Add class header comments

src/SelectionManager.ts

@@ -45,6 +45,14 @@ const LINE_DATA_WIDTH_INDEX = 2;
 const NON_BREAKING_SPACE_CHAR = String.fromCharCode(160);
 const ALL_NON_BREAKING_SPACE_REGEX = new RegExp(NON_BREAKING_SPACE_CHAR, 'g');
 
+/**
+ * A class that manages the selection of the terminal. With help from
+ * SelectionModel, SelectionManager handles with all logic associated with
+ * dealing with the selection, including handling mouse interaction, wide
+ * characters and fetching the actual text within the selection. Rendering is
+ * not handled by the SelectionManager but a 'refresh' event is fired when the
+ * selection is ready to be redrawn.
+ */
 export class SelectionManager extends EventEmitter {
   protected _model: SelectionModel;
 

src/SelectionModel.ts

@@ -4,6 +4,10 @@
 
 import { ITerminal } from './Interfaces';
 
+/**
+ * Represents a selection within the buffer. This model only cares about column
+ * and row coordinates, not wide characters.
+ */
 export class SelectionModel {
   /**
    * Whether select all is currently active.