rename

1 files changed, 2690 insertions, 0 deletions

diff --git a/pugl.js b/pugl.js
new file mode 100644
index 0000000..19333c9
--- /dev/null
+++ b/pugl.js
@@ -0,0 +1,2690 @@
+'use strict';
+
+/*
+TODO:
+- pause
+- settings:
+  - enable/disable auto-update
+  - resolution
+- mouse pos uniform
+*/
+
+const APP_ID = 'dh3YgVZQdX1Q';
+
+let gl;
+let program_main = null;
+let program_post = null;
+let vertex_buffer_rect;
+let vertex_buffer_main;
+let canvas_container;
+let canvas;
+let framebuffer;
+let framebuffer_color_texture;
+let sampler_texture;
+let current_time;
+let ui_shown = true;
+let ui_div;
+let ui_resize;
+let viewport_width, viewport_height;
+let next_html_id = 1;
+let next_widget_id = 1;
+let widget_choices;
+let widget_search;
+let widgets_container;
+let code_input;
+let error_element;
+let parsed_widgets;
+
+const render_width = 1080,
+	render_height = 1080;
+const GLSL_FLOAT_TYPES = ['float', 'vec2', 'vec3', 'vec4'];
+const GLSL_FLOAT_TYPE_PAIRS = GLSL_FLOAT_TYPES.flatMap((x) =>
+	GLSL_FLOAT_TYPES.map((y) => [x, y]),
+);
+
+const builtin_widgets = [
+	`
+//! .name: Buffer
+//! .category: basic
+//! .description: outputs its input unaltered. useful for defining constants.
+//! x.name: input
+//! x.id: input
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} buffer(${type} x) {
+	return x;
+}`,
+		).join('\n'),
+	`
+//! .name: Slider
+//! .category: basic
+//! .description: an adjustable slider between two values.
+//! x.id: x
+//! x.default: 0.5
+//! x.control: slider
+//! min_val.id: min
+//! min_val.default: 0
+//! max_val.id: max
+//! max_val.default: 1
+
+float slider(float x, float min_val, float max_val) {
+	return mix(min_val, max_val, x);
+}
+`,
+	`
+//! .name: Mix (lerp)
+//! .category: basic
+//! .id: mix
+//! .description: weighted average of two inputs
+//! a.name: source 1
+//! a.default: 0
+//! b.name: source 2
+//! b.default: 1
+//! x.name: mix
+//! x.default: 0.5
+//! c.name: clamp mix
+//! c.control: checkbox
+//! c.description: clamp the mix input to the [0, 1] range
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} mix_(${type} a, ${type} b, ${type} x, int c) {
+	if (c != 0) x = clamp(x, 0.0, 1.0);
+	return mix(a, b, x);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Last frame
+//! .category: basic
+//! .id: prev
+//! .description: sample from the previous frame
+//! pos.description: position to sample — bottom-left corner is (−1, −1), top-right corner is (1, 1)
+//! wrap.name: wrap mode
+//! wrap.control: select:clamp|wrap
+//! wrap.description: how to deal with the input components if they go outside [−1, 1]
+//! samp.id: sample
+//! samp.name: sample mode
+//! samp.control: select:linear|nearest
+//! samp.description: how positions in between pixels should be sampled
+
+vec3 last_frame(vec2 pos, int wrap, int samp) {
+	pos = pos * 0.5 + 0.5;
+	if (wrap == 0)
+		pos = clamp(pos, 0.0, 1.0);
+	else if (wrap == 1)
+		pos = mod(pos, 1.0);
+	if (samp == 1)
+		pos = floor(0.5 + pos * _texture_size) * (1.0 / _texture_size);
+	return texture(_texture, pos).xyz;
+}
+`,
+	`
+//! .name: Weighted add
+//! .category: math
+//! .description: add two numbers or vectors with weights
+//! aw.name: a weight
+//! aw.default: 1
+//! bw.name: b weight
+//! bw.default: 1
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} wtadd(${type} a, float aw, ${type} b, float bw) {
+	return a * aw + b * bw;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Multiply
+//! .category: math
+//! .description: multiply two numbers, scale a vector by a number, or perform component-wise multiplication between vectors
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} mul(${type} a, ${type} b) {
+	return a * b;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Power
+//! .category: math
+//! .id: pow
+//! .description: take one number to the power of another
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} pow_(${type} a, ${type} b) {
+	return pow(a, b);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Modulo
+//! .category: math
+//! .id: mod
+//! .description: wrap a value at a certain limit
+//! a.name: a
+//! b.default: 1
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} mod_(${type} a, ${type} b) {
+	return mod(a, b);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Square
+//! .category: geometry
+//! .description: select between two inputs depending on whether a point lies within a square (or cube in 3D)
+//! pos.name: pos
+//! pos.description: point to test
+//! pos.default: .pos
+//! inside.description: source to use if pos lies inside the square
+//! inside.default: #f00
+//! outside.description: source to use if pos lies outside the square
+//! outside.default: #0f0
+//! size.description: radius of the square
+//! size.default: 0.5
+
+` +
+		[
+			['float', 'a'],
+			['vec2', 'max(a.x, a.y)'],
+			['vec3', 'max(a.x, max(a.y, a.z))'],
+			['vec4', 'max(max(a.x, a.y), max(a.z, a.w))'],
+		]
+			.map((x) => {
+				const type = x[0];
+				const max = x[1];
+				return ['float', 'vec2', 'vec3', 'vec4']
+					.map(
+						(type2) => `
+${type2} square(${type} pos, ${type2} inside, ${type2} outside, ${type} size) {
+	${type} a = abs(pos) / size;
+	return ${max} < 1.0 ? inside : outside;
+}
+`,
+					)
+					.join('\n');
+			})
+			.join('\n'),
+	`
+//! .name: Circle
+//! .category: geometry
+//! .description: select between two inputs depending on whether a point lies within a circle (or sphere in 3D)
+//! pos.default: .pos
+//! pos.description: point to test
+//! inside.default: #f00
+//! inside.description: source to use if pos lies inside the circle
+//! outside.default: #0f0
+//! outside.description: source to use if pos lies outside the circle
+//! size.default: 0.5
+//! size.description: radius of the circle
+
+` +
+		GLSL_FLOAT_TYPE_PAIRS.map(
+			([type, type2]) => `
+${type2} circle(${type} pos, ${type2} inside, ${type2} outside, ${type} size) {
+	pos /= size;
+	return dot(pos, pos) < 1.0 ? inside : outside;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Comparator
+//! .category: basic
+//! .description: select between two inputs depending on a comparison between two values
+//! .id: cmp
+//! cmp1.name: compare 1
+//! cmp1.description: input to compare against "Compare 2"
+//! cmp2.name: compare 2
+//! cmp2.default: 0
+//! cmp2.description: input to compare against "Compare 1"
+//! less.name: if less
+//! less.default: 0
+//! less.description: value to output if "Compare 1" < "Compare 2"
+//! greater.name: if greater
+//! greater.default: 1
+//! greater.description: value to output if "Compare 1" ≥ "Compare 2"
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} compare(float cmp1, float cmp2, ${type} less, ${type} greater) {
+	return cmp1 < cmp2 ? less : greater;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Sine wave
+//! .category: curves
+//! .description: sine, triangle, square, sawtooth waves
+//! .id: sin
+//! type.control: select:sin|tri|squ|saw
+//! t.description: position in the wave
+//! t.default: .time
+//! period.description: period of the wave
+//! period.default: 1
+//! amp.name: amplitude
+//! amp.default: 1
+//! amp.description: amplitude (maximum value) of the wave
+//! phase.default: 0
+//! phase.description: phase of the wave (0.5 = phase by ½ period)
+//! center.name: baseline
+//! center.default: 0
+//! center.description: this value is added to the output at the end
+//! nonneg.name: non-negative
+//! nonneg.description: make the wave go from baseline to baseline+amp, rather than baseline-amp to baseline+amp
+//! nonneg.control: checkbox
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} sine_wave(int type, ${type} t, ${type} period, ${type} amp, ${type} phase, ${type} center, int nonneg) {
+	${type} v = ${type}(0.0);
+	t = t / period - phase;
+	if (type == 0) {
+		v = sin(t * 6.2831853);
+	} else if (type == 1) {
+		t = mod(t, 1.0);
+		${type} s = step(${type}(0.5), t);
+		v = mix(4.0 * t - 1.0, 3.0 - 4.0 * t, s);
+	} else if (type == 2) {
+		v = mod(floor(2.0 * t) + 1.0, 2.0) * 2.0 - 1.0;
+	} else if (type == 3) {
+		v = mod(t, 1.0) * 2.0 - 1.0;
+	}
+	if (nonneg != 0) v = v * 0.5 + 0.5;
+	return amp * v + center;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Rotate 2D
+//! .category: geometry
+//! .id: rot2
+//! .description: rotate a 2-dimensional vector
+//! v.description: vector to rotate
+//! theta.name: θ
+//! theta.description: angle to rotate by (in radians)
+//! dir.name: direction
+//! dir.description: direction of rotation
+//! dir.control: select:CCW|CW
+
+vec2 rotate2D(vec2 v, float theta, int dir) {
+	if (dir == 1) theta = -theta;
+	float c = cos(theta), s = sin(theta);
+	return vec2(c*v.x - s*v.y, s*v.x + c*v.y);
+}
+`,
+	`
+//! .name: Hue shift
+//! .category: colors
+//! .id: hue
+//! .description: shift hue of color
+//! color.description: input color
+//! shift.description: how much to shift hue by (0.5 = shift halfway across the rainbow)
+
+vec3 hue_shift(vec3 color, float shift) {
+	vec3 c = color;
+	// rgb to hsv
+	vec3 hsv;
+	{
+		vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
+		vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
+		vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));
+		float d = q.x - min(q.w, q.y);
+		float e = 1.0e-10;
+		hsv = vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
+	}
+	
+	hsv.x = mod(hsv.x + shift, 1.0);
+	c = hsv;
+	
+	// hsv to rgb
+	{
+		vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
+		vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
+		return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
+	}
+}
+`,
+	`
+//! .name: Saturate
+//! .category: colors
+//! .id: saturate
+//! .description: change saturation of color
+//! color.description: input color
+//! amount.description: how much to change saturation by (−1 to 1 range)
+
+vec3 saturate(vec3 color, float amount) {
+	vec3 c = color;
+	// rgb to hsv
+	vec3 hsv;
+	{
+		vec4 K = vec4(0.0, -1.0 / 3.0, 2.0 / 3.0, -1.0);
+		vec4 p = mix(vec4(c.bg, K.wz), vec4(c.gb, K.xy), step(c.b, c.g));
+		vec4 q = mix(vec4(p.xyw, c.r), vec4(c.r, p.yzx), step(p.x, c.r));
+		float d = q.x - min(q.w, q.y);
+		float e = 1.0e-10;
+		hsv = vec3(abs(q.z + (q.w - q.y) / (6.0 * d + e)), d / (q.x + e), q.x);
+	}
+	
+	hsv.y = clamp(hsv.y + amount, 0.0, 1.0);
+	c = hsv;
+	
+	// hsv to rgb
+	{
+		vec4 K = vec4(1.0, 2.0 / 3.0, 1.0 / 3.0, 3.0);
+		vec3 p = abs(fract(c.xxx + K.xyz) * 6.0 - K.www);
+		return c.z * mix(K.xxx, clamp(p - K.xxx, 0.0, 1.0), c.y);
+	}
+}
+`,
+	`
+//! .name: Brightness-contrast
+//! .category: colors
+//! .description: change brightness/contrast of color
+//! color.description: input color
+//! brightness.description: how much to change brightness by (−1 to 1 range)
+//! contrast.description: how much to change contrast by (−1 to 1 range)
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} brightcont(${type} color, ${type} brightness, ${type} contrast) {
+	brightness = clamp(brightness, -1.0, 1.0);
+	contrast = clamp(contrast, -1.0, 1.0);
+	return clamp((contrast + 1.0) / (1.0 - contrast) * (color - 0.5) + (brightness + 0.5), 0.0, 1.0);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Clamp
+//! .category: basic
+//! .id: clamp
+//! .description: clamp a value between a minimum and maximum
+//! x.name: value
+//! x.id: val
+//! x.description: input value
+//! minimum.name: min
+//! minimum.id: min
+//! maximum.name: max
+//! maximum.id: max
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} clamp_(${type} x, ${type} minimum, ${type} maximum) {
+	return clamp(x, minimum, maximum);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Rotate 3D
+//! .id: rot3
+//! .category: geometry
+//! .description: rotate a 3D vector about an axis
+//! v.description: the vector to rotate
+//! axis.description: the axis to rotate around. the magnitude must be non-zero but otherwise is ignored.
