commit 872da6b5713b966f628c54fcc2ad115054da4212
author Jim Van Verth <jvanverth@google.com> Tue Apr 10 11:24:11 2018 -0400
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Tue Apr 10 16:31:32 2018 +0000
tree ae466ee7c23eb0571a65a07f25baf048bd22a0eb
parent 3cdd7e22dd540fe472f40b50f99ecd82679d4dec

Add initial support for simple concave shadows.

Adds support for spot shadow outlines. Since filling the penumbra still
needs to be done, this code is disabled for now.

Bug: skia:
Change-Id: I3369eb13832b47ad16dd29ce7c7d6a1a10b39aeb
Reviewed-on: https://skia-review.googlesource.com/22363
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>

src/utils/SkOffsetPolygon.cpp

diff --git a/src/utils/SkOffsetPolygon.cpp b/src/utils/SkOffsetPolygon.cpp
index bfd12d2..94fe965 100755
--- a/src/utils/SkOffsetPolygon.cpp
+++ b/src/utils/SkOffsetPolygon.cpp
@@ -218,11 +218,26 @@
     OffsetSegment fInset;
     SkPoint       fIntersection;
     SkScalar      fTValue;
+    uint16_t      fStart;
+    uint16_t      fEnd;
+    uint16_t      fIndex;
     bool          fValid;
 
     void init() {
         fIntersection = fInset.fP0;
         fTValue = SK_ScalarMin;
+        fStart = 0;
+        fEnd = 0;
+        fIndex = 0;
+        fValid = true;
+    }
+
+    void init(uint16_t start, uint16_t end) {
+        fIntersection = fInset.fP0;
+        fTValue = SK_ScalarMin;
+        fStart = start;
+        fEnd = end;
+        fIndex = start;
         fValid = true;
     }
 };
@@ -571,7 +586,8 @@
 
 // TODO: assuming a constant offset here -- do we want to support variable offset?
 bool SkOffsetSimplePolygon(const SkPoint* inputPolygonVerts, int inputPolygonSize,
-                           SkScalar offset, SkTDArray<SkPoint>* offsetPolygon) {
+                           SkScalar offset, SkTDArray<SkPoint>* offsetPolygon,
+                           SkTDArray<int>* polygonIndices) {
     if (inputPolygonSize < 3) {
         return false;
     }
@@ -625,20 +641,20 @@
                 EdgeData& edge = edgeData.push_back();
                 edge.fInset.fP0 = inputPolygonVerts[currIndex] + prevNormal;
                 edge.fInset.fP1 = inputPolygonVerts[currIndex] + currNormal;
-                edge.init();
+                edge.init(currIndex, currIndex);
                 prevNormal = currNormal;
             }
             EdgeData& edge = edgeData.push_back();
             edge.fInset.fP0 = inputPolygonVerts[currIndex] + prevNormal;
             edge.fInset.fP1 = inputPolygonVerts[currIndex] + normals[currIndex];
-            edge.init();
+            edge.init(currIndex, currIndex);
         }
 
         // Add the edge
         EdgeData& edge = edgeData.push_back();
         edge.fInset.fP0 = inputPolygonVerts[currIndex] + normals[currIndex];
         edge.fInset.fP1 = inputPolygonVerts[nextIndex] + normals[currIndex];
-        edge.init();
+        edge.init(currIndex, nextIndex);
 
         prevIndex = currIndex;
         currIndex++;
@@ -654,6 +670,10 @@
             prevIndex = (prevIndex + edgeDataSize - 1) % edgeDataSize;
             continue;
         }
+        if (!edgeData[currIndex].fValid) {
+            currIndex = (currIndex + 1) % edgeDataSize;
+            continue;
+        }
 
         SkScalar s, t;
         SkPoint intersection;
@@ -676,6 +696,7 @@
                 // add intersection
                 edgeData[currIndex].fIntersection = intersection;
                 edgeData[currIndex].fTValue = t;
+                edgeData[currIndex].fIndex = edgeData[prevIndex].fEnd;
 
                 // go to next segment
                 prevIndex = currIndex;
@@ -714,6 +735,9 @@
                                                                        (*offsetPolygon)[currIndex],
                                                                        kCleanupTolerance))) {
             *offsetPolygon->push() = edgeData[i].fIntersection;
+            if (polygonIndices) {
+                *polygonIndices->push() = edgeData[i].fIndex;
+            }
             currIndex++;
         }
     }
@@ -722,6 +746,9 @@
         SkPointPriv::EqualsWithinTolerance((*offsetPolygon)[0], (*offsetPolygon)[currIndex],
                                            kCleanupTolerance)) {
         offsetPolygon->pop();
+        if (polygonIndices) {
+            polygonIndices->pop();
+        }
     }
 
     // compute signed area to check winding (it should be same as the original polygon)