22,8 @@
 #include "third_party/skia/include/core/SkStream.h"
 #include "third_party/skia/include/core/SkTypeface.h"
 #include "third_party/skia/include/effects/SkDashPathEffect.h"
+#include "third_party/skia/include/effects/SkGradientShader.h"
+#include "third_party/skia/include/pathops/SkPathOps.h"
 
 namespace {
 
@@ -150,6 +156,53 @@ SkXfermode::Mode GetSkiaBlendMode(int blend_type) {
   }
 }
 
+bool AddColors(const CPDF_Function* pFunc, SkTDArray<SkColor>* skColors) {
+  if (pFunc->CountInputs() != 1)
+    return false;
+  ASSERT(CPDF_Function::Type::kType2ExpotentialInterpolation ==
+         pFunc->GetType());
+  const CPDF_ExpIntFunc* expIntFunc =
+      static_cast<const CPDF_ExpIntFunc*>(pFunc);
+  if (expIntFunc->m_Exponent != 1)
+    return false;
+  if (expIntFunc->m_nOrigOutputs != 3)
+    return false;
+  skColors->push(SkColorSetARGB(
+      0xFF, SkUnitScalarClampToByte(expIntFunc->m_pBeginValues[0]),
+      SkUnitScalarClampToByte(expIntFunc->m_pBeginValues[1]),
+      SkUnitScalarClampToByte(expIntFunc->m_pBeginValues[2])));
+  skColors->push(
+      SkColorSetARGB(0xFF, SkUnitScalarClampToByte(expIntFunc->m_pEndValues[0]),
+                     SkUnitScalarClampToByte(expIntFunc->m_pEndValues[1]),
+                     SkUnitScalarClampToByte(expIntFunc->m_pEndValues[2])));
+  return true;
+}
+
+bool AddStitching(const CPDF_Function* pFunc,
+                  SkTDArray<SkColor>* skColors,
+                  SkTDArray<SkScalar>* skPos) {
+  int inputs = pFunc->CountInputs();
+  ASSERT(CPDF_Function::Type::kType3Stitching == pFunc->GetType());
+  const CPDF_StitchFunc* stitchFunc =
+      static_cast<const CPDF_StitchFunc*>(pFunc);
+  FX_FLOAT boundsStart = stitchFunc->GetDomain(0);
+
+  for (int i = 0; i < inputs; ++i) {
+    const CPDF_Function* pSubFunc = stitchFunc->m_pSubFunctions[i];
+    if (pSubFunc->GetType() !=
+        CPDF_Function::Type::kType2ExpotentialInterpolation)
+      return false;
+    if (!AddColors(pSubFunc, skColors))
+      return false;
+    FX_FLOAT boundsEnd =
+        i < inputs - 1 ? stitchFunc->m_pBounds[i] : stitchFunc->GetDomain(1);
+    skPos->push(boundsStart);
+    skPos->push(boundsEnd);
+    boundsStart = boundsEnd;
+  }
+  return true;
+}
+
 }  // namespace
 