+//! axis.default: 0,1,0
+//! angle.name: θ
+//! angle.description: the angle in radians
+//! angle.default: 0.57
+
+vec3 rot3(vec3 v, vec3 axis, float angle) {
+	axis = normalize(axis);
+	float c = cos(angle);
+	float s = sin(angle);
+	// https://en.wikipedia.org/wiki/Rodrigues%27_rotation_formula
+	return v * c + cross(axis, v) * s + axis * dot(axis, v) * (1.0 - c);
+}
+`,
+	`
+//! .name: Remap
+//! .id: remap
+//! .category: basic
+//! .description: linearly remap a value from one interval to another
+//! x.id: x
+//! a1.name: a₁
+//! a1.default: 0
+//! a1.description: negative endpoint of source interval
+//! b1.name: b₁
+//! b1.default: 1
+//! b1.description: positive endpoint of source interval
+//! a2.name: a₂
+//! a2.default: -1
+//! a2.description: positive endpoint of source interval
+//! b2.name: b₂
+//! b2.default: 1
+//! b2.description: positive endpoint of destination interval
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} remap(${type} x, ${type} a1, ${type} b1, ${type} a2, ${type} b2) {
+	return (x - a1) / (b1 - a1) * (b2 - a2) + a2;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Smoothstep
+//! .id: smoothstep
+//! .category: curves
+//! .description: smoothly transition between two values (with Hermite interpolation)
+//! t.id: t
+//! t1.name: t₁
+//! t1.description: first input point
+//! t1.default: 0
+//! t2.name: t₂
+//! t2.description: second input point
+//! t2.default: 1
+//! out1.name: out₁
+//! out1.description: output value when t ≤ t₁
+//! out1.default: 0
+//! out2.name: out₂
+//! out2.description: output value when t ≥ t₂
+//! out2.default: 1
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} smoothst(${type} t, ${type} t1, ${type} t2, ${type} out1, ${type} out2) {
+	return mix(out1, out2, smoothstep(t1, t2, t));
+}
+`,
+		).join('\n'),
+	`
+//! .name: Arctangent
+//! .id: arctan2
+//! .category: math
+//! .description: The arctangent function (radians) with 2 parameters (set x = 1 for normal arctangent)
+//! y.id: y
+//! x.id: x
+//! x.default: 1
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} arctan2(${type} y, ${type} x) {
+	return atan(y, x);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Tangent
+//! .id: tan
+//! .category: math
+//! .description: The tangent function (radians)
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} tang(${type} x) {
+	return tan(x);
+}
+`,
+		).join('\n'),
+	`
+//! .name: Arcsine
+//! .id: arcsin
+//! .category: math
+//! .description: The arcsine function (radians) — input will be clamped to [−1, 1]
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} arcsin(${type} x) {
+	return asin(clamp(x, -1.0, 1.0));
+}
+`,
+		).join('\n'),
+	`
+//! .name: Sigmoid
+//! .id: sigmoid
+//! .category: curves
+//! .description: The sigmoid function — smoothly maps the interval (−∞, ∞) to (a, b)
+//! x.description: input value
+//! a.description: output value for very negative inputs
+//! b.description: output value for very positive inputs
+//! sharpness.description: scale factor for input value — higher = quicker transition from a to b
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} sigmoid(${type} x, ${type} a, ${type} b, ${type} sharpness) {
+	return mix(a, b, 1.0 / (1.0 + exp(-sharpness * x)));
+}
+`,
+		).join('\n'),
+	`
+//! .name: Staircase (floor)
+//! .id: floor
+//! .category: curves
+//! .description: The floor function — largest integer less than x
+//! x.description: input value
+//! stepw.name: step w
+//! stepw.description: step width
+//! steph.name: step h
+//! steph.description: step height
+//! phase.description: proportion of a step to be added to input
+//! phase.default: 0
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+${type} floorf(${type} x, ${type} stepw, ${type} steph, ${type} phase) {
+	return floor(x / stepw + phase) * steph;
+}
+`,
+		).join('\n'),
+	`
+//! .name: Sin noise
+//! .category: noise
+//! .description: Noise generated from sine waves
+//! x.id: x
+//! falloff.description: values closer to 0 will emphasize lower-frequency noise, values towards 1 will emphasize higher-frequency noise
+//! falloff.default: 0.5
+//! freqstep.description: ratio between successive frequencies of noise
+//! freqstep.default: 2
+//! levels.description: number of frequencies of noises to add together
+//! levels.control: int:1|30
+//! levels.default: 8
+
+float noise_sin(float x, float falloff, float freqstep, int levels) {
+	float k = 1.0;
+	float phase = 2.45;
+	
+	falloff = clamp(falloff, 0.0, 1.0);
+	
+	float v = 0.0;
+	int i = 0;
+	for (i = 0; i < levels; i++) {
+		float s = sin(x + phase);
+		v += k * s * s;
+		x *= freqstep;
+		k *= falloff;
+		phase *= 1.7;
+		phase = mod(phase, 6.28);
+	}
+	return v * (1.0 - falloff);
+}
+
+float noise_sin(vec2 x, float falloff, float freqstep, int levels) {
+	float v = 0.0;
+	float k = 1.0;
+	vec2 phase = vec2(1.0, 3.6);
+	float theta = 2.7;
+	for (int i = 0; i < levels; i++) {
+		v += k * abs(sin(x.x + phase.x) * sin(x.y + phase.y));
+		phase *= 3.8;
+		phase = mod(phase, 6.28);
+		x *= freqstep;
+		x = mat2(cos(theta), sin(theta), -sin(theta), cos(theta)) * x;
+		k *= falloff;
+		theta *= 2.4;
+		theta = mod(theta, 6.28);
+	}
+	return v * (1.0 - falloff);
+}
+
+float noise_sin(vec3 x, float falloff, float freqstep, int levels) {
+	float v = 0.0;
+	float k = 1.0;
+	vec3 phase = vec3(1.0, 3.6, 2.2);
+	float theta = 2.7;
+	float phi = 4.6;
+	for (int i = 0; i < levels; i++) {
+		v += k * abs(sin(x.x + phase.x) * sin(x.y + phase.y) * sin(x.z + phase.z));
+		phase *= 4.7;
+		phase = mod(phase, 6.28);
+		x *= freqstep;
+		float ct = cos(theta), st = sin(theta);
+		float cp = cos(phi), sp = sin(phi);
+		x = mat3(st*cp, ct*cp, -sp, st*sp, ct*sp, cp, ct, -st, 0.0) * x;
+		k *= falloff;
+		theta *= 2.4;
+		theta = mod(theta, 6.28);
+	}
+	return v * (1.0 - falloff);
+}
+`,
+	`
+//! .name: Norm
+//! .alt: length/magnitude
+//! .description: the Euclidean norm ("length") of a vector
+//! .category: geometry
+
+float norm(float x) { return x; }
+float norm(vec2 x) { return length(x); }
+float norm(vec3 x) { return length(x); }
+float norm(vec4 x) { return length(x); }
+`,
+	`
+//! .name: Distance
+//! .description: the Euclidean distance between two points
+//! .category: geometry
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+float dist(${type} x, ${type} y) { return distance(x, y); }
+`,
+		).join('\n'),
+	`
+//! .name: Dot product
+//! .description: the dot product between two vectors
+//! .category: geometry
+//! .id: dot
+
+` +
+		GLSL_FLOAT_TYPES.map(
+			(type) => `
+float dot_prod(${type} x, ${type} y) { return dot(x, y); }
+`,
+		).join('\n'),
+	`
+//! .name: White noise
+//! .description: Uniform distribution over [0, 1)
+//! .category: noise
+
+float wnoise(float x)
+{
+	uint k = 134775813u;
+	uint u = floatBitsToUint(x) * k;
+	u = ((u >> 8) ^ u) * k;
+	u = ((u >> 8) ^ u) * k;
+	u = ((u >> 8) ^ u) * k;
+	return float(u) * (1.0 / 4294967296.0);
+}
+
+float wnoise(vec2 x)
+{
+	uint k = 134775813u;
+	uvec2 u = floatBitsToUint(x) * k;
+	u = ((u >> 8) ^ u.yx) * k;
+	u = ((u >> 8) ^ u.yx) * k;
+	u = ((u >> 8) ^ u.yx) * k;
+	return float(u) * (1.0 / 4294967296.0);
+}
+
+float wnoise(vec3 x)
+{
+	uint k = 134775813u;
+	uvec3 u = floatBitsToUint(x) * k;
+	u = ((u >> 8) ^ u.yzx) * k;
+	u = ((u >> 8) ^ u.yzx) * k;
+	u = ((u >> 8) ^ u.yzx) * k;
+	return float(u) * (1.0 / 4294967296.0);
+}
+
+float wnoise(vec4 x)
+{
+	uint k = 134775813u;
+	uvec4 u = floatBitsToUint(x) * k;
+	u = ((u >> 8) ^ u.yzwx) * k;
+	u = ((u >> 8) ^ u.yzwx) * k;
+	u = ((u >> 8) ^ u.yzwx) * k;
+	return float(u) * (1.0 / 4294967296.0);
+}
+`,
+	`
+//! .name: Perlin noise
+//! .description: Perlin noise with range [0, 1]
+//! .category: noise
+//! .require: wnoise
+//! x.default: .pos
+//! freq.description: input is scaled by this
+//! freq.default: 8
+
+float perlin(float x, float freq) {
+	x *= freq;
+	float grid0 = floor(x);
+	float grid1 = grid0 + 1.0;
+	
+	float d0 = x - grid0;
+	float d1 = x - grid1;
+	
+	float grad0 = wnoise(grid0) < 0.5 ? -1.0 : 1.0;
+	float grad1 = wnoise(grid1) < 0.5 ? -1.0 : 1.0;
+	
+	float n0 = dot(grad0, d0);
+	float n1 = dot(grad1, d1);
+	
+	float s = smoothstep(0.0, 1.0, d0);
+	float p = mix(n0, n1, s);
+	return p * 0.5 + 0.5;
+}
+
+float perlin(vec2 x, vec2 freq) {
+	x *= freq;
+	vec2 grid00 = floor(x);
+	vec2 grid01 = grid00 + vec2(0.0, 1.0);
+	vec2 grid10 = grid00 + vec2(1.0, 0.0);
+	vec2 grid11 = grid00 + 1.0;
+	
+	vec2 d00 = x - grid00;
+	vec2 d01 = x - grid01;
+	vec2 d10 = x - grid10;
+	vec2 d11 = x - grid11;
+	
+	float twopi = 6.2831853;
+	float theta00 = wnoise(grid00) * twopi;
+	float theta01 = wnoise(grid01) * twopi;
+	float theta10 = wnoise(grid10) * twopi;
