Added a "keep screen on" option using NoSleep.js (closes #427)

public/js/grocy_wakelockhandling.js

@@ -0,0 +1,72 @@
+Grocy.WakeLock = { };
+Grocy.WakeLock.NoSleepJsIntance = null;
+Grocy.WakeLock.InitDone = false;
+
+$("#keep_screen_on").on("change", function()
+{
+	var value = $(this).is(":checked");
+	if (value)
+	{
+		Grocy.WakeLock.Enable();
+	}
+	else
+	{
+		Grocy.WakeLock.Disable();
+	}
+});
+
+Grocy.WakeLock.Enable = function()
+{
+	if (Grocy.WakeLock.NoSleepJsIntance === null)
+	{
+		Grocy.WakeLock.NoSleepJsIntance = new NoSleep();
+	}
+	Grocy.WakeLock.NoSleepJsIntance.enable();
+	Grocy.WakeLock.InitDone = true;
+}
+
+Grocy.WakeLock.Disable = function()
+{
+	if (Grocy.WakeLock.NoSleepJsIntance !== null)
+	{
+		Grocy.WakeLock.NoSleepJsIntance.disable();
+	}
+}
+
+// Handle "Keep screen on while displaying a fullscreen-card" when the body class "fullscreen-card" has changed
+new MutationObserver(function(mutations)
+{
+	if (BoolVal(Grocy.UserSettings.keep_screen_on_when_fullscreen_card) && !BoolVal(Grocy.UserSettings.keep_screen_on))
+	{
+		mutations.forEach(function(mutation)
+		{
+			if (mutation.attributeName === "class")
+			{
+				var attributeValue = $(mutation.target).prop(mutation.attributeName);
+				if (attributeValue.contains("fullscreen-card"))
+				{
+					Grocy.WakeLock.Enable();
+				}
+				else
+				{
+					Grocy.WakeLock.Disable();
+				}
+			}
+		});
+	}
+}).observe(document.body, {
+	attributes: true
+});
+
+// Enabling NoSleep.Js only works in a user input event handler,
+// so if the user wants to keep the screen on always,
+// do this in on the first click on anything
+$(document).click(function()
+{
+	if (Grocy.WakeLock.InitDone === false && BoolVal(Grocy.UserSettings.keep_screen_on))
+	{
+		Grocy.WakeLock.Enable();
+	}
+
+	Grocy.WakeLock.InitDone = true;
+});