David Ludwig
I have created a new driver for SDL's Joystick and Game-Controller subsystem: a Virtual driver. This driver allows one to create a software-based joystick, which to SDL applications will look and react like a real joystick, but whose state can be set programmatically. A primary use case for this is to help enable developers to add touch-screen joysticks to their apps.
The driver comes with a set of new, public APIs, with functions to attach and detach joysticks, set virtual-joystick state, and to determine if a joystick is a virtual-one.
Use of virtual joysticks goes as such:
1. Attach one or more virtual joysticks by calling SDL_JoystickAttachVirtual. If successful, this returns the virtual-device's joystick-index.
2. Open the virtual joysticks (using indicies returned by SDL_JoystickAttachVirtual).
3. Call any of the SDL_JoystickSetVirtual* functions when joystick-state changes. Please note that virtual-joystick state will only get applied on the next call to SDL_JoystickUpdate, or when pumping or polling for SDL events (via SDL_PumpEvents or SDL_PollEvent).
Here is a listing of the new, public APIs, at present and subject to change:
------------------------------------------------------------
/**
* Attaches a new virtual joystick.
* Returns the joystick's device index, or -1 if an error occurred.
*/
extern DECLSPEC int SDLCALL SDL_JoystickAttachVirtual(SDL_JoystickType type, int naxes, int nballs, int nbuttons, int nhats);
/**
* Detaches a virtual joystick
* Returns 0 on success, or -1 if an error occurred.
*/
extern DECLSPEC int SDLCALL SDL_JoystickDetachVirtual(int device_index);
/**
* Indicates whether or not a virtual-joystick is at a given device index.
*/
extern DECLSPEC SDL_bool SDLCALL SDL_JoystickIsVirtual(int device_index);
/**
* Set values on an opened, virtual-joystick's controls.
* Returns 0 on success, -1 on error.
*/
extern DECLSPEC int SDLCALL SDL_JoystickSetVirtualAxis(SDL_Joystick * joystick, int axis, Sint16 value);
extern DECLSPEC int SDLCALL SDL_JoystickSetVirtualBall(SDL_Joystick * joystick, int ball, Sint16 xrel, Sint16 yrel);
extern DECLSPEC int SDLCALL SDL_JoystickSetVirtualButton(SDL_Joystick * joystick, int button, Uint8 value);
extern DECLSPEC int SDLCALL SDL_JoystickSetVirtualHat(SDL_Joystick * joystick, int hat, Uint8 value);
------------------------------------------------------------
Miscellaneous notes on the initial patch, which are also subject to change:
1. no test code is present in SDL, yet. This should, perhaps, change. Initial development was done with an ImGui-based app, which potentially is too thick for use in SDL-official. If tests are to be added, what kind of tests? Automated? Graphical?
2. virtual game controllers can be created by calling SDL_JoystickAttachVirtual with a joystick-type of SDL_JOYSTICK_TYPE_GAME_CONTROLLER, with naxes (num axes) set to SDL_CONTROLLER_AXIS_MAX, and with nbuttons (num buttons) set to SDL_CONTROLLER_BUTTON_MAX. When updating their state, values of type SDL_GameControllerAxis or SDL_GameControllerButton can be casted to an int and used for the control-index (in calls to SDL_JoystickSetVirtual* functions).
3. virtual joysticks' guids are mostly all-zeros with the exception of the last two bytes, the first of which is a 'v', to indicate that the guid is a virtual one, and the second of which is a SDL_JoystickType that has been converted into a Uint8.
4. virtual joysticks are ONLY turned into virtual game-controllers if and when their joystick-type is set to SDL_JOYSTICK_TYPE_GAMECONTROLLER. This is controlled by having SDL's default list of game-controllers have a single entry for a virtual game controller (of guid, "00000000000000000000000000007601", which is subject to the guid-encoding described above).
5. regarding having to call SDL_JoystickUpdate, either directly or indirectly via SDL_PumpEvents or SDL_PollEvents, before new virtual-joystick state becomes active (as specified via SDL_JoystickSetVirtual* function-calls), this was done to match behavior found in SDL's other joystick drivers, almost all of which will only update SDL-state during SDL_JoystickUpdate.