+	float theta11 = wnoise(grid11) * twopi;
+	
+	vec2 grad00 = vec2(cos(theta00), sin(theta00));
+	vec2 grad01 = vec2(cos(theta01), sin(theta01));
+	vec2 grad10 = vec2(cos(theta10), sin(theta10));
+	vec2 grad11 = vec2(cos(theta11), sin(theta11));
+	
+	float n00 = dot(grad00, d00);
+	float n01 = dot(grad01, d01);
+	float n10 = dot(grad10, d10);
+	float n11 = dot(grad11, d11);
+	
+	vec2 s = smoothstep(0.0, 1.0, d00);
+	float n0 = mix(n00, n10, s.x);
+	float n1 = mix(n01, n11, s.x);
+	float p = mix(n0, n1, s.y);
+	return p * 0.5 + 0.5;
+}
+
+float perlin(vec3 x, vec3 freq) {
+	x *= freq;
+	vec3 grid000 = floor(x);
+	vec3 grid001 = grid000 + vec3(0.0, 0.0, 1.0);
+	vec3 grid010 = grid000 + vec3(0.0, 1.0, 0.0);
+	vec3 grid011 = grid000 + vec3(0.0, 1.0, 1.0);
+	vec3 grid100 = grid000 + vec3(1.0, 0.0, 0.0);
+	vec3 grid101 = grid000 + vec3(1.0, 0.0, 1.0);
+	vec3 grid110 = grid000 + vec3(1.0, 1.0, 0.0);
+	vec3 grid111 = grid000 + vec3(1.0, 1.0, 1.0);
+	
+	vec3 d000 = x - grid000;
+	vec3 d001 = x - grid001;
+	vec3 d010 = x - grid010;
+	vec3 d011 = x - grid011;
+	vec3 d100 = x - grid100;
+	vec3 d101 = x - grid101;
+	vec3 d110 = x - grid110;
+	vec3 d111 = x - grid111;
+	
+	// thanks to https://math.stackexchange.com/a/1586185
+	// this behemoth computes 9 random points on the unit sphere,
+	// seeded by grid000–grid111
+	float halfpi = 1.5707963;
+	float twopi = 6.2831853;
+	float a000 = acos(2.0 * wnoise(grid000) - 1.0) - halfpi;
+	float a001 = acos(2.0 * wnoise(grid001) - 1.0) - halfpi;
+	float a010 = acos(2.0 * wnoise(grid010) - 1.0) - halfpi;
+	float a011 = acos(2.0 * wnoise(grid011) - 1.0) - halfpi;
+	float a100 = acos(2.0 * wnoise(grid100) - 1.0) - halfpi;
+	float a101 = acos(2.0 * wnoise(grid101) - 1.0) - halfpi;
+	float a110 = acos(2.0 * wnoise(grid110) - 1.0) - halfpi;
+	float a111 = acos(2.0 * wnoise(grid111) - 1.0) - halfpi;
+	
+	float b000 = twopi * wnoise(vec4(grid000,3.0));
+	float b001 = twopi * wnoise(vec4(grid001,3.0));
+	float b010 = twopi * wnoise(vec4(grid010,3.0));
+	float b011 = twopi * wnoise(vec4(grid011,3.0));
+	float b100 = twopi * wnoise(vec4(grid100,3.0));
+	float b101 = twopi * wnoise(vec4(grid101,3.0));
+	float b110 = twopi * wnoise(vec4(grid110,3.0));
+	float b111 = twopi * wnoise(vec4(grid111,3.0));
+	
+	vec3 grad000 = vec3(cos(a000)*cos(b000), cos(a000)*sin(b000), sin(a000));
+	vec3 grad001 = vec3(cos(a001)*cos(b001), cos(a001)*sin(b001), sin(a001));
+	vec3 grad010 = vec3(cos(a010)*cos(b010), cos(a010)*sin(b010), sin(a010));
+	vec3 grad011 = vec3(cos(a011)*cos(b011), cos(a011)*sin(b011), sin(a011));
+	vec3 grad100 = vec3(cos(a100)*cos(b100), cos(a100)*sin(b100), sin(a100));
+	vec3 grad101 = vec3(cos(a101)*cos(b101), cos(a101)*sin(b101), sin(a101));
+	vec3 grad110 = vec3(cos(a110)*cos(b110), cos(a110)*sin(b110), sin(a110));
+	vec3 grad111 = vec3(cos(a111)*cos(b111), cos(a111)*sin(b111), sin(a111));
+	
+	float n000 = dot(grad000, d000);
+	float n001 = dot(grad001, d001);
+	float n010 = dot(grad010, d010);
+	float n011 = dot(grad011, d011);
+	float n100 = dot(grad100, d100);
+	float n101 = dot(grad101, d101);
+	float n110 = dot(grad110, d110);
+	float n111 = dot(grad111, d111);
+	
+	vec3 s = smoothstep(0.0, 1.0, d000);
+	float n00 = mix(n000, n100, s.x);
+	float n10 = mix(n010, n110, s.x);
+	float n0 = mix(n00, n10, s.y);
+	float n01 = mix(n001, n101, s.x);
+	float n11 = mix(n011, n111, s.x);
+	float n1 = mix(n01, n11, s.y);
+	float p = mix(n0, n1, s.z);
+	return p * 0.5 + 0.5;
+}
+`,
+	`
+//! .name: Worley noise
+//! .description: n-dimensional Worley noise
+//! .category: noise
+//! p.name: x
+//! p.id: x
+//! p.default: .pos
+//! freq.default: 8
+//! .require: wnoise
+
+float worley(vec2 p, vec2 freq) {
+	p *= freq;
+	vec2 f = floor(p);
+	float sqd = 1.0;
+	for (float dx = -1.0; dx <= +1.0; dx += 1.0) {
+		for (float dy = -1.0; dy <= +1.0; dy += 1.0) {
+			vec2 g = f + vec2(dx, dy);
+			vec2 c = g + vec2(wnoise(g), wnoise(vec3(g, 1.0)));
+			sqd = min(sqd, dot(c - p, c - p));
+		}
+	}
+	return sqrt(sqd);
+}
+
+float worley(vec3 p, vec3 freq) {
+	p *= freq;
+	vec3 f = floor(p);
+	float sqd = 1.0;
+	for (float dx = -1.0; dx <= +1.0; dx += 1.0) {
+		for (float dy = -1.0; dy <= +1.0; dy += 1.0) {
+			for (float dz = -1.0; dz <= +1.0; dz += 1.0) {
+				vec3 g = f + vec3(dx, dy, dz);
+				vec3 c = g + vec3(wnoise(g), wnoise(vec4(g, 1.0)), wnoise(vec4(g, 2.0)));
+				sqd = min(sqd, dot(c - p, c - p));
+			}
+		}
+	}
+	return sqrt(sqd);
+}
+`,
+];
+
+function auto_update_enabled() {
+	return true;
+}
+
+function is_input(element) {
+	if (!element) return false;
+	for (let e = element; e; e = e.parentElement) {
+		if (
+			e.tagName === 'INPUT' ||
+			e.tagName === 'BUTTON' ||
+			e.tagName === 'SELECT' ||
+			e.isContentEditable
+		) {
+			return true;
+		}
+	}
+	return false;
+}
+
+class Parser {
+	constructor(string, line_number) {
+		this.string = string;
+		this.line_number = line_number;
+		this.i = 0;
+		this.error = null;
+	}
+
+	set_error(e) {
+		if (!this.error) this.error = { line: this.line_number, message: e };
+	}
+
+	eof() {
+		this.skip_space();
+		return this.i >= this.string.length;
+	}
+
+	has(c) {
+		this.skip_space();
+		return this.string.substring(this.i, this.i + c.length) === c;
+	}
+
+	skip_space() {
+		while (this.i < this.string.length && this.string[this.i].match(/\s/)) {
+			if (this.string[this.i] === '\n') this.line_number += 1;
+			this.i += 1;
+		}
+	}
+
+	parse_type() {
+		this.skip_space();
+		const i = this.i;
+		for (const type of ['float', 'vec2', 'vec3', 'vec4', 'int']) {
+			if (
+				this.string.substring(i, i + type.length) === type &&
+				this.string[i + type.length] === ' '
+			) {
+				this.i += type.length + 1;
+				return type;
+			}
+		}
+		let end = this.string.indexOf(' ', i);
+		if (end === -1) end = this.string.length;
+		this.set_error(`no such type: ${this.string.substring(i, end)}`);
+	}
+
+	parse_ident() {
+		this.skip_space();
+		if (this.eof()) {
+			this.set_error('expected identifier, got EOF');
+			return;
+		}
+		const first_char = this.string[this.i];
+		if (!first_char.match(/[a-zA-Z_]/)) {
+			this.set_error(`expected identifier, got '${first_char}'`);
+			return;
+		}
+		const start = this.i;
+		this.i += 1;
+		while (
+			this.i < this.string.length &&
+			this.string[this.i].match(/[a-zA-Z0-9_]/)
+		) {
+			this.i += 1;
+		}
+		return this.string.substring(start, this.i);
+	}
+
+	expect(c) {
+		this.skip_space();
+		const got = this.string.substring(this.i, this.i + c.length);
+		if (got !== c) {
+			this.set_error(`expected ${c}, got ${got}`);
+		}
+		this.i += 1;
+	}
+
+	advance() {
+		this.i += 1;
+	}
+}
+
+function control_type(control) {
+	if (control.startsWith('select:')) {
+		return 'int';
+	} else if (control === 'checkbox') {
+		return 'int';
+	} else if (control === 'slider') {
+		return 'float';
+	} else if (control.startsWith('int:')) {
+		return 'int';
+	}
+	return null;
+}
+
+function parse_widget_definition(code) {
+	code = code.trim();
+	const params = new Map();
+	const info = {
+		alt: '',
+		params,
+		description: '',
+		definitions: [],
+		require: [],
+	};
+	let lines = code.split('\n');
+	let def_start = undefined;
+	let error = undefined;
+	const param_regex = /^[a-zA-Z_][a-zA-Z0-9_]*/gu;
+
+	lines.forEach((line, index) => {
+		if (error) return;
+		if (def_start !== undefined) return;
+
+		line = line.trim();
+		if (line.startsWith('//! ')) {
+			const parts = line.substring('//! '.length).split(': ');
+			if (parts.length !== 2) {
+				error = `on line ${index + 1}: line must contain ": " exactly once`;
+				return;
+			}
+			const key = parts[0].trim();
+			const value = parts[1].trim();
+			if (key === '.name') {
+				info.name = value;
+			} else if (key === '.description') {
+				info.description = value;
+			} else if (key === '.id') {
+				info.id = value;
+			} else if (key === '.category') {
+				info.category = value;
+			} else if (key === '.alt') {
+				info.alt = value;
+			} else if (key === '.require') {
+				for (const r of value.split(',')) {
+					info.require.push(r.trim());
+				}
+			} else if (key.startsWith('.')) {
+				error = `on line ${index + 1}: key ${key} not recognized`;
+				return;
+			} else {
+				const key_parts = key.split('.');
+				if (key_parts.length !== 2) {
+					error = `on line ${
+						index + 1
+					}: expected key to be of form parameter.property, got ${key}`;
+					return;
+				}
+				const param_name = key_parts[0];
+				const property = key_parts[1];
+				if (!param_name.match(param_regex)) {
+					error = `on line ${index + 1}: bad parameter name: ${param_name}`;
+				}
+				if (!params.has(param_name)) {
+					params.set(param_name, {});
+				}
+				const param = params.get(param_name);
+				switch (property) {
