(shmif) mousestate helper improvements

Previously the caller was always responsible for maintaining the
storage for the state blob which was a poor decision. As to not break
API we overload and accept a NULL mstate holder to mean 'use the
internal shmif tracking structure'.

src/shmif/arcan_shmif_control.c

@@ -56,6 +56,19 @@ enum debug_level {
 	DETAILED = 2
 };
 
+struct mstate {
+	union {
+		struct {
+			int32_t ax, ay, lx, ly;
+			uint8_t rel : 1;
+			uint8_t inrel : 1;
+		};
+		uint8_t state[ASHMIF_MSTATE_SZ];
+	};
+};
+
+_Static_assert(sizeof(struct mstate) == ASHMIF_MSTATE_SZ, "invalid mstate sz");
+
 /*
  * Accessor for redirectable log output related to a shmif context
  * The context association is a placeholder for being able to handle
@@ -242,6 +255,8 @@ struct shmif_hidden {
 		char key[256];
 	} pseg;
 
+	struct mstate mstate;
+
 /* The 'guard' structure is used by a separate monitoring thread that will
  * track a pid or descriptor for aliveness. If the tracking fails, it will
  * unlock semaphores and trigger an at_exit- like handler. This is practically
@@ -3197,23 +3212,16 @@ int arcan_shmif_segkind(struct arcan_shmif_cont* con)
 	return (!con || !con->priv) ? SEGID_UNKNOWN : con->priv->type;
 }
 
-struct mstate {
-	union {
-		struct {
-			int32_t ax, ay, lx, ly;
-			uint8_t rel : 1;
-			uint8_t inrel : 1;
-		};
-		uint8_t state[ASHMIF_MSTATE_SZ];
-	};
-};
-
-_Static_assert(sizeof(struct mstate) == ASHMIF_MSTATE_SZ, "invalid mstate sz");
-
 void arcan_shmif_mousestate_setup(
 	struct arcan_shmif_cont* con, bool relative, uint8_t* state)
 {
+	if (!con || !con->priv)
+		return;
+
 	struct mstate* ms = (struct mstate*) state;
+	if (!ms)
+		ms = &con->priv->mstate;
+
 	*ms = (struct mstate){
 		.rel = relative
 	};
@@ -3259,8 +3267,13 @@ bool arcan_shmif_mousestate_ioev(
 	struct arcan_ioevent* inev, int* out_x, int* out_y)
 {
 	struct mstate* ms = (struct mstate*) state;
+	if (!con || !con->priv)
+		return false;
+
+	if (!state)
+		ms = &con->priv->mstate;
 
-	if (!state || !out_x || !out_y || !con)
+	if (!ms|| !out_x || !out_y)
 		return false;
 
 	if (!inev){
@@ -3271,7 +3284,7 @@ bool arcan_shmif_mousestate_ioev(
 		return true;
 	}
 
-	if (!state ||
+	if (!ms ||
 		inev->datatype != EVENT_IDATATYPE_ANALOG ||
 		inev->devkind != EVENT_IDEVKIND_MOUSE
 	)

src/shmif/arcan_shmif_interop.h

@@ -494,6 +494,11 @@ void arcan_shmif_bgcopy(
  * devkind == EVENT_IDEVKIND_MOUSE for datatype == EVENT_IDATATYPE_ANALOG.
  * If >true< the status of have changed since last time.
  *
+ * If [state=NULL] an internal state tracking store inside the context will be
+ * used. This might not always be desired if you want to inspect the values
+ * yourself or if you are juggling multiple contexts with a shared state
+ * machine.
+ *
  * uint8_t mstate[ASHMIF_MSTATE_SZ];
  * arcan_shmif_mousestate_setup(acon, false, mstate);
  * ... in event loop ...