/// <summary>
/// Return the operation(s) to perform at the beginning or end of a
/// scan line, given a dest and source word.
/// </summary>
private EdgeStrategy GetEdgeStrategy(CombinerFlags dstMask, CombinerFlags srcMask)
{
int lookup = (((int)_direction << 6) |
(((int)dstMask & 0x6) << 3) | // XXX
(((int)srcMask & 0x6) << 1) | // XXX
((_leftOver ? 1 : 0) << 1) |
((_extraSrcWord && _xOffset > 0) ? 1 : 0));
EdgeStrategy result = _rscTable[lookup];
#if TRACING_ENABLED
if (Trace.TraceOn)
{
Trace.Log(LogType.RasterOp, "RasterOp: EdgeStrategy lookup {0:x3} --> {1}", lookup, result);
}
#endif
#if DEBUG
// Draw attention for debugging; should throw an exception in release version...
if (result == EdgeStrategy.Unknown)
{
Console.WriteLine("==> Unknown edge strategy {0:x3}! <==", lookup);
}
#endif
return(result);
}
private RasterOp()
{
_ropShifter = new Shifter(); // Our own private Idaho
_srcFifo = new Queue <ROpWord>(16); // 4 quads (hardware limit)
_destFifo = new Queue <ROpWord>(4); // 1 quad
_halfPipe = new ROpWord(); // 1 word, for overlap
_rdsTable = new CombinerFlags[512]; // 9 bit index
_rscTable = new EdgeStrategy[128]; // 7 bit index
LoadRasterOpROMs();
}
/// <summary>
/// Returns the correct Mask for a given source word in the current quad.
/// </summary>
/// <param name="index">Source word index 0..3</param>
/// <returns>Combiner mask value</returns>
private CombinerFlags SrcWordMask(int index)
{
// Create a 9-bit index into the RDS ROM lookup tablee
int lookup = (((int)_phase & 0x3) << 7) |
((int)_direction << 6) |
(_srcWordPosition << 4) |
(_lastSrcPosition << 2) |
index;
// Same table as the dest word for source word mask!
CombinerFlags result = _rdsTable[lookup];
#if TRACING_ENABLED
if (Trace.TraceOn)
{
Trace.Log(LogType.RasterOp, "RasterOp: SrcWordMask lookup {0:x} --> {1}", lookup, result);
}
#endif
return(result);
}
/// <summary>
/// Returns the correct Mask for a given destination word in the current quad.
/// </summary>
/// <param name="index">Destination word index 0..3</param>
/// <returns>Combiner mask value</returns>
private CombinerFlags DestWordMask(int index)
{
// Create the 9-bit index into the RDS ROM lookup table
int lookup = (((int)_phase & 0x3) << 7) |
((int)_direction << 6) |
(_destWordPosition << 4) |
(_widthExtraWords << 2) |
index;
// Annnnd return the result!
CombinerFlags result = _rdsTable[lookup];
#if TRACING_ENABLED
if (Trace.TraceOn)
{
Trace.Log(LogType.RasterOp, "RasterOp: DestWordMask lookup {0:x} --> {1}", lookup, result);
}
#endif
return(result);
}
