Don't use analytic clip FPs when drawing to stencil

It doesn't make sense to multiply by coverage when drawing to stencil.
This could theoretically work with FPs that discard and/or modify
the sample mask, but for the time being an analytic FP means one that
calculates a coverage value.

Bug: skia:7190
Change-Id: Ic40cf6c19c377cba80bad458993582f5cc07022a
Reviewed-on: https://skia-review.googlesource.com/67423
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>

1 files changed, 59 insertions, 0 deletions

diff --git a/src/gpu/GrStencilClip.h b/src/gpu/GrStencilClip.h
new file mode 100644
index 0000000000..2bbf3b44de
--- /dev/null
+++ b/src/gpu/GrStencilClip.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrStencilClip_DEFINED
+#define GrStencilClip_DEFINED
+
+#include "GrAppliedClip.h"
+#include "GrFixedClip.h"
+
+/**
+ * Implements GrHardClip with the currently-existing stencil buffer contents and GrFixedClip.
+ */
+class GrStencilClip final : public GrHardClip {
+public:
+    GrStencilClip(uint32_t stencilStackID = SK_InvalidGenID) : fStencilStackID(stencilStackID) {}
+
+    explicit GrStencilClip(const SkIRect& scissorRect, uint32_t stencilStackID = SK_InvalidGenID)
+        : fFixedClip(scissorRect)
+        , fStencilStackID(stencilStackID) {
+    }
+
+    const GrFixedClip& fixedClip() const { return fFixedClip; }
+    GrFixedClip& fixedClip() { return fFixedClip; }
+
+    bool stencilStackID() const { return fStencilStackID; }
+    bool hasStencilClip() const { return SK_InvalidGenID != fStencilStackID; }
+    void setStencilClip(uint32_t stencilStackID) { fStencilStackID = stencilStackID; }
+
+    bool quickContains(const SkRect& rect) const override {
+        return !this->hasStencilClip() && fFixedClip.quickContains(rect);
+    }
+    void getConservativeBounds(int width, int height, SkIRect* bounds, bool* iior) const override {
+        fFixedClip.getConservativeBounds(width, height, bounds, iior);
+    }
+    bool isRRect(const SkRect& rtBounds, SkRRect* rr, GrAA* aa) const override {
+        return !this->hasStencilClip() && fFixedClip.isRRect(rtBounds, rr, aa);
+    }
+    bool apply(int rtWidth, int rtHeight, GrAppliedHardClip* out, SkRect* bounds) const override {
+        if (!fFixedClip.apply(rtWidth, rtHeight, out, bounds)) {
+            return false;
+        }
+        if (this->hasStencilClip()) {
+            out->addStencilClip(fStencilStackID);
+        }
+        return true;
+    }
+
+private:
+    GrFixedClip   fFixedClip;
+    uint32_t      fStencilStackID;
+
+    typedef GrClip INHERITED;
+};
+
+#endif