6. the initial patch is based off of SDL 2.0.12
7. the virtual joystick subsystem is disabled by default. It should be possible to enable it by building with SDL_JOYSTICK_VIRTUAL=1
Questions, comments, suggestions, or bug reports very welcome!
Prior to this fix, we would hit the existing_instance >= 0 case and move the joystick
again to a different index than the one requested by the caller. It also breaks the assumption
that a SDL_JoystickID is only present in SDL_joystick_players at one location.
Jake Breen
When I run SDL_INIT with SDL_INIT_JOYSTICK it stalls for about 10 seconds (last report was 10,615ms), but only if I'm currently playing audio. (Like in Spotify for example.)
querying something related to device access (last dll loaded)
'BabbysFirst64.exe' (Win32): Loaded 'C:\Windows\SysWOW64\deviceaccess.dll'.
I use a USB DAC because my mobo's audio out is pretty not great. And I've noticed unplugging it seems to solve the issue. I haven't noticed any other issues that are caused by my DAC.
My DAC is the Sound BlasterX G1 https://us.creative.com/p/gaming-headsets/sound-blasterx-g1
Vid = 041E
PID = 3249
My system specs:
- Windows 10 Pro
- Ryzen 2700x
- 16GB Ram
- Nvidia 2070 RTX
Additional USB devices plugged in:
- Valve Index
- Xbox One Elite Controller
LinGao
We build SDL with Visual studio 2017 compiler on Windows Server 2016, but it failed to build due to error LNK2019: unresolved external symbol memset referenced in function SDL_SetJoystickIDForPlayerIndex with MSVC x64 on Windows on latest default branch. And we found that it can be first reproduced on 0fff06175109 changeset. Could you please help have a look about this issue? Thanks in advance!
Steps to Reproduce:
1.hg clone https://hg.libsdl.org/SDL D:\SDL\src
2.Open a VS 2017 x64 command prompt as admin and browse to D:\SDL
3.msbuild /p:Configuration=Release /p:Platform=x64 /p:WindowsTargetPlatformVersion=10.0.17134.0 VisualC\SDL.sln /t:Rebuild
Actual result:
Creating library D:\SDL\src\VisualC\x64\Release\SDL2.lib and object D:\SDL\src\VisualC\x64\Release\SDL2.exp
SDL_joystick.obj : error LNK2019: unresolved external symbol memset referenced in function SDL_SetJoystickIDForPlayerIndex [D:\SDL\src\VisualC\SDL\SDL.vcxproj]
D:\SDL\src\VisualC\x64\Release\SDL2.dll : fatal error LNK1120: 1 unresolved externals [D:\SDL\src\VisualC\SDL\SDL.vcxproj]
Done Building Project "D:\SDL\src\VisualC\SDL\SDL.vcxproj" (Rebuild target(s)) -- FAILED.
Added the functions SDL_JoystickFromPlayerIndex(), SDL_JoystickSetPlayerIndex(), SDL_GameControllerFromPlayerIndex(), and SDL_GameControllerSetPlayerIndex()
It causes the HIDAPI devices to always be opened on enumeration, which causes crashes in the Windows drivers when multiple applications are reading and writing at the same time. We can revisit this after 2.0.10 release.
Note that a single USB device is responsible for all 4 joysticks, so a large
rewrite of the DeviceDriver functions was necessary to allow a single device to
produce multiple joysticks.
Daniel Gibson
Even though my game (dhewm3) doesn't use SDL_INIT_JOYSTICK, SDL_PumpEvent() calls SDL_JoystickUpdate() which ends up calling hid_enumerate() every three seconds, and sometimes on my Win7 box hid_enumerate() takes about 5 seconds, which causes the whole game to freeze for that time.
The code is now reliant on SDL_PrivateJoystickAdded() and SDL_PrivateJoystickRemoved() being called correctly when devices are added or removed on Windows
