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* 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.
author Sam Lantinga <slouken@libsdl.org>
date Fri, 29 Feb 2008 13:55:44 +0000
parents 355632dca928
children
line wrap: on
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<HTML
><HEAD
><TITLE
>SDL_SetVideoMode</TITLE
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><H1
><A
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></A
>SDL_SetVideoMode</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN1239"
></A
><H2
>Name</H2
>SDL_SetVideoMode&nbsp;--&nbsp;Set up a video mode with the specified width, height and bits-per-pixel.</DIV
><DIV
CLASS="REFSYNOPSISDIV"
><A
NAME="AEN1242"
></A
><H2
>Synopsis</H2
><DIV
CLASS="FUNCSYNOPSIS"
><A
NAME="AEN1243"
></A
><P
></P
><PRE
CLASS="FUNCSYNOPSISINFO"
>#include "SDL.h"</PRE
><P
><CODE
><CODE
CLASS="FUNCDEF"
>SDL_Surface *<B
CLASS="FSFUNC"
>SDL_SetVideoMode</B
></CODE
>(int width, int height, int bpp, Uint32 flags);</CODE
></P
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1249"
></A
><H2
>Description</H2
><P
>Set up a video mode with the specified width, height and bits-per-pixel.</P
><P
>If <TT
CLASS="PARAMETER"
><I
>bpp</I
></TT
> is 0, it is treated as the 
current display bits per pixel.</P
><P
>The <TT
CLASS="PARAMETER"
><I
>flags</I
></TT
> parameter is the same as the <TT
CLASS="STRUCTFIELD"
><I
>flags</I
></TT
> field of the <A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
> structure. OR'd combinations of the following values are valid.</P
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN1259"
></A
><P
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_SWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Create the video surface in system memory</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWSURFACE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Create the video surface in video memory</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_ASYNCBLIT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Enables the use of asynchronous updates of the display surface. This will
usually slow down blitting on single CPU machines, but may provide a speed
increase on SMP systems.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_ANYFORMAT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Normally, if a video surface of the requested bits-per-pixel (<TT
CLASS="PARAMETER"
><I
>bpp</I
></TT
>) is not available, SDL will emulate one with a shadow surface. Passing <TT
CLASS="LITERAL"
>SDL_ANYFORMAT</TT
> prevents this and causes SDL to use the video surface, regardless of its pixel depth.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_HWPALETTE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Give SDL exclusive palette access. Without this flag you may not always get the the colors you request with <A
HREF="sdlsetcolors.html"
><TT
CLASS="FUNCTION"
>SDL_SetColors</TT
></A
> or <A
HREF="sdlsetpalette.html"
><TT
CLASS="FUNCTION"
>SDL_SetPalette</TT
></A
>.</TD
></TR
><TR
><TD
ALIGN="LEFT"
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><TT
CLASS="LITERAL"
>SDL_DOUBLEBUF</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Enable hardware double buffering; only valid with SDL_HWSURFACE. Calling
<A
HREF="sdlflip.html"
><TT
CLASS="FUNCTION"
>SDL_Flip</TT
></A
> will flip the
buffers and update the screen. All drawing will take place on the surface
that is not displayed at the moment. If double buffering could not be enabled
then <TT
CLASS="FUNCTION"
>SDL_Flip</TT
> will just perform a
<A
HREF="sdlupdaterect.html"
><TT
CLASS="FUNCTION"
>SDL_UpdateRect</TT
></A
>
on the entire screen.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_FULLSCREEN</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>SDL will attempt to use a fullscreen mode. If a hardware resolution change is
not possible (for whatever reason), the next higher resolution will be used and
the display window centered on a black background.</TD
></TR
><TR
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ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_OPENGL</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Create an OpenGL rendering context. You should have previously set OpenGL video attributes with <A
HREF="sdlglsetattribute.html"
><TT
CLASS="FUNCTION"
>SDL_GL_SetAttribute</TT
></A
>.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_OPENGLBLIT</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Create an OpenGL rendering context, like above, but allow normal blitting
operations. The screen (2D) surface may have an alpha channel, and
<A
HREF="sdlupdaterects.html"
><TT
CLASS="FUNCTION"
>SDL_UpdateRects</TT
></A
>
must be used for updating changes to the screen surface. NOTE: This option
is kept for compatibility only, and is <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>not</I
></SPAN
> recommended for
new code.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_RESIZABLE</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Create a resizable window. When the window is resized by the user a <A
HREF="sdlresizeevent.html"
><TT
CLASS="LITERAL"
>SDL_VIDEORESIZE</TT
></A
> event is generated and <TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
> can be called again with the new size.</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="LITERAL"
>SDL_NOFRAME</TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>If possible, <TT
CLASS="LITERAL"
>SDL_NOFRAME</TT
> causes SDL to create a window with no title bar or frame decoration. Fullscreen modes automatically have this flag set.</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>Whatever <TT
CLASS="PARAMETER"
><I
>flags</I
></TT
> <TT
CLASS="FUNCTION"
>SDL_SetVideoMode</TT
> could satisfy are set in the <TT
CLASS="STRUCTFIELD"
><I
>flags</I
></TT
> member of the returned surface.</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>The <TT
CLASS="PARAMETER"
><I
>bpp</I
></TT
> parameter is the number of bits per pixel,
so a <TT
CLASS="PARAMETER"
><I
>bpp</I
></TT
> of 24 uses the packed representation of
3 bytes/pixel. For the more common 4 bytes/pixel mode, use a
<TT
CLASS="PARAMETER"
><I
>bpp</I
></TT
> of 32. Somewhat oddly, both 15 and 16 will
request a 2 bytes/pixel mode, but different pixel formats.</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1336"
></A
><H2
>Return Value</H2
><P
>The framebuffer surface, or <SPAN
CLASS="RETURNVALUE"
>NULL</SPAN
> if it fails.
The surface returned is freed by SDL_Quit() and should nt be freed by
the caller.</P
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN1340"
></A
><H2
>See Also</H2
><P
><A
HREF="sdllocksurface.html"
><TT
CLASS="FUNCTION"
>SDL_LockSurface</TT
></A
>,
<A
HREF="sdlsetcolors.html"
><TT
CLASS="FUNCTION"
>SDL_SetColors</TT
></A
>,
<A
HREF="sdlflip.html"
><TT
CLASS="FUNCTION"
>SDL_Flip</TT
></A
>,
<A
HREF="sdlsurface.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_Surface</SPAN
></A
></P
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