Highly Disappointed w/ the new XML API Database

[Simon Arbon]

As an example, to create a strongly-typed OpenGL header file for Pascal, you would do something like this:
Lets try glCullFace, in the XML file we find a list of valid enums for it, but the type name is a comment which makes it hard to extract.

<!-- /* CullFaceMode */ --> 
<enum name="GL_FRONT" /> 
<enum name="GL_BACK" /> 
<enum name="GL_FRONT_AND_BACK" />

The actual values are easy:

  <enum value="0x0404" name="GL_FRONT" /> 
<enum value="0x0405" name="GL_BACK" /> 
  <enum value="0x0408" name="GL_FRONT_AND_BACK" />

From this we can define a Pascal type:

CullFaceMode = (
        GL_FRONT = $0404,
        GL_BACK = $0405,
        GL_FRONT_AND_BACK = $0408
        );

Now for the command:

<command>
 <proto>
  void 
  <name>glCullFace</name> 
  </proto>
 <param>
  <ptype>GLenum</ptype> 
  <name>mode</name> 
  </param>
  <glx type="render" opcode="79" /> 
  </command>

Not very helpful, the parameter is only listed as GLenum, what we need is some way to create this:

type
TCullFace = procedure glCullface( mode: CullFaceMode );
var
glCullFace: TCullFace;

For commands like GetIntegerv you could overload the function definition so that if the enum is in one range of values then the second parameter must be a pointer to an integer variable, and for another range it must be a pointer to an array of integer.
For some enums you might specify that it is a pointer to a record type, for example if you are reading a color value you might make a record type containing R,G,B and A values.
This would need the information from the state tables in chapter 23 of the spec.

[mbentrup]

How would your strongly typed Pascal binding deal with glDrawBuffer(), which accepts GL_FRONT, GL_BACK, GL_FRONT_AND_BACK, but also GL_NONE, GL_FRONT_LEFT, GL_FRONT_RIGHT, etc. ?

[Simon Arbon]

Lots and lots of overloading

Heavily reused enums will need there own type eNone = ( GL_NONE = 0 ); // [ DrawBufferMode ],[ PixelTexGenMode ]
eBothFaces = ( GL_FRONT_AND_BACK = $0408 ); //[ DrawBufferMode ], [ ColorMaterialFace ],[ CullFaceMode ],[ MaterialFace ]

Then we do the main enum type:
eDrawBufferMode = (
GL_FRONT_LEFT = $0400, //[ DrawBufferMode ],[ ReadBufferMode ]
GL_FRONT_RIGHT = $0401, //[ DrawBufferMode ],[ ReadBufferMode ]
GL_BACK_LEFT = $0402, //[ DrawBufferMode ],[ ReadBufferMode ]
GL_BACK_RIGHT = $0403, //[ DrawBufferMode ],[ ReadBufferMode ]
GL_FRONT = $0404, //[ DrawBufferMode ],[ ReadBufferMode ],[ ColorMaterialFace ],[ CullFaceMode ],[ MaterialFace ]
GL_BACK = $0405, //[ DrawBufferMode ],[ ReadBufferMode ],[ ColorMaterialFace ],[ CullFaceMode ],[ MaterialFace ]
GL_LEFT = $0406, //[ DrawBufferMode ],[ ReadBufferMode ]
GL_RIGHT = $0407 ); //[ DrawBufferMode ],[ ReadBufferMode ]

Some reused enums are ranges inside of larger types so we can take the type for DrawBufferMode/ReadBufferMode and create a subrange type for ColorMaterialFace/CullFaceMode/MaterialFace:
eCullFaceMode = GL_FRONT..GL_BACK;

Then once we have the enums divided up into groups, we just overload the function to use all of the applicable groups.
procedure glDrawBuffer( Buffers: eNone ); stdcall; external 'OpenGL32.dll'; overload;
procedure glDrawBuffer( Buffers: eDrawBufferMode ); stdcall; external 'OpenGL32.dll'; overload;
procedure glDrawBuffer( Buffers: eBothFaces ); stdcall; external 'OpenGL32.dll'; overload;

[Jon Leech (oddhack)]

FYI, I've put the .spec file parameter type & array length annotations into gl.xml. See here and feel free to provide feedback on the board, or patches in Bugzilla, if this helps address the concerns in this thread.