OpenGLAda - Yet Another OpenGL binding for Ada
OpenGLAda is a thick OpenGL binding for the Ada 2005 programming language. Unlike other, thin, bindings (see the project's homepage for a list), OpenGLAda enriches the original API with concepts and features provided by Ada, like object orientation, type safety and generics.
Besides standard OpenGL functionality, OpenGLAda optionally provides bindings to the following OpenGL-related libraries:
- GLFW: This is a library for creating windows with an OpenGL context on them. It also provides functionality for capturing user input on keyboard, mouse and joystick. Having a window with an OpenGL context is the prerequisite for using any OpenGL functionality. The GLFW binding comes in two flavors: One for GLFW 2.x and one for GLFW 3+. There are significant differences between these two, the most prominent being that GLFW 3 can handle multiple windows. You can set the desired GLFW version for the binding at compile time.
- SOIL: The Simple OpenGL Image Library. This is a very tiny library for loading image files into OpenGL textures. It is public domain. Because it's so tiny, it is linked directly into OpenGLAda. Its source is included in the OpenGLAda sources.
- FTGL: A library built on top of FreeType that provides an API to load TrueType fonts and render text with OpenGL. The Ada wrapper only provides basic functionality to load fonts and render text. As it does not include a wrapper to FreeType, the more low-level functionality has been excluded.
OpenGLAda supports MacOSX, Windows and X11-based systems.
In order to build OpenGLAda, you need to have:
- A GNAT compiler¹. The GNAT/GCC binary release from GnuAda is known to work as of November 2016 and is preferable if you do not fancy a GPL'd runtime. A GPL'd version is available on AdaCore's Libre Site, though it is known to have issues at least on OSX 10.11². More information is available on the GCC website.
- GPRBuild (is bundled with AdaCore's GNAT distribution). Minimum
supported version is the one that comes with GNAT GPL 2012 (20120509). Do
gnatmaketo build the project files, it won't work.
- An OpenGL implementation (usually comes bundled with your graphics driver)
- Optionally GLFW
- Optionally FTGL
¹: You may also be able to build OpenGLAda with another Ada compiler and/or
without using the
*.gpr files. You just have to import the sources to your
project and whichever build system you are using. I never used other Ada
compilers apart from GNAT, so if I accidentally used some GNAT-specific features
in the code, please drop me a message.
²: With GNAT GPL 2016, runtime loading of OpenGL function pointers does not seem to work on OSX 10.11, see this bug. It is unknown whether this affects other OSX versions or operation systems. The exact cause for this error is unknown. Therefore, using GNAT/GCC is currently strongly recommended.
A Makefile is provided mainly for building the tests:
$ make tests
If you're on Windows and do not have the
make utility available, you can build
the test by executing
$ gprbuild -P glfw_test.gpr -XWindowing_System=windows $ gprbuild -P opengl_test.gpr -XWindowing_System=windows
The tests require GLFW, because they need to create windows. By default, they try to link against GLFW 3+. You can instead build the tests against GLFW 2.x by executing:
$ gprbuild -P opengl_test.gpr -XWindowing_System=windows -XGLFW_Version=2 $ gprbuild -P glfw_test.gpr -XWindowing_System=windows -XGLFW_Version=2
quartz if needed.)
Using OpenGLAda in your project
The easiest way to use OpenGLAda in your project is to just copy the sources in some dependency folder within your project folder, e.g.:
YourProject | |-dependencies | | | +-OpenGLAda | |-your |-project |-files +-...
If you're using the GPRBuild system, you can then just declare using OpenGLAda in your *.gpr file:
Alternatively, you can specify the path to the OpenGL project file in as environment variable:
... and then specify the dependency without the path:
If you want to use GLFW, you also need to refer to the project
instead (it automatically adds a dependency to the
The project files
opengl-glfw.gpr take the following
Windowing_System: Sets the backend windowing system. Used for GLFW and also for system-dependent parts of the API (GLX, WGL, CGL):
x11: X Windowing System (Linux, BSD, etc)
windows: Microsoft Windows
quartz: Quartz Compositor (OS X)
mode: May take one of the following values:
debug(default): Compile the project with debugging symbols and without optimization.
release: Compile the project for a release environment.
GLFW_Version(GLFW only): Sets the version of the GLFW library to link against. See here for a detailed comparison of the two API versions.
2: GLFW 2.x. Only one window.
3: GLFW 3+. Multiple windows, multiple monitor support, etc.
Auto_Exceptions: Configures exception handling:
enabled(default): After each call to OpenGL, OpenGLAda checks whether OpenGL has set an error flag and if it had, raises the corresponding exception.
disabled: The user has to query the error flag on his own.
With other build systems
You can add the OpenGLAda sources to your code, then use whatever build system you want. Just make sure that you link properly against your OpenGL implementation:
- OS X:
-framework OpenGL -framework CoreFoundation
- X11-based (Linux, BSD, etc):
If you're using GLFW, add
-lglfw for GLFW 2 or
-lglfw3 for GLFW 3. If you're
on Windows and link against GLFW as dynamic library, you also need to add
-lwinmm. If you're using FTGL, add
OpenGLAda is not designed to be installed as a standalone library. The reasoning behind this is that OpenGLAda is a wrapper library that doesn't provide much functionality on its own. Therefore, maintaining a library installing routine does not seem worth the effort - even less as it would be expected to support multiple platforms.
As mentioned, OpenGLAda contains some tests. You can also see them as examples
that demonstrate the basic usage of the API. After building them as described
above, you can execute them in the
bin directory. Some tests load shader
files from the source directory by using relative paths, so they only work with
bin as working directory.
For additional information and documentation, see the project's homepage.
OpenGLAda autogenerates its API binding to OpenGL. The autogenerated source
files are those in
src/gl/generated and they are generated from the
src/gl/specs. The syntax of the spec files is similar to Ada.
The reason behind this is that all functionality newer than OpenGL 1.1 is not expected to be provided by the OpenGL implementation. Instead, function pointers to the implementations should be queried at runtime. This makes it possible for the user to provide a fallback in case some OpenGL functionality is not available on the target system.
generate tool compiled from
src/generator will take care of creating
both the API imports from OpenGL and the code for loading the function pointers
at runtime. The tool is only necessary when adding OpenGL API functions to
OpenGLAda and thus not of interest to the general user, since the autogenerated
files are checked in to version control.
If you change the
*.spec files, running
make generate afterwards will
update the autogenerated files. Be sure to check them in along with the spec
OpenGLAda is distributed under the terms of the ISC License. The Ada 2012 logo that is used in the SOIL tests is distributed under the terms of the CC BY-ND 3.0 license, the original author is AdaCore.