view docs/man3/SDL_SemWait.3 @ 4223:63fd67e17705 SDL-1.2

Fixed bug #727 Lorenzo Desole 2009-04-19 07:36:10 PDT I am one of the developers of a multimedia application (My Media System MMS), which uses SDL. MMS is normally running in fullscreen mode but it switches it off before launching external applications (mplayer, xine, etc.). The problem with fullscreen is that when the latter is switched off either via SDL_WM_ToggleFullScreen() or SDL_SetVideoMode(), SDL compares the current screen sizes with the ones saved when the video system was initted, and if they don't match, it calls XF86VidModeSwitchToMode() to switch to the old modeline. This makes it impossible for external programs and for MMS itself to use RandR to change the screen size, because next time fullscreen mode is turned off, it bombs out with the following error: X Error of failed request: BadValue (integer parameter out of range for operation) Major opcode of failed request: 136 (XFree86-VidModeExtension) Minor opcode of failed request: 10 (XF86VidModeSwitchToMode) [...] Obviously this happens only if the new screen resolution is smaller than the original one and XF86VidModeSwitchToMode() can't succeed. I couldn't find any way to inform SDL that the screen resolution it uses as reference is no longer valid. This can be fixed by adding "save_mode(this)" to ./src/video/x11/SDL_x11modes.c, API X11_EnterFullScreen(_THIS), like this: int X11_EnterFullScreen(_THIS) { int okay; + save_mode(this); I can't rule out possible side effects, but I don't see any. While I admit this is a minor issue for the general users, it is a major showstopper for our program where the ability to change screen resolution and refresh rate according to the movie being played, is very important. Thanks in advance.
author Sam Lantinga <slouken@libsdl.org>
date Mon, 21 Sep 2009 11:14:36 +0000
parents 4e3b250c950e
children 1238da4a7112
line wrap: on
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.TH "SDL_SemWait" "3" "Tue 11 Sep 2001, 23:00" "SDL" "SDL API Reference" 
.SH "NAME"
SDL_SemWait \- Lock a semaphore and suspend the thread if the semaphore value is zero\&.
.SH "SYNOPSIS"
.PP
\fB#include "SDL\&.h"
#include "SDL_thread\&.h"
.sp
\fBint \fBSDL_SemWait\fP\fR(\fBSDL_sem *sem\fR);
.SH "DESCRIPTION"
.PP
\fBSDL_SemWait()\fP suspends the calling thread until either the semaphore pointed to by \fBsem\fR has a positive value, the call is interrupted by a signal or error\&. If the call is successful it will atomically decrement the semaphore value\&.
.PP
After \fBSDL_SemWait()\fP is successful, the semaphore can be released and its count atomically incremented by a successful call to \fISDL_SemPost\fR\&.
.SH "RETURN VALUE"
.PP
Returns \fB0\fR if successful or \fB-1\fR if there was an error (leaving the semaphore unchanged)\&.
.SH "EXAMPLES"
.PP
.PP
.nf
\f(CWif (SDL_SemWait(my_sem) == -1) {
        return WAIT_FAILED;
}

\&.\&.\&.

SDL_SemPost(my_sem);\fR
.fi
.PP
.SH "SEE ALSO"
.PP
\fI\fBSDL_CreateSemaphore\fP\fR, \fI\fBSDL_DestroySemaphore\fP\fR, \fI\fBSDL_SemTryWait\fP\fR, \fI\fBSDL_SemWaitTimeout\fP\fR, \fI\fBSDL_SemPost\fP\fR, \fI\fBSDL_SemValue\fP\fR
...\" created by instant / docbook-to-man, Tue 11 Sep 2001, 23:00