tree cecef3a3544f892b0510f7747a6e066fa320f86c
parent 132c94dcf0ab1e7faca491350e61fbdfc17ab206
author Sam Lantinga <slouken@libsdl.org> 1475578228 -0700
committer Sam Lantinga <slouken@libsdl.org> 1475578228 -0700

Fixed bug 3021 - HapticOpenFromJoystick() problems

Joe Thompson

With Direct Input device (MOMO Steering Wheel w/FF)
with SDL 2.0.3,
SDL_HapticOpenFromJoystick() would fail. (Can't set exclusive mode)
Now with 2.0.4 rc1,
SDL_HapticOpenFromJoystick() succeeds but the the returned SDL_Haptic* cannot be used. Calls to SDL_HapticNewEffect() fail with "Haptic error Unable to create effect"

If SDL_HapticOpen() is used instead of HapticOpenFromJoystick(), the device is usable. Calls to HapticNewEffect() succeed with the exact same parameters as the previous failing call.

I have attached a proposed patch for this issue.

When using SDL_HapticOpenFromJoystick(), the original code did not (re)enumerate the axes. This returned a new haptic device with 0 axes. Later, when a new effect is created, SDL_SYS_SetDirection() would set the flags to include DIEFF_SPHERICAL, regardless of what the caller actually set. (see Line 566 in SDL_dinputhaptic.c). This would cause the SDL_HapticNewEffect() to fail (or interpret the coordinates incorreclty.)

The patch moves the call to IDirectInputDevice8_EnumObjects() outside of the if() block so that the axes are (re)enumerated for the new haptic device.

Note: For steering wheels it is common for the joystick to have multiple axes (ie steering, throttle, brake), but the haptic portion of the joystick usually only applies to steering.