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

2 files changed, 152 insertions, 16 deletions

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,