IE7/8: Fix selection range function

lib/gollum/frontend/public/javascript/gollum-editor/gollum.editor.js

@@ -503,11 +503,46 @@
        */
       getFieldSelectionPosition: function( $field ) {
         if ($field.length) {
+          var start = 0, end = 0, normalizedValue, range,
+              textInputRange, len, endRange;
+          var el = $field.get(0);
+      
+          if (typeof el.selectionStart == "number" && 
+            typeof el.selectionEnd == "number") {
+            start = el.selectionStart;
+            end = el.selectionEnd;
+          } else {
+            range = document.selection.createRange();
+      
+            if (range && range.parentElement() == el) {
+              len = el.value.length;
+              normalizedValue = el.value.replace(/\r\n/g, "\n");
+              textInputRange = el.createTextRange();
+              textInputRange.moveToBookmark(range.getBookmark());
+              endRange = el.createTextRange();
+              endRange.collapse(false);
+      
+              if (textInputRange.compareEndPoints("StartToEnd", endRange) > -1) {
+                start = end = len;
+              } else {
+                start = -textInputRange.moveStart("character", -len);
+                start += normalizedValue.slice(0, start).split("\n").length - 1;
+      
+                if (textInputRange.compareEndPoints("EndToEnd", endRange) > -1) {
+                  end = len;
+                } else {
+                  end = -textInputRange.moveEnd("character", -len);
+                  end += normalizedValue.slice(0, end).split("\n").length - 1;
+                }
+              }
+            }
+          }
+      
           return {
-              start: $field[0].selectionStart,
+              start: start,
-              end: $field[0].selectionEnd
+              end: end
-          }
+          };
-        }
+        } // end if ($field.length)
       },