Docs!

src/main/java/com/minelittlepony/gui/IActionable.java

@@ -1,5 +1,12 @@
 package com.minelittlepony.gui;
 
+/**
+ * An element that can perform an action.
+ */
+@FunctionalInterface
 public interface IActionable {
+    /**
+     * Does whatever.
+     */
     void perform();
 }

src/main/java/com/minelittlepony/gui/IGUIAction.java

@@ -1,6 +1,15 @@
 package com.minelittlepony.gui;
 
+/**
+ * Response actions for UI events.
+ */
 @FunctionalInterface
 public interface IGUIAction<T> {
+    /**
+     * Performs this action now.
+     *
+     * @param value    New Value of the field being changed
+     * @return Adjusted value the field must take on
+     */
     T perform(T value);
 }