Xrandr - X Resize, Rotate and Reflection extension.


   #include <X11/extensions/Xrandr.h>

   Bool XRRQueryExtension (Display *dpy,
        int *event_base_return, int *error_base_return);

   Status XRRQueryVersion (Display *dpy,
        int *major_version_return,
        int *minor_version_return);

   XRRScreenConfiguration *XRRGetScreenInfo (Display *dpy,
        Drawable draw);

   void XRRFreeScreenConfigInfo (
        XRRScreenConfiguration *config);

   Status XRRSetScreenConfig (Display *dpy,
        XRRScreenConfiguration *config,
        Drawable draw,
        int size_index,
        Rotation rotation,
        Time timestamp);

   Status XRRSetScreenConfigAndRate (Display *dpy,
                         XRRScreenConfiguration *config,
                         Drawable draw,
                         int size_index,
                         Rotation rotation,
                         short rate,
                         Time timestamp);

   Rotation XRRConfigRotations(
        XRRScreenConfiguration *config,
        Rotation *current_rotation);

   Time XRRConfigTimes (
        XRRScreenConfiguration *config,
        Time *config_timestamp);

   XRRScreenSize *XRRConfigSizes(
        XRRScreenConfiguration *config,
        int *nsizes);

   short *XRRConfigRates (
        XRRScreenConfiguration *config,
        int size_index,
        int *nrates);

   SizeID XRRConfigCurrentConfiguration (
        XRRScreenConfiguration *config,
        Rotation *rotation);

   short XRRConfigCurrentRate (
        XRRScreenConfiguration *config);

   int XRRRootToScreen(
        Display *dpy,
        Window root);

   void XRRSelectInput(Display *dpy, Window window, int mask);

    * intended to take RRScreenChangeNotify,  or
    * ConfigureNotify (on the root window)
    * returns 1 if it is an event type it understands, 0 if not
   int XRRUpdateConfiguration(XEvent *event);

    * the following are always safe to call, even if RandR is
    * not implemented on a screen
   Rotation XRRRotations(
        Display *dpy, int screen,
        Rotation *current_rotation);

   XRRScreenSize *XRRSizes(Display *dpy,
        int screen, int *nsizes);

   short *XRRRates (Display *dpy, int screen,
        int size_index, int *nrates);

   Time XRRTimes (Display *dpy, int screen, Time *config_timestamp);


   display   Specifies the connection to the X server.

   screen    Specifies which screen.

   draw      Specifies the screen.

   rotation  Specifies  the  possible  rotations  or  reflections  of  the

             Specifies the current rotations and reflection of the screen.

   timestamp Specifies the server timestamp.

             Specifies  the   timestamp   when   the   screen   was   last

   config    Specifies the screen configuration being used.

   sizes     Specifies the array of supported sizes.

   rate      Specifies the refresh rate in Hz.



   Can be any of:
   #define RR_Rotate_0             1
   #define RR_Rotate_90            2
   #define RR_Rotate_180           4
   #define RR_Rotate_270           8

   / new in 1.0 protocol, to allow reflection of screen */
   / reflection is applied after rotation */

   #define RR_Reflect_X            16
   #define RR_Reflect_Y            32

   typedef struct {
       int   width, height;
       int   mwidth, mheight;
   } XRRScreenSize;

   typedef struct {
       int type;                 / event base */
       unsigned long serial;     / # of last request processed by server */
       Bool send_event;          / true if this came from a SendEvent request */
       Display *display;         / Display the event was read from */
       Window window;            / window which selected for this event */
       Window root;              / Root window for changed screen */
       Time timestamp;           / when the screen change occurred */
       Time config_timestamp;    / when the last configuration change */
       SizeID size_index;
       SubpixelOrder subpixel_order;
       Rotation rotation;
       int width;
       int height;
       int mwidth;
       int mheight;
   } XRRScreenChangeNotifyEvent;

   The XRRScreenSize structure contains a possible root size in pixels and
   in millimeters.

   A XRRScreenChangeNotifyEvent is sent to a  client  that  has  requested
   notification whenever the screen configuration is changed. A client can
   perform this request by calling XRRSelectInput,  passing  the  display,
   the root window, and the RRScreenChangeNotifyMask mask.

   XRRScreenConfiguration   is   an   opaque   data  type  containing  the
   configuration information for a screen.


   Time stamps are included and must be  used  to  ensure  the  client  is
   playing  with  a full deck: the screen may change properties on the fly
   and this ensures its knowledge of the  configuration  is  up  to  date.
   This  is  to  help  issues when screens may become hot-pluggable in the


   Xrandr is a simple library designed  to  interface  the  X  Resize  and
   Rotate  Extension.  This allows clients to change the size and rotation
   of the root window of a screen, along with the ability to  reflect  the
   screen   about  either  axis  (if  supported  by  the  implementation).
   Rotation and reflection may be implemented by software and  may  result
   in  slower  performance  if  rotation and reflection are implemented in
   this fashion (as are all implementations as of October 2002).

