sync code with last improvements from OpenBSD

doc/gl-docs/GL/gl/matrixmode.3gl

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+'\" e
+'\"! eqn | mmdoc
+'\"macro stdmacro
+.ds Vn Version 1.2
+.ds Dt 24 September 1999
+.ds Re Release 1.2.1
+.ds Dp Jan 14 18:30
+.ds Dm 01 matrixmod
+.ds Xs 9532 4 matrixmode.gl
+.TH GLMATRIXMODE 3G
+.SH NAME
+.B "glMatrixMode
+\- specify which matrix is the current matrix
+
+.SH C SPECIFICATION
+void \f3glMatrixMode\fP(
+GLenum \fImode\fP )
+.nf
+.fi
+
+.SH PARAMETERS
+.TP \w'\f2mode\fP\ \ 'u 
+\f2mode\fP
+Specifies which matrix stack is the target
+for subsequent matrix operations.
+Three values are accepted:
+\%\f3GL_MODELVIEW\fP,
+\%\f3GL_PROJECTION\fP, and
+\%\f3GL_TEXTURE\fP.
+The initial value is \%\f3GL_MODELVIEW\fP.
+.TE
+
+Additionally, if the \%\f3GL_ARB_imaging\fP extension is supported,
+\%\f3GL_COLOR\fP is also accepted.
+.SH DESCRIPTION
+\%\f3glMatrixMode\fP sets the current matrix mode.
+\f2mode\fP can assume one of four values:
+.TP 25
+\%\f3GL_MODELVIEW\fP
+Applies subsequent matrix operations to the modelview matrix stack.
+.TP
+\%\f3GL_PROJECTION\fP
+Applies subsequent matrix operations to the projection matrix stack.
+.TP
+\%\f3GL_TEXTURE\fP
+Applies subsequent matrix operations to the texture matrix stack.
+.TP
+\%\f3GL_COLOR\fP
+Applies subsequent matrix operations to the color matrix stack.
+.P
+To find out which matrix stack is currently the target of all matrix
+operations, call \%\f3glGet\fP with argument \%\f3GL_MATRIX_MODE\fP. The initial
+value is \%\f3GL_MODELVIEW\fP.
+.SH ERRORS
+\%\f3GL_INVALID_ENUM\fP is generated if \f2mode\fP is not an accepted value.
+.P
+\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glMatrixMode\fP
+is executed between the execution of \%\f3glBegin\fP
+and the corresponding execution of \%\f3glEnd\fP.
+.SH ASSOCIATED GETS
+\%\f3glGet\fP with argument \%\f3GL_MATRIX_MODE\fP
+.SH SEE ALSO
+\%\f3glLoadMatrix(3G)\fP,
+\%\f3glPushMatrix(3G)\fP