The package GL.Immediate

This package provides the tools to immediately push OpenGL primitives into the OpenGL pipeline. This functionality has been deprecated with OpenGL 3.0 because it has severe performance issues. In real software, you want to use Vertex Buffer Objects (VBOs). This package is provided to give beginners an easy start with OpenGLAda.

To input vertices into the OpenGL pipeline, you have to create an Input_Token that defines the connection between the vertices you supply. Creating such a token will tell OpenGL to expect vertices. While the token lives, you must not call any OpenCLAda subprograms except those in GL.Immediate (actually, you may call subprograms that are implemented by OpenCLAda itself, like the operators on vectors and matrices).

When the token is destroyed, the connection to the OpenGL pipeline is closed. If any errors are encountered during the lifetime of the token, they will be raised when the token is destroyed. Here is a example of how using a token looks like:

<?prettify lang=ada?>

declare
   Token : Input_Token := Start (Line_Strip);
begin
   Token.Add_Vertex (Vector'(-0.5, 0.5, 0.5, 1.0));
   Token.Add_Vertex (Vector'(0.5, 0.5, 0.5, 1.0));
   Token.Add_Vertex (Vector'(0.5, -0.5, 0.5, 1.0));
   Token.Add_Vertex (Vector'(-0.5, -0.5, 0.5, 1.0));
   Token.Add_Vertex (Vector'(-0.5, 0.5, 0.5, 1.0));
end; -- at this point, the token gets destroyed.

The token gets destroyed automatically by means of Ada.Finalization.Limited_Controlled. Calling Finalize manually will result in an exception. Declaring multiple tokens at the same time also won’t work.

The additional setter and getter subprograms in this package can be used without a token, but also while a token is active.