Re: OpenGL in Ada

[Shark8 <onewingedshark@gmail.com>]

On Jul 9, 9:11 am, Gene <gene.ress...@gmail.com> wrote:
> On Jul 7, 10:42 pm, Shark8 <onewingedsh...@gmail.com> wrote:
>
>
>
> > Hello everyone,
> > I posted about wanting to write an OS in Ada a while ago and, as part
> > of that effort I've taken to translating the OpenGL API. No, I don't
> > mean JUST running the headers through ato-Ada converter but actually
> > translating the API into a more Ada-natural form.
>
> > As an example, here is the glColor-'family' of functions:
> >     * WINGDIAPI void APIENTRY glColor3b (GLbyte red, GLbyte green,
> > GLbyte blue);
> >     * WINGDIAPI void APIENTRY glColor3bv (const GLbyte *v);
> >     * WINGDIAPI void APIENTRY glColor3d (GLdouble red, GLdouble green,
> > GLdouble blue);
> >     * WINGDIAPI void APIENTRY glColor3dv (const GLdouble *v);
> >     * WINGDIAPI void APIENTRY glColor3f (GLfloat red, GLfloat green,
> > GLfloat blue);
> >     * WINGDIAPI void APIENTRY glColor3fv (const GLfloat *v);
> >     * WINGDIAPI void APIENTRY glColor3i (GLint red, GLint green, GLint
> > blue);
> >     * WINGDIAPI void APIENTRY glColor3iv (const GLint *v);
> >     * WINGDIAPI void APIENTRY glColor3s (GLshort red, GLshort green,
> > GLshort blue);
> >     * WINGDIAPI void APIENTRY glColor3sv (const GLshort *v);
> >     * WINGDIAPI void APIENTRY glColor3ub (GLubyte red, GLubyte green,
> > GLubyte blue);
> >     * WINGDIAPI void APIENTRY glColor3ubv (const GLubyte *v);
> >     * WINGDIAPI void APIENTRY glColor3ui (GLuint red, GLuint green,
> > GLuint blue);
> >     * WINGDIAPI void APIENTRY glColor3uiv (const GLuint *v);
> >     * WINGDIAPI void APIENTRY glColor3us (GLushort red, GLushort
> > green, GLushort blue);
> >     * WINGDIAPI void APIENTRY glColor3usv (const GLushort *v);
> >     * WINGDIAPI void APIENTRY glColor4b (GLbyte red, GLbyte green,
> > GLbyte blue, GLbyte alpha);
> >     * WINGDIAPI void APIENTRY glColor4bv (const GLbyte *v);
> >     * WINGDIAPI void APIENTRY glColor4d (GLdouble red, GLdouble green,
> > GLdouble blue, GLdouble alpha);
> >     * WINGDIAPI void APIENTRY glColor4dv (const GLdouble *v);
> >     * WINGDIAPI void APIENTRY glColor4f (GLfloat red, GLfloat green,
> > GLfloat blue, GLfloat alpha);
> >     * WINGDIAPI void APIENTRY glColor4fv (const GLfloat *v);
> >     * WINGDIAPI void APIENTRY glColor4i (GLint red, GLint green, GLint
> > blue, GLint alpha);
> >     * WINGDIAPI void APIENTRY glColor4iv (const GLint *v);
> >     * WINGDIAPI void APIENTRY glColor4s (GLshort red, GLshort green,
> > GLshort blue, GLshort alpha);
> >     * WINGDIAPI void APIENTRY glColor4sv (const GLshort *v);
> >     * WINGDIAPI void APIENTRY glColor4ub (GLubyte red, GLubyte green,
> > GLubyte blue, GLubyte alpha);
> >     * WINGDIAPI void APIENTRY glColor4ubv (const GLubyte *v);
> >     * WINGDIAPI void APIENTRY glColor4ui (GLuint red, GLuint green,
> > GLuint blue, GLuint alpha);
> >     * WINGDIAPI void APIENTRY glColor4uiv (const GLuint *v);
> >     * WINGDIAPI void APIENTRY glColor4us (GLushort red, GLushort
> > green, GLushort blue, GLushort alpha);
> >     * WINGDIAPI void APIENTRY glColor4usv (const GLushort *v);
>
> > which was rewritten as:
> >  -- Color Formats
> >  Procedure Color    ( red, green, blue : in Byte );
> >  Procedure Color    ( v : RGB_Byte_Vector );
> >  Procedure Color    ( red, green, blue : in double );
> >  Procedure Color    ( v : RGB_Double_Vector );
> >  Procedure Color    ( red, green, blue : in float );
> >  Procedure Color    ( V : RGB_Float_Vector );
> >  Procedure Color    ( red, green, blue : int );
> >  Procedure Color    ( V : RGB_Integer_Vector );
