dix: add motion history support

Add motion history support (sort of based on the XFree86 DDX's
implementation) to the DIX.

dix/devices.c

@@ -793,7 +793,12 @@ InitValuatorClassDeviceStruct(DeviceIntPtr dev, int numAxes,
 				    numAxes * sizeof(unsigned int));
     if (!valc)
 	return FALSE;
+
+    valc->motion = NULL;
+    valc->first_motion = 0;
+    valc->last_motion = 0;
     valc->GetMotionProc = motionProc;
+
     valc->numMotionEvents = numMotionEvents;
     valc->motionHintWindow = NullWindow;
     valc->numAxes = numAxes;
@@ -805,6 +810,11 @@ InitValuatorClassDeviceStruct(DeviceIntPtr dev, int numAxes,
     valc->dxremaind = 0;
     valc->dyremaind = 0;
     dev->valuator = valc;
+
+    /* biggest hack ever. */
+    if (motionProc == GetMotionHistory)
+        AllocateMotionHistory(dev);
+
     for (i=0; i<numAxes; i++) {
         InitValuatorAxisStruct(dev, i, 0, -1, 0, 0, 0);
 	valc->axisVal[i]=0;

dix/getevents.c

@@ -66,6 +66,9 @@ extern Bool XkbCopyKeymap(XkbDescPtr src, XkbDescPtr dst, Bool sendNotifies);
 /* Maximum number of valuators, divided by six, rounded up. */
 #define MAX_VALUATOR_EVENTS 6
 
+/* Number of motion history events to store. */
+#define MOTION_HISTORY_SIZE 256
+
 /**
  * Returns the maximum number of events GetKeyboardEvents,
  * GetKeyboardValuatorEvents, and GetPointerEvents will ever return.
@@ -367,6 +370,108 @@ getValuatorEvents(xEvent *events, DeviceIntPtr pDev, int first_valuator,
     return events;
 }
 
+/**
+ * Pick some arbitrary size for Xi motion history.
+ */
+_X_EXPORT int
+GetMotionHistorySize()
+{
+    return MOTION_HISTORY_SIZE;
+}
+
+/**
+ * Allocate the motion history buffer.
+ */
+_X_EXPORT void
+AllocateMotionHistory(DeviceIntPtr pDev)
+{
+    if (pDev->valuator->motion)
+        xfree(pDev->valuator->motion);
+
+    if (pDev->valuator->numMotionEvents < 1)
+        return;
+
+    pDev->valuator->motion = xalloc(((sizeof(INT32) * pDev->valuator->numAxes) +
+                                     sizeof(Time)) *
+                                    pDev->valuator->numMotionEvents);
+    pDev->valuator->first_motion = 0;
+    pDev->valuator->last_motion = 0;
+}
+
+/**
+ * Dump the motion history between start and stop into the supplied buffer.
+ * Only records the event for a given screen in theory, but in practice, we
+ * sort of ignore this.
+ */
+_X_EXPORT int
+GetMotionHistory(DeviceIntPtr pDev, xTimecoord *buff, unsigned long start,
+                 unsigned long stop, ScreenPtr pScreen)
+{
+    int i = 0, ret = 0;
+    /* The size of a single motion event. */
+    int size = (sizeof(INT32) * pDev->valuator->numAxes) + sizeof(Time);
+    Time current;
+    char *ibuff = NULL, *obuff = (char *) buff;
+
+    if (!pDev->valuator || !pDev->valuator->numMotionEvents)
+        return 0;
+
+    for (i = pDev->valuator->first_motion;
+         i != pDev->valuator->last_motion;
+         i = (i + 1) % pDev->valuator->numMotionEvents) {
+        /* We index the input buffer by which element we're accessing, which
+         * is not monotonic, and the output buffer by how many events we've
+         * written so far. */
+        ibuff = (char *) pDev->valuator->motion + (i * size);
+        memcpy(&current, ibuff, sizeof(Time));
+
+        if (current > stop) {
+            return ret;
+        }
+        else if (current >= start) {
+            memcpy(obuff, ibuff, size);
+            obuff += size;
+            ret++;
+        }
+    }
+
+    return ret;
+}
+
+/**
+ * Update the motion history for a specific device, with the list of
+ * valuators.
+ */
+static void
+updateMotionHistory(DeviceIntPtr pDev, CARD32 ms, int first_valuator,
+                    int num_valuators, int *valuators)
+{
+    char *buff = (char *) pDev->valuator->motion;
+
+    if (!pDev->valuator->numMotionEvents)
+        return;
+
+    buff += ((sizeof(INT32) * pDev->valuator->numAxes) + sizeof(CARD32)) *
+            pDev->valuator->last_motion;
+    memcpy(buff, &ms, sizeof(Time));
+
+    buff += sizeof(Time);
+    bzero(buff, sizeof(INT32) * pDev->valuator->numAxes);
+
+    buff += sizeof(INT32) * first_valuator;
+    memcpy(buff, valuators, sizeof(INT32) * num_valuators);
+
+    pDev->valuator->last_motion = (pDev->valuator->last_motion + 1) %
+                                  pDev->valuator->numMotionEvents;
+    
+    /* If we're wrapping around, just keep the circular buffer going. */
+    if (pDev->valuator->first_motion == pDev->valuator->last_motion)
+        pDev->valuator->first_motion = (pDev->valuator->first_motion + 1) %
+                                       pDev->valuator->numMotionEvents;
+
+    return;
+}
+
 /**
  * Generate a series of xEvents (returned in xE) representing pointer
  * motion, or button presses.  Xi and XKB-aware.

include/input.h

@@ -418,6 +418,19 @@ extern int GetProximityEvents(
     int num_valuators,
     int *valuators);
 
+extern int GetMotionHistorySize(
+    void);
+
+extern void AllocateMotionHistory(
+    DeviceIntPtr pDev);
+
+extern int GetMotionHistory(
+    DeviceIntPtr pDev,
+    xTimecoord *buff,
+    unsigned long start,
+    unsigned long stop,
+    ScreenPtr pScreen);
+
 extern void SwitchCoreKeyboard(DeviceIntPtr pDev);
 extern void SwitchCorePointer(DeviceIntPtr pDev);
 

include/inputstr.h

@@ -146,15 +146,20 @@ typedef struct _AxisInfo {
 
 typedef struct _ValuatorClassRec {
     ValuatorMotionProcPtr GetMotionProc;
-    int		 	numMotionEvents;
-    WindowPtr    	motionHintWindow;
-    AxisInfoPtr 	axes;
-    unsigned short	numAxes;
-    int			*axisVal;
-    CARD8	 	mode;
-    int                 lastx, lasty; /* last event recorded, not posted to
-                                       * client; see dix/devices.c */
-    int                 dxremaind, dyremaind; /* for acceleration */
+    int		 	  numMotionEvents;
+    int                   first_motion;
+    int                   last_motion;
+    void                  *motion;
+
+    WindowPtr    	  motionHintWindow;
+
+    AxisInfoPtr 	  axes;
+    unsigned short	  numAxes;
+    int			  *axisVal;
+    int                   lastx, lasty; /* last event recorded, not posted to
+                                         * client; see dix/devices.c */
+    int                   dxremaind, dyremaind; /* for acceleration */
+    CARD8	 	  mode;
 } ValuatorClassRec, *ValuatorClassPtr;
 
 typedef struct _ButtonClassRec {