expo-gl 11.0.3 patch / concurrency and background rendering

expo-gl+11.0.3.patch

diff --git a/node_modules/expo-gl/ios/EXGL/EXGLContext.mm b/node_modules/expo-gl/ios/EXGL/EXGLContext.mm
index 0a904ab..2bd2fdf 100644
--- a/node_modules/expo-gl/ios/EXGL/EXGLContext.mm
+++ b/node_modules/expo-gl/ios/EXGL/EXGLContext.mm
@@ -18,6 +18,7 @@ @interface EXGLContext ()
 @property (nonatomic, strong) dispatch_queue_t glQueue;
 @property (nonatomic, weak) EXModuleRegistry *moduleRegistry;
 @property (nonatomic, weak) EXGLObjectManager *objectManager;
+@property (atomic) BOOL appIsBackground; // tracks the app's foreground/background state
 
 @end
 
@@ -32,6 +33,7 @@ - (instancetype)initWithDelegate:(id<EXGLContextDelegate>)delegate andModuleRegi
     _objectManager = (EXGLObjectManager *)[_moduleRegistry getExportedModuleOfClass:[EXGLObjectManager class]];
     _glQueue = dispatch_queue_create("host.exp.gl", DISPATCH_QUEUE_SERIAL);
     _eaglCtx = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3] ?: [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
+    _appIsBackground = NO;
   }
   return self;
 }
@@ -48,6 +50,11 @@ - (EAGLContext *)createSharedEAGLContext
 
 - (void)runInEAGLContext:(EAGLContext*)context callback:(void(^)(void))callback
 {
+  if (_appIsBackground) {
+      // iOS does not allow calls to OpenGL when the app is in background
+      return;
+  }
+
   [EAGLContext setCurrentContext:context];
   callback();
   glFlush();
@@ -86,6 +93,16 @@ - (void)initialize:(void(^)(BOOL))callback
       self->_contextId = UEXGLContextCreate(jsRuntimePtr);
       [self->_objectManager saveContext:self];
 
+      // listen for foreground/background transitions
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                            selector:@selector(onApplicationDidBecomeActive:)
+                                            name:UIApplicationDidBecomeActiveNotification
+                                            object:nil];
+      [[NSNotificationCenter defaultCenter] addObserver:self
+                                            selector:@selector(onApplicationWillResignActive:)
+                                            name:UIApplicationWillResignActiveNotification
+                                            object:nil];
+
       UEXGLContextSetFlushMethodObjc(self->_contextId, ^{
         [self flush];
       });
@@ -112,6 +129,21 @@ - (void)flush
   }];
 }
 
+- (void) onApplicationWillResignActive:(NSNotification *) note
+{
+  // flush all pending GL activity, wait for completion, and then set the appIsBackground flag
+  [self runAsync:^{
+    glFinish();
+    self->_appIsBackground = YES;
+  }];
+}
+
+- (void) onApplicationDidBecomeActive:(NSNotification *) note {
+  // unset the appIsBackground flag so that rendering can resume
+  _appIsBackground = NO;
+  // [self flush];
+}
+
 - (void)destroy
 {
   [self runAsync:^{
@@ -119,6 +151,10 @@ - (void)destroy
       [self.delegate glContextWillDestroy:self];
     }
 
+    // stop listening for foreground/background transitions
+    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
+    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationWillResignActiveNotification object:nil];
+
     // Flush all the stuff
     UEXGLContextFlush(self->_contextId);
 
diff --git a/node_modules/expo-gl/ios/EXGL/EXGLView.mm b/node_modules/expo-gl/ios/EXGL/EXGLView.mm
index e7ca617..324e148 100644
--- a/node_modules/expo-gl/ios/EXGL/EXGLView.mm
+++ b/node_modules/expo-gl/ios/EXGL/EXGLView.mm
@@ -235,6 +235,8 @@ - (void)removeFromSuperview
 
 - (void)draw
 {
+  @synchronized(self) { // DJM
+
   // exglCtxId may be unset if we get here (on the UI thread) before UEXGLContextCreate(...) is
   // called on the JS thread to create the EXGL context and save its id (see EXGLContext.initializeContextWithBridge method).
   // In this case no GL work has been sent yet so we skip this frame.
@@ -248,7 +250,7 @@ - (void)draw
     // This happens exactly at `gl.endFrameEXP()` in the queue
     if (_viewColorbuffer != 0 && !_renderbufferPresented) {
       // bind renderbuffer and present it on the layer
-      [_glContext runInEAGLContext:_uiEaglCtx callback:^{
+      [_glContext runAsync:^{
         glBindRenderbuffer(GL_RENDERBUFFER, self->_viewColorbuffer);
         [self->_uiEaglCtx presentRenderbuffer:GL_RENDERBUFFER];
       }];
@@ -257,12 +259,14 @@ - (void)draw
       _renderbufferPresented = YES;
     }
   }
+  } // @synchronized(self)
 }
 
 // [GL thread] blits framebuffers and then sets a flag that informs UI thread
 // about presenting the new content of the renderbuffer on the next draw call
 - (void)blitFramebuffers
 {
+  @synchronized(self) { // DJM
   if (_glContext.isInitialized && _viewFramebuffer != 0 && _viewColorbuffer != 0) {
     // Save surrounding framebuffer
     GLint prevFramebuffer;
@@ -290,6 +294,7 @@ - (void)blitFramebuffers
     // mark renderbuffer as not presented
     _renderbufferPresented = NO;
   }
+  } // @synchronized(self)
 }
 
 #pragma mark - EXGLContextDelegate