+					case 'id':
+					case 'name':
+					case 'description':
+					case 'default':
+					case 'control':
+						param[property] = value;
+						break;
+					default:
+						error = `on line ${
+							index + 1
+						}: parameter property '${property}' not recognized`;
+						return;
+				}
+			}
+		} else if (line.startsWith('//!')) {
+			error = `on line ${index + 1}: missing space after //!`;
+		} else if (line.startsWith('//')) {
+			// comment
+		} else {
+			def_start = index;
+			return;
+		}
+	});
+	if (error) {
+		return { error };
+	}
+	lines = lines.slice(def_start);
+	if (lines.some((x) => x.startsWith('//!'))) {
+		return { error: '//! appears after first function definition' };
+	}
+	lines = lines.map((x) => {
+		x = x.trim();
+		if (x.startsWith('//')) {
+			return '';
+		}
+		return x;
+	});
+
+	const parser = new Parser(lines.join('\n'), def_start + 1);
+	while (!parser.error && !parser.eof()) {
+		const definition_start = parser.i;
+		const return_type = parser.parse_type();
+		const fname = parser.parse_ident();
+		if (!info.function_name) info.function_name = fname;
+		if (!parser.error && fname !== info.function_name) {
+			return {
+				error: `function defined as both '${info.function_name}' and '${fname}'`,
+			};
+		}
+		if (!info.id) info.id = info.function_name;
+
+		const definition_params = [];
+		parser.expect('(');
+		while (!parser.eof() && !parser.has(')')) {
+			if (parser.has(',')) parser.expect(',');
+			const type = parser.parse_type();
+			const name = parser.parse_ident();
+			definition_params.push({ type, name });
+
+			if (!params.has(name)) {
+				if (!info.definitions.size) {
+					params.set(name, {});
+				} else if (!parser.error) {
+					return { error: `parameter ${name} does not exist` };
+				}
+			}
+		}
+
+		// we have all parameters now — fill out missing fields
+		if (!info.definitions.size) {
+			for (const param_name of params.keys()) {
+				const param = params.get(param_name);
+				if (!param.id) param.id = param_name;
+				if (!param.name) param.name = param.id;
+				if (!param.description) param.description = '';
+			}
+		}
+
+		const input_types = new Map();
+		const param_order = new Map();
+		definition_params.forEach((p, index) => {
+			const param = params.get(p.name);
+			if (param.control) {
+				const expected_type = control_type(param.control);
+				if (!expected_type) {
+					parser.set_error(`bad control type: '${param.control}'`);
+				}
+				if (p.type !== expected_type) {
+					parser.set_error(
+						`parameter ${p.name} should have type ${expected_type} since it's a ${param.control}, but it has type ${p.type}`,
+					);
+				}
+			}
+
+			if (!param.control && p.type === 'int') {
+				parser.set_error(
+					`parameter ${p.name} has type int, so you should set a control type for it, e.g. //! ${p.name}.control: checkbox`,
+				);
+			}
+			if (!param.control) {
+				input_types.set(param.id, p.type);
+			}
+			param_order.set(param.id, index);
+		});
+		for (const param of params.values()) {
+			if (!input_types.has(param.id) && !param.control) {
+				parser.set_error(
+					`parameter ${param.id} not specified in definition of ${info.function_name}`,
+				);
+			}
+		}
+
+		parser.expect(')');
+		parser.expect('{');
+		let brace_depth = 1;
+		while (!parser.eof() && brace_depth > 0) {
+			if (parser.has('{')) brace_depth += 1;
+			if (parser.has('}')) brace_depth -= 1;
+			parser.advance();
+		}
+		const definition_end = parser.i;
+		const definition = parser.string.substring(
+			definition_start,
+			definition_end,
+		);
+		info.definitions.push({
+			input_types,
+			param_order,
+			return_type,
+			code: definition,
+		});
+	}
+	if (parser.error) {
+		const err = parser.error;
+		return { error: `on line ${err.line}: ${err.message}` };
+	}
+	if (!info.name) info.name = info.id;
+	if (!info.category) {
+		return { error: `no category set for ${info.id}` };
+	}
+	return info;
+}
+
+const widget_info = new Map();
+for (const code of builtin_widgets) {
+	const result = parse_widget_definition(code);
+	if (result && result.error) {
+		console.error(result.error);
+	} else {
+		widget_info.set(result.id, result);
+	}
+}
+
+window.addEventListener('load', startup);
+
+function set_ui_shown(to) {
+	ui_shown = to;
+	const ui_viz = to ? 'visible' : 'collapse';
+	ui_div.style.visibility = ui_viz;
+	ui_resize.style.visibility = ui_viz;
+}
+
+function color_hex_to_float(hex) {
+	let r;
+	let g;
+	let b;
+	let a;
+	hex = hex.trim();
+
+	if (hex.length === 7 || hex.length === 9) {
+		// #rrggbb or #rrggbbaa
+		r = parseInt(hex.substring(1, 3), 16) / 255;
+		g = parseInt(hex.substring(3, 5), 16) / 255;
+		b = parseInt(hex.substring(5, 7), 16) / 255;
+		a = hex.length === 7 ? 1 : parseInt(hex.substring(7, 9), 16) / 255;
+	} else if (hex.length === 4 || hex.length === 5) {
+		// #rgb or #rgba
+		r = parseInt(hex[1], 16) / 15;
+		g = parseInt(hex[2], 16) / 15;
+		b = parseInt(hex[3], 16) / 15;
+		a = hex.length === 4 ? 1 : parseInt(hex[4], 16) / 15;
+	}
+
+	if (isNaN(r) || isNaN(g) || isNaN(b) || isNaN(a)) {
+		return null;
+	}
+
+	const color = {
+		r: r,
+		g: g,
+		b: b,
+		a: a,
+	};
+	Object.preventExtensions(color);
+	return color;
+}
+
+function color_float_to_hex(color) {
+	const r = Math.round(color.r * 255);
+	const g = Math.round(color.g * 255);
+	const b = Math.round(color.b * 255);
+	const a = Math.round((color.a ?? 1) * 255);
+	function component(x) {
+		x = x.toString(16);
+		while (x.length < 2) x = '0' + x;
+		return x;
+	}
+	let ca = component(a);
+	if (ca === 'ff') ca = '';
+	return `#${component(r)}${component(g)}${component(b)}${ca}`;
+}
+
+function update_shader() {
+	clear_error();
+	const source = get_shader_source();
+	if (source === null) {
+		return;
+	}
+	const fragment_code = `#version 300 es
+
+#ifdef GL_ES
+precision highp float;
+#endif
+
+uniform sampler2D _texture;
+uniform float _time;
+uniform vec2 _texture_size;
+in vec2 _pos;
+out vec4 _out_color;
+
+${source}
+
+void main() {
+	_out_color = vec4(_get_color(), 1.0);
+}
+`;
+	const vertex_code = `#version 300 es
+in vec2 v_pos;
+out vec2 _pos;
+void main() {
+	_pos = v_pos;
+	gl_Position = vec4(v_pos, 0.0, 1.0);
+}
+`;
+	program_main = compile_program('main', {
+		vertex: vertex_code,
+		fragment: fragment_code,
+	});
+}
+
+function on_key_press(e) {
+	const code = e.keyCode;
+	if (is_input(e.target)) {
+		return;
+	}
+	console.log('key press', code);
+
+	switch (code) {
+		case 32: // space
+			perform_step();
+			break;
+		case 9: // tab
+			set_ui_shown(!ui_shown);
+			e.preventDefault();
+			break;
+		case 13: // return
+			update_shader();
+			e.preventDefault();
+			break;
+	}
+}
+
+function float_glsl(f) {
+	if (isNaN(f)) return '(0.0 / 0.0)';
+	if (f === Infinity) return '1e+1000';
+	if (f === -Infinity) return '-1e+1000';
+	const s = f + '';
+	if (s.indexOf('.') !== -1 || s.indexOf('e') !== -1) return s;
+	return s + '.0';
+}
+
+function type_component_count(type) {
+	switch (type) {
+		case 'float':
+			return 1;
+		case 'vec2':
+			return 2;
+		case 'vec3':
+			return 3;
+		case 'vec4':
+			return 4;
+		default:
+			return 0;
+	}
+}
+
+function type_base_type(type) {
+	switch (type) {
+		case 'float':
+		case 'vec2':
+		case 'vec3':
+		case 'vec4':
+			return 'float';
+		default:
+			return null;
+	}
+}
+
+function type_vec(base_type, component_count) {
+	switch (base_type) {
+		case 'float':
+			switch (component_count) {
+				case 1:
+					return 'float';
+				case 2:
+					return 'vec2';
+				case 3:
+					return 'vec3';
+				case 4:
+					return 'vec4';
+				default:
+					return null;
+			}
+		default:
+			return null;
+	}
+}
+
+function get_widget_by_name(name) {
+	for (const w of document.getElementsByClassName('widget')) {
+		if (get_widget_name(w) === name) {
+			return w;
+		}
+	}
+	return null;
+}
+
+function get_widget_by_id(id) {
+	return document.querySelector(`.widget[data-id="${id}"]`);
+}
+
+function get_widget_name(widget_div) {
+	const names = widget_div.getElementsByClassName('widget-name');
+	console.assert(
+		names.length === 1,
+		'there should be exactly one widget-name input per widget',
+	);
+	return names[0].innerText;
+}
+
+function get_widget_names() {
+	const s = new Set();
+	for (const w of document.getElementsByClassName('widget-name')) {
+		s.add(w.innerText);
+	}
+	return s;
+}
+
+function set_display_output_and_update_shader(to) {
+	for (const widget of document.querySelectorAll('.widget[data-display="1"]')) {
+		widget.dataset.display = '0';
+	}
+	if (to) {
+		to.dataset.display = '1';
+	}
+	update_shader();
+}
+
+function update_input_element(input_element) {
+	const container = input_element.parentElement;
+
+	{
