[feisty2]

update:
revamped: Preprocess() is now replaced by RegisterInvokingSequence(), you may invoke a sequence of filters (including the very filter that is being defined, you may invoke this "self" filter via SelfInvoker) any way you like. basically, you get to write something like a vpy script in RegisterInvokingSequence and if this function is absent in your filter, it is assumed that the output is SelfInvoker()

say you defined a 3x3 blurring filter in DrawFrame and you wanna repeat it 10 times:

auto RegisterInvokingSequence(auto Core, auto&& SelfInvoker, auto Console) {
	for (auto _ : Range{ 10 })
		InputClip = SelfInvoker("clip", InputClip);
	Console.Receive(InputClip);
}

you wanna upsize it by a factor of 2 after blurring.

auto RegisterInvokingSequence(auto Core, auto&& SelfInvoker, auto Console) {
	for (auto _ : Range{ 10 })
		InputClip = SelfInvoker("clip", InputClip);
	InputClip = Core["fmtc"]["resample"]("clip", InputClip, "width", InputClip.Width * 2, "height", InputClip.Height * 2);
	Console.Receive(InputClip);
}

and you wanna transpose the clip before all this happens

auto RegisterInvokingSequence(auto Core, auto&& SelfInvoker, auto Console) {
	InputClip = Core["std"]["Transpose"]("clip", InputClip);
	for (auto _ : Range{ 10 })
		InputClip = SelfInvoker("clip", InputClip);
	InputClip = Core["fmtc"]["resample"]("clip", InputClip, "width", InputClip.Width * 2, "height", InputClip.Height * 2);
	Console.Receive(InputClip);
}