Add initial implementation of GrShape and GrStyle classes and tests

src/gpu/GrShape.h

Index: src/gpu/GrShape.h
diff --git a/src/gpu/GrShape.h b/src/gpu/GrShape.h
new file mode 100644
index 0000000000000000000000000000000000000000..3c3f9ecec7b661ecbee709b21a85d11b81a214c9
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+++ b/src/gpu/GrShape.h
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+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrShape_DEFINED
+#define GrShape_DEFINED
+
+#include "GrStyle.h"
+#include "SkPath.h"
+#include "SkRRect.h"
+#include "SkTemplates.h"
+#include "SkTLazy.h"
+
+/**
+ * Represents a geometric shape (rrect or path) and the GrStyle that it should be rendered with.
+ * It is possible to apply the style to the GrShape to produce a new GrShape where the geometry
+ * reflects the styling information (e.g. is stroked). It is also possible to apply just the
+ * path effect from the style. In this case the resulting shape will include any remaining
+ * stroking information that is to be applied after the path effect.
+ *
+ * Shapes can produce keys that represent only the geometry information, not the style. Note that
+ * when styling information is applied to produce a new shape then the style has been converted
+ * to geometric information and is included in the new shape's key. When the same style is applied
+ * to two shapes that reflect the same underlying geometry the computed keys of the stylized shapes
+ * will be the same.
+ *
+ * Currently this can only be constructed from a rrect, though it can become a path by applying
+ * style to the geometry. The idea is to expand this to cover most or all of the geometries that
+ * have SkCanvas::draw APIs.
+ */
+class GrShape {
+public:
+    GrShape() : fType(Type::kEmpty) {}
+
+    explicit GrShape(const SkRRect& rrect) : fType(Type::kRRect), fRRect(rrect) {}
+    explicit GrShape(const SkRect& rect) : fType(Type::kRRect), fRRect(SkRRect::MakeRect(rect)) {}
+
+    GrShape(const SkRRect& rrect, const GrStyle& style)
+        : fType(Type::kRRect)
+        , fRRect(rrect)
+        , fStyle(style) {}
+
+    GrShape(const SkRect& rect, const GrStyle& style)
+        : fType(Type::kRRect)
+        , fRRect(SkRRect::MakeRect(rect))
+        , fStyle(style) {}
+
+    GrShape(const SkRRect& rrect, const SkPaint& paint)
+        : fType(Type::kRRect)
+        , fRRect(rrect)
+        , fStyle(paint) {}
+
+    GrShape(const SkRect& rect, const SkPaint& paint)
+        : fType(Type::kRRect)
+        , fRRect(SkRRect::MakeRect(rect))
+        , fStyle(paint) {}
+
+    GrShape(const GrShape&);
+    GrShape& operator=(const GrShape& that);
+
+    ~GrShape() {
+        if (Type::kPath == fType) {
+            fPath.reset();
+        }
+    }
+
+    const GrStyle& style() const { return fStyle; }
+
+    /**
+     * Returns a GrShape where the shape's geometry fully reflects the original shape's GrStyle.
+     * The GrStyle of the returned shape will either be fill or hairline.
+     */
+    GrShape applyFullStyle() { return GrShape(*this, false); }
+
+    /**
+     * Similar to above but applies only the path effect. Path effects take the original geometry
+     * and fill/stroking information and compute a new geometry and residual fill/stroking
+     * information to be applied. The path effect's output geometry and stroking will be captured
+     * in the returned GrShape.
+     */
+    GrShape applyPathEffect() { return GrShape(*this, true); }
+
+    bool asRRect(SkRRect* rrect) const {
+        if (Type::kRRect != fType) {
+            return false;
+        }
+        if (rrect) {
+            *rrect = fRRect;
+        }
+        return true;
+    }
+
+    void asPath(SkPath* out) const {
+        switch (fType) {
+            case Type::kRRect:
+                out->reset();
+                out->addRRect(fRRect);
+                break;
+            case Type::kPath:
+                *out = *fPath.get();
+                break;
+            case Type::kEmpty:
+                out->reset();
+                break;
+        }
+    }
+
+    /**
+     * Gets the size of the key for the shape represented by this GrShape (ignoring its styling).
+     * A negative value is returned if the shape has no key (shouldn't be cached).
+     */
+    int unstyledKeySize() const;
+
+    /**
+     * Writes unstyledKeySize() bytes into the provided pointer. Assumes that there is enough
+     * space allocated for the key and that unstyledKeySize() does not return a negative value
+     * for this shape.
+     */
+    void writeUnstyledKey(uint32_t* key) const;
+
+private:
+    /**
+     * Computes the key length for a GrStyle. The return will be negative if it cannot be turned
+     * into a key.
+     */
+    static int StyleKeySize(const GrStyle& , bool stopAfterPE);
+
+    /**
+     * Writes a unique key for the style into the provided buffer. This function assumes the buffer
+     * has room for at least StyleKeySize() values. It assumes that StyleKeySize() returns a
+     * positive value for the style and stopAfterPE param. This is written so that the key for just
+     * dash application followed by the key for the remaining SkStrokeRec is the same as the
+     * key for applying dashing and SkStrokeRec all at once.
+     */
+    static void StyleKey(uint32_t*, const GrStyle&, bool stopAfterPE);
+
+    /** Constructor used by Apply* functions */
+    GrShape(const GrShape& parentShape, bool stopAfterPE);
+
+    /**
+     * Determines the key we should inherit from the input shape's geometry and style when
+     * we are applying the style to create a new shape.
+     */
+    void setInheritedKey(const GrShape& parentShape, bool stopAfterPE);
+
+    enum class Type {
+        kEmpty,
+        kRRect,
+        kPath,
+    } fType;
+
+    SkRRect                     fRRect;
+    SkTLazy<SkPath>             fPath;
+    GrStyle                     fStyle;
+    SkAutoSTArray<8, uint32_t>  fInheritedKey;
+};
+#endif