Fix some bugs/issues with the message queue

- It's no longer possible for messages to be sent out of order
- Check if logger is enabled before doing pointless API calls
- Fix linked list bug (a part of the code almost never executes)

src/message_queue.c

@@ -98,6 +98,7 @@ static void cqueue_mark_read(ToxWindow *self, struct cqueue_msg *msg)
 /* removes message with matching receipt from queue, writes to log and updates line to show the message was received. */
 void cqueue_remove(ToxWindow *self, Tox *m, uint32_t receipt)
 {
+    struct chatlog *log = self->chatwin->log;
     struct chat_queue *q = self->chatwin->cqueue;
     struct cqueue_msg *msg = q->root;
 
@@ -107,13 +108,16 @@ void cqueue_remove(ToxWindow *self, Tox *m, uint32_t receipt)
             continue;
         }
 
+        if (log->log_on) {
             char selfname[TOX_MAX_NAME_LENGTH];
             tox_self_get_name(m, (uint8_t *) selfname);
 
             size_t len = tox_self_get_name_size(m);
-        selfname[len] = '\0';
+            selfname[len] = 0;
+
+            write_to_log(msg->message, selfname, log, msg->type == OUT_ACTION);
+        }
 
-        write_to_log(msg->message, selfname, self->chatwin->log, msg->type == OUT_ACTION);
         cqueue_mark_read(self, msg);
 
         struct cqueue_msg *next = msg->next;
@@ -123,24 +127,37 @@ void cqueue_remove(ToxWindow *self, Tox *m, uint32_t receipt)
                 next->prev = NULL;
             }
 
-            free(msg);
             q->root = next;
         } else {
             struct cqueue_msg *prev = msg->prev;
-            free(msg);
             prev->next = next;
+            next->prev = prev;
         }
 
+        free(msg);
+
         return;
     }
 }
 
-/* We use knowledge of toxcore internals (bad!) to determine that if we haven't received a read receipt
- * for a sent packet after this amount of time, the connection has been severed and the packet needs
- * to be re-sent despite toxcore not returning an error on its initial send.
- */
+// We use knowledge of toxcore internals (bad!) to determine that if we haven't received a read receipt for a
+// sent packet after this amount of time, the connection has been severed and the packet needs to be re-sent.
 #define TRY_SEND_TIMEOUT 32
 
+/*
+ * Marks all timed out messages in queue as unsent.
+ */
+static void cqueue_check_timeouts(struct cqueue_msg *msg)
+{
+    while (msg) {
+        if (timed_out(msg->last_send_try, TRY_SEND_TIMEOUT)) {
+            msg->receipt = -1;
+        }
+
+        msg = msg->next;
+    }
+}
+
 /*
  * Tries to send all messages in the send queue in sequential order.
  * If a message fails to send the function will immediately return.
@@ -151,7 +168,14 @@ void cqueue_try_send(ToxWindow *self, Tox *m)
     struct cqueue_msg *msg = q->root;
 
     while (msg) {
-        if (msg->receipt == -1) {
+        if (msg->receipt != -1) {
+            // we can no longer try to send unsent messages until we get receipts for our previous sent
+            // messages, but we continue to iterate the list, checking timestamps for any further
+            // successfully sent messages that have not yet gotten a receipt.
+            cqueue_check_timeouts(msg);
+            return;
+        }
+
         TOX_ERR_FRIEND_SEND_MESSAGE err;
         Tox_Message_Type type = msg->type == OUT_MSG ? TOX_MESSAGE_TYPE_NORMAL : TOX_MESSAGE_TYPE_ACTION;
         uint32_t receipt = tox_friend_send_message(m, self->num, type, (uint8_t *) msg->message, msg->len, &err);
@@ -162,10 +186,6 @@ void cqueue_try_send(ToxWindow *self, Tox *m)
 
         msg->receipt = receipt;
         msg->last_send_try = get_unix_time();
-        } else if (timed_out(msg->last_send_try, TRY_SEND_TIMEOUT)) {  // unlikely but possible
-            msg->receipt = -1;
-        }
-
         msg = msg->next;
     }
 }