gistfile1.txt

function floodFillScanline(x, y, width, height, diagonal, test, paint) {
    // xMin, xMax, y, down[true] / up[false], extendLeft, extendRight
    var ranges = [[x, x, y, null, true, true]];
    paint(x, y);
 
    while(ranges.length) {
        var r = ranges.pop();
        var down = r[3] === true;
        var up =   r[3] === false;
 
        // extendLeft
        var minX = r[0];
        var y = r[2];
        if(r[4]) {
            while(minX>0 && test(minX-1, y)) {
                minX–;
                paint(minX, y);
            }
        }
        var maxX = r[1];
        // extendRight
        if(r[5]) {
            while(maxX<width-1 && test(maxX+1, y)) {
                maxX++;
                paint(maxX, y);
            }
        }
 
        if(diagonal) {
            // extend range looked at for next lines
            if(minX>0) minX&#8211;;
            if(maxX<width-1) maxX++;
        }
        else {
            // extend range ignored from previous line
            r[0]--;
            r[1]++;
        }
 
        function addNextLine(newY, isNext, downwards) {
            var rMinX = minX;
            var inRange = false;
            for(var x=minX; x<=maxX; x++) {
                // skip testing, if testing previous line within previous range
                var empty = (isNext || (x<r[0] || x>r[1])) && test(x, newY);
                if(!inRange && empty) {
                    rMinX = x;
                    inRange = true;
                }
                else if(inRange && !empty) {
                    ranges.push([rMinX, x-1, newY, downwards, rMinX==minX, false]);
                    inRange = false;
                }
                if(inRange) {
                    paint(x, newY);
                }
                // skip
                if(!isNext && x==r[0]) {
                    x = r[1];
                }
            }
            if(inRange) {
                ranges.push([rMinX, x-1, newY, downwards, rMinX==minX, true]);
            }
        }
 
        if(y<height)
            addNextLine(y+1, !up, true);
        if(y>0)
            addNextLine(y-1, !down, false);
    }
}