add isolate (init-with-previous) savelayer flag

BUG=skia:4884

Change-Id: If7fabf5cc2c87b870f48dfb87e27a2524fec5ae5
Reviewed-on: https://skia-review.googlesource.com/9045
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>

1 files changed, 20 insertions, 3 deletions

diff --git a/gm/savelayer.cpp b/gm/savelayer.cpp
index 510fc2f1f4..6a01edd4f0 100644
--- a/gm/savelayer.cpp
+++ b/gm/savelayer.cpp
@@ -80,6 +80,8 @@ private:
 
     typedef skiagm::GM INHERITED;
 };
+DEF_GM(return new UnclippedSaveLayerGM(UnclippedSaveLayerGM::Mode::kClipped);)
+DEF_GM(return new UnclippedSaveLayerGM(UnclippedSaveLayerGM::Mode::kUnclipped);)
 
 DEF_SIMPLE_GM(picture_savelayer, canvas, 320, 640) {
     SkPaint paint1, paint2, paint3;
@@ -99,8 +101,23 @@ DEF_SIMPLE_GM(picture_savelayer, canvas, 320, 640) {
     }
 };
 
-//////////////////////////////////////////////////////////////////////////////
+#include "Resources.h"
 
-DEF_GM(return new UnclippedSaveLayerGM(UnclippedSaveLayerGM::Mode::kClipped);)
-DEF_GM(return new UnclippedSaveLayerGM(UnclippedSaveLayerGM::Mode::kUnclipped);)
+// Test kInitWithPrevious_SaveLayerFlag by drawing an image, save a layer with the flag, which
+// should seed the layer with the image (from below). Then we punch a hole in the layer and
+// restore with kPlus mode, which should show the mandrill super-bright on the outside, but
+// normal where we punched the hole.
+DEF_SIMPLE_GM(savelayer_initfromprev, canvas, 256, 256) {
+    canvas->drawImage(GetResourceAsImage("mandrill_256.png"), 0, 0, nullptr);
+
+    SkCanvas::SaveLayerRec rec;
+    SkPaint paint;
+    paint.setBlendMode(SkBlendMode::kPlus);
+    rec.fSaveLayerFlags = SkCanvas::kInitWithPrevious_SaveLayerFlag;
+    rec.fPaint = &paint;
+    canvas->saveLayer(rec);
+    paint.setBlendMode(SkBlendMode::kClear);
+    canvas->drawCircle(128, 128, 96, paint);
+    canvas->restore();
+};