Experiment to track coverage in a layer

Bug: skia:
Change-Id: I5ed334f63e64991944394dc8103092a2c6280546
Reviewed-on: https://skia-review.googlesource.com/122000
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>

1 files changed, 39 insertions, 0 deletions

diff --git a/gm/savelayer.cpp b/gm/savelayer.cpp
index 32f95bfc7d..77218206c7 100644
--- a/gm/savelayer.cpp
+++ b/gm/savelayer.cpp
@@ -238,3 +238,42 @@ DEF_SIMPLE_GM(savelayer_clipmask, canvas, 1200, 1200) {
         }
     }
 }
+
+DEF_SIMPLE_GM(savelayer_coverage, canvas, 500, 500) {
+    canvas->saveLayer(nullptr, nullptr);
+
+    SkRect r = { 0, 0, 200, 200 };
+    SkPaint layerPaint;
+    layerPaint.setBlendMode(SkBlendMode::kModulate);
+
+    auto image = GetResourceAsImage("images/mandrill_128.png");
+
+    auto proc = [layerPaint](SkCanvas* canvas, SkCanvas::SaveLayerRec& rec) {
+        SkPaint paint;
+        paint.setColor(SK_ColorRED);
+
+        canvas->saveLayer(rec);
+        canvas->drawCircle(100, 100, 50, paint);
+        paint.setColor(0x8800FF00);
+        canvas->drawRect({10, 90, 190, 110}, paint);
+        canvas->restore();
+    };
+
+    const int yflags[] = { 0, SkCanvas::kInitWithPrevious_SaveLayerFlag };
+    for (int y = 0; y <= 1; ++y) {
+        const int xflags[] = { 0, SkCanvas::kMaskAgainstCoverage_EXPERIMENTAL_DONT_USE_SaveLayerFlag };
+        for (int x = 0; x <= 1; ++x) {
+            canvas->save();
+            canvas->translate(x * 200.f, y * 200.f);
+
+            SkCanvas::SaveLayerRec rec(&r, &layerPaint, yflags[y] | xflags[x]);
+            canvas->drawImageRect(image, r, nullptr);
+            proc(canvas, rec);
+
+            canvas->restore();
+        }
+    }
+
+    canvas->restore();
+}
+