+		// add color input if the text is a color
+		let color_input = container.querySelector('input[type="color"]');
+		const color_value = color_hex_to_float(input_element.innerText);
+		if (color_value) {
+			if (!color_input) {
+				color_input = document.createElement('input');
+				color_input.type = 'color';
+				color_input.addEventListener('input', () => {
+					// this is kinda complicated because we
+					// want to preserve whether or not there's an alpha channel
+					// (but input[type=color] doesn't support alpha)
+					const prev_value = input_element.innerText;
+					const color = color_hex_to_float(color_input.value);
+					color.a = color_hex_to_float(prev_value).a;
+					const specify_alpha =
+						prev_value.length === 5 || prev_value.length === 9;
+					let new_value = color_float_to_hex(color);
+					console.assert(new_value.length === 7 || new_value.length === 9);
+					if (specify_alpha) {
+						if (new_value.length === 7) new_value += 'ff';
+					} else {
+						new_value = new_value.slice(0, 7);
+					}
+					input_element.innerText = new_value;
+					if (auto_update_enabled()) update_shader();
+				});
+				container.appendChild(color_input);
+			}
+			// if a color input has already been created for this input,
+			// we just need to update its value and show it.
+			color_input.value = color_float_to_hex({
+				r: color_value.r,
+				g: color_value.g,
+				b: color_value.b,
+			}).slice(0, 7);
+			color_input.style.display = 'inline-block';
+		} else {
+			if (color_input) {
+				color_input.style.display = 'none';
+			}
+		}
+	}
+}
+
+let dragging_widget = null;
+window.addEventListener('mouseup', () => {
+	dragging_widget = null;
+	const element = document.querySelector('.widget.dragging');
+	if (element) element.classList.remove('dragging');
+});
+
+function add_widget(func) {
+	const info = widget_info.get(func);
+	console.assert(info !== undefined, 'bad widget ID: ' + func);
+	const root = document.createElement('div');
+	root.dataset.func = func;
+	root.dataset.id = next_widget_id++;
+	root.classList.add('widget');
+	root.addEventListener('mouseover', () => {
+		if (!dragging_widget) return;
+
+		switch (root.compareDocumentPosition(dragging_widget)) {
+			case Node.DOCUMENT_POSITION_DISCONNECTED:
+			case Node.DOCUMENT_POSITION_CONTAINS:
+			case Node.DOCUMENT_POSITION_CONTAINED_BY:
+				console.error('unexpected compareDocumentPosition return value');
+				break;
+			case Node.DOCUMENT_POSITION_PRECEDING:
+				// dragging up
+				dragging_widget.before(root);
+				break;
+			case Node.DOCUMENT_POSITION_FOLLOWING:
+				// dragging down
+				dragging_widget.after(root);
+				break;
+		}
+	});
+
+	{
+		// delete button
+		const delete_button = document.createElement('button');
+		delete_button.ariaLabel = 'delete';
+		delete_button.classList.add('widget-delete');
+		delete_button.classList.add('widget-button');
+		delete_button.addEventListener('click', () => {
+			root.remove();
+			update_shader();
+		});
+		root.appendChild(delete_button);
+	}
+
+	{
+		// move button
+		const move_button = document.createElement('button');
+		move_button.ariaLabel = 'move';
+		move_button.classList.add('widget-move');
+		move_button.classList.add('widget-button');
+		move_button.addEventListener('mousedown', () => {
+			dragging_widget = root;
+			root.classList.add('dragging');
+		});
+		root.appendChild(move_button);
+	}
+
+	{
+		// title
+		const title = document.createElement('div');
+		title.classList.add('widget-title');
+		if (info.description) {
+			title.title = info.description;
+		}
+		const type = document.createElement('span');
+		type.classList.add('widget-type');
+		type.appendChild(document.createTextNode(info.name));
+		type.addEventListener('click', (e) => {
+			set_display_output_and_update_shader(root);
+			e.preventDefault();
+		});
+
+		title.appendChild(type);
+		title.appendChild(document.createTextNode(' '));
+
+		const name_input = document.createElement('div');
+		name_input.contentEditable = true;
+		name_input.spellcheck = false;
+		name_input.classList.add('widget-name');
+		name_input.addEventListener('input', () => update_shader());
+
+		// generate unique name
+		const names = get_widget_names();
+		let i;
+		for (i = 1; ; i++) {
+			if (!names.has(func + i)) {
+				break;
+			}
+		}
+		name_input.innerText = func + i;
+
+		title.appendChild(name_input);
+		root.appendChild(title);
+	}
+
+	// parameters
+	for (const param of info.params.values()) {
+		if (param.control) {
+			// control
+			const container = document.createElement('div');
+			container.classList.add('control');
+			container.dataset.id = param.id;
+			const type = param.control;
+			let input;
+			if (type === 'checkbox') {
+				input = document.createElement('input');
+				input.classList.add('entry');
+				input.type = 'checkbox';
+				if (param['default']) {
+					input.checked = 'checked';
+				}
+			} else if (type.startsWith('select:')) {
+				const options = type.substring('select:'.length).split('|');
+
+				input = document.createElement('select');
+				input.classList.add('entry');
+				for (const opt of options) {
+					const option = document.createElement('option');
+					option.appendChild(document.createTextNode(opt));
+					option.value = opt;
+					input.appendChild(option);
+				}
+
+				if (param['default']) {
+					input.value = param['default'];
+				}
+			} else if (type === 'slider') {
+				input = document.createElement('input');
+				input.classList.add('entry');
+				input.type = 'range';
+				input.min = 0;
+				input.max = 1;
+				input.step = 0.001;
+				input.value = 0;
+				const update_title = () => {
+					input.title = '' + input.value;
+				};
+				input.addEventListener('mouseover', update_title);
+				input.addEventListener('input', update_title);
+				if (param['default']) {
+					input.value = param['default'];
+				}
+			} else if (type.startsWith('int:')) {
+				const range = type.substring('int:'.length).split('|');
+				console.assert(range.length === 2, 'bad format for int control');
+				const [min, max] = range;
+				input = document.createElement('input');
+				input.dataset.isInt = true;
+				input.classList.add('entry');
+				input.type = 'number';
+				input.min = min;
+				input.max = max;
+				input.step = 1;
+				input.value = Math.round((min + max) / 2);
+				if (param['default']) {
+					input.value = param['default'];
+				}
+			} else {
+				console.error('bad control type');
+			}
+
+			input.id = 'gen-control-' + next_html_id++;
+			input.classList.add('control-input');
+			const label = document.createElement('label');
+			label.htmlFor = input.id;
+			label.appendChild(document.createTextNode(param.name));
+			if (param.description) {
+				container.title = param.description;
+			}
+			container.appendChild(label);
+			container.appendChild(document.createTextNode('='));
+			container.appendChild(input);
+			root.appendChild(container);
+			root.appendChild(document.createTextNode(' '));
+		} else {
+			// input
+			const container = document.createElement('div');
+			container.classList.add('in');
+			container.dataset.id = param.id;
+			const input_element = document.createElement('div');
+			input_element.contentEditable = true;
+			input_element.spellcheck = false;
+			input_element.addEventListener('keydown', (e) => {
+				if (e.keyCode === 13) {
+					input_element.blur();
+					e.preventDefault();
+				}
+			});
+			input_element.classList.add('entry');
+			input_element.appendChild(document.createElement('br'));
+			input_element.type = 'text';
+			input_element.id = 'gen-input-' + next_html_id++;
+			const label = document.createElement('label');
+			label.htmlFor = input_element.id;
+			if (param.description) {
+				container.title = param.description;
+			}
+			if (param['default']) {
+				input_element.innerText = param['default'];
+			}
+			label.appendChild(document.createTextNode(param.name));
+			container.appendChild(label);
+			container.appendChild(document.createTextNode('='));
+			container.appendChild(input_element);
+			root.appendChild(container);
+			root.appendChild(document.createTextNode(' '));
+
+			input_element.addEventListener('input', () => {
+				update_input_element(input_element);
+				if (auto_update_enabled()) {
+					update_shader();
+				}
+			});
+			update_input_element(input_element);
+		}
+	}
+
+	widgets_container.appendChild(root);
+	return root;
+}
+
+class GLSLGenerationState {
+	constructor(widgets) {
+		this.widgets = widgets;
+		this.declarations = new Set();
+		this.code = [];
+		this.computing_inputs = new Set();
+		this.variable = 0;
+	}
+
+	next_variable() {
+		this.variable += 1;
+		return 'v' + this.variable;
+	}
+