> >  Procedure Color    ( red, green, blue : Short );
> >  Procedure Color    ( V : RGB_Short_Vector );
> >  Procedure Color    ( red, green, blue : Unsigned_Byte );
> >  Procedure Color    ( v : RGB_Unsigned_Byte_Vector );
> >  Procedure Color    ( red, green, blue : in Unsigned_Integer );
> >  Procedure Color    ( v : RGB_Unsigned_Integer_Vector );
> >  Procedure Color    ( red, green, blue : in Unsigned_Short );
> >  Procedure Color    ( v : RGB_Unsigned_Short_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in byte );
> >  Procedure Color    ( v: RGBA_Byte_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in double );
> >  Procedure Color    ( v : RGBA_Double_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in float );
> >  Procedure Color    ( v: RGBA_Float_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in int );
> >  Procedure Color    ( v: RGBA_Integer_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in short );
> >  Procedure Color    ( v: RGBA_Short_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in Unsigned_Byte );
> >  Procedure Color    ( v: RGBA_Unsigned_Byte_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in Unsigned_Integer );
> >  Procedure Color    ( v: RGBA_Unsigned_Integer_Vector );
> >  Procedure Color    ( red, green, blue, alpha : in Unsigned_Short );
> >  Procedure Color    ( v: RGBA_Unsigned_Short_Vector );
>
> > where X_Y_Vector is an array of elements of type Y and indexed on type
> > X.
>
> > Another thing that I've done is, to the best of my ability, used Ada's
> > strong typing to make passing invalid parameters less of a problem;
> > for example:
> >    Type Begin_Mode_Type is
> >      (  POINTS, LINES, LINE_LOOP, LINE_STRIP, TRIANGLES,
> > TRIANGLE_STRIP,
> >         TRIANGLE_FAN, QUADS, QUAD_STRIP, POLYGON
> >      );
>
> >     For Begin_Mode_Type use
> >      (  POINTS          => GL_POINTS,
> >         LINES           => GL_LINES,
> >         LINE_LOOP       => GL_LINE_LOOP,
> >         LINE_STRIP      => GL_LINE_STRIP,
> >         TRIANGLES       => GL_TRIANGLES,
> >         TRIANGLE_STRIP  => GL_TRIANGLE_STRIP,
> >         TRIANGLE_FAN    => GL_TRIANGLE_FAN,
> >         QUADS           => GL_QUADS,
> >         QUAD_STRIP      => GL_QUAD_STRIP,
> >         POLYGON         => GL_POLYGON
> >      );
>
> > is a type for the glBegin-wrapper which only allows the  passing of
> > valid "mode"-parameters. {That is, range points..polygon.}
>
> > My questions are these:
> > Would anyone, other than myself, find such a translation of interest?
> > and
> > When I finish, would anyone want to test it out?
>
> Having done this a couple of times myself, you should consider the
> approach of writing a specialized program that processes the OpenGL
> header into a binding.  OpenGL will remain a moving target as graphics
> hardware continues to evolve.  Compilers will always have their unique
> quirks.  With all this room for variation, it will probably be easier
> to maintain a translator than to revise the binding every time the
> standard changes or grows.

I see what you're saying. The problem is in the specs, the moving
target you mentioned, for example the glBegin function could be
extended to take a new enumeration, say, GL_AWESOME! This disrupts the
allowable inputs for glBegin, now we have a non-contiguous range of
GL_POINTS..GL_POLYGON & GL_AWESOME..GL_AWESOME since these are
constants instead of true enumeration-types {thank you c/c++} and the
glFUNCTIONs take a 32-bit value as the "enumeration."

Basically it's the result of a) lack of foresight, and b) lazy
programming.