diff --git a/js-assembler/runtime-src/baselib-srclocs.js b/js-assembler/runtime-src/baselib-srclocs.js
new file mode 100644
index 0000000..2a4eee1
--- /dev/null
+++ b/js-assembler/runtime-src/baselib-srclocs.js
@@ -0,0 +1,30 @@
+(function(baselib) {
+    'use strict';
+
+    var exports = {};
+    baselib.srclocs = exports;
+
+
+    // (define-struct srcloc (source line column position span))
+    var srcloc = baselib.structs.makeStructureType(
+        'srcloc', false, 5, 0, false, false);
+
+    
+    var makeSrcloc = srcloc.constructor;
+
+    var isSrcloc = srcloc.predicate;
+    var srclocSource = function(x) { return srcloc.accessor(x, 0); }
+    var srclocLine = function(x) { return srcloc.accessor(x, 1); }
+    var srclocColumn = function(x) { return srcloc.accessor(x, 2); }
+    var srclocPosition = function(x) { return srcloc.accessor(x, 3); }
+    var srclocSpan = function(x) { return srcloc.accessor(x, 4); }
+
+    //////////////////////////////////////////////////////////////////////
+    exports.makeSrcloc = makeSrcloc;
+    exports.isSrcloc = isSrcloc;
+    exports.srclocSource = srclocSource;
+    exports.srclocColumn = srclocColumn;
+    exports.srclocPosition = srclocPosition;
+    exports.srclocSpan = srclocSpan;
+
+}(this.plt.baselib))
\ No newline at end of file
diff --git a/scribblings/cs19.scrbl b/scribblings/cs19.scrbl
index b2971e2..240e78d 100644
--- a/scribblings/cs19.scrbl
+++ b/scribblings/cs19.scrbl
@@ -357,32 +357,55 @@ moment.
 }
 
 
+Once we have a view, we can refocus the view to different elements by using
+@racket[view-left], @racket[view-right], @racket[view-up], and @racket[view-down].
+
+
+@defproc[(view-left? [v view]) boolean]{
+See if the view can be moved to the previous sibling.
+}
 @defproc[(view-left [v view]) view]{
 Move the focus to the previous sibling.
 }
+@defproc[(view-right? [v view]) boolean]{
+See if the view can be moved to the next sibling.
+}
 @defproc[(view-right [v view]) view]{
 Move the focus to the next sibling.}
 
+@defproc[(view-up? [v view]) boolean]{
+See if the view can be moved to the parent.
+}
 @defproc[(view-up [v view]) view]{
 Move the focus to the parent.}
 
+@defproc[(view-down? [v view]) boolean]{
+See if the view can be moved to the first child.
+}
 @defproc[(view-down [v view]) view]{
 Move the view to the first child.}
 
+
+
+Once we focus the view on an element, we can bind a world handler to it that
+responds to events.
+@defproc[(view-bind [v view] [type string] [world-updater ([w world] [v view]  [e event]? -> world)]) view]{
+Attach a world-updating event to the focus.  When the world-updater is
+called, the view will be focused on the element that triggered the
+event.  Common event types include @racket["click"],
+@racket["mouseenter"], @racket["change"].}
+
+
+
+When the view is on an element that we'd like to query or update, we can use
+several functions:
+
 @defproc[(view-text [v view]) string]{
 Get the textual content at the focus.
 }
 @defproc[(update-view-text [v view] [s string]) view]{
 Update the textual content at the focus.}
 
-@defproc[(view-bind [v view] [type string] [world-updater ([w world] [v view]  [e event]? -> world)]) view]{
-Attach a world-updating event to the focus.
-
-Attach a world-updating event to the focus.  When the world-updater is
-called, the view will be focused on the element that triggered the
-event.
-
-Common event types include @racket["click"], @racket["mouseenter"], @racket["change"].}
 
 @defproc[(view-show [v view]) view]{
 Show the element at the focus.
diff --git a/scribblings/manual.scrbl b/scribblings/manual.scrbl
index 50ddbed..925c1a9 100644
--- a/scribblings/manual.scrbl
+++ b/scribblings/manual.scrbl
@@ -743,15 +743,26 @@ moment.
 }
 
 
+@defproc[(view-left? [v view]) boolean]{
+See if the view can be moved to the previous sibling.
+}
 @defproc[(view-left [v view]) view]{
 Move the focus to the previous sibling.
 }
+@defproc[(view-right? [v view]) boolean]{
+See if the view can be moved to the next sibling.
+}
 @defproc[(view-right [v view]) view]{
 Move the focus to the next sibling.}
-
+@defproc[(view-up? [v view]) boolean]{
+See if the view can be moved to the parent.
+}
 @defproc[(view-up [v view]) view]{
 Move the focus to the parent.}
 
+@defproc[(view-down? [v view]) boolean]{
+See if the view can be moved to the first child.
+}
 @defproc[(view-down [v view]) view]{
 Move the view to the first child.}