Re: [Pharo-project] Need your opinion: What is most appealing form for GL function bindings?

May 20, 2010

      On 20 May 2010 21:50, Henrik Sperre Johansen
<henrik.s.johansen@veloxit.no> wrote:
...
Â On 20.05.2010 19:42, Schwab,Wilhelm K wrote:
...
Sig,
Since you are focusing on the name of the selector, can I conclude that
you are using the selector name to make the call? Â I am not sure I like that
(strongly suspect I do not). Â Dolphin and FFI use a pragma(-ish??) syntax
with the return type, function name and argument types explicitly listed. Â I
very much would like to see you handle the details of getting things on and
off of the stack, but I would like to control the selector name and the
types.
As an example, calling something
Â  waveletTransformForward:comma:comma:
is not nearly as helpful to me as
Â  waveletTransformForward:size:flag:
The selector can be even more informative than that, but hopefully it
starts to make the case for the independent selector.
Bill
No, but he is automatically generating the interface from a spec file, thus
some standard for how to convert it to a selector is needed.
If he's using the NB FFI convention we discussed some time ago, the only
"magic" is that the arg names are used in the apiCall specification.
Example copy-pasted from the announcement of that functionality:
primGetModuleFileName: hModule with: lpFileName with: nSize
Â  Â  Â  Â <primitive: #primitiveNativeCall module: #NativeBoostPlugin>
Â  Â  Â  Â ^ NBFFICallout
Â  Â  Â  Â  Â  Â  Â  Â apiCall: #(
Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â DWORD GetModuleFileName (
Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â HMODULE hModule,
Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â LPTSTR lpFilename,
Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â  Â DWORD nSize))
Â  Â  Â  Â  Â  Â  Â  Â module: #Kernel32
Â  Â  Â  Â  Â  Â  Â  Â options: #( - coerceNilToNull )
Right, you are free to change it to anything you like. But it would be
unwise to poke manually with more
than 2500 functions (i listed the numbers earlier), so there is an
automated process which generating code for them.

Here is how generated method looks like:

glDrawArraysInstancedARB: mode first: first count: count primcount: primcount
	"This method was automatically generated from OpenGL specs"
	"See http://squeaksource.com/OpenGLSpecs for details"
	<primitive: #primitiveNativeCall module: #NativeBoostPlugin>

	^ self
		glApiCall: #( void glDrawArraysInstancedARB ( GLenum mode , long
first , GLsizei count , GLsizei primcount ) )
		attributes: #(
			#alias 'DrawArraysInstanced'
			#category #'ARB_draw_instanced'
			#version #'2.0'
		)

As you may see, in addition to function prototype 'void
glTbufferMask3DFX ( GLuint mask )'
it contains an additional meta-information, which could be userful to
diagnose problem, if call fails.

And as an example, how you can change it, here it is:

choosePixelFormat

	<primitive: #primitiveNativeCall module: #NativeBoostPlugin>

	^ NBFFICallout
		stdcall: #( int ChoosePixelFormat (
			HDC  dc ,
			GLPixelFormatDescriptor pixelFormat
		)) module: #gdi32

as you can see, this method doesn't taking any arguments, while
function expects 2.
Still its a working implementation.
A dc and pixelFormat is an instance variables of method's receiver,
and NBFFICallout knows
how to deal with it.
...
Cheers,
Henry
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-- 
Best regards,
Igor Stasenko AKA sig.