Add a little Glade3 + GtkAda post
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R. Tyler Croy
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---
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layout: post
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title: "Using Glade3 with GtkAda"
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tags:
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- ada
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- gtk
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- glade
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- gtkada
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---
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I have been a hobby hacker for my entire adult life, and a bit before that too.
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When your profession is making software, or even making open source software,
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the joy from hobby-hacking can diminish or even disappear. One of the things I
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learned from [burning out](/2015/11/10/choose-happiness.html) was that, if I am
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going to continue to enjoy hacking as a personal hobby, I would need to pursue
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"frivolous hacking."
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*Frivolous hacking*:
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> Hacking on something for no practical or otherwise useful reason.
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Late last week I was struck with the desire to play around with
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[GtkAda](https://libre.adacore.com/tools/gtkada/). Ada has [long been a hobby
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language](/2010/12/06/ada-surely-you-jest-mr-pythonman.html) for me, but I have
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never gotten the desire to make a GUI-based application. For this weekend's
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_frivolous hacking_, I created [arun](https://github.com/berriedale/arun) a
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simple Ada Command Runner with GtkAda and [Glade 3](https://glade.gnome.org/).
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---
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The primary reason to use Glade, in my opinion, is that it's 2017 and
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hand-coding interface components is beyond tedious. At a high level, Glade
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provides a WYSIWYG approach for defining the various interface components a
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program requires, exports that as an XML file which can later be loaded by the
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program at runtime.
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### Prerequisites
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My first attempt relied on using the Glade3 and GtkAda packages which exist for
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Debian-based systems. Unfortunately `libgtkada2.24.4-dev` binds to Gtk+ version
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2, rather than Gtk+ version 3, which Glade3 targets.
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Instead of native packages, you can also [download GtkAda from
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AdaCore](http://libre.adacore.com) directly. Opting for this route I was
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disappointed to learn that the file named `gtkada-gpl-2016-x86_64-linux-bin.tar.gz`
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isn't actually a set of binaries but just a source tarball which must be built
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and installed. At first, [that didn't work for me
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either](https://github.com/AdaCore/gtkada/issues/7#issue-199381675)! A bug in
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that source tarball leaves a user like me with one of two options:
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1. Configure the installation with `./configure --with-GL=no`
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1. Grab the latest (`fc8b2f9` at this time) from GitHub: `git://github.com/AdaCore/GtkAda.git`
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I opted for the latter and within short order (`make -j4`!) I had fresh
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installation of GtkAda on my system.
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### Writing an app
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Fortunately the [Ada DK wiki](http://wiki.ada-dk.org/start) has an example I
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could start from, which covers the [basics of building a GUI with Glade3 in
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GtkAda](http://wiki.ada-dk.org/building_gui_with_glade_3). After cribbing some
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Ada code from the wiki page, I found another stumbling block, it wouldn't
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compile.
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Turns out some APIs had changed since the page was originally written, but as
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luck would have it [Stack Overflow had the
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answer](https://stackoverflow.com/a/17029228).
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Without going into too much detail on how to use GtkAda,
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[this
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version](https://github.com/berriedale/arun/commit/35b17986d4adb45ed91f8ecfc94f37f846f5a59e#diff-84ad0731ead1a1baefde1c6df1194789)
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of the `Arun.Main` procedure demonstrates a basic version of loading and
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starting a Glade3-based GtkAda app:
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```
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Gtk.Main.Init;
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Gtk_New (Builder);
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-- Load `arun.glade` which contains the interface definition
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Return_Code := Add_From_File (Builder => Builder,
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Filename => "arun.glade",
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Error => Error'Access);
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if Error /= null then
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Put_Line ("Error : " & Get_Message (Error));
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Error_Free (Error);
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return;
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end if;
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-- Register a signal handler for when
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-- the "Main_Quit" signal is fired
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Register_Handler (Builder => Builder,
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Handler_Name => "Main_Quit",
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Handler => Arun.Handlers.Quit'Access);
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Do_Connect (Builder);
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-- Get the Gtk_Widget object from the Gtkada.Builder API
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-- for our commandWindow so it will be shown.
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Gtk.Widget.Show_All (
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Gtk_Widget (Gtkada.Builder.Get_Object (Builder, "commandWindow")));
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Gtk.Main.Main;
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Unref (Builder);
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```
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With the `arun` binary compiled, I decided to try it out:
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```
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obj % ./arun
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Starting arun
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Error : Failed to open file 'arun.glade': No such file or directory
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obj %
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```
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As one might expect, there is a downside to loading files at executable
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runtime.
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Another [Stack Overflow answer](http://stackoverflow.com/a/28876764) introduced me
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to the `glib-compile-resources` executable, which provides the solution
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for loading the `.glade` file at runtime in a more portable way. Instead of
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referring to a `.glade` file, `glib-compile-resources` creates a C file which
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can be compiled and linked into the application. Of course, this adds some more
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build-time complexity, as `glib-compile-resources` needs to be called, the C
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file needs to be compiled, and then the object file must be linked into the
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resulting binary.
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With the Makefile put together, instead of `Add_From_File` the application uses
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`Add_From_Resource` as is demonstrated in [this commit](https://github.com/berriedale/arun/commit/5bf248399355582af49e83e59199fcb985210137).
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With a resource the binary can then be distributed without the `.glade` file:
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```
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obj % ./arun
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Starting arun
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Searching for x
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Searching for xeye
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Searching for xeyes
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Looking for an executable in /home/tyler/.rvm/gems/ruby-2.1.5/bin
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Looking for an executable in /home/tyler/.rvm/gems/ruby-2.1.5@global/bin
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Looking for an executable in /home/tyler/.rvm/rubies/ruby-2.1.5/bin
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Looking for an executable in /home/tyler/bin
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Looking for an executable in /home/tyler/scratch/bin
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Looking for an executable in /home/tyler/.rvm/bin
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Looking for an executable in /home/tyler/scratch/node_modules/.bin
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Looking for an executable in /home/tyler/scratch/ada/gnat-gpl-2016-x86_64-linux-bin/bin
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Looking for an executable in /home/tyler/scratch/ada/spark-gpl-2016-x86_64-linux-bin/bin
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Looking for an executable in /home/tyler/bin
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Looking for an executable in /usr/local/bin
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Looking for an executable in /usr/bin
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Found executable at /usr/bin/xeyes
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Should Execute: xeyes
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Spawning /usr/bin/xeyes
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obj %
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```
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Suffice it to say, using GtkAda isn't _difficult_ per se, it's only difficult
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to use when there are toolchain specific idiosyncrasies that are hard to
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Google. Aside from that challenge, I far prefer writing GtkAda rather than
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"pure" Gtk+ with C or C++.
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Of course I don't expect anybody else to find my code useful, nor do I have
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lofty ambitions about it, thereby meeting my "frivolous hacking" requirement!
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