actual Godot compatibility changes

src/kiss_flixel/ShaderFrontend.hx

@@ -102,6 +102,7 @@ class ShaderFrontend implements FrontendPlugin {
 		var colorOut = "";
 		var coordIn = "";
 
+		transformedCode += "const float PI = 3.1415926535897932384626433832795;\n";
 
         function nextToken() {
             glslStream.dropWhitespace();
@@ -132,36 +133,59 @@ class ShaderFrontend implements FrontendPlugin {
                         default:
                     }
 
+				// Shadertoy compatibility:
 				case Some("iResolution"):
 					transformedCode += "openfl_TextureSize";
 
-                case Some("mainImage"):
-                    dropNext("(");
-                    dropNext("out");
-                    dropNext("vec4");
-                    switch (nextToken()) {
-                        case Some(symbol):
-                            colorOut = symbol;
-                        default:
-                            error();
-                    }
-                    dropNext(",");
-                    dropNext("in");
-                    dropNext("vec2");
-                    switch (nextToken()) {
-                        case Some(symbol):
-                            coordIn = symbol;
-                        default:
-                            error();
-                    }
-                    dropNext(")");
-                    transformedCode += "main() ";
+				case Some("void"):
+					switch (nextToken()) {
+						case Some("mainImage"):
+							dropNext("(");
+							dropNext("out");
+							dropNext("vec4");
+							switch (nextToken()) {
+								case Some(symbol):
+									colorOut = symbol;
+								default:
+									error();
+							}
+							dropNext(",");
+							dropNext("in");
+							dropNext("vec2");
+							switch (nextToken()) {
+								case Some(symbol):
+									coordIn = symbol;
+								default:
+									error();
+							}
+							dropNext(")");
+							transformedCode += "void main() ";
+						case Some("fragment"):
+							dropNext("()");
+							transformedCode += "void main() ";
+						case Some(other):
+							transformedCode += 'void $other';
+						default:
+							throw "expected name of void function";
+					}
 
                 case Some(name) if (name == colorOut):
                     transformedCode += "gl_FragColor";
                 case Some(name) if (name == coordIn):
                     transformedCode += "openfl_TextureCoordv * openfl_TextureSize";
 
+				// Godot compatibility
+				case Some("TIME"):
+					transformedCode += "iTime";
+				case Some("COLOR"):
+					transformedCode += "gl_FragColor";
+				
+				// Not totally sure this actually is a 1-to-1 equivalency:
+				case Some("SCREEN_UV"):
+					transformedCode += "openfl_TextureCoordv";
+				case Some("SCREEN_PIXEL_SIZE"):
+					transformedCode += "vec2(1 / openfl_TextureSize.x, 1 / openfl_TextureSize.y)";
+
 				case Some("uniform"):
 					var uType = expect("uniform type", nextToken);
 

src/kiss_flixel/shaders/MirroredOrnament.frag

@@ -0,0 +1,45 @@
+#pragma header
+
+// Source: https://godotshaders.com/shader/animated-mirrored-ornament/
+// Modified by Nat
+
+uniform vec3 color_a = vec3(0.5);
+uniform vec3 color_b = vec3(0.5);
+uniform vec3 color_c = vec3(1.0);
+uniform vec3 color_d = vec3(0.0, 0.33, 0.67);
+uniform int iterations = 10; // : hint_range(1, 50, 1) 
+uniform float speed = 1.0; // : hint_range(0.1, 10.0)
+uniform float zoom = 1.0; // : hint_range(0.1, 5.0)
+uniform float subtract = 0.5; // : hint_range(0.1, 1.0)
+uniform float multiply = 1.1; // : hint_range(1.0, 2.0)
+
+vec3 palette(float t, vec3 a, vec3 b, vec3 c, vec3 d) {
+	return a + b * cos(2.0 * PI * (c * t + d));
+}
+
+vec2 rotate(vec2 uv, float angle) {
+	return uv * mat2(
+			vec2(cos(angle), -sin(angle)),
+			vec2(sin(angle), cos(angle))
+		);
+}
+
+vec3 invert_color(vec3 color, float intensity) {
+	return mix(color.rgb, 1.0 - color.rgb, intensity);
+}
+
+void fragment() {
+	float time = TIME;
+	float angle = time * speed * 0.1;
+	vec2 uv = (SCREEN_UV - 0.5) / vec2(SCREEN_PIXEL_SIZE.x / SCREEN_PIXEL_SIZE.y, 1.0);
+	vec3 color = vec3(0.0);
+	uv /= zoom + sin(time * 0.1) * 0.5 + 0.5;
+	for (int i = 0; i < iterations; i++) {
+		uv = rotate((abs(uv) - subtract) * multiply, angle);
+	}
+	vec3 p = palette(length(uv) + dot(uv, uv), color_a, color_b, color_c, color_d);
+	color = clamp(vec3(length(uv) * p), vec3(0.0), vec3(1.0));
+	float intensity = sin(time) * 0.25 - 0.2;
+	color = invert_color(color, intensity);
+	COLOR = vec4(color, 1.0);
+}