+	add_code(code) {
+		this.code.push(code);
+	}
+
+	get_code() {
+		return `
+${Array.from(this.declarations).join('')}
+vec3 _get_color() {
+${this.code.join('')}
+}`;
+	}
+
+	compute_input(input) {
+		input = input.trim();
+		if (input.length === 0) {
+			return { error: 'empty input' };
+		}
+		if (!isNaN(input)) {
+			return { code: float_glsl(parseFloat(input)), type: 'float' };
+		}
+
+		if (input.indexOf(',') !== -1) {
+			// vector construction
+			const items = input.split(',');
+			console.assert(items.length >= 2, 'huhhhhh??');
+			const components = [];
+			for (const item of items) {
+				const component = this.compute_input(item);
+				if ('error' in component) {
+					return component;
+				}
+				components.push(component);
+			}
+			let component_count = 0;
+			let base_type = undefined;
+			for (const component of components) {
+				const type = component.type;
+				const c = type_component_count(type);
+				if (c === 0) {
+					return { error: `cannot use type ${type} with ,` };
+				}
+				component_count += c;
+				if (base_type === undefined) {
+					base_type = type_base_type(type);
+				}
+				if (base_type !== type_base_type(type)) {
+					return { error: 'bad combination of types for ,' };
+				}
+			}
+			const type = type_vec(base_type, component_count);
+			if (type === null) {
+				// e.g. trying to combine 5 floats
+				return { error: 'bad combination of types for ,' };
+			}
+			const v = this.next_variable();
+			const component_values = components.map((c) => c.code);
+			this.add_code(`${type} ${v} = ${type}(${component_values.join()});\n`);
+			return { type: type, code: v };
+		}
+
+		if (input[0] === '#') {
+			const color = color_hex_to_float(input);
+			if (color === null) {
+				return { error: 'bad color: ' + input };
+			}
+			return input.length === 4 || input.length === 7
+				? {
+						code: `vec3(${float_glsl(color.r)},${float_glsl(
+							color.g,
+						)},${float_glsl(color.b)})`,
+						type: 'vec3',
+				  }
+				: {
+						code: `vec4(${float_glsl(color.r)},${float_glsl(
+							color.g,
+						)},${float_glsl(color.b)},${float_glsl(color.a)})`,
+						type: 'vec4',
+				  };
+		}
+
+		const dot = input.lastIndexOf('.');
+		const field = dot === -1 ? 'out' : input.substring(dot + 1);
+
+		if (field.length === 0) {
+			return { error: 'inputs should not end in .' };
+		}
+
+		if (
+			field.length >= 1 &&
+			field.length <= 4 &&
+			field.split('').every((c) => 'xyzw'.indexOf(c) !== -1)
+		) {
+			// swizzle
+			const vector = this.compute_input(input.substring(0, dot));
+			if ('error' in vector) {
+				return { error: vector.error };
+			}
+			const base = type_base_type(vector.type);
+			const count = type_component_count(vector.type);
+
+			for (const c of field) {
+				const i = 'xyzw'.indexOf(c);
+				if (i >= count) {
+					return { error: `type ${vector.type} has no field ${c}.` };
+				}
+			}
+
+			return {
+				code: `(${vector.code}).${field}`,
+				type: type_vec(base, field.length),
+			};
+		}
+
+		if (dot === 0) {
+			switch (input) {
+				case '.pos':
+					return { code: '_pos', type: 'vec2' };
+				case '.pos01':
+					return { code: '(0.5+0.5*_pos)', type: 'vec2' };
+				case '.time':
+					return { code: '_time', type: 'float' };
+				default:
+					return { error: `no such builtin: ${input}` };
+			}
+		}
+
+		if (field !== 'out') {
+			return { error: `no such field: ${field}` };
+		}
+		const widget = this.widgets.get(input);
+		if (widget === undefined) {
+			return { error: `cannot find widget '${input}'` };
+		}
+
+		if (this.computing_inputs.has(input)) {
+			return { error: 'circular dependency at ' + input };
+		}
+		this.computing_inputs.add(input);
+		const value = this.compute_widget_output(widget);
+		if (value.error) {
+			if (!value.widget) {
+				value.widget = widget.id;
+			}
+			return value;
+		}
+		this.computing_inputs.delete(input);
+		return value;
+	}
+
+	add_requirements_of(widget) {
+		for (const req_name of widget.require) {
+			const req = widget_info.get(req_name);
+			console.assert(req, 'bad widget requirement:', req_name);
+			const size0 = this.declarations.size;
+			for (const def of req.definitions) {
+				this.declarations.add(def.code);
+			}
+			if (this.declarations.size !== size0) {
+				this.add_requirements_of(req);
+			}
+		}
+	}
+
+	compute_widget_output(widget) {
+		if (widget.output) return widget.output;
+
+		const info = widget_info.get(widget.func);
+		this.add_requirements_of(info);
+		console.assert(info, 'bad widget func');
+		const args = new Map();
+		const input_types = new Map();
+		for (let [input, value] of widget.inputs) {
+			value = this.compute_input(value);
+			if (value.error) {
+				widget.output = value;
+				return value;
+			}
+			args.set(input, value.code);
+			input_types.set(input, value.type);
+		}
+		for (const control of widget.controls) {
+			args.set(control.id, control.uniform);
+		}
+
+		let best_definition = undefined;
+		let best_score = -Infinity;
+		for (const definition of info.definitions) {
+			if (definition.input_types.length !== input_types.length) continue;
+			if (definition.param_order.length !== args.length) continue;
+			let score = 0;
+			for (const [input_name, input_type] of definition.input_types) {
+				const got_type = input_types.get(input_name);
+				if (got_type === input_type) {
+					score += 1;
+				} else if (got_type === 'float') {
+					// implicit conversion
+				} else {
+					score = -Infinity;
+				}
+			}
+			if (score > best_score) {
+				best_definition = definition;
+				best_score = score;
+			}
+		}
+
+		if (!best_definition) {
+			const s = [];
+			for (const [n, t] of input_types) {
+				s.push(`${n}:${t}`);
+			}
+			return { error: `bad types for ${info.name}: ${s.join(', ')}` };
+		}
+
+		const output_var = this.next_variable();
+		const definition = best_definition;
+		const args_code = new Array(args.length);
+		for (let [arg_name, arg_code] of args) {
+			if (definition.input_types.has(arg_name)) {
+				const expected_type = definition.input_types.get(arg_name);
+				const got_type = input_types.get(arg_name);
+				if (got_type !== expected_type) {
+					arg_code = `${expected_type}(${arg_code})`;
+				}
+			}
+			args_code[definition.param_order.get(arg_name)] = arg_code;
+		}
+		const type = definition.return_type;
+		this.declarations.add(definition.code);
+		this.add_code(
+			`${type} ${output_var} = ${info.function_name}(${args_code.join(
+				',',
+			)});\n`,
+		);
+		widget.output = {
+			code: output_var,
+			type,
+		};
+		return widget.output;
+	}
+}
+
+function parse_widgets() {
+	const widgets = new Map();
+	for (const widget_div of document.getElementsByClassName('widget')) {
+		const name = get_widget_name(widget_div);
+		const func = widget_div.dataset.func;
+		const widget_id = parseInt(widget_div.dataset.id);
+		if (!name) {
+			return {
+				error: 'widget has no name. please give it one.',
+				widget: widget_id,
+			};
+		}
+		for (const c of name) {
+			if ('.,;|/\\:(){}[]+-<>\'"`~?!#%^&*'.indexOf(c) !== -1) {
+				return {
+					error: `widget name cannot contain the character ${c}`,
+					widget: widget_id,
+				};
+			}
+		}
+		if (widgets.has(name)) {
+			return { error: `duplicate widget name: ${name}`, widget: widget_id };
+		}
+
+		const inputs = new Map();
+		const controls = [];
+		for (const input of widget_div.getElementsByClassName('in')) {
+			const input_id = input.dataset.id;
+			inputs.set(input_id, input.getElementsByClassName('entry')[0].innerText);
+		}
+		for (const control of widget_div.getElementsByClassName('control')) {
+			const control_id = control.dataset.id;
+			controls.push({
+				id: control_id,
+				uniform: `_control${widget_id}_${control_id}`,
+				type: get_control_value(widget_id, control_id).type,
+			});
+		}
+		widgets.set(name, {
+			func,
+			id: widget_id,
+			inputs,
+			controls,
+		});
+	}
+	parsed_widgets = widgets;
+	return widgets;
+}
+
+function get_control_value(widget_id, control_id) {
+	const widget = get_widget_by_id(widget_id);
+	const control = widget.querySelector(`.control[data-id="${control_id}"]`);
+	const input = control.querySelector('.control-input');
+	if (input.tagName === 'INPUT' && input.type === 'checkbox') {
+		return {
+			type: 'int',
+			value: input.checked ? 1 : 0,
+		};
+	} else if (input.tagName === 'INPUT') {
+		if (input.dataset.isInt) {
+			return {
+				type: 'int',
+				value: parseInt(input.value),
+			};
+		} else {
+			return {
+				type: 'float',
+				value: parseFloat(input.value),
+			};
+		}
+	} else if (input.tagName === 'SELECT') {
+		return {
+			type: 'int',
+			value: Array.from(input.getElementsByTagName('option'))
