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<STRONG>NAME</STRONG>
<STRONG>glReadBuffer</STRONG> - select a color buffer source for pixels
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glReadBuffer</STRONG>( GLenum <EM>mode</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>mode</EM> Specifies a color buffer. Accepted values are
<STRONG>GL_FRONT_LEFT</STRONG>, <STRONG>GL_FRONT_RIGHT</STRONG>, <STRONG>GL_BACK_LEFT</STRONG>,
<STRONG>GL_BACK_RIGHT</STRONG>, <STRONG>GL_FRONT</STRONG>, <STRONG>GL_BACK</STRONG>, <STRONG>GL_LEFT</STRONG>, <STRONG>GL_RIGHT</STRONG>,
and <STRONG>GL_AUX</STRONG><EM>i</EM>, where <EM>i</EM> is between 0 and <STRONG>GL_AUX_BUFFERS</STRONG>
-1.
<STRONG>DESCRIPTION</STRONG>
<STRONG>glReadBuffer</STRONG> specifies a color buffer as the source for
subsequent <STRONG>glReadPixels</STRONG>, <STRONG>glCopyTexImage1D</STRONG>, <STRONG>glCopyTexImage2D</STRONG>,
<STRONG>glCopyTexSubImage1D</STRONG>, <STRONG>glCopyTexSubImage2D</STRONG>, and <STRONG>glCopyPixels</STRONG>
commands. <EM>mode</EM> accepts one of twelve or more predefined
values. (<STRONG>GL_AUX0</STRONG> through <STRONG>GL_AUX3</STRONG> are always defined.) In a
fully configured system, <STRONG>GL_FRONT</STRONG>, <STRONG>GL_LEFT</STRONG>, and
<STRONG>GL_FRONT_LEFT</STRONG> all name the front left buffer, <STRONG>GL_FRONT_RIGHT</STRONG>
and <STRONG>GL_RIGHT</STRONG> name the front right buffer, and <STRONG>GL_BACK_LEFT</STRONG>
and <STRONG>GL_BACK</STRONG> name the back left buffer.
Nonstereo double-buffered configurations have only a front
left and a back left buffer. Single-buffered configurations
have a front left and a front right buffer if stereo, and
only a front left buffer if nonstereo. It is an error to
specify a nonexistent buffer to <STRONG>glReadBuffer</STRONG>.
<EM>mode</EM> is initially <STRONG>GL_FRONT</STRONG> in single-buffered
configurations, and <STRONG>GL_BACK</STRONG> in double-buffered
configurations.
<STRONG>ERRORS</STRONG>
<STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>mode</EM> is not one of the
twelve (or more) accepted values.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <EM>mode</EM> specifies a buffer
that does not exist.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glReadBuffer</STRONG> is
executed between the execution of <STRONG>glBegin</STRONG> and the
corresponding execution of <STRONG>glEnd</STRONG>.
<STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG>
<STRONG>glGet</STRONG> with argument <STRONG>GL_READ_BUFFER</STRONG>
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glCopyPixels</STRONG>, <STRONG>glCopyTexImage1D</STRONG>, <STRONG>glCopyTexImage2D</STRONG>,
<STRONG>glCopyTexSubImage1D</STRONG>, <STRONG>glCopyTexSubImage2D</STRONG>, <STRONG>glDrawBuffer</STRONG>,
<STRONG>glReadPixels</STRONG>
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