[tools] testbot/cgi: Only refresh pages when the top is visible.

[Francois Gouget]

This stops pages from refreshing and losing the scroll position while
one is inspecting a log file, looking at old job results, etc.

Signed-off-by: Francois Gouget 
---
 testbot/lib/WineTestBot/CGI/PageBase.pm | 33 ++++++++++++++++++-------
 1 file changed, 24 insertions(+), 9 deletions(-)

diff --git a/testbot/lib/WineTestBot/CGI/PageBase.pm b/testbot/lib/WineTestBot/CGI/PageBase.pm
index 55e015d58..477a2ff15 100644
--- a/testbot/lib/WineTestBot/CGI/PageBase.pm
+++ b/testbot/lib/WineTestBot/CGI/PageBase.pm
@@ -416,11 +416,6 @@ sub GenerateHttpHeaders($)
   # HTTP/1.0
   $Request->headers_out->add("Pragma", "no-cache");

-  if ($self->{Refresh})
-  {
-    $self->{Request}->headers_out->add("Refresh", $self->{Refresh});
-  }
-
   # Force char set
   $Request->content_type("text/html; charset=UTF-8");

@@ -462,12 +457,32 @@ EOF
   }
   print ">\n";

-  print <<EOF;
+  print "<div id='logo_blurb'>${ProjectName} Test Bot</div>\n";
+  if ($self->{Refresh})
+  {
+    print <<EOF;
+<script type='text/javascript'>
+<!--
+var Reloader;
+var Observer = new IntersectionObserver(function(entries) {
+  if (Reloader)
+  {
+    clearTimeout(Reloader);
+    Reloader = undefined;
+  }
+  if (entries[0].isIntersecting === true)
+  {
+    Reloader = setTimeout(function() { location.reload(); }, $self->{Refresh} * 1000);
+  }
+}, { threshold: [0] });

-<div id="logo_blurb">
-${ProjectName} Test Bot
-</div>
+Observer.observe(document.querySelector("#logo_blurb"));
+//-->
+</script>
+EOF
+  }

+  print <<EOF;
 <div id='tabs'>
   <ul>
     <li><a href='//www.winehq.org/'>WineHQ</a></li>