[ новости /+++ | форум | теги | ]

NAME
     glXMakeCurrentReadSGI - attach a  GLX  context  to  separate
     write  and  read  drawables  (windows,  GLX  pixmaps, or GLX
     pbuffers)

C SPECIFICATION
     Bool glXMakeCurrentReadSGI( Display *dpy,
                                 GLXDrawable drawable,
                                 GLXDrawable readable,
                                 GLXContext ctx )


PARAMETERS
     dpy       Specifies the connection to the X server.

     drawable  Specifies a GLX drawable.  Must  be  either  an  X
               window ID or a GLX pixmap ID.

     readable  Specifies a GLX readable.  Must  be  either  an  X
               window ID or a GLX pixmap ID.

     ctx       Specifies a GLX rendering context that  is  to  be
               attached to drawable.

DESCRIPTION
     glXMakeCurrentReadSGI  specifies  the  association  of   the
     current   context   with   a   drawable   is  extended  from
     glXMakeCurrent to allow separate write and  read  drawables.
     This  allows  preprocessing  of  image data in an off screen
     window which is then read into the visible window for  final
     display. Similarly it sets the framework for direct transfer
     of video to the GL library, by treating the video as a  spe-
     cial kind of read drawable (a.k.a, readable).

     glXMakeCurrentReadSGI returns True if it succeeds, and False
     if it fails.

NOTES
     If glXMakeCurrentReadSGI is used to associate  two  glXDraw-
     ables  with the current rendering context, glXDrawable draw-
     able is used for all OpenGL operations except:

     1.   Any pixel data that is sourced based on  the  value  of
          GL_READ_BUFFER.  Note, that accumulation operations use
          the value of GL_READ_BUFFER, but are not  allowed  when
          drawable in not identical to readable.

     2.   Any depth values that are  retrieved  by  glReadPixels,
          glCopyPixels,  or  any  OpenGL  extension  that sources
          depth images from the frame buffer  in  the  manner  of
          glReadPixels and glCopyPixels.

     3.   Any stencil values that are retrieved by  glReadPixels,
          glCopyPixels,  or  any  OpenGL  extension  that sources
          stencil images from the frame buffer in the  manner  of
          glReadPixels and glCopyPixels.

     These frame buffer values are taken from  glXDrawable  read-
     able.

     No error will be generated if the value of GL_READ_BUFFER at
     the  time  the  glXMakeCurrentReadSGI  call is made does not
     correspond to a valid color buffer  in  readable.  Also,  no
     error  due  to  GL_READ_BUFFER mismatch will be generated by
     subsequent calls to any of the operations enumerated  above,
     but   the   pixels  values  used  will  be  undefined  until
     GL_READ_BUFFER is set to a color buffer that is valid in the
     readable.  Operations that query the value of GL_READ_BUFFER
     (i.e., glGet, glPushAttrib) use the value set  last  in  the
     context,  independent  of  whether  it  is a valid buffer in
     readable. Subsequent to a  glXMakeCurrentRead  call,  it  is
     possible  that  the  GL_READ_BUFFER  may  be  set to a color
     buffer that is not valid with respect to the visual  of  the
     context.  This also applies to glXMakeCurrent where readable
     is replaced by the single drawable parameter to the call.

     Error conditions  set  by  glDrawBuffer  (even  when  called
     implicitly via glPopAttrib) and by the operations enumerated
     above are with respect to color and ancillary buffers avail-
     able  in  readable (i.e., glReadBuffer (GL_BACK_BUFFER) will
     generate an error when readable is single buffered,  and  so
     will  an  operation that tries to source stencil images when
     readable does not have a stencil buffer).

     Accumulation operations are only allowed when  the  glXDraw-
     bles drawable and readable are identical.

     glXMakeCurrentReadSGI may fail if a window or a GLXPixmap as
     the  readable  GLXDrawable  refuses  to  accept the readable
     GLXDrawable, or a GLXPbuffer with color, depth, stencil,  or
     accumulation  storage  facilities  that differ from those of
     drawable.

     glXMakeCurrentReadSGI may return False if drawable and read-
     able cannot exist in framebuffer memory simultaneously.

     glXMakeCurrentReadSGI       is       part       of       the
     GLX_SGI_make_current_read  extension,  not  part of the core
     GLX command set. If GLX_SGI_make_current_read is included in
     the  string  returned by glXQueryExtensionsString, extension
     GLX_SGI_make_current_read is supported by the connection.

ERRORS
     GLXBadDrawable is generated if drawable was not created with
     the  same  X screen and visual as ctx. glXMakeCurrentReadSGI
     associates two GLXDrawables with a single GLXContext.

     BadMatch is generated if readable was not created  with  the
     same X screen as ctx. The color, depth, stencil, and accumu-
     lation buffers of readable need not match the  resources  of
     drawable.

SEE ALSO
     glXCreateGLXPixmap,    glXMakeCurrent,    glXGetCurrentRead-
     DrawableSGI,   glGet,  glPushAttrib,  glPopAttrib,  glAccum,
     glReadPixels, glCopyPixels

Партнёры:

Хостинг: