[ios, macos] Implement CustomLayerHost. Save a weak reference to the style layer, and upgrade to a strong layer when initialized by the renderer

Co-authored-by: Julian Rex <julian.rex@mapbox.com>

6 files changed, 235 insertions, 73 deletions

diff --git a/include/mbgl/style/layers/custom_layer.hpp b/include/mbgl/style/layers/custom_layer.hpp
index be656b0e14..5aa80a3afe 100644
--- a/include/mbgl/style/layers/custom_layer.hpp
+++ b/include/mbgl/style/layers/custom_layer.hpp
@@ -2,6 +2,8 @@
 
 #include <mbgl/style/layer.hpp>
 
+#include <functional>
+
 namespace mbgl {
 namespace style {
 
diff --git a/platform/darwin/src/MGLOpenGLStyleLayer.mm b/platform/darwin/src/MGLOpenGLStyleLayer.mm
index 8933a77382..d9aa4f2575 100644
--- a/platform/darwin/src/MGLOpenGLStyleLayer.mm
+++ b/platform/darwin/src/MGLOpenGLStyleLayer.mm
@@ -1,4 +1,4 @@
-#import "MGLOpenGLStyleLayer.h"
+ #import "MGLOpenGLStyleLayer.h"
 
 #import "MGLMapView_Private.h"
 #import "MGLStyle_Private.h"
@@ -7,49 +7,50 @@
 #include <mbgl/style/layers/custom_layer.hpp>
 #include <mbgl/math/wrap.hpp>
 
-/**
- Runs the preparation handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
+class MGLOpenGLLayerHost : public mbgl::style::CustomLayerHost {
+public:
+    MGLOpenGLLayerHost(MGLOpenGLStyleLayer *styleLayer) {
+        layerRef = styleLayer;
+        layer = nil;
+    }
+    ~MGLOpenGLLayerHost () {
+        layer = nil;
+    }
 
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLPrepareCustomStyleLayer(void *context) {
-    MGLOpenGLStyleLayer *layer = (__bridge MGLOpenGLStyleLayer *)context;
-    [layer didMoveToMapView:layer.style.mapView];
-}
+    void initialize() {
+        if (layerRef == nil) return;
+        else if (layer == nil) layer = layerRef;
 
-/**
- Runs the drawing handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
+        [layer didMoveToMapView:layer.style.mapView];
+    }
 
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLDrawCustomStyleLayer(void *context, const mbgl::style::CustomLayerRenderParameters &params) {
-    MGLOpenGLStyleLayer *layer = (__bridge MGLOpenGLStyleLayer *)context;
-    MGLStyleLayerDrawingContext drawingContext = {
-        .size = CGSizeMake(params.width, params.height),
-        .centerCoordinate = CLLocationCoordinate2DMake(params.latitude, params.longitude),
-        .zoomLevel = params.zoom,
-        .direction = mbgl::util::wrap(params.bearing, 0., 360.),
-        .pitch = static_cast<CGFloat>(params.pitch),
-        .fieldOfView = static_cast<CGFloat>(params.fieldOfView),
-    };
-    [layer drawInMapView:layer.style.mapView withContext:drawingContext];
-}
+    void render(const mbgl::style::CustomLayerRenderParameters &params) {
+        assert(layerRef);
+
+        MGLStyleLayerDrawingContext drawingContext = {
+            .size = CGSizeMake(params.width, params.height),
+            .centerCoordinate = CLLocationCoordinate2DMake(params.latitude, params.longitude),
+            .zoomLevel = params.zoom,
+            .direction = mbgl::util::wrap(params.bearing, 0., 360.),
+            .pitch = static_cast<CGFloat>(params.pitch),
+            .fieldOfView = static_cast<CGFloat>(params.fieldOfView),
+        };
+        [layer drawInMapView:layer.style.mapView withContext:drawingContext];
+    }
 
-/**
- Runs the completion handler block contained in the given context, which is
- implicitly an instance of `MGLOpenGLStyleLayer`.
+    void contextLost() {}
 
- @param context An `MGLOpenGLStyleLayer` instance that was provided as context
-    when creating an OpenGL style layer.
- */
-void MGLFinishCustomStyleLayer(void *context) {
-    MGLOpenGLStyleLayer *layer = (__bridge_transfer MGLOpenGLStyleLayer *)context;
-    [layer willMoveFromMapView:layer.style.mapView];
-}
+    void deinitialize() {
+        if (layer == nil) return;
+
+        [layer willMoveFromMapView:layer.style.mapView];
+        layerRef = layer;
+        layer = nil;
+    }
+private:
+    __weak MGLOpenGLStyleLayer * layerRef;
+    MGLOpenGLStyleLayer * layer = nil;
+};
 
 /**
  An `MGLOpenGLStyleLayer` is a style layer that is rendered by OpenGL code that
@@ -98,10 +99,7 @@ void MGLFinishCustomStyleLayer(void *context) {
  */
 - (instancetype)initWithIdentifier:(NSString *)identifier {
     auto layer = std::make_unique<mbgl::style::CustomLayer>(identifier.UTF8String,
-                                                            MGLPrepareCustomStyleLayer,
-                                                            MGLDrawCustomStyleLayer,
-                                                            MGLFinishCustomStyleLayer,
-                                                            (__bridge_retained void *)self);
+                                                            std::make_unique<MGLOpenGLLayerHost>(self));
     return self = [super initWithPendingLayer:std::move(layer)];
 }
 
