/*
* lcdc.0
*
* when 0 => sprites are always displayed on top of the bg
*
* bg tile attribute.7
*
* when 0 => use oam priority bit
* when 1 => bg priority
*
* sprite attribute.7
*
* when 0 => sprite above bg
* when 1 => sprite above bg color 0
*/
public void SetOverlay(int[] pixelLine, int offset, TileAttributes spriteAttr, int oamIndex)
{
for (var j = offset; j < pixelLine.Length; j++)
{
var p = pixelLine[j];
var i = j - offset;
if (p == 0)
{
continue; // color 0 is always transparent
}
var oldPriority = _priorities.Get(i);
var put = false;
if ((oldPriority == -1 || oldPriority == 100) && !_lcdc.IsBgAndWindowDisplay())
{
// this one takes precedence
put = true;
}
else if (oldPriority == 100)
{
// bg with priority
put = _pixels.Get(i) == 0;
}
else if (oldPriority == -1 && !spriteAttr.IsPriority())
{
// bg without priority
put = true;
}
else if (oldPriority == -1 && spriteAttr.IsPriority() && _pixels.Get(i) == 0)
{
// bg without priority
put = true;
}
else if (oldPriority >= 0 && oldPriority < 10)
{
// other sprite
put = oldPriority > oamIndex;
}
if (put)
{
_pixels.Set(i, p);
_palettes.Set(i, spriteAttr.GetColorPaletteIndex());
_priorities.Set(i, oamIndex);
}
}
}