Index Map (#1093)

* Index Map

* Formatting

* improve description a bit.

src/Classes/ShaderLoader.gd

@@ -15,10 +15,31 @@ static func create_ui_for_shader_uniforms(
 ) -> void:
 	var code := shader.code.split("\n")
 	var uniforms: PackedStringArray = []
+	var description: String = ""
+	var descriprion_began := false
 	for line in code:
+		## Management of "end" tags
+		if line.begins_with("// (end DESCRIPTION)"):
+			descriprion_began = false
+		if descriprion_began:
+			description += "\n" + line.strip_edges()
+
+		## Detection of uniforms
 		if line.begins_with("uniform"):
 			uniforms.append(line)
 
+		## Management of "begin" tags
+		elif line.begins_with("// (begin DESCRIPTION)"):
+			descriprion_began = true
+	## Validation of begin/end tags
+	if descriprion_began == true:  ## Description started but never ended. treat it as an error
+		print("Shader description started but never finished. Assuming empty description")
+		description = ""
+	if not description.is_empty():
+		parent_node.tooltip_text = str(
+			"Description:\n", description.replace("//", "").strip_edges()
+		)
+
 	for uniform in uniforms:
 		# Example uniform:
 		# uniform float parameter_name : hint_range(0, 255) = 100.0;

src/Shaders/Effects/IndexMap.gdshader

@@ -0,0 +1,18 @@
+// Authored by Variable (6 May 2022)
+shader_type canvas_item;
+render_mode unshaded;
+
+uniform sampler2D map_texture : filter_nearest;  // The map texture
+
+// (begin DESCRIPTION)
+// The Red and Green values (0-255) of tool color will be treated as an x and y position
+// respectively instead of color components.
+// When you draw, color will be taken from the x-y position in the "Map Texture".
+// (end DESCRIPTION)
+void fragment(){
+	vec4 col = texture(TEXTURE, UV);
+	vec2 map_size = vec2(textureSize(map_texture, 0));
+	vec2 lookup_uv = vec2(round(col.x * 255.0)/(map_size.x), round(col.y * 255.0)/(map_size.y));
+	vec4 index_color = texture(map_texture, lookup_uv);
+	COLOR = index_color;
+}

src/UI/Timeline/LayerEffects/LayerEffectsSettings.gd

@@ -23,6 +23,7 @@ var effects: Array[LayerEffect] = [
 	LayerEffect.new("Pixelize", preload("res://src/Shaders/Effects/Pixelize.gdshader")),
 	LayerEffect.new("Posterize", preload("res://src/Shaders/Effects/Posterize.gdshader")),
 	LayerEffect.new("Gradient Map", preload("res://src/Shaders/Effects/GradientMap.gdshader")),
+	LayerEffect.new("Index Map", preload("res://src/Shaders/Effects/IndexMap.gdshader")),
 ]
 
 @onready var enabled_button: CheckButton = $VBoxContainer/HBoxContainer/EnabledButton