Vendor helgoboss/helgobox (ReaLearn) as basis for custom UI fork

Stripped upstream git history; starting point for replacing the native
SWELL/Win32 mapping UI with something more suited to bulk editing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

plugin-reaper-realearn/resources/main-presets/factory/util.luau

@@ -0,0 +1,56 @@
+--!strict
+
+local realearn = require("realearn")
+local partial = require("partial")
+
+local util = {}
+
+--- Creates a partial mapping.
+---
+--- A partial mapping can be conveniently mixed with other partial mappings by using the + operator.
+--- This enables a very intuitive but still flexible way of writing mappings.
+---
+--- Ideally, we would return Partial & Mapping but Luau has still issues with that. In particular, it
+--- can't resolve the + operator when used in an intersection.
+function util.partial_mapping(m: realearn.Mapping): partial.Partial
+	return partial.Partial.new(m)
+end
+
+--- Returns the values of the given key-value table as array.
+function util.to_array<V>(t: { [string]: V }): { V }
+	local array = {}
+	for _, v in t do
+		table.insert(array, v)
+	end
+	return array
+end
+
+--- Returns the values of the given key-value table as array, sorted by the values'
+--- `index` key.
+function util.sorted_by_index<V>(t: { [string]: V }): { V }
+	local sorted = util.to_array(t)
+	local compare_index = function(left: any, right: any): boolean
+		return left.index < right.index
+	end
+	table.sort(sorted, compare_index)
+	return sorted
+end
+
+--- Takes a key-value table and adds a new attribute `id` to each value that
+--- corresponds to the key.
+function util.set_keys_as_ids(t: { [string]: { [string]: any } })
+	for key, value in pairs(t) do
+		value.id = key
+	end
+end
+
+--- Puts each `label` property value of the given array of tables into a new array.
+function util.extract_labels(array: { { [string]: any } }): { string }
+	local labels = {}
+	for _, element in ipairs(array) do
+		table.insert(labels, element.label)
+	end
+	return labels
+end
+
+return util