+} /* nav_zoom_in */
+
+function nav_set_reference (img_id)
+{
+ var img;
+ var all_images;
+ var tmp;
+ var i;
+
+ img = document.getElementById (img_id);
+ if (!img || (img.className != "graph_image")
+ || !img.navTimeBegin || !img.navTimeEnd)
+ return;
+
+ all_images = document.getElementsByTagName ("img");
+ for (i = 0; i < all_images.length; i++)
+ {
+ tmp = all_images[i];
+ if (!tmp || (tmp.className != "graph_image")
+ || !tmp.navTimeBegin || !tmp.navTimeEnd)
+ continue;
+
+ if (tmp.id == img_id)
+ continue;
+
+ tmp.navTimeBegin = img.navTimeBegin;
+ tmp.navTimeEnd = img.navTimeEnd;
+
+ nav_image_repaint (tmp);
+ }
+} /* nav_set_reference */
+
+/*
+ * TODO: calculate the mouse position relative to the image in a cross-browser
+ * manner.
+ */
+function nav_calculate_offset_x (obj)
+{
+ var offset = 0;
+
+ if (!obj)
+ return (offset);
+
+ offset = obj.offsetLeft;
+ if (obj.offsetParent)
+ offset += nav_calculate_offset_x (obj.offsetParent);
+
+ return (offset);
+} /* nav_calculate_offset_x */
+
+function nav_calculate_event_x (e)
+{
+ var pos = 0;
+
+ if (!e || !e.target)
+ return;
+
+ nav_calculate_offset_x (e.target);
+
+ if (e.pageX || e.pageY)
+ {
+ pos = e.pageX;
+ }
+ else if (e.clientX || e.clientY)
+ {
+ pos = e.clientX + document.body.scrollLeft
+ + document.documentElement.scrollLeft;
+ }
+
+ return (pos);
+} /* nav_calculate_event_x */
+
+function nav_recenter (e)
+{
+ var x;
+ var y;
+ var img;
+ var diff;
+ var time_old_center;
+ var time_new_center;
+ var width;
+
+ img = e.target;
+ if (!img || (img.className != "graph_image")
+ || !img.navTimeBegin || !img.navTimeEnd)
+ return;
+
+ width = img.width - 97;
+
+ x = e.layerX - 70;
+ if (!x || (x < 0) || (x > width))
+ return;
+
+ y = e.layerY;
+ if (!y || (y < 35) || (y > 135))
+ return;
+
+ diff = img.navTimeEnd - img.navTimeBegin;
+
+ time_old_center = img.navTimeBegin + (diff / 2.0);
+ time_new_center = img.navTimeBegin + (x * diff / width);
+
+ img.navTimeBegin += (time_new_center - time_old_center);
+ img.navTimeEnd += (time_new_center - time_old_center);
+} /* nav_recenter */
+
+function nav_handle_dblclick (e)
+{
+ var img;
+
+ /* M$IE */
+ if (!e)
+ e = window.event;
+
+ img = e.target;
+ if (!img || (img.className != "graph_image")
+ || !img.navTimeBegin || !img.navTimeEnd)
+ return;
+
+ nav_recenter (e);
+ nav_image_repaint (img);
+
+ // e.returnValue = false;
+} /* nav_handle_dblclick */
+
+/* Taken from <http://adomas.org/javascript-mouse-wheel/> */
+function nav_handle_wheel (e)
+{
+ var delta = 0;
+ var img;
+
+ /* M$IE */
+ if (!e)
+ e = window.event;
+
+ img = e.target;
+ if (!img || (img.className != "graph_image")
+ || !img.navTimeBegin || !img.navTimeEnd)
+ return;
+
+ /* Opera and M$IE */
+ if (e.wheelDelta)
+ {
+ delta = e.wheelDelta;
+ if (window.opera)
+ delta = delta * (-1);
+ }
+ else if (e.detail)
+ {
+ delta = e.detail * (-1);
+ }
+
+ if (!delta)
+ return;
+
+ nav_recenter (e);
+ if (delta > 0)
+ nav_zoom_in (img.id);
+ else
+ nav_zoom_out (img.id);
+
+ if (e.preventDefault)
+ e.preventDefault ();
+ e.returnValue = false;
+} /* function nav_handle_wheel */
+