Add an, as of yet undocumented, fourth argument to addWidget

Can be one of 'below' (default), 'over', or 'fit', and controls the way
the widget is positioned in relation to the given character position.
'fit' means CodeMirror does its best to keep the widget inside the current
dimensions of the editor.

lib/codemirror.js

@@ -154,16 +154,22 @@ var CodeMirror = (function() {
       clearMarker: removeGutterMarker,
       setLineClass: operation(setLineClass),
       lineInfo: lineInfo,
-      addWidget: function(pos, node, scroll) {
-        pos = clipPos(pos);
-        var wcoords = localCoords(pos, true);
-        node.style.top = (showingFrom * lineHeight() + wcoords.yBot + paddingTop()) + "px";
-        node.style.left = (wcoords.x + paddingLeft()) + "px";
+      addWidget: function(pos, node, scroll, where) {
+        pos = localCoords(clipPos(pos));
+        var top = pos.yBot, left = pos.x;
+        node.style.position = "absolute";
         code.appendChild(node);
-        if (scroll) {
-          var vcoords = localCoords(pos);
-          scrollIntoView(vcoords.x, vcoords.yBot, vcoords.x + node.offsetWidth, vcoords.yBot + node.offsetHeight);
+        node.style.left = left + "px";
+        if (where == "over") top = pos.y;
+        else if (where == "fit") {
+          var vspace = lines.length * lineHeight(), hspace = code.clientWidth - paddingLeft();
+          top = pos.y + node.offsetHeight > vspace ? vspace - node.offsetHeight : pos.y;
+          if (left + node.offsetWidth > hspace) left = hspace - node.offsetWidth;
         }
+        node.style.top = (top + paddingTop()) + "px";
+        node.style.left = (left + paddingLeft()) + "px";
+        if (scroll)
+          scrollIntoView(left, top, left + node.offsetWidth, top + node.offsetHeight);
       },
 
       lineCount: function() {return lines.length;},
@@ -757,6 +763,8 @@ var CodeMirror = (function() {
 
       var textWidth = stringWidth(maxLine);
       lineSpace.style.width = textWidth > scroller.clientWidth ? textWidth + "px" : "";
+      // Needed to prevent odd wrapping/hiding of widgets placed in here.
+      code.style.width = (lineSpace.offsetWidth + lineSpace.offsetLeft) + "px";
 
       // Since this is all rather error prone, it is honoured with the
       // only assertion in the whole file.