Merge lp:~cmiller/adium-theme-ubuntu/lp959084-avoid-scroll-infinite-loop into lp:adium-theme-ubuntu

[Chad Miller]

Avoid infinite loop in scrolling to bottom of message window.

[Ken VanDine (ken-vandine)]

Looks great, thanks!

review: Approve

=== modified file 'ubuntu.AdiumMessageStyle/Contents/Resources/Template.html'
--- ubuntu.AdiumMessageStyle/Contents/Resources/Template.html	2010-06-13 12:25:55 +0000
+++ ubuntu.AdiumMessageStyle/Contents/Resources/Template.html	2012-10-25 20:06:25 +0000
@@ -7,7 +7,7 @@
 	
 	<script type="text/javascript">
 	//<![CDATA[	
-	   isDebug = false;
+	   var isDebug = false;
 
 	   //Do this on load
 		function initEvents() {
@@ -83,14 +83,29 @@
 			alignChat(shouldScroll);
 		}
 		
-		
-		//Auto-scroll to bottom.  Use nearBottom to determine if a scrollToBottom is desired.
 		function nearBottom() {
-			return ( document.body.scrollTop >= ( document.body.offsetHeight - ( window.innerHeight * 1.2 ) ) );
+			var fastResizeSafety = 20; //px
+			// Quick window shrink may move marker offscreen before we notice
+			// and re-scroll to catch up.  With a little buffer here, the
+			// bottom marker has to go off-screen more before we forget that we
+			// were at the end.
+
+			var bottomOfConversation = document.getElementById("bottomMarker").offsetTop - 20;
+			var bottomOfWindow = document.body.scrollTop + window.innerHeight;
+			return (bottomOfConversation <= bottomOfWindow);
+
 		}
 		
 		var intervall_scroll;
 		function scrollToBottom() {
+			var bottomMarker = document.getElementById("bottomMarker");
+
+			// Use smart scroll function if we have it.  (We probably do.)
+			if (bottomMarker && bottomMarker.scrollIntoView) {
+				bottomMarker.scrollIntoView(true);
+				return;
+			}
+
 			//document.body.scrollTop = (document.body.scrollHeight-window.innerHeight);
 			//return;
 			if( intervall_scroll ) clearInterval( intervall_scroll );
@@ -141,7 +156,13 @@
 		}
 		
 		function windowDidResize() {
-			alignChat(false); //nearBottom buggy with inavtive tabs
+			// Window is changing size.  Should we keep up with the bottom,
+			// where new messages are coming in, or at the top, where the user
+			// is perhaps reading?  Use a heuristic of checking to see if we're
+			// scrolled to the bottom to decide whether to stick with the
+			// bottom.
+
+			alignChat(nearBottom());
 		}
 		
 		window.onresize = windowDidResize;
@@ -158,5 +179,7 @@
 %@
 <div id="debug"></div>
 
+<div id="bottomMarker" />
+
 </body>
 </html>