ShaderSwitch32.osl

////////////////////////////////////////////////////////////////////////////
// Shader Switch (32-way)
//
// An extension on Redshift's built-in 10-way RS Shader Switch. Instead of
// chaining shaders to achieve more slots, you can use this OSL shader. It
// utilizes a decision tree to perform the switch with 5 comparisons. One
// additional comparison is performed only for the first and last input.
//
// Author: Geoff Bolton
// Created: 2023-04-24
//
// This work is licensed under a Creative Commons Attribution 3.0 Unported
// License: https://creativecommons.org/licenses/by/3.0/deed.en_US
////////////////////////////////////////////////////////////////////////////
#define INPUT_ID(id) shader ## id
#define INPUT_DEF(id) color INPUT_ID(id) = 1 [[ string label="Shader "#id ]]

#define CHOOSE2(id0, id1)				\
	outColor = (index < id1)			\
		? INPUT_ID(id0)					\
		: INPUT_ID(id1)

#define CHOOSE(id0, id1, id2, id3)		\
	if (index < id2) {					\
		CHOOSE2(id0, id1);				\
	} else {							\
		CHOOSE2(id2, id3);				\
	}

// Left-bounded at id0
#define CHOOSE_L(id0, id1, id2, id3)	\
	if (index < id2) {					\
		outColor = (index < id1)		\
			? (index == id0				\
				? INPUT_ID(id0)			\
				: default_shader)		\
			: INPUT_ID(id1);			\
	} else {							\
		CHOOSE2(id2, id3);				\
	}

// Right-bounded at id3
#define CHOOSE_R(id0, id1, id2, id3)	\
	if (index < id2) {					\
		CHOOSE2(id0, id1);				\
	} else {							\
		outColor = (index < id3)		\
			? INPUT_ID(id2)				\
			: (index == id3				\
				? INPUT_ID(id3)			\
				: default_shader);		\
	}
////////////////////////////////////////////////////////////////////////////

shader ShaderSwitch32(
	int selector = 0 [[ string label="Shader Selector" ]],
	int selector_offset = 0 [[ string label="Offset", int connectable=0 ]],
	INPUT_DEF(0), 	INPUT_DEF(1),	INPUT_DEF(2),	INPUT_DEF(3),
	INPUT_DEF(4), 	INPUT_DEF(5),	INPUT_DEF(6),	INPUT_DEF(7),
	INPUT_DEF(8), 	INPUT_DEF(9),	INPUT_DEF(10),	INPUT_DEF(11),
	INPUT_DEF(12),	INPUT_DEF(13),	INPUT_DEF(14),	INPUT_DEF(15),
	INPUT_DEF(16),	INPUT_DEF(17),	INPUT_DEF(18),	INPUT_DEF(19),
	INPUT_DEF(20),	INPUT_DEF(21),	INPUT_DEF(22),	INPUT_DEF(23),
	INPUT_DEF(24),	INPUT_DEF(25),	INPUT_DEF(26),	INPUT_DEF(27),
	INPUT_DEF(28),	INPUT_DEF(29),	INPUT_DEF(30),	INPUT_DEF(31),
	color default_shader = 1 [[ string label="Default Shader" ]],
	output color outColor = 0,
	output int outIndex = 0)
{
	int index = selector - selector_offset;
	outIndex = index;

	if (index < 16)	{
		if (index < 8) {
			if (index < 4) {
				CHOOSE_L(0, 1, 2, 3);
			} else {
				CHOOSE(4, 5, 6, 7);
			}
		} else {
			if (index < 12) {
				CHOOSE(8, 9, 10, 11);
			} else {
				CHOOSE(12, 13, 14, 15);
			}
		}
	} else {
		if (index < 24) {
			if (index < 20) {
				CHOOSE(16, 17, 18, 19);
			} else {
				CHOOSE(20, 21, 22, 23);
			}
		} else {
			if (index < 28) {
				CHOOSE(24, 25, 26, 27);
			} else {
				CHOOSE_R(28, 29, 30, 31);
			}
		}
	}
}