 // convert a stroking path to scanlines
@@ -303,7 +356,8 @@ int CFX_SkiaDeviceDriver::GetDeviceCaps(int caps_id) {
       return 0;
     case FXDC_RENDER_CAPS:
       return FXRC_GET_BITS | FXRC_ALPHA_PATH | FXRC_ALPHA_IMAGE |
-             FXRC_BLEND_MODE | FXRC_SOFT_CLIP | FXRC_ALPHA_OUTPUT;
+             FXRC_BLEND_MODE | FXRC_SOFT_CLIP | FXRC_ALPHA_OUTPUT |
+             FXRC_FILLSTROKE_PATH | FXRC_SHADING;
     case FXDC_DITHER_BITS:
       return m_ditherBits;
   }
@@ -385,32 +439,44 @@ FX_BOOL CFX_SkiaDeviceDriver::DrawPath(
   SkIRect rect;
   rect.set(0, 0, GetDeviceCaps(FXDC_PIXEL_WIDTH),
            GetDeviceCaps(FXDC_PIXEL_HEIGHT));
+  SkMatrix skMatrix = ToSkMatrix(*pObject2Device);
+  SkPaint skPaint;
+  skPaint.setAntiAlias(true);
+  int stroke_alpha = FXGETFLAG_COLORTYPE(alpha_flag)
+                         ? FXGETFLAG_ALPHA_STROKE(alpha_flag)
+                         : FXARGB_A(stroke_color);
+  if (pGraphState && stroke_alpha)
+    PaintStroke(&skPaint, pGraphState, skMatrix);
   SkPath skPath = BuildPath(pPathData);
-  SkPaint spaint;
-  spaint.setAntiAlias(true);
-  spaint.setXfermodeMode(GetSkiaBlendMode(blend_type));
   m_pCanvas->save();
-  SkMatrix skMatrix = ToSkMatrix(*pObject2Device);
   m_pCanvas->concat(skMatrix);
   if ((fill_mode & 3) && fill_color) {
     skPath.setFillType((fill_mode & 3) == FXFILL_WINDING
                            ? SkPath::kWinding_FillType
                            : SkPath::kEvenOdd_FillType);
-
-    spaint.setStyle(SkPaint::kFill_Style);
-    spaint.setColor(fill_color);
-    m_pCanvas->drawPath(skPath, spaint);
+    SkPath strokePath;
+    const SkPath* fillPath = &skPath;
+    if (pGraphState && stroke_alpha) {
+      SkAlpha fillA = SkColorGetA(fill_color);
+      SkAlpha strokeA = SkColorGetA(stroke_color);
+      if (fillA && fillA < 0xFF && strokeA && strokeA < 0xFF) {
+        skPaint.getFillPath(skPath, &strokePath);
+        if (Op(skPath, strokePath, SkPathOp::kDifference_SkPathOp,
+               &strokePath)) {
+          fillPath = &strokePath;
+        }
+      }
+    }
+    skPaint.setStyle(SkPaint::kFill_Style);
+    skPaint.setColor(fill_color);
+    m_pCanvas->drawPath(*fillPath, skPaint);
   }
-  int stroke_alpha = FXGETFLAG_COLORTYPE(alpha_flag)
-                         ? FXGETFLAG_ALPHA_STROKE(alpha_flag)
-                         : FXARGB_A(stroke_color);
-
   if (pGraphState && stroke_alpha) {
-    spaint.setColor(stroke_color);
-    PaintStroke(&spaint, pGraphState, skMatrix);
     DebugShowSkiaPath(skPath);
     DebugShowCanvasMatrix(m_pCanvas);
-    m_pCanvas->drawPath(skPath, spaint);
+    skPaint.setStyle(SkPaint::kStroke_Style);
+    skPaint.setColor(stroke_color);
+    m_pCanvas->drawPath(skPath, skPaint);
   }
   m_pCanvas->restore();
   return TRUE;
@@ -432,6 +498,71 @@ FX_BOOL CFX_SkiaDeviceDriver::FillRect(const FX_RECT* pRect,
   return TRUE;
 }
 
+FX_BOOL CFX_SkiaDeviceDriver::DrawShading(CPDF_ShadingPattern* pPattern,
+                                          CFX_Matrix* pMatrix,
+                                          int alpha,
+                                          FX_BOOL bAlphaMode) {
+  CPDF_Function** pFuncs = pPattern->m_pFunctions;
+  int nFuncs = pPattern->m_nFuncs;
+  if (nFuncs != 1)  // TODO(caryclark) remove this restriction
+    return false;
+  CPDF_Dictionary* pDict = pPattern->m_pShadingObj->GetDict();
+  CPDF_Array* pCoords = pDict->GetArrayBy("Coords");
+  if (!pCoords)
+    return true;
+  FX_FLOAT start_x = pCoords->GetNumberAt(0);
+  FX_FLOAT start_y = pCoords->GetNumberAt(1);
+  FX_FLOAT end_x = pCoords->GetNumberAt(2);
+  FX_FLOAT end_y = pCoords->GetNumberAt(3);
+  FX_FLOAT t_min = 0;
+  FX_FLOAT t_max = 1;
+  CPDF_Array* pArray = pDict->GetArrayBy("Domain");
+  if (pArray) {
+    t_min = pArray->GetNumberAt(0);
+    t_max = pArray->GetNumberAt(1);
+  }
+  FX_BOOL bStartExtend = FALSE, bEndExtend = FALSE;
+  pArray = pDict->GetArrayBy("Extend");
+  if (pArray) {
+    bStartExtend = pArray->GetIntegerAt(0);
+    bEndExtend = pArray->GetIntegerAt(1);
+  }
+  SkTDArray<SkColor> skColors;
+  SkTDArray<SkScalar> skPos;
+  for (int j = 0; j < nFuncs; j++) {
+    const CPDF_Function* pFunc = pFuncs[j];
+    if (!pFunc)
+      continue;
+    switch (pFunc->GetType()) {
+      case CPDF_Function::Type::kType2ExpotentialInterpolation:
+        if (!AddColors(pFunc, &skColors))
+          return false;
+        skPos.push(0);
+        skPos.push(1);
+        break;
+      case CPDF_Function::Type::kType3Stitching:
+        if (!AddStitching(pFunc, &skColors, &skPos))
+          return false;
+        break;
+      default:
+        return false;
+    }
+  }
+  SkMatrix skMatrix = ToSkMatrix(*pMatrix);
+  SkPoint pts[] = {{start_x, start_y}, {end_x, end_y}};
+  SkPaint paint;
+  paint.setAntiAlias(true);
+  paint.setShader(SkGradientShader::MakeLinear(pts, skColors.begin(),
+                                               skPos.begin(), skColors.count(),
+                                               SkShader::kClamp_TileMode));
+  paint.setAlpha(alpha);
+  m_pCanvas->save();
+  m_pCanvas->concat(skMatrix);
+  m_pCanvas->drawRect(SkRect::MakeWH(1, 1), paint);
+  m_pCanvas->restore();
+  return true;
+}
+
 FX_BOOL CFX_SkiaDeviceDriver::GetClipBox(FX_RECT* pRect) {
   // TODO(caryclark) call m_canvas->getClipDeviceBounds() instead
   pRect->left = 0;
diff --git a/core/fxge/skia/fx_skia_device.h b/core/fxge/skia/fx_skia_device.h
index 012e370717..8ce7c6c61f 100644
--- a/core/fxge/skia/fx_skia_device.h
+++ b/core/fxge/skia/fx_skia_device.h
@@ -128,6 +128,11 @@ class CFX_SkiaDeviceDriver : public IFX_RenderDeviceDriver {
                          int alpha_flag = 0,
                          void* pIccTransform = NULL) override;
 
