new CYGWIN docs from Eric Lassauge
diff --git a/docs/README.CYGWIN b/docs/README.CYGWIN
new file mode 100644
index 0000000..58d5af3
--- /dev/null
+++ b/docs/README.CYGWIN
@@ -0,0 +1,256 @@
+
+ Mesa Cygwin/X11 Information
+
+
+WARNING
+=======
+
+If you installed X11 (packages xorg-x11-devel and xorg-x11-bin-dlls ) with the
+latest setup.exe from Cygwin the GL (Mesa) libraries and include are already
+installed in /usr/X11R6.
+
+The following will explain how to "replace" them.
+
+Installation
+============
+
+How to compile Mesa on Cygwin/X11 systems:
+
+1. Shared libs:
+ type 'make cygwin-sl'.
+
+ When finished, the Mesa DLL will be in the Mesa-x.y/lib/ and
+ Mesa-x.y/bin directories.
+
+
+2. Static libs:
+ type 'make cygwin-static'.
+ When finished, the Mesa libraries will be in the Mesa-x.y/lib/ directory.
+
+Header and library files:
+ After you've compiled Mesa and tried the demos I recommend the following
+ procedure for "installing" Mesa.
+
+ Copy the Mesa include/GL directory to /usr/X11R6/include:
+ cp -a include/GL /usr/X11R6/include
+
+ Copy the Mesa library files to /usr/X11R6/lib:
+ cp -a lib/* /usr/X11R6ocal/lib
+
+ Copy the Mesa bin files (used by the DLL stuff) to /usr/X11R6/bin:
+ cp -a lib/cyg* /usr/X11R6/bin
+
+Xt/Motif widgets:
+ If you want to use Mesa or OpenGL in your Xt/Motif program you can build
+ the widgets found in either the widgets-mesa or widgets-sgi directories.
+ The former were written for Mesa and the later are the original SGI
+ widgets. Look in those directories for more information.
+ For the Motif widgets you must have downloaded the lesstif package.
+
+
+Using the library
+=================
+
+Configuration options:
+ The file src/mesa/main/config.h has many parameters which you can adjust
+ such as maximum number of lights, clipping planes, maximum texture size,
+ etc. In particular, you may want to change DEPTH_BITS from 16 to 32
+ if a 16-bit depth buffer isn't precise enough for your application.
+
+
+Shared libraries:
+ If you compile shared libraries (Win32 DLLS) you may have to set an
+ environment variable to specify where the Mesa libraries are located.
+ Set the PATH variable to include /your-dir/Mesa-2.6/bin.
+ Otherwise, when you try to run a demo it may fail with a message saying
+ that one or more DLL couldn't be found.
+
+
+Xt/Motif Widgets:
+ Two versions of the Xt/Motif OpenGL drawing area widgets are included:
+
+ widgets-sgi/ SGI's stock widgets
+ widgets-mesa/ Mesa-tuned widgets
+
+ Look in those directories for details
+
+
+Togl:
+ Togl is an OpenGL/Mesa widget for Tcl/Tk.
+ See http://togl.sourceforge.net for more information.
+
+
+
+X Display Modes:
+ Mesa supports RGB(A) rendering into almost any X visual type and depth.
+
+ The glXChooseVisual function tries its best to pick an appropriate visual
+ for the given attribute list. However, if this doesn't suit your needs
+ you can force Mesa to use any X visual you want (any supported by your
+ X server that is) by setting the MESA_RGB_VISUAL and MESA_CI_VISUAL
+ environment variables. When an RGB visual is requested, glXChooseVisual
+ will first look if the MESA_RGB_VISUAL variable is defined. If so, it
+ will try to use the specified visual. Similarly, when a color index
+ visual is requested, glXChooseVisual will look for the MESA_CI_VISUAL
+ variable.
+
+ The format of accepted values is: <visual-class> <depth>
+ Here are some examples:
+
+ using the C-shell:
+ % setenv MESA_RGB_VISUAL "TrueColor 8" // 8-bit TrueColor
+ % setenv MESA_CI_VISUAL "PseudoColor 12" // 12-bit PseudoColor
+ % setenv MESA_RGB_VISUAL "PseudoColor 8" // 8-bit PseudoColor
+
+ using the KornShell:
+ $ export MESA_RGB_VISUAL="TrueColor 8"
+ $ export MESA_CI_VISUAL="PseudoColor 12"
+ $ export MESA_RGB_VISUAL="PseudoColor 8"
+
+
+Double buffering:
+ Mesa can use either an X Pixmap or XImage as the backbuffer when in
+ double buffer mode. Using GLX, the default is to use an XImage. The
+ MESA_BACK_BUFFER environment variable can override this. The valid
+ values for MESA_BACK_BUFFER are: Pixmap and XImage (only the first
+ letter is checked, case doesn't matter).
+
+ A pixmap is faster when drawing simple lines and polygons while an
+ XImage is faster when Mesa has to do pixel-by-pixel rendering. If you
+ need depth buffering the XImage will almost surely be faster. Exper-
+ iment with the MESA_BACK_BUFFER variable to see which is faster for
+ your application.
+
+
+Colormaps:
+ When using Mesa directly or with GLX, it's up to the application writer
+ to create a window with an appropriate colormap. The aux, tk, and GLUT
+ toolkits try to minimize colormap "flashing" by sharing colormaps when
+ possible. Specifically, if the visual and depth of the window matches
+ that of the root window, the root window's colormap will be shared by
+ the Mesa window. Otherwise, a new, private colormap will be allocated.
