Method GetCachedBitmap

source/common/textures/image.cpp:193–272

//==========================================================================

FBitmap FImageSource::GetCachedBitmap(const PalEntry *remap, int conversion, int *ptrans, int frame)
{
	FBitmap ret;

	int trans = -1;
	auto imageID = ImageID;

	if (NumOfFrames == 1 && frame == 1)
	{
		frame = 0;
	}

	if (remap != nullptr)
	{
		// Remapped images are never run through the cache because they would complicate matters too much for very little gain.
		// Translated images are normally sprites which normally just consist of a single image and use no composition.
		// Additionally, since translation requires the base palette, the really time consuming stuff will never be subjected to it.
		ret.Create(Width, Height);
		trans = CopyTranslatedPixels(&ret, remap, frame);
	}
	else
	{
		if (conversion == luminance) conversion = normal;	// luminance has no meaning for true color.
		// Do we have this image in the cache?
		unsigned index = conversion != normal? UINT_MAX : precacheDataRgba.FindEx([=](PrecacheDataRgba &entry) { return entry.ImageID == imageID && entry.Frame == frame; });
		if (index < precacheDataRgba.Size())
		{
			auto cache = &precacheDataRgba[index];

			trans = cache->TransInfo;
			if (cache->RefCount > 1)
			{
				//Printf("returning reference to %s, refcount = %d\n", name.GetChars(), cache->RefCount);
				ret.Copy(cache->Pixels, false);
				cache->RefCount--;
			}
			else if (cache->Pixels.GetPixels())
			{
				//Printf("returning contents of %s, refcount = %d\n", name.GetChars(), cache->RefCount);
				ret = std::move(cache->Pixels);
				precacheDataRgba.Delete(index);
			}
			else
			{
				// This should never happen if the function is implemented correctly
				//Printf("something bad happened for %s, refcount = %d\n", name.GetChars(), cache->RefCount);
				ret.Create(Width, Height);
				trans = CopyPixels(&ret, normal, frame);
			}
		}
		else
		{
			// The image wasn't cached. Now there's two possibilities:
			auto info = precacheInfo.CheckKey(ImageID);
			if (!info || info->first <= 1 || conversion != normal)
			{
				// This is either the only copy needed or some access outside the caching block. In these cases create a new one and directly return it.
				//Printf("returning fresh copy of %s\n", name.GetChars());