+  FX_BOOL DrawShading(CPDF_ShadingPattern* pPattern,
+                      CFX_Matrix* pMatrix,
+                      int alpha,
+                      FX_BOOL bAlphaMode) override;
+
   virtual uint8_t* GetBuffer() const { return m_pAggDriver->GetBuffer(); }
   void PaintStroke(SkPaint* spaint,
                    const CFX_GraphStateData* pGraphState,
diff --git a/core/fxge/win32/win32_int.h b/core/fxge/win32/win32_int.h
index 923aa84f33..d903d3abf5 100644
--- a/core/fxge/win32/win32_int.h
+++ b/core/fxge/win32/win32_int.h
@@ -145,7 +145,7 @@ class CGdiDeviceDriver : public IFX_RenderDeviceDriver {
                            void* pIccTransform,
                            int blend_type) override;
   FX_BOOL GetClipBox(FX_RECT* pRect) override;
-  void* GetPlatformSurface() override { return (void*)m_hDC; }
+  void* GetPlatformSurface() const override { return (void*)m_hDC; }
 
   virtual void* GetClipRgn();
   virtual FX_BOOL SetClipRgn(void* pRgn);
@@ -352,7 +352,7 @@ class CPSPrinterDriver : public IFX_RenderDeviceDriver {
                          FX_DWORD color,
                          int alpha_flag,
                          void* pIccTransform) override;
-  void* GetPlatformSurface() override { return (void*)m_hDC; }
+  void* GetPlatformSurface() const override { return (void*)m_hDC; }
 
   HDC m_hDC;
   FX_BOOL m_bCmykOutput;
diff --git a/core/include/fxge/fx_ge.h b/core/include/fxge/fx_ge.h
index 8e9df8c544..d824d08228 100644
--- a/core/include/fxge/fx_ge.h
+++ b/core/include/fxge/fx_ge.h
@@ -14,6 +14,7 @@ class CFX_Font;
 class CFX_FontMgr;
 class CFX_FontCache;
 class CFX_FaceCache;
+class CPDF_ShadingPattern;
 class IFX_RenderDeviceDriver;
 class CCodec_ModuleMgr;
 class SkPictureRecorder;
@@ -215,6 +216,8 @@ class CFX_GraphStateData {
 #define FXRC_BITMASK_OUTPUT 0x400
 #define FXRC_BYTEMASK_OUTPUT 0x800
 #define FXRENDER_IMAGE_LOSSY 0x1000
+#define FXRC_FILLSTROKE_PATH 0x2000
+#define FXRC_SHADING 0x4000
 #define FXFILL_ALTERNATE 1
 #define FXFILL_WINDING 2
 #define FXFILL_FULLCOVER 4
@@ -397,6 +400,15 @@ class CFX_RenderDevice {
  private:
   void InitDeviceInfo();
   void UpdateClipBox();
+  FX_BOOL DrawFillStrokePath(const CFX_PathData* pPathData,
+                             const CFX_Matrix* pObject2Device,
+                             const CFX_GraphStateData* pGraphState,
+                             FX_DWORD fill_color,
+                             FX_DWORD stroke_color,
+                             int fill_mode,
+                             int alpha_flag,
+                             void* pIccTransform,
+                             int blend_type);
 
   CFX_DIBitmap* m_pBitmap;
   int m_Width;
@@ -587,11 +599,16 @@ class IFX_RenderDeviceDriver {
     return FALSE;
   }
 
-  virtual void* GetPlatformSurface() { return NULL; }
-
-  virtual int GetDriverType() { return 0; }
-
+  virtual void* GetPlatformSurface() const { return NULL; }
+  virtual int GetDriverType() const { return 0; }
   virtual void ClearDriver() {}
+
+  virtual FX_BOOL DrawShading(CPDF_ShadingPattern* pPattern,
+                              CFX_Matrix* pMatrix,
+                              int alpha,
+                              FX_BOOL bAlphaMode) {
+    return false;
+  }
 };
 
 class IFX_PSOutput {