Commit 5f9ea7edebf99368d8ccb668abfae4cfeb412cd6
2014-09-17T14:49:36
Haptic: Deal with negative periodic magnitudes (thanks, Elias!). A negative periodic magnitude doesn't exist in Windows' and MacOS' FF APIs The periodic magnitude parameter of the SDL Haptic API is based on the Linux FF API, so it means they are not directly compatible: 'dwMagnitude' is a 'DWORD', which is unsigned. Fixes Bugzilla #2701.
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diff --git a/include/SDL_haptic.h b/include/SDL_haptic.h
index 9c4b427..569c635 100644
--- a/include/SDL_haptic.h
+++ b/include/SDL_haptic.h
@@ -553,7 +553,7 @@ typedef struct SDL_HapticPeriodic
/* Periodic */
Uint16 period; /**< Period of the wave. */
- Sint16 magnitude; /**< Peak value. */
+ Sint16 magnitude; /**< Peak value; if negative, equivalent to 180 degrees extra phase shift. */
Sint16 offset; /**< Mean value of the wave. */
Uint16 phase; /**< Horizontal shift given by hundredth of a degree. */
diff --git a/src/haptic/darwin/SDL_syshaptic.c b/src/haptic/darwin/SDL_syshaptic.c
index dc9416b..6d85bf0 100644
--- a/src/haptic/darwin/SDL_syshaptic.c
+++ b/src/haptic/darwin/SDL_syshaptic.c
@@ -23,6 +23,7 @@
#ifdef SDL_HAPTIC_IOKIT
#include "SDL_assert.h"
+#include "SDL_stdinc.h"
#include "SDL_haptic.h"
#include "../SDL_syshaptic.h"
#include "SDL_joystick.h"
@@ -872,9 +873,10 @@ SDL_SYS_ToFFEFFECT(SDL_Haptic * haptic, FFEFFECT * dest, SDL_HapticEffect * src)
SDL_memset(periodic, 0, sizeof(FFPERIODIC));
/* Specifics */
- periodic->dwMagnitude = CONVERT(hap_periodic->magnitude);
+ periodic->dwMagnitude = CONVERT(SDL_abs(hap_periodic->magnitude));
periodic->lOffset = CONVERT(hap_periodic->offset);
- periodic->dwPhase = hap_periodic->phase;
+ periodic->dwPhase =
+ (hap_periodic->phase + (hap_periodic->magnitude < 0 ? 18000 : 0)) % 36000;
periodic->dwPeriod = hap_periodic->period * 1000;
dest->cbTypeSpecificParams = sizeof(FFPERIODIC);
dest->lpvTypeSpecificParams = periodic;
diff --git a/src/haptic/windows/SDL_dinputhaptic.c b/src/haptic/windows/SDL_dinputhaptic.c
index 35edcb3..9ff46a9 100644
--- a/src/haptic/windows/SDL_dinputhaptic.c
+++ b/src/haptic/windows/SDL_dinputhaptic.c
@@ -21,6 +21,7 @@
#include "../../SDL_internal.h"
#include "SDL_error.h"
+#include "SDL_stdinc.h"
#include "SDL_haptic.h"
#include "SDL_timer.h"
#include "SDL_windowshaptic_c.h"
@@ -714,9 +715,10 @@ SDL_SYS_ToDIEFFECT(SDL_Haptic * haptic, DIEFFECT * dest,
SDL_memset(periodic, 0, sizeof(DIPERIODIC));
/* Specifics */
- periodic->dwMagnitude = CONVERT(hap_periodic->magnitude);
+ periodic->dwMagnitude = CONVERT(SDL_abs(hap_periodic->magnitude));
periodic->lOffset = CONVERT(hap_periodic->offset);
- periodic->dwPhase = hap_periodic->phase;
+ periodic->dwPhase =
+ (hap_periodic->phase + (hap_periodic->magnitude < 0 ? 18000 : 0)) % 36000;
periodic->dwPeriod = hap_periodic->period * 1000;
dest->cbTypeSpecificParams = sizeof(DIPERIODIC);
dest->lpvTypeSpecificParams = periodic;
diff --git a/test/testhaptic.c b/test/testhaptic.c
index 2efd214..ac8ab41 100644
--- a/test/testhaptic.c
+++ b/test/testhaptic.c
@@ -122,7 +122,8 @@ main(int argc, char **argv)
SDL_Log(" effect %d: Sine Wave\n", nefx);
efx[nefx].type = SDL_HAPTIC_SINE;
efx[nefx].periodic.period = 1000;
- efx[nefx].periodic.magnitude = 0x4000;
+ efx[nefx].periodic.magnitude = -0x2000; /* Negative magnitude and ... */
+ efx[nefx].periodic.phase = 18000; /* ... 180 degrees phase shift => cancel eachother */
efx[nefx].periodic.length = 5000;
efx[nefx].periodic.attack_length = 1000;
efx[nefx].periodic.fade_length = 1000;