Difference between revisions of "Developing On Linux"

Revision as of 01:09, 1 July 2017

These instructions are for Audacity 2.1.1 or earlier. Audacity 2.1.2 requires wxWidgets 3.x (at time of writing, preferably 3.0.2). This page will be updated in due course.

Overview

Compiling Audacity, or any GNU/Linux application for that matter, is basically a six stage process.

1. Install build tools: the applications needed to create other applications.
2. Install dependencies: other software used by the application you are trying to compile
3. Download the source code into a local directory.
4. Configure the compile with options, if any.
5. Compile
6. Install

The first and second stages are crucial: lack of build tools and required dependencies are the cause of 99% of failed compiles. This page should help with that.

The standard commands to compile a piece of software for stages 4, 5 and 6 are as follows, issued from within the local directory containing the source code.

1. CONFIGURE: $ ./configure --[options-list]
2. COMPILE: $ make
3. INSTALL: $ sudo make install

Build Tools

Most Linux distributions come with the core set of development tools already installed, but if not you will need to install the following packages, probably from your distribution's package manager:

• Shell. The configure script for Audacity is generated for a bourne-compatible shell. It is very unlikely that your system does not have one of these, but if in doubt, install the Bash shell.
• GNU Make Other Makes may work, but may well not. Make on any Linux system will be GNU make.
• CMake  CMake is required to build libsoxr which is the Audacity default resampling library.
• GCC (at least the C and C++ compilers) from GNU Compiler Collection. The only other compiler actively maintained by the Audacity development team is Microsoft's Visual C++, although we welcome patches to make Audacity compile with other compilers, for example the OpenSolaris compiler.
• pkg-config
• Autoconf Application which writes configure scripts. Needed to modify the build system
• Automake Application which writes Makefiles. Needed to modify the build system
• Git Source code version control application
• Patch Application for applying patches to files
• GDB The GNU Debugger (for debugging crashes; see note below)
• gettext. In order to build the translations for Audacity the GNU gettext  tools are required. These are normally installed in order to be able to build wxWidgets (see below).

Dependencies

Audacity requires relatively few libraries and tools to build a minimum working application. There are then a larger number of optional libraries that extend Audacity to enable more features and facilities. It's therefore up to you whether you install these or not. If you don't install them, then decide later you need the extra features, you will need to rebuild Audacity after installing the extra libraries.

Note that some Linux distributions make a practice of splitting each library they package into two parts, those required for running applications using the library, and all the other files only needed when compiling applications using the library. The latter are often found in a package with a -dev suffix to the name. For the purposes of these instructions, whenever a library is listed as being needed, it means that both parts are needed in order to compile Audacity.

Prerequisites

These libraries are required to build Audacity.

wxWidgets

The main requirement to build Audacity is wxWidgets. WX 3.0 is required, preferably 3.0.2. Older wxGTK 3.0.x versions may have bugs or missing features which stop Audacity working.

Audacity supports for Linux (and other Unices) requires the wxGTK implementation of wxWidgets. There is no support for wxQt, wxX11 or other wx variants, as they are incomplete in key areas. The GTK+ headers are also required as Audacity includes extensions to wxGTK which need the underlying toolkit headers to compile.

Whilst building Audacity with a standard distribution-supplied wxGTK 3.0.2 package will work fine, it will be difficult to debug some features as wxWidgets will have been built in Release mode (even if the debugging symbols package has been installed). For Audacity development you will want to compile wxGTK from source in debug mode, thus obtaining both a full set of debug symbols and additional checking in the wxWidgets code. This copy of wxWidgets does not have to be installed as the system copy, provided that the WX_CONFIG environment variable is used to tell the configure script to use the debug build. For example if your debug build of wxWidgets is in /home/user/dev/wxbuild/ then run

(by putting the environment variable after the configure script invocation, the setting will be cached by the configure script and you don't need to re-specify it when re-configuring Audacity as you would if it was placed before the invocation).

We also have some notes on the libraries already supplied with different Linux Distributions. For example, Ubuntu tend to update to newer libraries sooner than Debian do.

libsndfile

libsndfile is required to build Audacity. It is almost certainly already installed on your system, although you may have to install the development package (see above). It is rarely necessary to compile libsndfile from source, although a copy is also included in Audacity on GitHub.

Packages and features options

The configure script of Audacity gives the option to link in or not to link in a number of optional packages or features, and to link to a local or system version of the required libsndfile library.

