WGL extensions not found when using Python 3

[tomgoddard]

WGL extensions are not found when using Python 3 due to use of strings where bytes are required. Below is a traceback trying to use the WGL_EXT_swap_control extension. Changing 3 lines in OpenGL/raw/WGL/_types.py to use bytes instead of strings using the as_8_bit() function fixes the problem. I've attached a patch with these changes.

In Python 3.1 with PyOpenGL 3.1.1a:
wgl_python3.patch.gz

from OpenGL.WGL.EXT import swap_control
swap_control.wglGetSwapIntervalEXT()

---

TypeError Traceback (most recent call last)
in ()
----> 1 swap_control.wglGetSwapIntervalEXT()

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\platform\baseplatform.py in call(self, *args, **named)
399 return None
400 def call( self, *args, **named ):
--> 401 if self.load():
402 return self( *args, **named )
403 else:

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\platform\baseplatform.py in load(self)
388 argNames = self.argNames,
389 extension = self.extension,
--> 390 error_checker = self.error_checker,
391 )
392 except AttributeError as err:

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\platform\win32.py in constructFunction(self, functionName, dll, resultType, argTypes, doc, argNames, extension, deprecated, module, error_checker)
127 deprecated,
128 module,
--> 129 error_checker=error_checker,
130 )
131 except AttributeError:

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\platform\baseplatform.py in constructFunction(self, functionName, dll, resultType, argTypes, doc, argNames, extension, deprecated, module, force_extension, error_checker)
146 """
147 is_core = (not extension) or extension.split('_')[1] == 'VERSION'
--> 148 if (not is_core) and not self.checkExtension( extension ):
149 raise AttributeError( """Extension not available""" )
150 argTypes = [ self.finalArgType( t ) for t in argTypes ]

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\platform\baseplatform.py in checkExtension(self, name)
268 if current is None:
269 from OpenGL import extensions
--> 270 result = extensions.ExtensionQuerier.hasExtension( name )
271 set[name] = result
272 return result

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\extensions.py in hasExtension(self, specifier)
96 def hasExtension( self, specifier ):
97 for registered in self.registered:
---> 98 result = registered( specifier )
99 if result:
100 return result

C:\Program Files\ChimeraX\bin\lib\site-packages\OpenGL\extensions.py in call(self, specifier)
103 def call( self, specifier ):
104 specifier = as_8_bit(specifier).replace(as_8_bit('.'),as_8_bit('_'))
--> 105 if not specifier.startswith( self.prefix ):
106 return None
107

TypeError: startswith first arg must be bytes or a tuple of bytes, not str

[tomgoddard]

Here's the patch to PyOpenGL 3.1.1a

wgl_python3.patch.gz

[mcfletch]

This should be fixed in the latest release.

[michaelbradley91]

I see the same or a similar problem on 3.1.4 with the same example code. The WGL extension prefix appears to be a string but should be bytes. (prefix is "WGL_")

Edit: the problem seems to go deeper. The prefix is a string, as is the prefix_version check, but further more so is the call to PLATFORM.getExtensionProcedure( 'wglGetExtensionsStringARB' ) which should be passed bytes and is used when loading the extensions

Edit: after patching PLATFORM.getExtensionProcedure( 'wglGetExtensionsStringARB' ) in _WGLQuerier to use bytes as well as the above, it seems to work for this example.

In case it is helpful, an ugly monkey patch for the sake of enabling VSYNC looks like this:

from ctypes import c_char_p
from OpenGL.GLUT import PLATFORM
from OpenGL.raw.WGL._types import HDC
from OpenGL.raw.WGL._types import WGLQuerier


def pullExtensions():
    wglGetCurrentDC = PLATFORM.OpenGL.wglGetCurrentDC
    wglGetCurrentDC.restyle = HDC
    try:
        dc = wglGetCurrentDC()
        proc_address = PLATFORM.getExtensionProcedure(b'wglGetExtensionsStringARB')
        wglGetExtensionStringARB = PLATFORM.functionTypeFor(PLATFORM.WGL)(
            c_char_p,
            HDC,
        )(proc_address)
    except TypeError as err:
        return None
    except AttributeError as err:
        return []
    else:
        return wglGetExtensionStringARB(dc).split()


def monkey_patch():
    WGLQuerier.prefix = WGLQuerier.prefix.encode("utf-8")
    WGLQuerier.version_prefix = WGLQuerier.version_prefix.encode("utf-8")
    WGLQuerier.pullExtensions = pullExtensions

[mcfletch]

So far I can't replicate this. The functions seem to be correctly loaded and run on Python 3.7 with current develop. I've made trivial changes to use b-strings and thus avoid the calls to as_8_bit, but the effect of as_8_bit is to convert any unicode value to utf-8 encoding via a .encode() call (as in your monkey patch), so the code was, AFAICT already using byte-strings in all of the places you are monkey-patching.