src/core/SkAntiRun.h

/* libs/graphics/sgl/SkAntiRun.h
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License"); 
** you may not use this file except in compliance with the License. 
** You may obtain a copy of the License at 
**
**     http://www.apache.org/licenses/LICENSE-2.0 
**
** Unless required by applicable law or agreed to in writing, software 
** distributed under the License is distributed on an "AS IS" BASIS, 
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
** See the License for the specific language governing permissions and 
** limitations under the License.
*/

#ifndef SkAntiRun_DEFINED
#define SkAntiRun_DEFINED

#include "SkBlitter.h"

class SkAlphaRuns {
public:
    int16_t*    fRuns;
    uint8_t*     fAlpha;

    bool empty() const {
        SkASSERT(fRuns[0] > 0);
        return fAlpha[0] == 0 && fRuns[fRuns[0]] == 0;
    }

    void    reset(int width);
    
    /**
     *  Returns the offsetX value that should be passed on the next call,
     *  assuming we're on the same scanline. If the caller is switching
     *  scanlines, then offsetX should be 0 when this is called.
     */
    int add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha,
            U8CPU maxValue, int offsetX);

    SkDEBUGCODE(void assertValid(int y, int maxStep) const;)
    SkDEBUGCODE(void dump() const;)

    static void Break(int16_t runs[], uint8_t alpha[], int x, int count);

    static void BreakAt(int16_t runs[], uint8_t alpha[], int x) {
        while (x > 0) {
            int n = runs[0];
            SkASSERT(n > 0);

            if (x < n) {
                alpha[x] = alpha[0];
                runs[0] = SkToS16(x);
                runs[x] = SkToS16(n - x);
                break;
            }
            runs += n;
            alpha += n;
            x -= n;
        }
    }

private:
    SkDEBUGCODE(int fWidth;)
    SkDEBUGCODE(void validate() const;)
};

#endif