Probable bug in WGL implementation (AIGLX) of GLX calls in XWin -wgl

[Tim Edwards <tim@opencircuitdesign.com>]

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Hello Cywgin-X developers:

    I have a tool I maintain called "magic", a VLSI layout editor.  One
of its nicer features is a graphics mode based on OpenGL.  Occasionally
I generate Cygwin versions of it, and was delighted to discover on my
last update of Cygwin that there is a support for hardware-accelerated
OpenGL using some translation between GLX and WGL calls at the level
of the X server.  I tried using this with my Cygwin version of magic,
and for the most part it works.  But it does have the strange effect
of overwriting the OpenGL window with contents of other windows.

    My setup is very non-standard but works under Linux and OS-X.  The
application is built as an extension of Tcl/Tk.  Because the application
makes all the OpenGL calls from C routines, it generates a generic
window using a call to Tk_CreateWindow(), and maps it using Tk_MapWindow().
The returned window is then passed to glXMakeCurrent().  All of this
works fine.

    The window that is used for the OpenGL rendering is framed by
scrollbars on the side and bottom that are "canvas" windows in Tk.
What I am seeing is that any time the scrollbars are redrawn, the
OpenGL window is over-drawn, looks like with the default Tk background
gray color.  A similar thing happens if I pop a window on top of the
OpenGL window;  when I pop it down, the image of the window remains
in the OpenGL window.  I presume that in the way GLX is supposed to
work, X11 has reserved pixmap space somewhere for the window, but
once the call to glXMakeCurrent() has been made, the contents of this
pixmap should not show up on the screen.  Yet that is what I am seeing.
Any clue as to what might be going on?

    One I tarball up this version of magic, I can send a pointer to
where it can be obtained if anybody wants to download it and test
for the bug.

					Thanks,
					Tim

+--------------------------------+-------------------------------------+
| Dr. R. Timothy Edwards (Tim)   | email: tim@opencircuitdesign.com    |
| Open Circuit Design, Inc.      | web:   http://opencircuitdesign.com |
| 22815 Timber Creek Lane        | phone: (301) 528-5030               |
| Clarksburg, MD 20871-4001      | cell:  (240) 401-0616               |
+--------------------------------+-------------------------------------+

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Welcome to the XWin X Server
Vendor: The Cygwin/X Project
Release: 1.12.4.0
OS: CYGWIN_NT-6.1-WOW64 TEDWARDS-L01 1.7.16(0.262/5/3) 2012-07-20 22:55 i686
OS: Windows 7 Service Pack 1 [Windows NT 6.1 build 7601] (WoW64)
Package: version 1.12.4-1 built 2012-08-31

XWin was started with the following command line:

XWin -multiwindow -wgl +bs 

ddxProcessArgument - Initializing default screens
winInitializeScreenDefaults - primary monitor w 1600 h 900
winInitializeScreenDefaults - native DPI x 96 y 96
[436241.757] (II) xorg.conf is not supported
[436241.757] (II) See http://x.cygwin.com/docs/faq/cygwin-x-faq.html for more information
[436241.757] LoadPreferences: /home/TEdwards/.XWinrc not found
[436241.757] LoadPreferences: Loading /etc/X11/system.XWinrc
[436241.757] LoadPreferences: Done parsing the configuration file...
[436241.773] winDetectSupportedEngines - DirectDraw installed, allowing ShadowDD
[436241.773] winDetectSupportedEngines - Windows NT, allowing PrimaryDD
[436241.773] winDetectSupportedEngines - DirectDraw4 installed, allowing ShadowDDNL
[436241.773] winDetectSupportedEngines - Returning, supported engines 0000001f
[436241.773] winSetEngine - Multi Window or Rootless => ShadowGDI
[436241.773] winScreenInit - Using Windows display depth of 32 bits per pixel
[436241.788] winAllocateFBShadowGDI - Creating DIB with width: 1600 height: 900 depth: 32
[436241.788] winFinishScreenInitFB - Masks: 00ff0000 0000ff00 000000ff
[436241.788] winInitVisualsShadowGDI - Masks 00ff0000 0000ff00 000000ff BPRGB 8 d 24 bpp 32
[436241.788] winInitMultiWindowWM - Calling pthread_mutex_lock ()
[436241.788] winMultiWindowXMsgProc - Calling pthread_mutex_lock ()
[436241.788] MIT-SHM extension disabled due to lack of kernel support
[436241.804] XFree86-Bigfont extension local-client optimization disabled due to lack of shared memory support in the kernel
[436241.835] GL_VERSION:     3.0.0 - Build 8.15.10.2321
[436241.835] GL_VENDOR:      Intel
[436241.835] GL_RENDERER:    Intel(R) HD Graphics Family
[436241.835] (II) AIGLX: enabled GLX_SGI_make_current_read
[436241.835] (II) AIGLX: enabled GLX_MESA_copy_sub_buffer
[436241.835] (II) AIGLX: enabled GLX_SGI_swap_control and GLX_MESA_swap_control
[436241.835] (II) AIGLX: enabled GLX_SGIX_pbuffer
[436241.835] (II) AIGLX: enabled GLX_ARB_multisample and GLX_SGIS_multisample
[436241.835] (II) 60 pixel formats reported by wglGetPixelFormatAttribivARB
[436241.835] (II) AIGLX: Set GLX version to 1.4
[436241.835] (II) 39 fbConfigs
[436241.835] (II) GLX: Initialized Win32 native WGL GL provider for screen 0
[436241.835] [dix] Could not init font path element /usr/share/fonts/OTF/, removing from list!
[436241.960] winPointerWarpCursor - Discarding first warp: 800 450
[436241.960] (--) 3 mouse buttons found
[436241.960] (--) Setting autorepeat to delay=500, rate=31
[436241.960] (--) Windows keyboard layout: "00000409" (00000409) "US", type 7
[436241.960] (--) Found matching XKB configuration "English (USA)"
[436241.960] (--) Model = "pc105" Layout = "us" Variant = "none" Options = "none"
[436241.960] Rules = "base" Model = "pc105" Layout = "us" Variant = "none" Options = "none"
[436241.960] winBlockHandler - pthread_mutex_unlock()
[436241.960] winInitMultiWindowWM - pthread_mutex_lock () returned.
[436241.960] winInitMultiWindowWM - pthread_mutex_unlock () returned.
[436241.960] winMultiWindowXMsgProc - pthread_mutex_lock () returned.
[436241.960] winInitMultiWindowWM - DISPLAY=:0.0
[436241.960] winMultiWindowXMsgProc - pthread_mutex_unlock () returned.
[436241.960] winProcEstablishConnection - winInitClipboard returned.
[436241.960] winMultiWindowXMsgProc - DISPLAY=:0.0
[436241.960] winClipboardProc - DISPLAY=:0.0
[436241.960] winInitMultiWindowWM - XOpenDisplay () returned and successfully opened the display.
[436241.960] winMultiWindowXMsgProc - XOpenDisplay () returned and successfully opened the display.
[436241.960] winClipboardProc - XOpenDisplay () returned and successfully opened the display.
[436245.548] winGetWindowInfo: forcing window to exist
[437037.846] winWindowProc - WM_DISPLAYCHANGE - new width: 1600 new height: 900 new bpp: 32
[437037.955] winWindowProc - WM_DISPLAYCHANGE - new width: 1600 new height: 900 new bpp: 32
[437045.817] winGetWindowInfo: forcing window to exist
[443449.674] winGetWindowInfo: forcing window to exist
[443565.879] [mi] Increasing EQ size to 512 to prevent dropped events.


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