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Building a NaCl App

In the browser!

Follow along with Brad Nelson’s Google I/O 2014 talk. Explore our new in-browser development environment and debugger.

Learn how easy it is to edit, build, and debug NaCl application all in your desktop web browser or on a Chromebook. Work either on-line or off-line!

Installation

The setup process currently requires several steps. We’re working to reduce the number of steps in future releases. As the process gets easier, we’ll update this page.

You currently need to:

  • Navigate to: chrome://flags and:

    • Enable Native Client.
    • Enable Native Client GDB-based debugging. (For the debugger)

  • Install the NaCl in-browser debugger.

  • Install the NaCl Development Environment.

    • First run is slow (as it downloads and installs packages).

Editor

To follow along in this tutorial, you’ll need to use a text editor to modify various files in our development environment. There are currently two editor options, nano or vim. Emacs is coming soon... If you’re unsure what to pick, nano is simpler to start with and has on-screen help.

  • You can open nano like this:

    $ nano <filename>

    Here’s an online nano tutorial.

  • You can open vim like this:

    $ vim <filename>

    Here’s an online vim tutorial.

Git Setup

This tutorial also uses a revision control program called git. In order to commit to a git repository, you need to setup your environment to with your identity.

You’ll need to add these lines to ~/.bashrc to cause them to be invoked each time you start the development environment.

git config --global user.name "John Doe"
git config --global user.email johndoe@example.com

Tour (follow the video)

Create a working directory and go into it:

$ mkdir work
$ cd work

Download a zip file containing our sample:

$ curl http://nacltools.storage.googleapis.com/io2014/voronoi.zip -O
$ ls -l

Unzip the sample:

$ unzip voronoi.zip

Go into the sample and take a look at the files inside:

$ cd voronoi
$ ls

Our project combines voronoi.cc with several C++ libraries to produce a NEXE (or Native Client Executable).

/native-client/images/voronoi1.png

The resulting application combines the NEXE with some Javascript to load the NaCl module, producing the complete application.

/native-client/images/voronoi2.png

Let’s use git (a revision control program) to track our changes.

First, create a new repository:

$ git init

Add everything here:

$ git add .

Then commit our starting state:

$ git commit -m "imported voronoi demo"

Now, likes run make to compile our program (NOTE: Changed since video, we’ve got Makefiles!):

$ make

Oops, we get this error:

voronoi.cc: In member function 'void Voronoi::Update()':
voronoi.cc:506: error: 'struct PSContext2D_t' has no member named 'hieght'

We’ll need to start an editor to fix this. You’ll want to change hieght to height on line 506. Then rebuild:

$ make

Lets look at the diff:

$ git diff

And commit our fix:

$ git commit -am "fixed build error"

To test our application, we run a local web server, written in python. Run the server with this command (NOTE: Running through a Makefile now):

$ make serve

Then, navigate to http://localhost:5103/ to test the demo.

If you follow along with the demo video, you will discover the sample crashes when you change the thread count.

Debugger walk-thru coming soon.

Once you’ve identified the problem. You’ll want to stop the test server. Press enter to halt it.

Open your editor again, navigate to line 485 and change valu to value.

Then rebuild:

$ make

Check the diff and commit our fix:

$ git diff
$ git commit -am "fixed thread ui bug"

Now look at your commit history:

$ git log

Run the demo again. And everything now works:

$ make serve
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