+				.map((o) => o.value)
+				.indexOf(input.value),
+		};
+	} else {
+		console.error(`unrecognized control tag: ${input.tagName}`);
+	}
+}
+
+function export_widgets() {
+	const widgets = parse_widgets();
+	if (widgets.error) {
+		show_error(widgets);
+		return;
+	}
+	console.assert(widgets instanceof Map);
+	const data = [];
+	for (const [name, widget] of widgets) {
+		data.push(widget.func);
+		data.push(';');
+		data.push('n:');
+		data.push(name);
+		data.push(';');
+		for (const [input, value] of widget.inputs) {
+			data.push('i');
+			data.push(input);
+			data.push(':');
+			data.push(value);
+			data.push(';');
+		}
+		for (const control of widget.controls) {
+			data.push('c');
+			data.push(control.id);
+			data.push(':');
+			data.push(get_control_value(widget.id, control.id).value);
+			data.push(';');
+		}
+		data.pop(); // remove terminal separator
+		data.push(';;');
+	}
+	data.push('_out=');
+	data.push(
+		get_widget_name(document.querySelector('.widget[data-display="1"]')),
+	);
+	return data.join('');
+}
+
+function import_widgets(string) {
+	let widgets = [];
+	let output = null;
+	if (string) {
+		console.log(string);
+		for (const widget_str of string.split(';;')) {
+			if (widget_str.startsWith('_out=')) {
+				output = widget_str.substring('_out='.length);
+				continue;
+			}
+
+			const parts = widget_str.split(';');
+			const func = parts[0];
+			const widget = {
+				name: null,
+				func,
+				inputs: new Map(),
+				controls: new Map(),
+			};
+			parts.splice(0, 1);
+			for (const part of parts) {
+				const kv = part.split(':');
+				if (kv.length !== 2) {
+					return { error: `bad key-value pair (kv count ${kv.length})` };
+				}
+				const type = kv[0][0];
+				const key = kv[0].substring(1);
+				const value = kv[1];
+				if (type === 'n') {
+					// name
+					widget.name = value;
+				} else if (type === 'i') {
+					// input
+					widget.inputs.set(key, value);
+				} else if (type === 'c') {
+					// control
+					widget.controls.set(key, value);
+				} else {
+					return { error: `bad widget part type: '${type}'` };
+				}
+			}
+
+			if (widget.name === null) {
+				return { error: 'widget has no name' };
+			}
+			widgets.push(widget);
+		}
+	} else {
+		widgets = [
+			{
+				name: 'output',
+				func: 'buffer',
+				inputs: new Map([['input', '#acabff']]),
+				controls: new Map(),
+			},
+		];
+		output = 'output';
+	}
+
+	function assign_value(container, value) {
+		const element = container.getElementsByClassName('entry')[0];
+		if (!element) {
+			console.error('container', container, 'has no input entry');
+		} else if (element.type === 'checkbox') {
+			element.checked = value === 'true' || value === '1' ? 'checked' : '';
+		} else if (element.tagName === 'INPUT') {
+			element.value = value;
+		} else if (element.tagName === 'SELECT') {
+			const options = Array.from(element.getElementsByTagName('option')).map(
+				(o) => o.value,
+			);
+			if (value >= 0 && value < options.length) {
+				element.value = options[value];
+			} else if (options.indexOf(value) !== -1) {
+				element.value = value;
+			} else {
+				return { error: `bad import string (unrecognized value ${value})` };
+			}
+		} else if (element.tagName === 'DIV') {
+			element.innerText = value;
+			update_input_element(element);
+		} else {
+			console.error('bad element', element);
+		}
+	}
+	widgets_container.innerHTML = '';
+	for (const widget of widgets) {
+		const name = widget.name;
+		if (!widget_info.has(widget.func)) {
+			return {
+				error: `bad import string (widget type '${widget.func}' does not exist)`,
+			};
+		}
+		const element = add_widget(widget.func);
+		element.getElementsByClassName('widget-name')[0].innerText = name;
+
+		for (const [input, value] of widget.inputs) {
+			const container = Array.from(element.getElementsByClassName('in')).find(
+				(e) => e.dataset.id === input,
+			);
+			if (!container) {
+				return { error: `bad import string (input ${input} does not exist)` };
+			}
+			assign_value(container, value);
+		}
+		for (const [control, value] of widget.controls) {
+			const container = Array.from(
+				element.getElementsByClassName('control'),
+			).find((e) => e.dataset.id === control);
+			if (!container) {
+				return {
+					error: `bad import string (control ${control} does not exist)`,
+				};
+			}
+			assign_value(container, value);
+		}
+	}
+
+	set_display_output_and_update_shader(get_widget_by_name(output));
+}
+
+function import_widgets_from_local_storage() {
+	const result = import_widgets(localStorage.getItem(`${APP_ID}-widgets`));
+	if (result && result.error) {
+		show_error(result);
+	}
+}
+
+function export_widgets_to_local_storage() {
+	const widget_str = export_widgets();
+	code_input.value = widget_str;
+	localStorage.setItem(`${APP_ID}-widgets`, widget_str);
+}
+
+function get_shader_source() {
+	const display_output = document.querySelector('.widget[data-display="1"]');
+	if (!display_output) {
+		show_error('no output chosen');
+		return null;
+	}
+	const widgets = parse_widgets();
+	if (widgets.error) {
+		show_error(widgets);
+		return null;
+	}
+	const state = new GLSLGenerationState(widgets);
+	for (const widget of widgets.values()) {
+		for (const control of widget.controls) {
+			state.declarations.add(`uniform ${control.type} ${control.uniform};\n`);
+		}
+	}
+	const output = state.compute_input(get_widget_name(display_output));
+	if (output.error) {
+		show_error(output);
+		return null;
+	}
+
+	switch (output.type) {
+		case 'float':
+			state.add_code(`return vec3(${output.code});\n`);
+			break;
+		case 'vec2':
+			state.add_code(`return vec3(${output.code}, 0.0);\n`);
+			break;
+		case 'vec3':
+			state.add_code(`return ${output.code};\n`);
+			break;
+		case 'vec4':
+			state.add_code(`return ${output.code}.xyz;\n`);
+			break;
+		default:
+			show_error(`bad type for output: ${output.type}`);
+			return null;
+	}
+
+	const code = state.get_code();
+	console.log(code);
+	export_widgets_to_local_storage();
+	return code;
+}
+
+function update_widget_choices() {
+	const search_term = widget_search.value.toLowerCase();
+	const choices = widget_choices.getElementsByClassName('widget-choice');
+	for (const choice of choices) {
+		const widget = widget_info.get(choice.dataset.id);
+		const shown =
+			widget.name.toLowerCase().indexOf(search_term) !== -1 ||
+			widget.alt.toLowerCase().indexOf(search_term) !== -1;
+		choice.style.display = shown ? 'block' : 'none';
+	}
+	for (const category of widget_choices.getElementsByClassName(
+		'widget-category',
+	)) {
+		if (
+			Array.from(category.getElementsByClassName('widget-choice')).some(
+				(x) => x.style.display === 'block',
+			)
+		) {
+			category.style.display = 'block';
+			category.open = search_term !== '';
+		} else {
+			category.style.display = 'none';
+		}
+	}
+}
+
+let resizing_ui = false;
+let ui_resize_offset = 0;
+
+function startup() {
+	canvas_container = document.getElementById('canvas-container');
+	canvas = document.getElementById('canvas');
+	ui_div = document.getElementById('ui');
+	ui_resize = document.getElementById('ui-resize');
+	widget_choices = document.getElementById('widget-choices');
+	widget_search = document.getElementById('widget-search');
+	widgets_container = document.getElementById('widgets-container');
+	code_input = document.getElementById('code');
+	error_element = document.getElementById('error');
+
+	ui_div.style.flexBasis = ui_div.offsetWidth + 'px'; // convert to px
+
+	// drag to resize ui
+	ui_resize.addEventListener('mousedown', (e) => {
+		resizing_ui = true;
+		const basis = ui_div.style.flexBasis;
+		console.assert(basis.endsWith('px'));
+		ui_resize_offset = basis.substring(0, basis.length - 2) - e.clientX;
+		e.preventDefault();
+	});
+	window.addEventListener('mouseup', () => {
+		resizing_ui = false;
+	});
+	window.addEventListener('mousemove', (e) => {
+		if (resizing_ui) {
+			if (e.buttons & 1) {
+				ui_div.style.flexBasis = e.clientX + ui_resize_offset + 'px';
+			} else {
+				resizing_ui = false;
+			}
+			e.preventDefault();
+		}
+	});
+
+	document.getElementById('code-form').addEventListener('submit', () => {
+		import_widgets(code_input.value);
+	});
+
+	gl = canvas.getContext('webgl2');
+	if (gl === null) {
+		// support for very-old-but-not-ancient browsers
+		gl = canvas.getContext('experimental-webgl2');
+		if (gl === null) {
+			show_error('your browser doesnt support webgl.\noh well.');
+			return;
+		}
+	}
+
+	program_post = compile_program('post', {
+		vertex: `#version 300 es
+in vec2 v_pos;
+out vec2 uv;
+
+void main() {
+	uv = v_pos * 0.5 + 0.5;
+	gl_Position = vec4(v_pos, 0.0, 1.0);
+}
+`,
+		fragment: `#version 300 es
+#ifdef GL_ES
