sync code with last improvements from OpenBSD

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

@@ -0,0 +1,120 @@
+'\" t
+'\"! tbl | 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 minmax.gl
+.ds Xs 45595 6 minmax.gl
+.TH GLMINMAX 3G
+.SH NAME
+.B "glMinmax
+\- define minmax table
+
+.SH C SPECIFICATION
+void \f3glMinmax\fP(
+GLenum \fItarget\fP,
+.nf
+.ta \w'\f3void \fPglMinmax( 'u
+	GLenum \fIinternalformat\fP,
+	GLboolean \fIsink\fP )
+.fi
+
+.SH PARAMETERS
+.TP \w'\fIinternalformat\fP\ \ 'u 
+\f2target\fP
+The minmax table whose parameters are to be set.
+Must be
+\%\f3GL_MINMAX\fP.
+.TP
+\f2internalformat\fP
+The  of entries in the minmax table.
+Must be one of
+\%\f3GL_ALPHA\fP,
+\%\f3GL_ALPHA4\fP,
+\%\f3GL_ALPHA8\fP,
+\%\f3GL_ALPHA12\fP,
+\%\f3GL_ALPHA16\fP,
+\%\f3GL_LUMINANCE\fP,
+\%\f3GL_LUMINANCE4\fP,
+\%\f3GL_LUMINANCE8\fP,
+\%\f3GL_LUMINANCE12\fP,
+\%\f3GL_LUMINANCE16\fP,
+\%\f3GL_LUMINANCE_ALPHA\fP,
+\%\f3GL_LUMINANCE4_ALPHA4\fP,
+\%\f3GL_LUMINANCE6_ALPHA2\fP,
+\%\f3GL_LUMINANCE8_ALPHA8\fP,
+\%\f3GL_LUMINANCE12_ALPHA4\fP,
+\%\f3GL_LUMINANCE12_ALPHA12\fP,
+\%\f3GL_LUMINANCE16_ALPHA16\fP,
+\%\f3GL_R3_G3_B2\fP,
+\%\f3GL_RGB\fP,
+\%\f3GL_RGB4\fP,
+\%\f3GL_RGB5\fP,
+\%\f3GL_RGB8\fP,
+\%\f3GL_RGB10\fP,
+\%\f3GL_RGB12\fP,
+\%\f3GL_RGB16\fP,
+\%\f3GL_RGBA\fP,
+\%\f3GL_RGBA2\fP,
+\%\f3GL_RGBA4\fP,
+\%\f3GL_RGB5_A1\fP,
+\%\f3GL_RGBA8\fP,
+\%\f3GL_RGB10_A2\fP,
+\%\f3GL_RGBA12\fP, or
+\%\f3GL_RGBA16\fP.
+.TP
+\f2sink\fP
+If \%\f3GL_TRUE\fP, pixels will be consumed by the minmax
+process and no drawing or texture loading will take place.
+If \%\f3GL_FALSE\fP, pixels will proceed to the final conversion process after
+minmax.
+.SH DESCRIPTION
+When \%\f3GL_MINMAX\fP is enabled, the RGBA components of incoming pixels are
+compared to the minimum and maximum values for each component, which are
+stored in the 2-element minmax table.
+(The first element stores the minima, and the second element stores
+the maxima.)
+If a pixel component is greater than the corresponding component
+in the maximum element, then the maximum element is updated with the
+pixel component value.
+If a pixel component is less than the corresponding component in
+the minimum element, then the minimum element is updated with the
+pixel component value.
+(In both cases, if the internal  of the minmax table includes
+luminance, then the R color component of incoming pixels is used
+for comparison.)
+The contents of the minmax table may be retrieved at a later time
+by calling \%\f3glGetMinmax\fP.
+The minmax operation is enabled or disabled by calling \%\f3glEnable\fP or
+\%\f3glDisable\fP, respectively, with an argument of \%\f3GL_MINMAX\fP.
+.P
+\%\f3glMinmax\fP redefines the current minmax table to have entries of the 
+specified by \f2internalformat\fP.
+The maximum element is initialized with the smallest possible component
+values, and the minimum element is initialized with the largest possible
+component values.
+The values in the previous minmax table, if any, are lost.
+If \f2sink\fP is \%\f3GL_TRUE\fP, then pixels are discarded after minmax;
+no further processing of the pixels takes place, and no drawing,
+texture loading, or pixel readback will result.
+.P
+.SH NOTES
+\%\f3glMinmax\fP is present only if \%\f3GL_ARB_imaging\fP is returned when \%\f3glGetString\fP
+is called with an argument of \%\f3GL_EXTENSIONS\fP.
+.SH ERRORS
+\%\f3GL_INVALID_ENUM\fP is generated if \f2target\fP is not one of the allowable
+values.
+.P
+\%\f3GL_INVALID_ENUM\fP is generated if \f2internalformat\fP is not one of the
+allowable values.
+.P
+\%\f3GL_INVALID_OPERATION\fP is generated if \%\f3glMinmax\fP is executed
+between the execution of \%\f3glBegin\fP and the corresponding
+execution of \%\f3glEnd\fP.
+.SH ASSOCIATED GETS
+\%\f3glGetMinmaxParameter\fP
+.SH SEE ALSO
+\%\f3glGetMinmax(3G)\fP,
+\%\f3glResetMinmax(3G)\fP