   The Xrandr library does some minimal caching  to  avoid  roundtrips  to
   provide  clients  frequently  used  information.  See "The X Resize and
   Rotate Extension" for a detailed  description;  also  note  that  depth
   switching, as described in the document is not implemented, and may (or
   may not) ever be implemented, as display memory is growing rapidly, and
   toolkits  are  already  beginning  to support migration, mitigating the
   need for depth switching.  If it  is  implemented  in  the  future,  we
   expect  to  do  so  via  an  upward compatible extension to the current
   library/protocol; functionality described here should continue to work.

   Rotation and reflection and how they interact  can  be  confusing.   In
   Randr,   the  coordinate  system  is  rotated  in  a  counter-clockwise
   direction relative to the normal orientation.  Reflection is along  the
   window  system coordinate system, not the physical screen X and Y axis,
   so that rotation and reflection do not  interact.   The  other  way  to
   consider  reflection  is  to  treat  it  as  specified  in the "normal"
   orientation, before rotation.

   The XRRScreenChangeNotify event is sent  to  clients  that  ask  to  be
   informed whenever the root window configuration changes.  Configuration
   changes may include resolution,  physical  size,  subpixel  order  (see
   XRender(3)),  and  rotation.   Note that changes to any or all of these
   could occur due to external events (user control in  the  X  server,  a
   different monitor/flat panel display being hot-plugged) and is not only
   the result of a protocol/library request to the X server.

   Additionally, to eliminate a potential race condition, this  event  may
   be  generated immediately upon selecting for notification if the screen
   has changed since the client of Xrandr connected to the  X  server,  to
   enable  reliable  screen resolution changing when a user may log in and
   change the configuration while one or many clients are starting up.

   Xlib notification

   Clients must call back  into  Xlib  using  XRRUpdateConfiguration  when
   screen configuration change notify events are generated (or root window
   configuration changes occur, to update Xlib's view of  the  resolution,
   size, rotation, reflection or subpixel order.  Generally, toolkits will
   perform this operation on behalf of applications; we did  not  want  to
   change  display  structure  data  behind  the  back  of toolkits, as in
   multithreaded clients, various race conditions might  occur.   Toolkits
   should  provide  clients  some  mechanism  for  notification  of screen
   change, of course.


   There are two classes of interfaces: those which can be  safely  called
   even if RandR is not implemented on a screen (to make common idioms not
   dependent on the server having support), and those  which  will  return
   errors if the extension is not present.

   XRRRotations  returns  both  the  possible set of rotations/reflections
   supported (as a bitmask) as the value of the function, along  with  the
   current rotation/reflection of the screen.

   XRRSizes  returns the size and a pointer to the current sizes supported
   by the specified screen.  The first size specified is the default  size
   of  the  server. If RandR is not supported, it returns 0 for the number
   of sizes.

   XRRRates returns a pointer to the  rates  supported  by  the  specified
   size.  If RandR is not supported, it returns 0 for the number of rates.

   XRRTimes  returns  the  time last reported by the server along with the
   timestamp the last configuration changed.   If  the  configuration  has
   changed  since  the  client  last  updated its view of the server time,
   requests to change the configuration will fail until the client has  an
   up to date timestamp.

   XRRRootToScreen  returns  the  screen  number  given a root window (for
   example, from an XRRScreenChangeNotifyEvent).

   The rest  of  the  functions  will  fail  if  applied  to  screens  not
   implementing  the  RandR extension.  XRRSetScreenConfig sets the screen
   size and rotation and reflection to the desired values  on  the  screen
   specified  by  draw, or returns a BadValue error.  size_index specifies
   which size configuration  is  to  be  used,  rotation  specifies  which
   rotation or reflection is to be used (or a BadValue error is returned).
   The timestamp is used by the server to make sure the client has  up  to
   date  configuration information. Status is returned to indicate success
   or failure; a client must refresh its configuration information  if  it
   fails and try the call again (by calling XRRGetScreenInfo).

   XRRSetScreenConfigAndRate  is like XRRSetScreenConfig but also sets the
   refresh rate. If specified rate is not supported a  BadValue  error  is

   XRRConfigRotations,    XRRConfigSizes,   XRRConfigCurrentConfiguration,
   XRRConfigTimes, XRRConfigRates, and XRRConfigCurrentRate  are  used  to
   get specific configuration information out of a screen configuration.

   XRRGetScreenInfo  returns  a  screen  configuration  for later use; the
   information is private to the library.  Call XRRFreeScreenConfigInfo to
   free this information when you are finished with it.  It forces a round
   trip to the server.

   Other functions include: XRRQueryExtension which returns the event  and
   error  base  codes, XRRQueryVersion , which returns the current version
   of the extension (this information is cached by the library).


   Xrandr will remain upward compatible after the current 1.0 release.


   Jim Gettys, and Keith Packard, HP.


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