glCopyTexSubImage1D -	copy a one-dimensional texture
subimage

glCopyTexSubImage1D
	glCopyTexSubImage1D(target, level, xoffset, x, y, width) -> None

void glCopyTexSubImage1D( GLenum target,
                          GLint level,
                          GLint xoffset,
                          GLint x,
                          GLint y,
                          GLsizei width )

target   Specifies the target	texture.  Must be
         GL_TEXTURE_1D.

level	   Specifies the level-of-detail number.  Level	0 is
         the base image level.  Level	n is the nth mipmap
         reduction image.

xoffset  Specifies the texel offset within the texture
         array.

x, y	   Specify the window coordinates of the left corner
         of the row of pixels	to be copied.

width	   Specifies the width of the texture subimage.

glCopyTexSubImage1D replaces a portion of a one-dimensional
texture image	with pixels from the current GL_READ_BUFFER
(rather than from main memory, as is the case	for
glTexSubImage1D).

The screen-aligned pixel row with left corner	at (x, y), and
with length width replaces the portion of the	texture	array
with x indices xoffset through xoffset + width - 1,
inclusive. The destination in	the texture array may not
include any texels outside the texture array as it was
originally specified.

The pixels in	the row	are processed exactly as if
glCopyPixels had been	called,	but the	process	stops just
before final conversion.  At this point all pixel component
values are clamped to	the range [0, 1] and then converted to
the texture's	internal format	for storage in the texel
array.

It is	not an error to	specify	a subtexture with zero width,
but such a specification has no effect.  If any of the
pixels within	the specified row of the current
GL_READ_BUFFER are outside the read window associated	with
the current rendering	context, then the values obtained for
those	pixels are undefined.

No change is made to the internalformat, width, or border
parameters of	the specified texture array or to texel	values
outside the specified	subregion.

glCopyTexSubImage1D is available only	if the GL version is
1.1 or greater.

Texturing has	no effect in color index mode.

glPixelStore and glPixelTransfer modes affect	texture	images
in exactly the way they affect glDrawPixels.

GL_INVALID_ENUM is generated if target is not	GL_TEXTURE_1D.

GL_INVALID_OPERATION is generated if the texture array has
not been defined by a	previous glTexImage1D or
glCopyTexImage1D operation.

GL_INVALID_VALUE is generated	if level is less than 0.

GL_INVALID_VALUE may be generated if level>log  max, where
max is the returned value of GL_MAX_TEXTURE_SIZE.

GL_INVALID_VALUE is generated	if y <	-b or if width <  -b,
where	b is the border	width of the texture array.

GL_INVALID_VALUE is generated	if xoffset <  -b, or
(xoffset + width) > (w-b), where w is	the GL_TEXTURE_WIDTH,
and b	is the GL_TEXTURE_BORDER of the	texture	image being
modified.  Note that w includes twice	the border width.

glGetTexImage
glIsEnabled with argument GL_TEXTURE_1D

glCopyPixels,	glCopyTexImage1D, glCopyTexImage2D,
glCopyTexSubImage2D, glPixelStore, glPixelTransfer,
glTexEnv, glTexGen, glTexImage1D, glTexImage2D,
glTexParameter, glTexSubImage1D, glTexSubImage2D