Added validation feature for window.app object.

This provides possibilities of more reliable testing and debugging.
See the comments in "docstate.js" file.

Signed-off-by: Gökay Şatır <gokaysatir@collabora.com>
Change-Id: I28ba2098cbe7e206f363fb2b0acbf5c5c2bf155d

browser/src/docstate.js

@@ -1,3 +1,5 @@
+/* global Proxy */
+
 window.app = { // Shouldn't have any functions defined.
 	definitions: {}, // Class instances are created using definitions under this variable.
 	dpiScale: window.devicePixelRatio,
@@ -43,3 +45,37 @@ window.app = { // Shouldn't have any functions defined.
 	socket: window.app.socket,
 	console: window.app.console,
 };
+
+var activateValidation = false;
+
+if (activateValidation) {
+/*
+	For debugging purposes.
+
+	* Easier debugging.
+	* Value range checks.
+
+	It logs the changes of the variables of "window.app" object.
+	This provides debugging of window.app object and makes easier use of these global states of the document.
+	window.app object can contain cursor position etc. variables related to document state.
+	One needs to only watch the data structure and add new variables into related sub-object (file, view, tile etc.).
+
+	This validator also enables global data validation.
+	If a variable of window.app should stay in a specified range:
+		* One can add a check for that variable into "set" function below.
+	This validation feature may also be useful with Cypress tests and Javascript unit tests.
+
+	This first version only contains the logging of the changes.
+*/
+	var validator = {
+		set: function(obj, prop, value) {
+			// The default behavior to store the value
+			obj[prop] = value;
+			console.log('window.app property changed: ' + prop, value);
+			// Indicate success
+			return true;
+		}
+	};
+
+	window.app = new Proxy(window.app, validator);
+}