+
+ When sharing the root colormap, Mesa may be unable to allocate the colors
+ it needs, resulting in poor color quality. This can happen when a
+ large number of colorcells in the root colormap are already allocated.
+ To prevent colormap sharing in aux, tk and GLUT, define the environment
+ variable MESA_PRIVATE_CMAP. The value isn't significant.
+
+
+Gamma correction:
+ To compensate for the nonlinear relationship between pixel values
+ and displayed intensities, there is a gamma correction feature in
+ Mesa. Some systems, such as Silicon Graphics, support gamma
+ correction in hardware (man gamma) so you won't need to use Mesa's
+ gamma facility. Other systems, however, may need gamma adjustment
+ to produce images which look correct. If in the past you thought
+ Mesa's images were too dim, read on.
+
+ Gamma correction is controlled with the MESA_GAMMA environment
+ variable. Its value is of the form "Gr Gg Gb" or just "G" where
+ Gr is the red gamma value, Gg is the green gamma value, Gb is the
+ blue gamma value and G is one gamma value to use for all three
+ channels. Each value is a positive real number typically in the
+ range 1.0 to 2.5. The defaults are all 1.0, effectively disabling
+ gamma correction. Examples using csh:
+
+ % setenv MESA_GAMMA "2.3 2.2 2.4" // separate R,G,B values
+ % setenv MESA_GAMMA "2.0" // same gamma for R,G,B
+
+ The demos/gamma.c program may help you to determine reasonable gamma
+ value for your display. With correct gamma values, the color intensities
+ displayed in the top row (drawn by dithering) should nearly match those
+ in the bottom row (drawn as grays).
+
+ Alex De Bruyn reports that gamma values of 1.6, 1.6 and 1.9 work well
+ on HP displays using the HP-ColorRecovery technology.
+
+ Mesa implements gamma correction with a lookup table which translates
+ a "linear" pixel value to a gamma-corrected pixel value. There is a
+ small performance penalty. Gamma correction only works in RGB mode.
+ Also be aware that pixel values read back from the frame buffer will
+ not be "un-corrected" so glReadPixels may not return the same data
+ drawn with glDrawPixels.
+
+ For more information about gamma correction see:
+ http://www.inforamp.net/~poynton/notes/colour_and_gamma/GammaFAQ.html
+
+
+Overlay Planes
+
+ Overlay planes in the frame buffer are supported by Mesa but require
+ hardware and X server support. To determine if your X server has
+ overlay support you can test for the SERVER_OVERLAY_VISUALS property:
+
+ xprop -root | grep SERVER_OVERLAY_VISUALS
+
+
+HPCR glClear(GL_COLOR_BUFFER_BIT) dithering
+
+ If you set the MESA_HPCR_CLEAR environment variable then dithering
+ will be used when clearing the color buffer. This is only applicable
+ to HP systems with the HPCR (Color Recovery) system.
+
+
+Extensions
+==========
+ There are three Mesa-specific GLX extensions at this time.
+
+ GLX_MESA_pixmap_colormap
+
+ This extension adds the GLX function:
+
+ GLXPixmap glXCreateGLXPixmapMESA( Display *dpy, XVisualInfo *visual,
+ Pixmap pixmap, Colormap cmap )
+
+ It is an alternative to the standard glXCreateGLXPixmap() function.
+ Since Mesa supports RGB rendering into any X visual, not just True-
+ Color or DirectColor, Mesa needs colormap information to convert RGB
+ values into pixel values. An X window carries this information but a
+ pixmap does not. This function associates a colormap to a GLX pixmap.
+ See the xdemos/glxpixmap.c file for an example of how to use this
+ extension.
+
+ GLX_MESA_release_buffers
+
+ Mesa associates a set of ancillary (depth, accumulation, stencil and
+ alpha) buffers with each X window it draws into. These ancillary
+ buffers are allocated for each X window the first time the X window
+ is passed to glXMakeCurrent(). Mesa, however, can't detect when an
+ X window has been destroyed in order to free the ancillary buffers.
+
+ The best it can do is to check for recently destroyed windows whenever
+ the client calls the glXCreateContext() or glXDestroyContext()
+ functions. This may not be sufficient in all situations though.
+
+ The GLX_MESA_release_buffers extension allows a client to explicitly
+ deallocate the ancillary buffers by calling glxReleaseBuffersMESA()
+ just before an X window is destroyed. For example:
+
+ #ifdef GLX_MESA_release_buffers
+ glXReleaseBuffersMESA( dpy, window );
+ #endif
+ XDestroyWindow( dpy, window );
+
+ This extension is new in Mesa 2.0.
+
+ GLX_MESA_copy_sub_buffer
+
+ This extension adds the glXCopySubBufferMESA() function. It works
+ like glXSwapBuffers() but only copies a sub-region of the window
+ instead of the whole window.
+
+ This extension is new in Mesa version 2.6
+
+
+
+Summary of X-related environment variables:
+ MESA_RGB_VISUAL - specifies the X visual and depth for RGB mode (X only)
+ MESA_CI_VISUAL - specifies the X visual and depth for CI mode (X only)
+ MESA_BACK_BUFFER - specifies how to implement the back color buffer (X only)
+ MESA_PRIVATE_CMAP - force aux/tk libraries to use private colormaps (X only)
+ MESA_GAMMA - gamma correction coefficients (X only)
+
+
+----------------------------------------------------------------------
+README.CYGWIN - lassauge April 2004 - based on README.X11