commit d70e275db0232ebed12e3c10f9f50ce0d8373695
author Hui Yingst <nigi@chromium.org> Fri Jan 17 19:34:28 2020 +0000
committer Chromium commit bot <commit-bot@chromium.org> Fri Jan 17 19:34:28 2020 +0000
tree 5a6c998252f728ca9807ea416d3875545227e0ca
parent 8de9f0684adb396c230e8d370f51f2f3b46c6d7b

[SkiaPaths] Tiling pattern with overlapping paths causes unwanted grid.

When a colored tiling pattern's opacity value is not 1.0, the section
of overlapped patterns will have a different shade of color.
bug_1286.in is not rendered correctly because the patterns' paths
(borders) are overlapping and SkiaPaths chose to use
kDifference_SkPathOp to subtract the latter path from the previous one,
which result in the overlapping paths to have a lighter color than the
pattern itself and displayed as a grid. Need to use kUnion_SkPathOp to
union the overlapping paths and skip stroking the path if the path's
fill color is the same as the stroke color, so that the overlapping
part of the unionized paths won't show in a darker shade.

Bug: pdfium:1342
Change-Id: Ideb665ae42bd077f6fe3be364a056286a520a1e6
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/60230
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Hui Yingst <nigi@chromium.org>

core/fxge/skia/fx_skia_device.cpp

diff --git a/core/fxge/skia/fx_skia_device.cpp b/core/fxge/skia/fx_skia_device.cpp
index ad42393..aae7a5d 100644
--- a/core/fxge/skia/fx_skia_device.cpp
+++ b/core/fxge/skia/fx_skia_device.cpp
@@ -787,15 +787,21 @@
     SkCanvas* skCanvas = m_pDriver->SkiaCanvas();
     SkAutoCanvasRestore scoped_save_restore(skCanvas, /*doSave=*/true);
     skCanvas->concat(skMatrix);
+    bool do_stroke = true;
     if (m_fillPath) {
       SkPath strokePath;
       const SkPath* fillPath = &m_skPath;
       if (stroke_alpha) {
         if (m_groupKnockout) {
           skPaint.getFillPath(m_skPath, &strokePath);
-          if (Op(m_skPath, strokePath, SkPathOp::kDifference_SkPathOp,
+          if (m_strokeColor == m_fillColor &&
+              Op(m_skPath, strokePath, SkPathOp::kUnion_SkPathOp,
                  &strokePath)) {
             fillPath = &strokePath;
+            do_stroke = false;
+          } else if (Op(m_skPath, strokePath, SkPathOp::kDifference_SkPathOp,
+                        &strokePath)) {
+            fillPath = &strokePath;
           }
         }
       }
@@ -807,7 +813,7 @@
       DebugShowSkiaDrawPath(m_pDriver.Get(), skCanvas, skPaint, *fillPath);
       skCanvas->drawPath(*fillPath, skPaint);
     }
-    if (stroke_alpha) {
+    if (stroke_alpha && do_stroke) {
       skPaint.setStyle(SkPaint::kStroke_Style);
       skPaint.setColor(m_strokeColor);
 #ifdef _SKIA_SUPPORT_PATHS_
@@ -2050,6 +2056,7 @@
   SkPath skPath = BuildPath(pPathData);
   SkAutoCanvasRestore scoped_save_restore(m_pCanvas, /*doSave=*/true);
   m_pCanvas->concat(skMatrix);
+  bool do_stroke = true;
   if (GetAlternateOrWindingFillMode(fill_mode) && fill_color) {
     skPath.setFillType(GetAlternateOrWindingFillType(fill_mode));
     SkPath strokePath;
@@ -2057,8 +2064,12 @@
     if (is_paint_stroke) {
       if (m_bGroupKnockout) {
         skPaint.getFillPath(skPath, &strokePath);
-        if (Op(skPath, strokePath, SkPathOp::kDifference_SkPathOp,
-               &strokePath)) {
+        if (stroke_color == fill_color &&
+            Op(skPath, strokePath, SkPathOp::kUnion_SkPathOp, &strokePath)) {
+          fillPath = &strokePath;
+          do_stroke = false;
+        } else if (Op(skPath, strokePath, SkPathOp::kDifference_SkPathOp,
+                      &strokePath)) {
           fillPath = &strokePath;
         }
       }
@@ -2071,7 +2082,7 @@
     DebugShowSkiaDrawPath(this, m_pCanvas, skPaint, *fillPath);
     m_pCanvas->drawPath(*fillPath, skPaint);
   }
-  if (is_paint_stroke) {
+  if (is_paint_stroke && do_stroke) {
     skPaint.setStyle(SkPaint::kStroke_Style);
     skPaint.setColor(stroke_color);
 #ifdef _SKIA_SUPPORT_PATHS_