+precision highp float;
+#endif
+uniform sampler2D u_texture;
+in vec2 uv;
+out vec4 color;
+
+void main() {
+	color = texture(u_texture, uv);
+}
+`,
+	});
+	if (program_post === null) {
+		return;
+	}
+
+	vertex_buffer_rect = gl.createBuffer();
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_rect);
+	gl.bufferData(
+		gl.ARRAY_BUFFER,
+		new Float32Array([
+			-1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0, 1.0, -1.0, 1.0,
+		]),
+		gl.STATIC_DRAW,
+	);
+
+	vertex_buffer_main = gl.createBuffer();
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_main);
+	gl.bufferData(
+		gl.ARRAY_BUFFER,
+		new Float32Array([
+			-1.0, -1.0, 1.0, -1.0, 1.0, 1.0, -1.0, -1.0, 1.0, 1.0, -1.0, 1.0,
+		]),
+		gl.STATIC_DRAW,
+	);
+
+	framebuffer_color_texture = gl.createTexture();
+	sampler_texture = gl.createTexture();
+
+	{
+		// add widget buttons
+		const categories = new Map();
+		for (const info of widget_info.values()) {
+			if (!categories.has(info.category)) {
+				categories.set(info.category, []);
+			}
+			categories.get(info.category).push(info.id);
+		}
+		const category_names = Array.from(categories.keys());
+		category_names.sort();
+
+		for (const cat of category_names) {
+			const category_element = document.createElement('details');
+			category_element.classList.add('widget-category');
+			const category_title = document.createElement('summary');
+			category_title.appendChild(document.createTextNode(cat));
+			category_element.appendChild(category_title);
+			widget_choices.appendChild(category_element);
+
+			const widgets = categories.get(cat);
+			widgets.sort((a, b) =>
+				widget_info.get(a).name.localeCompare(widget_info.get(b).name),
+			);
+			for (const id of widgets) {
+				const widget = widget_info.get(id);
+				const button = document.createElement('button');
+				button.classList.add('widget-choice');
+				if ('description' in widget) {
+					button.title = widget.description;
+				}
+				button.appendChild(document.createTextNode(widget.name));
+				button.dataset.id = id;
+				category_element.appendChild(button);
+				button.addEventListener('click', () => {
+					const root = add_widget(id);
+					const widget_name = root.querySelector('.widget-name');
+					widget_name.focus();
+					const range = document.createRange();
+					range.selectNodeContents(widget_name);
+					const sel = window.getSelection();
+					sel.removeAllRanges();
+					sel.addRange(range);
+				});
+			}
+		}
+	}
+
+	set_up_framebuffer();
+	update_widget_choices();
+	widget_search.addEventListener('input', () => {
+		update_widget_choices();
+	});
+	import_widgets_from_local_storage();
+
+	frame(0.0);
+	window.addEventListener('keydown', on_key_press);
+}
+
+function frame(time) {
+	current_time = time * 1e-3;
+
+	const container_width = canvas_container.offsetWidth;
+	const container_height = canvas_container.offsetHeight;
+	const aspect_ratio = render_width / render_height;
+	let canvas_x = 0,
+		canvas_y = 0;
+	if (container_width / aspect_ratio < container_height) {
+		// landscape mode
+		canvas_y = Math.floor((container_height - viewport_height) * 0.5);
+		viewport_width = container_width;
+		viewport_height = Math.floor(container_width / aspect_ratio);
+	} else {
+		// portrait mode
+		canvas_x = Math.floor((container_width - viewport_width) * 0.5);
+		viewport_width = Math.floor(container_height * aspect_ratio);
+		viewport_height = container_height;
+	}
+
+	canvas.width = viewport_width;
+	canvas.height = viewport_height;
+	canvas.style.left = canvas_x + 'px';
+	canvas.style.top = canvas_y + 'px';
+
+	perform_step();
+
+	gl.bindFramebuffer(gl.FRAMEBUFFER, null);
+	gl.viewport(0, 0, viewport_width, viewport_height);
+	gl.clearColor(0.0, 0.0, 0.0, 1.0);
+	gl.clear(gl.COLOR_BUFFER_BIT);
+
+	gl.useProgram(program_post);
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_rect);
+	gl.activeTexture(gl.TEXTURE0);
+	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
+	gl.uniform1i(gl.getUniformLocation(program_post, 'u_texture'), 0);
+	const v_pos = gl.getAttribLocation(program_post, 'v_pos');
+	gl.enableVertexAttribArray(v_pos);
+	gl.vertexAttribPointer(v_pos, 2, gl.FLOAT, false, 0, 0);
+	gl.drawArrays(gl.TRIANGLES, 0, 6);
+
+	if (!requestAnimationFrame) {
+		show_error('your browser doesnt support requestAnimationFrame.\noh well.');
+		return;
+	}
+	requestAnimationFrame(frame);
+}
+
+function perform_step() {
+	if (!program_main) {
+		// not properly loaded yet
+		return;
+	}
+
+	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+	gl.viewport(0, 0, render_width, render_height);
+	gl.clearColor(0.0, 0.0, 0.0, 1.0);
+	gl.clear(gl.COLOR_BUFFER_BIT);
+
+	gl.useProgram(program_main);
+	gl.activeTexture(gl.TEXTURE0);
+	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
+	gl.uniform1i(gl.getUniformLocation(program_main, '_texture'), 0);
+	gl.uniform1f(
+		gl.getUniformLocation(program_main, '_time'),
+		current_time % 3600,
+	);
+	gl.uniform2f(
+		gl.getUniformLocation(program_main, '_texture_size'),
+		render_width,
+		render_height,
+	);
+
+	if (parsed_widgets) {
+		for (const widget of parsed_widgets.values()) {
+			for (const control of widget.controls) {
+				const loc = gl.getUniformLocation(program_main, control.uniform);
+				const { type, value } = get_control_value(widget.id, control.id);
+				switch (type) {
+					case 'int':
+						gl.uniform1i(loc, value);
+						break;
+					case 'float':
+						gl.uniform1f(loc, value);
+						break;
+				}
+			}
+		}
+	}
+
+	gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer_main);
+	const v_pos = gl.getAttribLocation(program_main, 'v_pos');
+	gl.enableVertexAttribArray(v_pos);
+	gl.vertexAttribPointer(v_pos, 2, gl.FLOAT, false, 8, 0);
+	gl.drawArrays(gl.TRIANGLES, 0, 6);
+
+	gl.bindTexture(gl.TEXTURE_2D, sampler_texture);
+	gl.copyTexImage2D(
+		gl.TEXTURE_2D,
+		0,
+		gl.RGBA,
+		0,
+		0,
+		render_width,
+		render_height,
+		0,
+	);
+}
+
+function compile_program(name, shaders) {
+	const program = gl.createProgram();
+	for (const type in shaders) {
+		const source = shaders[type];
+		let gl_type;
+		if (type === 'vertex') {
+			gl_type = gl.VERTEX_SHADER;
+		} else if (type === 'fragment') {
+			gl_type = gl.FRAGMENT_SHADER;
+		} else {
+			show_error('unrecognized shader type: ' + type);
+			return null;
+		}
+		const shader = compile_shader(name + ' ' + type, gl_type, source);
+		if (shader === null) return null;
+		gl.attachShader(program, shader);
+	}
+
+	gl.linkProgram(program);
+	if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
+		show_error(
+			'Error linking shader program:\n' + gl.getProgramInfoLog(program),
+		);
+		return null;
+	}
+	return program;
+}
+
+function set_up_framebuffer() {
+	framebuffer = gl.createFramebuffer();
+	const sampler_pixels = new Uint8Array(render_width * render_height * 4);
+	sampler_pixels.fill(0);
+	set_up_rgba_texture(
+		sampler_texture,
+		render_width,
+		render_height,
+		sampler_pixels,
+	);
+	set_up_rgba_texture(
+		framebuffer_color_texture,
+		render_width,
+		render_height,
+		null,
+	);
+	gl.bindFramebuffer(gl.FRAMEBUFFER, framebuffer);
+	gl.framebufferTexture2D(
+		gl.FRAMEBUFFER,
+		gl.COLOR_ATTACHMENT0,
+		gl.TEXTURE_2D,
+		framebuffer_color_texture,
+		0,
+	);
+	const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
+	if (status !== gl.FRAMEBUFFER_COMPLETE) {
+		show_error('Error: framebuffer incomplete (status ' + status + ')');
+		return;
+	}
+}
+
+function set_up_rgba_texture(texture, width, height, pixels) {
+	gl.bindTexture(gl.TEXTURE_2D, texture);
+	gl.texImage2D(
+		gl.TEXTURE_2D,
+		0,
+		gl.RGBA,
+		width,
+		height,
+		0,
+		gl.RGBA,
+		gl.UNSIGNED_BYTE,
+		pixels,
+	);
+	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
+	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
+	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
+	gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
+}
+
+function compile_shader(name, type, source) {
+	const shader = gl.createShader(type);
+	gl.shaderSource(shader, source);
+	gl.compileShader(shader);
+
+	if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+		show_error(
+			'Error compiling shader ' + name + ':\n' + gl.getShaderInfoLog(shader),
+		);
+		return null;
+	}
+	return shader;
+}
+
+function clear_error() {
+	error_element.style.display = 'none';
+	for (const widget of document.querySelectorAll('.widget.error')) {
+		widget.classList.remove('error');
+	}
+}
+
+function show_error(error) {
+	if (error.error) {
+		if (error.widget) {
+			get_widget_by_id(error.widget).classList.add('error');
+		}
+		error = error.error;
+	}
+	console.log('error:', error);
+	error_element.style.display = 'block';
+	error_element.innerText = error;
+}