Making a sample for shadow maps for more intensive development

src/utils/SkShadowPaintFilterCanvas.h

+/*
+ * 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 SkShadowPaintFilterCanvas_DEFINED
+#define SkShadowPaintFilterCanvas_DEFINED
+
+#include "SkPaintFilterCanvas.h"
+
+#ifdef SK_EXPERIMENTAL_SHADOWING
+
+/** \class SkShadowPaintFilterCanvas
+ *
+ *  A utility proxy class for implementing shadow maps.
+ *
+ *  We override the onFilter method to draw depths into the canvas
+ *  depending on the current draw depth of the canvas, throwing out
+ *  the actual draw color.
+ *
+ *  Note that we can only do this for one light at a time!
+ *  It is up to the user to set the 0th light in fLights to
+ *  the light the want to render the depth map with.
+ */
+class SkShadowPaintFilterCanvas : public SkPaintFilterCanvas {
+public:
+
+    SkShadowPaintFilterCanvas(SkCanvas *canvas);
+
+    // TODO use a shader instead
+    bool onFilter(SkTCopyOnFirstWrite<SkPaint>* paint, Type type) const override;
+
+    static SkISize ComputeDepthMapSize(const SkLights::Light& light, int maxDepth,
+                                       int width, int height);
+
+protected:
+    void onDrawPicture(const SkPicture *picture, const SkMatrix *matrix,
+                       const SkPaint *paint) override;
+
+    void updateMatrix();
+
+    void onDrawPaint(const SkPaint &paint) override;
+
+    void onDrawPoints(PointMode mode, size_t count, const SkPoint pts[],
+                      const SkPaint &paint) override;
+
+    void onDrawRect(const SkRect &rect, const SkPaint &paint) override;
+
+    void onDrawRRect(const SkRRect &rrect, const SkPaint &paint) override;
+
+    void onDrawDRRect(const SkRRect &outer, const SkRRect &inner,
+                      const SkPaint &paint) override;
+
+    void onDrawOval(const SkRect &rect, const SkPaint &paint) override;
+
+    void onDrawPath(const SkPath &path, const SkPaint &paint) override;
+
+    void onDrawBitmap(const SkBitmap &bm, SkScalar left, SkScalar top,
+                      const SkPaint *paint) override;
+
+    void onDrawBitmapRect(const SkBitmap &bm, const SkRect *src, const SkRect &dst,
+                          const SkPaint *paint, SrcRectConstraint constraint) override;
+
+    void onDrawBitmapNine(const SkBitmap &bm, const SkIRect &center,
+                          const SkRect &dst, const SkPaint *paint) override;
+
+    void onDrawImage(const SkImage *image, SkScalar left, SkScalar top,
+                     const SkPaint *paint) override;
+
+    void onDrawImageRect(const SkImage *image, const SkRect *src,
+                         const SkRect &dst, const SkPaint *paint,
+                         SrcRectConstraint constraint) override;
+
+    void onDrawImageNine(const SkImage *image, const SkIRect &center,
+                         const SkRect &dst, const SkPaint *paint) override;
+
+    void onDrawVertices(VertexMode vmode, int vertexCount,
+                        const SkPoint vertices[], const SkPoint texs[],
+                        const SkColor colors[], SkXfermode *xmode,
+                        const uint16_t indices[], int indexCount,
+                        const SkPaint &paint) override;
+
+    void onDrawPatch(const SkPoint cubics[], const SkColor colors[],
+                     const SkPoint texCoords[], SkXfermode *xmode,
+                     const SkPaint &paint) override;
+
+    void onDrawText(const void *text, size_t byteLength, SkScalar x, SkScalar y,
+                    const SkPaint &paint) override;
+
+    void onDrawPosText(const void *text, size_t byteLength, const SkPoint pos[],
+                       const SkPaint &paint) override;
+
+    void onDrawPosTextH(const void *text, size_t byteLength, const SkScalar xpos[],
+                        SkScalar constY, const SkPaint &paint) override;
+
+    void onDrawTextOnPath(const void *text, size_t byteLength, const SkPath &path,
+                          const SkMatrix *matrix, const SkPaint &paint) override;
+
+    void onDrawTextRSXform(const void *text, size_t byteLength,
+                           const SkRSXform xform[], const SkRect *cull,
+                           const SkPaint &paint) override;
+
+    void onDrawTextBlob(const SkTextBlob *blob, SkScalar x,
+                        SkScalar y, const SkPaint &paint) override;
+private:
+    typedef SkPaintFilterCanvas INHERITED;
+};
+
+
+#endif
+#endif