In the case of resampling libraries there is a choice of three packages but only one or none must be used.

Obtaining Audacity

For development you will always want to obtain the GitHub HEAD version of Audacity so you can stay abreast of the latest changes. For more information, see our development code download page and GitHub.

Configure possibilities for libraries range from whether to include them or not, and whether to use local or system versions. In almost all cases these are standard libraries, and only provided in GitHub for convenience, so if you have up-to-date versions installed as shared libraries you should select the external copies. The exceptions are Nyquist (which we have modified to integrate it with Audacity), and PortAudio (which has had to be patched to make it work).

Examples:

To enable support for ogg files:

To use an external sndfile library (which you have previously built and installed):

To disable Nyquist:

Compiling on Unix

To compile Audacity on Linux (or for that matter, Mac and most other Unix systems), use a modified "configure; make" sequence:

However, you may want to start by running ./configure --help first to see the options, and possibly add special options.

If you are re-compiling from Git HEAD you can re-generate the configure script by running

in the top level directory first.

In order to use ALSA devices with PortAudio v19 it is necessary to have the ALSA development library installed before compiling Audacity. In Debian-based Linux including Ubuntu and Ubuntu Studio, for example, this can be installed by running:

On other distributions for example RHEL/CentOS, the required package is called "alsa-lib-devel".

Modifying the source

Applying and reverting patches

To apply a patch use the following syntax ( see help with patch syntax and the p or strip option ) :

To revert a patch:

Useful rules when modifying the source

If you modify a file or an #include in a file:

make

If you modify configure.ac, Makefile.am, or any files in m4/ :

autoreconf --no-recursive -i; ./configure; make

If you add or remove files:

./configure; make

Old example dependencies: Audacity 1.3.4/Ubuntu 7.10

Dependencies:

gettext 
libasound2-dev 
libflac-dev 
libflac++-dev 
libgtk2.0-dev
libgtk-dev 
libid3tag0-dev 
libjack0.100.0-dev 
libmad0-dev 
libogg-dev 
libtwolame0 
libtwolame-dev 
libvorbis-dev 
libwxbase2.6-dev 
libwxgtk-dev 
libwxgtk2.6-dev 
twolame 
portaudio19-dev 
wx2.6-headers 
zlib1g-dev 

A suggested apt-get command to install the above dependencies:

A suggested ./configure command for full functionality:

See also Compiling Audacity for Beginners.

KDevelop

KDevelop is a free, open source and cross-platform Integrated Development Environment (IDE) produced by KDE. Although not officially supported by Audacity, KDevelop can in principle be used for building or developing Audacity on Linux using any desktop environment. There is some information on building Audacity on KDevelop here - note the link thereon to www.crotchett.com for a tutorial on Audacity and KDevelop is no longer retrievable.

Problems with GDB and keyboard/mouse grabs

Running GUI applications in GDB is tricky, because GDB doesn't understand keyboard/mouse grabbing. In most X11 applications when you're in a menu, dragging a slider, or similar, the application grabs control of the keyboard or mouse to prevent other applications from getting their events until the drag/menu action is over. If you hit a breakpoint with the keyboard or mouse grabbed you're really stuck. For this reason, people often debug in a nested X server like Xephyr (similar to the older Xnest). Here's how you do that:

• Install the Xephyr package. On Ubuntu it's called xserver-xephyr... probably similar in other distros
• Install a simple window manager to run in the nested X server... I usually use wm2, because it doesn't require any configuration.
• Run Xephyr. To get a 1024x768 window with address :5 (usually your main X server is at :0, and sometimes if you have two monitors the second is at :1) run

• Start up wm2 (or whatever you like for a simple window manager) in the Xephyr window:

• Pop open a new terminal for GDB. Set the shell variable DISPLAY to ":5" so that all X11 applications started from that shell will use the new server at :5:

• cd to the source tree and run gdb as usual. The Audacity window should come up inside the xephyr window.

If your keyboard map is messed up in the Audacity window you can run the following command, which copies the keyboard map from your main display to the new one

Alternately there's a way to force-ungrab the KB/mouse, but it requires some X configuration (I like Xephyr, but you might prefer this). AWD: The force-ungrab stuff has apparently been removed from recent versions of X.org. So you shouldn't rely on it unless you're specifically using an old version that still has this feature.