Disable "Load Local File" button unless a file is selected.

my_modules/c1pjs-client/lib/serial.js

@@ -129,6 +129,16 @@ C1PSerialPort.prototype.setBinding = function(c, t, s, e)
         if (window.FileReader && window.File && window.FileList && window.Blob ) {
             var serial = this;
             this.bindings[s] = e;
+
+            // Enable "Load Local File" button only if a file is actually selected
+            e.addEventListener('change', function () {
+                var fieldset = e.children[0];
+                var files = fieldset.children[0].files;
+                var submit = fieldset.children[1];
+
+                submit.disabled = (files.length == 0);
+            });
+
             e.onsubmit = function (event) {
                 var file = event.currentTarget[1].files[0];
 

my_modules/c1pjs-client/templates/components.xsl

@@ -289,7 +289,7 @@
 					<form class="{$APPCLASS}-{@class}" data-value="{$type},{$binding}">
 						<fieldset>
 							<input type="file"/>
-							<input type="submit" value="Load Local File" />
+							<input type="submit" value="Load Local File" disabled="true"/>
 						</fieldset>
 					</form>
 				</xsl:when>