diff --git a/js/x11/core/examples/simple/gcinvert.js b/js/x11/core/examples/simple/gcinvert.js
new file mode 100644
index 0000000..b9d5a82
--- /dev/null
+++ b/js/x11/core/examples/simple/gcinvert.js
@@ -0,0 +1,36 @@
+/*
+ * GCFunction usage example
+ */
+var x11 = require('../../lib');
+
+x11.createClient(function(err, display) {
+  var X = display.client;
+  var root = display.screen[0].root;
+  var white = display.screen[0].white_pixel;
+  var black = display.screen[0].black_pixel;
+
+  var wid = X.AllocID();
+  X.CreateWindow(wid, root, 0, 0, 400, 300, 0, 0, 0, 0, { 
+    backgroundPixel: black,
+    eventMask: x11.eventMask.ButtonPress|x11.eventMask.Exposure });
+  var gc = X.AllocID();
+  X.CreateGC(gc, wid, {foreground : white, 'function' : x11.gcFunction.GXinvert});
+  X.MapWindow(wid);
+
+
+  X.on('event', function(ev) {
+
+    if (ev.type === 12) {
+      X.PolyFillRectangle(wid, gc, [0, 0, 400, 300]);
+    }
+
+    if (ev.type === 4) {
+      var x = ev.x;
+      var y = ev.y;
+
+      X.PolyFillRectangle(wid, gc, [x - 25, y - 25, 50, 50]);
+    }
+
+  });
+});
+