task.js: cooperative multitasking for long-running tasks

chrome/content/task_test_ui.js

Index: chrome/content/task_test_ui.js
===================================================================
--- a/chrome/content/task_test_ui.js
+++ b/chrome/content/task_test_ui.js
@@ -1,4 +1,84 @@
-function task_test_click()
+/*
+ * This Source Code is subject to the terms of the Mozilla Public License
+ * version 2.0 (the "License"). You can obtain a copy of the License at
+ * http://mozilla.org/MPL/2.0/.
+ */
+
+var {Long_Task} = require( "task" );
+var {tg_count} = require( "counter_task" );
+
+var current_task = null;
+
+function update_status( s, perform_log )
 {
-    Cu.reportError( "Clicked" );
-}
+    var status_field = document.getElementById( "task_status" );
+    if ( status_field.childNodes.length > 0 )
+    {
+        status_field.removeChild( status_field.childNodes[0] );
+    }
+    status_field.appendChild( document.createTextNode( s ) );
+    if ( arguments.length >= 2 && perform_log )
+    {
+        log( s );
+    }
+}
+
+function update_button( b )
+{
+    var button = document.getElementById( "task_go" );
+    if ( b ) {
+        button.label = "Cancel"
+    } else {
+        button.label = "Start"
+    }
+
+}
+
+function task_finished()
+{
+    if ( current_task.cancelled )
+    {
+        var status = "Cancelled";
+    }
+    else
+    {
+        status = "Finished";
+    }
+    update_status( status );
+    update_button( false );
+    current_task = null;
+}
+
+function task_count( n )
+{
+    update_status( "Count " + n, false );
+}
+
+/*
+ * We're overloading the start button also to handle cancellation.
+ */
+function task_start_click()
+{
+    if ( !current_task )
+    {
+        log( "Clicked start" );
+        let count = document.getElementById( "task_count" ).value;
+        let limit = document.getElementById( "task_limit" ).value;
+        current_task = new Long_Task( tg_count( count, task_count, task_finished ), limit );
+        update_status( "Started" );
+        update_button( true );
+        current_task.run();
+    }
+    else
+    {
+        current_task.cancel();
+        update_button( false );
+        // We have a running task, so cancel it.
+    }
+}
+
+
+function log( msg )
+{
+    Cu.reportError( "task_ui: " + msg );
+}