[host] don't allocate LGMP_Q_POINTER_LEN cursor shape buffers

There is no need to allocate a buffer for each message as the client is
only required to show the latest version of the cursor. Whie the logic
should prevent cursor corruption, it's not guaranteed, however this is
not a problem as this can only happen if the client is lagging behind
and as such when it gets another update message it will re-read the
now new shape anyway.

host/src/app.c

@@ -40,6 +40,7 @@ Place, Suite 330, Boston, MA 02111-1307 USA
 #include <string.h>
 
 #define CONFIG_FILE "looking-glass-host.ini"
+#define POINTER_SHAPE_BUFFERS 3
 
 #define ALIGN_DN(x) ((uintptr_t)(x) & ~0x7F)
 #define ALIGN_UP(x) ALIGN_DN(x + 0x7F)
@@ -73,7 +74,7 @@ struct app
   PLGMPHost     lgmp;
 
   PLGMPHostQueue pointerQueue;
-  PLGMPMemory    pointerMemory[LGMP_Q_POINTER_LEN];
+  PLGMPMemory    pointerMemory[POINTER_SHAPE_BUFFERS];
   LG_Lock        pointerLock;
   CapturePointer pointerInfo;
   PLGMPMemory    pointerShape;
@@ -285,14 +286,6 @@ static bool captureRestart()
 
 bool captureGetPointerBuffer(void ** data, uint32_t * size)
 {
-  // spin until there is room
-  while(lgmpHostQueuePending(app.pointerQueue) == LGMP_Q_POINTER_LEN)
-  {
-    usleep(1);
-    if (app.state == APP_STATE_RUNNING)
-      return false;
-  }
-
   PLGMPMemory mem = app.pointerMemory[app.pointerIndex];
   *data = ((uint8_t*)lgmpHostMemPtr(mem)) + sizeof(KVMFRCursor);
   *size = MAX_POINTER_SIZE - sizeof(KVMFRCursor);
@@ -318,7 +311,7 @@ static void sendPointer(bool newClient)
   else
     mem = app.pointerMemory[app.pointerIndex];
 
-  if (++app.pointerIndex == LGMP_Q_POINTER_LEN)
+  if (++app.pointerIndex == POINTER_SHAPE_BUFFERS)
     app.pointerIndex = 0;
 
   uint32_t flags = 0;
@@ -489,7 +482,7 @@ int app_main(int argc, char * argv[])
     goto fail;
   }
 
-  for(int i = 0; i < LGMP_Q_POINTER_LEN; ++i)
+  for(int i = 0; i < POINTER_SHAPE_BUFFERS; ++i)
   {
     if ((status = lgmpHostMemAlloc(app.lgmp, MAX_POINTER_SIZE, &app.pointerMemory[i])) != LGMP_OK)
     {