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.

src/haptic/windows/SDL_dinputhaptic.c

@@ -331,14 +331,6 @@ SDL_DINPUT_HapticOpenFromDevice(SDL_Haptic * haptic, LPDIRECTINPUTDEVICE8 device
             goto acquire_err;
         }
 
-        /* Get number of axes. */
-        ret = IDirectInputDevice8_EnumObjects(haptic->hwdata->device,
-                                              DI_DeviceObjectCallback,
-                                              haptic, DIDFT_AXIS);
-        if (FAILED(ret)) {
-            DI_SetError("Getting device axes", ret);
-            goto acquire_err;
-        }
 
         /* Acquire the device. */
         ret = IDirectInputDevice8_Acquire(haptic->hwdata->device);
@@ -348,6 +340,15 @@ SDL_DINPUT_HapticOpenFromDevice(SDL_Haptic * haptic, LPDIRECTINPUTDEVICE8 device
         }
     }
 
+    /* Get number of axes. */
+    ret = IDirectInputDevice8_EnumObjects(haptic->hwdata->device,
+                                          DI_DeviceObjectCallback,
+                                          haptic, DIDFT_AXIS);
+    if (FAILED(ret)) {
+        DI_SetError("Getting device axes", ret);
+        goto acquire_err;
+    }
+
     /* Reset all actuators - just in case. */
     ret = IDirectInputDevice8_SendForceFeedbackCommand(haptic->hwdata->device,
                                                        DISFFC_RESET);