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      1 /*
      2 * Copyright 2014 Google Inc.
      3 *
      4 * Use of this source code is governed by a BSD-style license that can be
      5 * found in the LICENSE file.
      6 */
      7 
      8 #ifndef GrRectanizer_pow2_DEFINED
      9 #define GrRectanizer_pow2_DEFINED
     10 
     11 #include "GrRectanizer.h"
     12 #include "SkPoint.h"
     13 
     14 // This Rectanizer quantizes the incoming rects to powers of 2. Each power
     15 // of two can have, at most, one active row/shelf. Once a row/shelf for
     16 // a particular power of two gets full its fRows entry is recycled to point
     17 // to a new row.
     18 // The skyline algorithm almost always provides a better packing.
     19 class GrRectanizerPow2 : public GrRectanizer {
     20 public:
     21     GrRectanizerPow2(int w, int h) : INHERITED(w, h) {
     22         this->reset();
     23     }
     24 
     25     virtual ~GrRectanizerPow2() { }
     26 
     27     virtual void reset() SK_OVERRIDE {
     28         fNextStripY = 0;
     29         fAreaSoFar = 0;
     30         sk_bzero(fRows, sizeof(fRows));
     31     }
     32 
     33     virtual bool addRect(int w, int h, SkIPoint16* loc) SK_OVERRIDE;
     34 
     35     virtual float percentFull() const SK_OVERRIDE {
     36         return fAreaSoFar / ((float)this->width() * this->height());
     37     }
     38 
     39 private:
     40     static const int kMIN_HEIGHT_POW2 = 2;
     41     static const int kMaxExponent = 16;
     42 
     43     struct Row {
     44         SkIPoint16  fLoc;
     45         // fRowHeight is actually known by this struct's position in fRows
     46         // but it is used to signal if there exists an open row of this height
     47         int         fRowHeight;
     48 
     49         bool canAddWidth(int width, int containerWidth) const {
     50             return fLoc.fX + width <= containerWidth;
     51         }
     52     };
     53 
     54     Row fRows[kMaxExponent];    // 0-th entry will be unused
     55 
     56     int fNextStripY;
     57     int32_t fAreaSoFar;
     58 
     59     static int HeightToRowIndex(int height) {
     60         SkASSERT(height >= kMIN_HEIGHT_POW2);
     61         int index = 32 - SkCLZ(height - 1);
     62         SkASSERT(index < kMaxExponent);
     63         return index;
     64     }
     65 
     66     bool canAddStrip(int height) const {
     67         return fNextStripY + height <= this->height();
     68     }
     69 
     70     void initRow(Row* row, int rowHeight) {
     71         row->fLoc.set(0, fNextStripY);
     72         row->fRowHeight = rowHeight;
     73         fNextStripY += rowHeight;
     74     }
     75 
     76     typedef GrRectanizer INHERITED;
     77 };
     78 
     79 #endif
     80