Added an example of how to create non-blocking widget code

examples/widgets/Nonblocking Console.ipynb

@@ -0,0 +1,217 b''
+{
+ "metadata": {
+  "name": ""
+ },
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "from subprocess import Popen, PIPE\n",
+      "import fcntl\n",
+      "import os\n",
+      "\n",
+      "from IPython.html import  widgets\n",
+      "from IPython.display import display"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Create the output, input, and console toggle widgets."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "console_container = widgets.ContainerWidget(visible=False)\n",
+      "console_container.set_css('padding', '10px')\n",
+      "\n",
+      "console_style = {\n",
+      "    'font-family': 'monospace',\n",
+      "    'color': '#AAAAAA',\n",
+      "    'background': 'black',\n",
+      "    'width': '800px',\n",
+      "}\n",
+      "\n",
+      "output_box = widgets.StringWidget(parent=console_container, default_view_name='TextAreaView')\n",
+      "output_box.set_css(console_style)\n",
+      "output_box.set_css('height', '400px')\n",
+      "\n",
+      "input_box = widgets.StringWidget(parent=console_container)\n",
+      "input_box.set_css(console_style)\n",
+      "\n",
+      "toggle_button = widgets.ButtonWidget(description=\"Start Console\")\n",
+      "def toggle_console():\n",
+      "    console_container.visible = not console_container.visible\n",
+      "    if console_container.visible:\n",
+      "        toggle_button.description=\"Stop Console\"\n",
+      "        input_box.disabled = False\n",
+      "    else:\n",
+      "        toggle_button.description=\"Start Console\"\n",
+      "toggle_button.on_click(toggle_console)\n"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 2
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Define function to run a process without blocking the input."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "def read_process(process, append_output):\n",
+      "    \"\"\" Try to read the stdout and stderr of a process and render it using \n",
+      "    the append_output method provided\n",
+      "    \n",
+      "    Parameters\n",
+      "    ----------\n",
+      "    process: Popen handle\n",
+      "    append_output: method handle\n",
+      "        Callback to render output.  Signature of\n",
+      "        append_output(output, [prefix=])\"\"\"\n",
+      "    \n",
+      "    try:\n",
+      "        stdout = process.stdout.read()\n",
+      "        if stdout is not None and len(stdout) > 0:\n",
+      "            append_output(stdout)\n",
+      "    except:\n",
+      "        pass\n",
+      "        \n",
+      "    try:\n",
+      "        stderr = process.stderr.read()\n",
+      "        if stderr is not None and len(stderr) > 0:\n",
+      "            append_output(stderr, prefix='ERR ')\n",
+      "    except:\n",
+      "        pass\n",
+      "\n",
+      "\n",
+      "def set_pipe_nonblocking(pipe):\n",
+      "    \"\"\"Set a pipe as non-blocking\"\"\"\n",
+      "    fl = fcntl.fcntl(pipe, fcntl.F_GETFL)\n",
+      "    fcntl.fcntl(pipe, fcntl.F_SETFL, fl | os.O_NONBLOCK)\n",
+      "\n",
+      "\n",
+      "kernel = get_ipython().kernel\n",
+      "def run_command(command, append_output, has_user_exited=None):\n",
+      "    \"\"\"Run a command asyncronously\n",
+      "    \n",
+      "    Parameters\n",
+      "    ----------\n",
+      "    command: str\n",
+      "        Shell command to launch a process with.\n",
+      "    append_output: method handle\n",
+      "        Callback to render output.  Signature of\n",
+      "        append_output(output, [prefix=])\n",
+      "    has_user_exited: method handle\n",
+      "        Check to see if the user wants to stop the command.\n",
+      "        Must return a boolean.\"\"\"\n",
+      "    \n",
+      "    # Echo input.\n",
+      "    append_output(command, prefix='>>> ')\n",
+      "    \n",
+      "    # Create the process.  Make sure the pipes are set as non-blocking.\n",
+      "    process = Popen(command, shell=True, stdout=PIPE, stderr=PIPE)\n",
+      "    set_pipe_nonblocking(process.stdout)\n",
+      "    set_pipe_nonblocking(process.stderr)\n",
+      "    \n",
+      "    # Only continue to read from the command \n",
+      "    while (has_user_exited is None or not has_user_exited()) and process.poll() is None:\n",
+      "        read_process(process, append_output)\n",
+      "        kernel.do_one_iteration() # Run IPython iteration.  This is the code that\n",
+      "                                  # makes this operation non-blocking.  This will\n",
+      "                                  # allow widget messages and callbacks to be \n",
+      "                                  # processed.\n",
+      "        \n",
+      "    # If the process is still running, the user must have exited.\n",
+      "    if process.poll() is None:\n",
+      "        process.kill()\n",
+      "    else:\n",
+      "        read_process(process, append_output) # Read remainer\n",
+      "        \n",
+      "    \n",
+      "        \n",
+      "        "
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Hook the process execution methods up to our console widgets."
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "def append_output(output, prefix='    '):\n",
+      "    output_lines = output.split('\\n')\n",
+      "    formatted_output = '\\n'.join([prefix + line for line in output_lines if len(line) > 0]) + '\\n'\n",
+      "    output_box.value += formatted_output\n",
+      "    output_box.scroll_to_bottom()\n",
+      "    \n",
+      "def has_user_exited():\n",
+      "    return not console_container.visible\n",
+      "\n",
+      "def handle_input(sender):\n",
+      "    sender.disabled = True\n",
+      "    try:\n",
+      "        command = sender.value\n",
+      "        sender.value = ''\n",
+      "        run_command(command, append_output=append_output, has_user_exited=has_user_exited)\n",
+      "    finally:\n",
+      "        sender.disabled = False\n",
+      "        \n",
+      "input_box.on_submit(handle_input)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 4
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "Show the console"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "display(toggle_button)\n",
+      "display(console_container)"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [],
+     "prompt_number": 5
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}
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