From df4d8bab310d7c5e96e237ff6511178e11b36830 Mon Sep 17 00:00:00 2001
From: Julian Rex <julian.rex@mapbox.com>
Date: Wed, 2 May 2018 11:55:58 -0400
Subject: [PATCH] [ios, macos] Raise exception if MGLMapSnapshotter is used
 from thread without active run loop.

---
 platform/darwin/src/MGLMapSnapshotter.mm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/platform/darwin/src/MGLMapSnapshotter.mm b/platform/darwin/src/MGLMapSnapshotter.mm
index 73db8ea15..a63fbfb0a 100644
--- a/platform/darwin/src/MGLMapSnapshotter.mm
+++ b/platform/darwin/src/MGLMapSnapshotter.mm
@@ -108,6 +108,11 @@ const CGFloat MGLSnapshotterMinimumPixelSize = 64;
 
 - (void)startWithQueue:(dispatch_queue_t)queue completionHandler:(MGLMapSnapshotCompletionHandler)completion
 {
+    if (!mbgl::Scheduler::GetCurrent()) {
+        [NSException raise:NSInvalidArgumentException
+                    format:@"startWithQueue:completionHandler: must be called from a thread with an active run loop."];
+    }
+
     if ([self isLoading]) {
         [NSException raise:NSInternalInconsistencyException
                     format:@"Already started this snapshotter."];