[ios] Prevent map view on external display from sleeping in background

When the application enters background mode, only put the map view to sleep if it’s installed on the main screen or hasn’t been added to any window. Otherwise, if it’s targeting an external display, such as via AirPlay or CarPlay, allow the map view to continue rendering.

1 files changed, 11 insertions, 1 deletions

diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index 4d4bf39123..d188ffb91f 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -1222,7 +1222,7 @@ public:
             self.mbglMap.setConstrainMode(mbgl::ConstrainMode::HeightOnly);
         }
 
-        _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(updateFromDisplayLink)];
+        _displayLink = [self.window.screen displayLinkWithTarget:self selector:@selector(updateFromDisplayLink)];
         [self updateDisplayLinkPreferredFramesPerSecond];
         [_displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSRunLoopCommonModes];
         _needsDisplayRefresh = YES;
@@ -1301,6 +1301,16 @@ public:
 
 - (void)sleepGL:(__unused NSNotification *)notification
 {
+    // If this view targets an external display, such as AirPlay or CarPlay, we
+    // can safely continue to render OpenGL content without tripping
+    // gpus_ReturnNotPermittedKillClient in libGPUSupportMercury, because the
+    // external connection keeps the application from truly receding to the
+    // background.
+    if (self.window.screen != [UIScreen mainScreen])
+    {
+        return;
+    }
+    
     MGLLogInfo(@"Entering background.");
     MGLAssertIsMainThread();