Add offset parameter to from_dtype.

This lets you provide a base offset for the
dtype structure instead of it always assuming
the data starts at 0.

Author: adamlwgriffiths

pygly/vertex_buffer.py

@@ -264,15 +264,15 @@ def pop_attributes( self ):
 class BufferAttribute( object ):
 
     @classmethod
-    def from_dtype( cls, buffer, dtype, name, **kwargs ):
+    def from_dtype( cls, buffer, dtype, name, offset = 0, **kwargs ):
         import numpy_utils
 
         args = {
             'buffer':   buffer,
             'values_per_vertex':    numpy_utils.dtype_element_count( dtype, name ),
             'gl_type':  numpy_utils.dtype_gl_enum( dtype, name ),
             'stride':   dtype.itemsize,
-            'offset':   numpy_utils.dtype_offset( dtype, name )
+            'offset':   offset + numpy_utils.dtype_offset( dtype, name )
             }
         args.update( kwargs )