[ios] Replace flush/glFinish call with call to reduceMemoryUse()

2 files changed, 97 insertions, 9 deletions

diff --git a/platform/ios/Integration Tests/MGLBackgroundIntegrationTest.m b/platform/ios/Integration Tests/MGLBackgroundIntegrationTest.m
index b4d3eed4e8..a6932dd60c 100644
--- a/platform/ios/Integration Tests/MGLBackgroundIntegrationTest.m
+++ b/platform/ios/Integration Tests/MGLBackgroundIntegrationTest.m
@@ -266,4 +266,96 @@ typedef void (^MGLNotificationBlock)(NSNotification*);
     XCTAssert(self.mapView.application.applicationState == UIApplicationStateActive);
 }
 
+- (void)testRendererDelayingAdjustingViewsWhenInBackground {
+    
+    XCTAssertFalse(self.mapView.isDormant);
+    XCTAssertFalse(self.mapView.displayLink.isPaused);
+    XCTAssert(self.mapView.application.applicationState == UIApplicationStateActive);
+    
+    __weak typeof(self) weakSelf = self;
+    
+    //
+    // Enter background
+    //
+    
+    XCTestExpectation *didEnterBackgroundExpectation = [self expectationWithDescription:@"didEnterBackground"];
+    didEnterBackgroundExpectation.expectedFulfillmentCount = 1;
+    didEnterBackgroundExpectation.assertForOverFulfill = YES;
+
+    XCTestExpectation *adjustedViewsExpectation = [self expectationWithDescription:@"adjustedViewsExpectation"];
+    adjustedViewsExpectation.expectedFulfillmentCount = 1;
+    adjustedViewsExpectation.assertForOverFulfill = YES;
+
+    __block NSInteger displayLinkCount = 0;
+    
+    self.displayLinkDidUpdate = ^{
+        displayLinkCount++;
+    };
+    
+    NSTimeInterval delay = 5.0;
+    
+    self.didEnterBackground = ^(__unused NSNotification *notification){
+        typeof(self) strongSelf = weakSelf;
+        MGLMapView *mapView = strongSelf.mapView;
+        
+        // In general, because order of notifications is not guaranteed
+        // the following asserts are somewhat meaningless (don't do this in
+        // production) - however, because we're mocking their delivery (and
+        // we're tracking a bug)...
+        
+        // MGLMapView responds to UIApplicationDidEnterBackgroundNotification and
+        // marks the map view as dormant. However, depending on the order of
+        // creation it's totally possible for client code also responding to
+        // this notification to be called first - and then trigger a scenario where
+        // GL can be rendering in the background - which can cause crashes.
+        
+        MGLTestAssert(strongSelf, !mapView.isDormant);
+        
+        // However, the display should be paused (because this has now moved
+        // to ...WillResignActive...
+        MGLTestAssert(strongSelf, mapView.displayLink.isPaused);
+        
+        // Remove the map view, and re-add to try and force a bad situation
+        // This will delete/re-create the display link
+        UIView *parentView = mapView.superview;
+
+        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delay * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
+
+            displayLinkCount = 0;
+
+            NSLog(@"Removing MGLMapView from super view");
+            [mapView removeFromSuperview];
+        
+            // Re-add
+            NSLog(@"Re-adding MGLMapView as child");
+            [parentView addSubview:mapView];
+        
+            MGLTestAssert(strongSelf, displayLinkCount == 0, @"updateDisplayLink was called %ld times", displayLinkCount);
+        
+            [mapView.topAnchor constraintEqualToAnchor:parentView.topAnchor].active = YES;
+            [mapView.leftAnchor constraintEqualToAnchor:parentView.leftAnchor].active = YES;
+            [mapView.rightAnchor constraintEqualToAnchor:parentView.rightAnchor].active = YES;
+            [mapView.bottomAnchor constraintEqualToAnchor:parentView.bottomAnchor].active = YES;
+            
+            [adjustedViewsExpectation fulfill];
+        });
+
+        [didEnterBackgroundExpectation fulfill];
+    };
+    
+    [self.mockApplication enterBackground];
+    [self waitForExpectations:@[didEnterBackgroundExpectation] timeout:1.0];
+    
+    XCTAssert(self.mapView.isDormant);
+    
+    // TODO: What do we want here?
+    XCTAssert(!self.mapView.displayLink || self.mapView.displayLink.isPaused);
+    XCTAssert(self.mapView.application.applicationState == UIApplicationStateBackground);
+    
+    
+    [self waitForExpectations:@[adjustedViewsExpectation] timeout:delay];
+    XCTAssert(self.mapView.isDormant);
+    XCTAssert(!self.mapView.displayLink || self.mapView.displayLink.isPaused);
+}
+
 @end
diff --git a/platform/ios/src/MGLMapView.mm b/platform/ios/src/MGLMapView.mm
index 86b4c51c49..6f053f0ac2 100644
--- a/platform/ios/src/MGLMapView.mm
+++ b/platform/ios/src/MGLMapView.mm
@@ -1524,7 +1524,7 @@ public:
     [self resumeGL];
 }
 
-- (BOOL)supportBackgroundRendering
+- (BOOL)supportsBackgroundRendering
 {
     // If this view targets an external display, such as AirPlay or CarPlay, we
     // can safely continue to render OpenGL content without tripping
@@ -1536,7 +1536,7 @@ public:
 
 - (void)resignGL
 {
-    if ([self supportBackgroundRendering])
+    if ([self supportsBackgroundRendering])
     {
         return;
     }
@@ -1550,15 +1550,16 @@ public:
     
     // For OpenGL this calls glFinish as recommended in
     // https://developer.apple.com/library/archive/documentation/3DDrawing/Conceptual/OpenGLES_ProgrammingGuide/ImplementingaMultitasking-awareOpenGLESApplication/ImplementingaMultitasking-awareOpenGLESApplication.html#//apple_ref/doc/uid/TP40008793-CH5-SW1
+    // reduceMemoryUse(), calls performCleanup(), which calls glFinish
     if (_rendererFrontend)
     {
-        _rendererFrontend->flush();
+        _rendererFrontend->reduceMemoryUse();
     }
 }
 
 - (void)sleepGL:(__unused NSNotification *)notification
 {
-    if ([self supportBackgroundRendering])
+    if ([self supportsBackgroundRendering])
     {
         return;
     }
@@ -1605,11 +1606,6 @@ public:
 
         [self.glView deleteDrawable];
     }
-    
-    if (_rendererFrontend)
-    {
-        _rendererFrontend->flush();
-    }
 }
 
 - (void)wakeGL:(__unused NSNotification *)notification