Method HeliIntroBlit_OpaqueAlignedX

Source/PC/Graphics_PC.cpp:881–961

}

void cGraphics_PC::HeliIntroBlit_OpaqueAlignedX(tSharedBuffer pDsSi, int16 pCx)
{
	uint8* Ds = pDsSi->data();

	// Original logic works in 4-pixel groups (80 groups for 320px wide).
	const int16 groupX = (pCx >> 2);
	int16 ax = groupX;
	int16 dx = ax;

	ax -= 80;
	int16 word_4285F = -ax;

	const int planeShift = (pCx & 3); // <-- the bit the old code discards

	// Base points at the first 4-pixel group for pCx, Y offset unchanged.
	uint8* base = mSurface->GetSurfaceBuffer() + mMission_Intro_DrawY + (groupX * 4);

	++dx;

	for (uint8 srcPlane = 0; srcPlane < 4; ++srcPlane)
	{
		// Map source plane (0..3) to the correct destination plane for pixel-accurate X.
		const int dstPlane = (srcPlane + planeShift) & 3;

		// If the plane rotation wraps (e.g. planeShift=3, srcPlane=2 -> 5),
		// that plane's pixels start one 4-pixel group later.
		const int groupCarry = ((srcPlane + planeShift) >> 2) & 1;

		// we might start in the next group depending on carry.
		uint8* destPtr = base + (groupCarry * 4) + dstPlane;
		uint8* di = destPtr;

		for (int16 bx = mMission_Intro_DrawX; bx > 0; --bx)
		{
			int16 cx = word_4285F;

			if (cx & 1)
			{
				*di = *Ds++;
				di += 4;
			}

			cx >>= 1;
			while (cx > 0)
			{
				*di = *Ds++;
				di += 4;

				*di = *Ds++;
				di += 4;

				--cx;
			}

			cx = dx;

			di -= mSurface->GetWidth() - 12 - 16;
			--Ds;