Manual Pages for UNIX Operating System command usage for man XReadScreen

X FUNCTIONS                                    XReadScreen(3xext)



NAME
     XReadScreen - returns the displayed colors in a rectangle of
     the screen

SYNOPSIS
     cc [ flag... ] file... -lXext [ library... ]

     #include 


     XImage
          XReadScreen (Display *display, Window w, int x, int  y,
          unsigned  int width, unsigned int height, Bool include-
          Cursor)

Arguments
     display
          Specifies the connection to the X server.

     w    Specifies the window from  whose  screen  the  data  is
          read.

     x, y Specify the X  and  Y  coordinates  of  the  upper-left
          corner  of  the rectangle relative to the origin of the
          window w.

     width, height
          Specify the width and height of the rectangle.

     includeCursor
          Specifies whether the cursor image is to be included in
          the colors returned.

DESCRIPTION
     This routine provides access to the colors displayed on  the
     screen  of  the  given  window.   On  some types of advanced
     display devices, the displayed colors can be a composite  of
     the  data  contained  in  several different frame stores and
     these frame stores can be  of  different  depth  and  visual
     types.

     In addition, there can be overlay/underlay window  pairs  in
     which  part  of the underlay is visible beneath the overlay.
     Because the data returned by XGetImage is undefined for por-
     tions of the rectangle that have different depths, XGetImage
     is inadequate to return a picture of the what user is  actu-
     ally  seeing  on  the screen.  In addition, XGetImage cannot
     composite pixel information for an  overlay/underlay  window
     pair  because  the pixel information lies in different draw-
     ables.  XReadScreen addresses these problems.





X Version 11       Last change: libXext 1.1.2                   1






X FUNCTIONS                                    XReadScreen(3xext)



     Rather than returning pixel information, XReadScreen returns
     color information-the actual displayed colors visible on the
     screen.  It returns the color information  from  any  window
     within  the  boundaries  of the specified rectangle.  Unlike
     XGetImage, the returned contents of visible regions of infe-
     rior  or  overlapping  windows of a different depth than the
     specified window's depth are not  undefined.   Instead,  the
     actual displayed colors for these windows is returned.

     Note: The  colors  returned  are  the  ones  that  would  be
     displayed if an unlimited number of hardware color LUTs were
     available on the screen.  Thus, the colors returned are  the
     theoretical display colors.  If colormap flashing is present
     on the screen because there  aren't  enough  hardware  color
     LUTs  to  display  all  of the software colormaps simultane-
     ously, the returned colors may be different from the  colors
     that are actually displayed.

     If w is an overlay window, the overlay color information  is
     returned  everywhere  there is opaque paint in the specified
     rectangle.   The  color  information  of  the  underlay   is
     returned  everywhere there is transparent paint in the over-
     lay.  In general, since this underlay can be an overlay win-
     dow  containing transparent paint, the color information for
     a coordinate (x, y) which contains transparent paint is  the
     youngest non-inferior that has opaque paint at (x, y).

     The color data is returned as an XImage. The returned  image
     has  the  same  width and height as the arguments specified.
     The format of the image is ZPixmap. The depth of  the  image
     is  24 and the bits_per_pixel is 32.  The most significant 8
     bits of color information for each color channel (red, green
     blue)  will  be  returned  in  the  bit positions defined by
     red_mask, green_mask,  and  blue_mask  in  the  XImage.  The
     values  of the following attributes of the XImage are server
     dependent:    byte_order,   bitmap_unit,   bitmap_bit_order,
     bitmap_pad, bytes_per_line, red_mask, green_mask, blue_mask.

     If includeCursor is True, the cursor image  is  included  in
     the returned colors.  Otherwise, it is excluded.

     Note that the borders of the argument window (and other win-
     dows) can be included and read with this request.

     If a problem occurs, XReadScreen returns NULL.


ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:





X Version 11       Last change: libXext 1.1.2                   2






X FUNCTIONS                                    XReadScreen(3xext)



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | x11/library/libxext         |
    |_____________________________|_____________________________|
    | Interface Stability         | Committed                   |
    |_____________________________|_____________________________|
    | MT-Level                    | See XInitThreads(3X11)      |
    |_____________________________|_____________________________|














































X Version 11       Last change: libXext 1.1.2                   3