* Added configure option --enable-screensaver, to allow enabling the screensaver by default. * Use XResetScreenSaver() instead of disabling screensaver entirely. Full discussion summary from Erik on the SDL mailing list: Current behaviour ================= SDL changes the user's display power management settings without permission from the user and without telling the user. The interface that it uses to do so is DPMSDisable/DPMSEnable, which should only ever be used by configuration utilities like KControl, never by normal application programs, let alone by the libraries that they use. Using an interface that is not at all intended for what SDL tries to achieve means that it will not work as it should. Firstly, the power management is completely disabled during the whole lifetime of the SDL program, not only when it should be. Secondly, it makes SDL non-reentrant, meaning that things will break when multiple SDL programs are clients of the same X server simultaneously. Thirdly, no cleanup mechanism ensures that the setting is restored if the client does not do that (for example if it crashes). In addition to that, this interface is broken on xorg, [http://bugs.freedesktop.org/show_bug.cgi?id=13962], so what SDL tries to do does not work at all on that implementation of the X Window System. (The reason that the DPMSEnable works in KControl is that it calls DPMSSetTimeout immediately after, [http://websvn.kde.org/tags/KDE/3.5.9/kdebase/kcontrol/energy/energy.cpp?annotate=774532#l343]). The problems that the current behaviour causes ============================================== 1. Information leak. When the user is away, someone might see what the user has on the display when the user counts on the screensaver preventing this. This does not even require physical access to the workstation, it is enough to see it from a distance. 2. Draining battery. An SDL program that runs on a laptop will quickly drain the battery while the user is away. The system will soon shut down and require recharging before being usable again, while it should in fact have consumed very little energy if the user's settings would have been obeyed. 3. Wasting energy. Even if battery issues are not considered, energy as such is wasted. 4. Display wear. The display may be worn out. The problems that the current behaviour tries to solve ====================================================== 1. Preventing screensaver while playing movies. Many SDL applications are media players. They have reasons to prevent screensavers from being activated while a movie is being played. When a user clicks on the play button it can be interpreted as saying "play this movie, but do not turn off the display while playing it, because I will watch it even though I do not interact with the system". 2. Preventing screensaver when some input bypasses X. Sometimes SDL uses input from another source than the X server, so that the X server is bypassed. This obviously breaks the screensaver handling. SDL tries to work around that. 3. Preventing screensaver when all input bypasses X. There is something called Direct Graphics Access mode, where a program takes control of both the display and the input devices from the X server. This obviously means that the X server can not handle the screensaver alone, since screensaver handling depends on input handling. SDL does not do what it should to help the X server to handle the screensaver. Nor does SDL take care of screeensaver handling itself. SDL simply disables the screensaver completely. How the problems should be solved ================================= The correct way for an application program to prevent the screensaver under X is to call XResetScreenSaver. This was recently discovered and implemented by the mplayer developers, [http://svn.mplayerhq.hu/mplayer?view=rev&revision=25637]. SDL needs to wrap this in an API call (SDL_ResetScreenSaver) and implement it for the other video targets (if they do not have a corresponding call, SDL should do what it takes on that particular target, for example sending fake key events). 1. When a movie is played, the player should reset the screensaver when the animation is advanced to a new frame. The same applies to anything similar, like slideshows. 2. When the X server is handling input, it must handle all input (keyboards, mice, gamepads, ...). This is necessary, not only to be able to handle the screensaver, but also so that it can send the events to the correct (the currently active) client. If there is an input device that the X server can not handle for some reason (such as lack of Plug and Play capability), the program that handles the device as a workaround must simulate what would happen if the X server would have handled the device, by calling XResetScreenSaver when input is received from the device. 3. When the X server is not handling the input, it depends on the program that does to call XResetScreenSaver whenever an input event occurs. Alternatively the program must handle the screensaver countdown internally and call XActivateScreenSaver.

/*
   Header definitions for the MMX routines for the HERMES library
   Copyright (c) 1998 Christian Nentwich (c.nentwich@cs.ucl.ac.uk)
   This source code is licensed under the GNU LGPL
  
   Please refer to the file COPYING.LIB contained in the distribution for
   licensing conditions
*/
#include "SDL_config.h"

#ifndef __HERMES_HEAD_MMX__
#define __HERMES_HEAD_MMX__


/* If you cannot stand ifdefs, then please do not look into this file, it's
   going to end your life :) */

#ifdef X86_ASSEMBLER


#ifdef __cplusplus
extern "C" {
#endif

void STACKCALL ConvertMMX(HermesConverterInterface *);

void STACKCALL ClearMMX_32(HermesClearInterface *);
void STACKCALL ClearMMX_24(HermesClearInterface *);
void STACKCALL ClearMMX_16(HermesClearInterface *);
void STACKCALL ClearMMX_8(HermesClearInterface *);

void ConvertMMXpII32_24RGB888();
void ConvertMMXpII32_16RGB565();
void ConvertMMXpII32_16BGR565();
void ConvertMMXpII32_16RGB555();
void ConvertMMXpII32_16BGR565();
void ConvertMMXpII32_16BGR555();

void ConvertMMXp32_16RGB555();

#ifdef __cplusplus
}
#endif



/* Fix the underscore business with ELF compilers */

#if defined(__ELF__) && defined(__GNUC__)
  #ifdef __cplusplus 
  extern "C" {   
  #endif

  extern void _ConvertMMX(HermesConverterInterface *);
  extern void _ConvertMMXpII32_24RGB888();
  extern void _ConvertMMXpII32_16RGB565();
  extern void _ConvertMMXpII32_16BGR565();
  extern void _ConvertMMXpII32_16RGB555();
  extern void _ConvertMMXpII32_16BGR555();

  #define ConvertMMX _ConvertMMX
  #define ConvertMMXpII32_24RGB888 _ConvertMMXpII32_24RGB888
  #define ConvertMMXpII32_16RGB565 _ConvertMMXpII32_16RGB565
  #define ConvertMMXpII32_16BGR565 _ConvertMMXpII32_16BGR565
  #define ConvertMMXpII32_16RGB555 _ConvertMMXpII32_16RGB555
  #define ConvertMMXpII32_16BGR555 _ConvertMMXpII32_16BGR555

  #ifdef __cplusplus
  }
  #endif

#endif /* ELF and GNUC */




/* Make it work with Watcom */
#ifdef __WATCOMC__
#pragma warning 601 9

#pragma aux ConvertMMX "_*" modify [EAX EBX ECX EDX ESI EDI]

#pragma aux ClearMMX_32 "_*" modify [EAX EBX ECX EDX ESI EDI]
#pragma aux ClearMMX_24 "_*" modify [EAX EBX ECX EDX ESI EDI]
#pragma aux ClearMMX_16 "_*" modify [EAX EBX ECX EDX ESI EDI]
#pragma aux ClearMMX_8 "_*" modify [EAX EBX ECX EDX ESI EDI]

#pragma aux ConvertMMXpII32_24RGB888 "_*"
#pragma aux ConvertMMXpII32_16RGB565 "_*"
#pragma aux ConvertMMXpII32_16BGR565 "_*"
#pragma aux ConvertMMXpII32_16RGB555 "_*"
#pragma aux ConvertMMXpII32_16BGR555 "_*"
#pragma aux ConvertMMXp32_16RGB555 "_*"

#endif /* WATCOM */

#endif /* X86_ASSEMBLER */


#endif