From 7329f6b99596c386ac8dfb5dd2849d3bc80fff44 Mon Sep 17 00:00:00 2001
From: "Eugeniy E. Mikhailov" <evgmik@gmail.com>
Date: Mon, 28 May 2018 22:29:43 -0400
Subject: added javascript to read and set cookies for display style, as well
 to use these cookies

---
 GradeBook.js | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 47 insertions(+), 2 deletions(-)

diff --git a/GradeBook.js b/GradeBook.js
index 269f008..18652c8 100644
--- a/GradeBook.js
+++ b/GradeBook.js
@@ -1,15 +1,32 @@
 function toggleHTMLClassVisibility(className) {
 	var x = document.getElementsByClassName(className);
 	var i;
+	var display_style = "block"; // default
 	for (i = 0; i < x.length; i++) {
 		if (x[i].style.display === "none") {
-			x[i].style.display = "block";
+			display_style = "block";
 		} else {
-			x[i].style.display = "none";
+			display_style = "none";
 		}
+		x[i].style.display = display_style;
 	}
+	document.cookie=""+className+"_display_style"+"="+display_style;
 };
 
+function setHTMLClassVisibility(className, display_style) {
+	// use "block" or "none" for display_style
+	if (display_style === "") {
+		display_style = "block"; // default
+	}
+	var x = document.getElementsByClassName(className);
+	var i;
+	for (i = 0; i < x.length; i++) {
+		x[i].style.display = display_style;
+	}
+	document.cookie=""+className+"_display_style"+"="+display_style;
+};
+
+
 function toggleHistogramMarker() {
 	toggleHTMLClassVisibility("histogram_marker");
 };
@@ -18,3 +35,31 @@ function toggleGradingScheme() {
 	toggleHTMLClassVisibility("grading_scheme");
 };
 
+// getCookie is copied from https://www.w3schools.com/js/js_cookies.asp
+function getCookie(cname) {
+	var name = cname + "=";
+	var decodedCookie = decodeURIComponent(document.cookie);
+	var ca = decodedCookie.split(';');
+	for(var i = 0; i <ca.length; i++) {
+		var c = ca[i];
+		while (c.charAt(0) == ' ') {
+			c = c.substring(1);
+		}
+		if (c.indexOf(name) == 0) {
+			return c.substring(name.length, c.length);
+		}
+	}
+	return "";
+}
+
+function readAndSetVisibility(className) {
+	setHTMLClassVisibility( className, getCookie(""+className+"_display_style") );
+	return "";
+}
+
+function onPageLoad() {
+	readAndSetVisibility("histogram_marker");
+	readAndSetVisibility("grading_scheme");
+	return "";
+}
+
-- 
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