view include/SDL_joystick.h @ 4139:568c9b3c0167 SDL-1.2

* 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 c71e05b4dc2e
children 782fd950bd46 c121d94672cb a1b03ba2fcd0
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/*
    SDL - Simple DirectMedia Layer
    Copyright (C) 1997-2006 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    Sam Lantinga
    slouken@libsdl.org
*/

/* Include file for SDL joystick event handling */

#ifndef _SDL_joystick_h
#define _SDL_joystick_h

#include "SDL_stdinc.h"
#include "SDL_error.h"

#include "begin_code.h"
/* Set up for C function definitions, even when using C++ */
#ifdef __cplusplus
extern "C" {
#endif

/* In order to use these functions, SDL_Init() must have been called
   with the SDL_INIT_JOYSTICK flag.  This causes SDL to scan the system
   for joysticks, and load appropriate drivers.
*/

/* The joystick structure used to identify an SDL joystick */
struct _SDL_Joystick;
typedef struct _SDL_Joystick SDL_Joystick;


/* Function prototypes */
/*
 * Count the number of joysticks attached to the system
 */
extern DECLSPEC int SDLCALL SDL_NumJoysticks(void);

/*
 * Get the implementation dependent name of a joystick.
 * This can be called before any joysticks are opened.
 * If no name can be found, this function returns NULL.
 */
extern DECLSPEC const char * SDLCALL SDL_JoystickName(int device_index);

/*
 * Open a joystick for use - the index passed as an argument refers to
 * the N'th joystick on the system.  This index is the value which will
 * identify this joystick in future joystick events.
 *
 * This function returns a joystick identifier, or NULL if an error occurred.
 */
extern DECLSPEC SDL_Joystick * SDLCALL SDL_JoystickOpen(int device_index);

/*
 * Returns 1 if the joystick has been opened, or 0 if it has not.
 */
extern DECLSPEC int SDLCALL SDL_JoystickOpened(int device_index);

/*
 * Get the device index of an opened joystick.
 */
extern DECLSPEC int SDLCALL SDL_JoystickIndex(SDL_Joystick *joystick);

/*
 * Get the number of general axis controls on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumAxes(SDL_Joystick *joystick);

/*
 * Get the number of trackballs on a joystick
 * Joystick trackballs have only relative motion events associated
 * with them and their state cannot be polled.
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumBalls(SDL_Joystick *joystick);

/*
 * Get the number of POV hats on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumHats(SDL_Joystick *joystick);

/*
 * Get the number of buttons on a joystick
 */
extern DECLSPEC int SDLCALL SDL_JoystickNumButtons(SDL_Joystick *joystick);

/*
 * Update the current state of the open joysticks.
 * This is called automatically by the event loop if any joystick
 * events are enabled.
 */
extern DECLSPEC void SDLCALL SDL_JoystickUpdate(void);

/*
 * Enable/disable joystick event polling.
 * If joystick events are disabled, you must call SDL_JoystickUpdate()
 * yourself and check the state of the joystick when you want joystick
 * information.
 * The state can be one of SDL_QUERY, SDL_ENABLE or SDL_IGNORE.
 */
extern DECLSPEC int SDLCALL SDL_JoystickEventState(int state);

/*
 * Get the current state of an axis control on a joystick
 * The state is a value ranging from -32768 to 32767.
 * The axis indices start at index 0.
 */
extern DECLSPEC Sint16 SDLCALL SDL_JoystickGetAxis(SDL_Joystick *joystick, int axis);

/*
 * Get the current state of a POV hat on a joystick
 * The return value is one of the following positions:
 */
#define SDL_HAT_CENTERED	0x00
#define SDL_HAT_UP		0x01
#define SDL_HAT_RIGHT		0x02
#define SDL_HAT_DOWN		0x04
#define SDL_HAT_LEFT		0x08
#define SDL_HAT_RIGHTUP		(SDL_HAT_RIGHT|SDL_HAT_UP)
#define SDL_HAT_RIGHTDOWN	(SDL_HAT_RIGHT|SDL_HAT_DOWN)
#define SDL_HAT_LEFTUP		(SDL_HAT_LEFT|SDL_HAT_UP)
#define SDL_HAT_LEFTDOWN	(SDL_HAT_LEFT|SDL_HAT_DOWN)
/*
 * The hat indices start at index 0.
 */
extern DECLSPEC Uint8 SDLCALL SDL_JoystickGetHat(SDL_Joystick *joystick, int hat);

/*
 * Get the ball axis change since the last poll
 * This returns 0, or -1 if you passed it invalid parameters.
 * The ball indices start at index 0.
 */
extern DECLSPEC int SDLCALL SDL_JoystickGetBall(SDL_Joystick *joystick, int ball, int *dx, int *dy);

/*
 * Get the current state of a button on a joystick
 * The button indices start at index 0.
 */
extern DECLSPEC Uint8 SDLCALL SDL_JoystickGetButton(SDL_Joystick *joystick, int button);

/*
 * Close a joystick previously opened with SDL_JoystickOpen()
 */
extern DECLSPEC void SDLCALL SDL_JoystickClose(SDL_Joystick *joystick);


/* Ends C function definitions when using C++ */
#ifdef __cplusplus
}
#endif
#include "close_code.h"

#endif /* _SDL_joystick_h */