#268 glGetBufferSubData odd behavior

[keksnicoh]

pyopengl version

Name: PyOpenGL
Version: 3.1.0
Location: /Library/Python/2.7/site-packages

When performing glGetBufferSubData on MacOS some weird behavior appears.
1. If data argument is non empty the application yields segfault
2. the function returns unit8 numpy.ndarray data even if you try to force it to float32 (using data argument).

One can convert the uint8 data to float32 by using some numpy conversions:

glBindBuffer(GL_ARRAY_BUFFER, vbo)
raw_unit8_data = glGetBufferSubData(GL_ARRAY_BUFFER, 0, 6*4)
glBindBuffer(GL_ARRAY_BUFFER, 0)
print(np.fromstring(raw_unit8_data.tostring(), dtype='<f4'))

I documented this problem on Stackoverflow:
http://stackoverflow.com/questions/34637222/glgetbuffersubdata-pyopengl-random-result-and-segfault