@@ -116,7 +114,9 @@ void MGLFinishCustomStyleLayer(void *context) {
         [NSException raise:@"MGLLayerReuseException"
                     format:@"%@ cannot be added to more than one MGLStyle at a time.", self];
     }
+    _style.openGLLayers[self.identifier] = nil;
     _style = style;
+    _style.openGLLayers[self.identifier] = self;
 }
 
 - (void)addToStyle:(MGLStyle *)style belowLayer:(MGLStyleLayer *)otherLayer {
diff --git a/platform/darwin/src/MGLStyle.mm b/platform/darwin/src/MGLStyle.mm
index 199f6c2e02..62b6b25747 100644
--- a/platform/darwin/src/MGLStyle.mm
+++ b/platform/darwin/src/MGLStyle.mm
@@ -83,6 +83,7 @@
 @property (nonatomic, readonly, weak) MGLMapView *mapView;
 @property (nonatomic, readonly) mbgl::style::Style *rawStyle;
 @property (readonly, copy, nullable) NSURL *URL;
+@property (nonatomic, readwrite, strong) NS_MUTABLE_DICTIONARY_OF(NSString *, MGLOpenGLStyleLayer *) *openGLLayers;
 @property (nonatomic) NS_MUTABLE_DICTIONARY_OF(NSString *, NS_DICTIONARY_OF(NSObject *, MGLTextLanguage *) *) *localizedLayersByIdentifier;
 
 @end
@@ -125,6 +126,7 @@ static_assert(6 == mbgl::util::default_styles::numOrderedStyles,
     if (self = [super init]) {
         _mapView = mapView;
         _rawStyle = rawStyle;
+        _openGLLayers = [NSMutableDictionary dictionary];
         _localizedLayersByIdentifier = [NSMutableDictionary dictionary];
     }
     return self;
diff --git a/platform/darwin/src/MGLStyle_Private.h b/platform/darwin/src/MGLStyle_Private.h
index 4cbe953a44..3597a0a0a6 100644
--- a/platform/darwin/src/MGLStyle_Private.h
+++ b/platform/darwin/src/MGLStyle_Private.h
@@ -25,7 +25,7 @@ namespace mbgl {
 @property (nonatomic, readonly) mbgl::style::Style *rawStyle;
 
 - (nullable NS_ARRAY_OF(MGLAttributionInfo *) *)attributionInfosWithFontSize:(CGFloat)fontSize linkColor:(nullable MGLColor *)linkColor;
-
+@property (nonatomic, readonly, strong) NS_MUTABLE_DICTIONARY_OF(NSString *, MGLOpenGLStyleLayer *) *openGLLayers;
 - (void)setStyleClasses:(NS_ARRAY_OF(NSString *) *)appliedClasses transitionDuration:(NSTimeInterval)transitionDuration;
 
 @end
diff --git a/platform/ios/Integration Tests/MBGLIntegrationTests.m b/platform/ios/Integration Tests/MBGLIntegrationTests.m
index deb362cd64..7b82f41b57 100644
--- a/platform/ios/Integration Tests/MBGLIntegrationTests.m
+++ b/platform/ios/Integration Tests/MBGLIntegrationTests.m
@@ -1,6 +1,6 @@
 #import <XCTest/XCTest.h>
-
-@import Mapbox;
+#import <objc/message.h>
+#import <Mapbox/Mapbox.h>
 
 @interface MBGLIntegrationTests : XCTestCase <MGLMapViewDelegate>
 
@@ -11,8 +11,11 @@
 
 @implementation MBGLIntegrationTests {
     XCTestExpectation *_styleLoadingExpectation;
+    XCTestExpectation *_renderFinishedExpectation;
 }
 
+#pragma mark - Setup/Teardown
+
 - (void)setUp {
     [super setUp];
 
@@ -32,6 +35,16 @@
     [window makeKeyAndVisible];
 }
 
+- (void)tearDown {
+    _styleLoadingExpectation = nil;
+    self.mapView = nil;
+    self.style = nil;
+
+    [super tearDown];
+}
+
+#pragma mark - MGLMapViewDelegate
+
 - (void)mapView:(MGLMapView *)mapView didFinishLoadingStyle:(MGLStyle *)style {
     XCTAssertNotNil(mapView.style);
     XCTAssertEqual(mapView.style, style);
@@ -39,30 +52,112 @@
     [_styleLoadingExpectation fulfill];
 }
 
-- (void)tearDown {
-    _styleLoadingExpectation = nil;
-    self.mapView = nil;
+- (void)mapViewDidFinishRenderingFrame:(MGLMapView *)mapView fullyRendered:(__unused BOOL)fullyRendered {
+    [_renderFinishedExpectation fulfill];
+    _renderFinishedExpectation = nil;
+}
 
-    [super tearDown];
+#pragma mark - Utilities
+
+- (void)waitForMapViewToBeRendered {
+    [self.mapView setNeedsDisplay];
+    _renderFinishedExpectation = [self expectationWithDescription:@"Map view should be rendered"];
+    [self waitForExpectations:@[_renderFinishedExpectation] timeout:1];
 }
 
 - (MGLStyle *)style {
     return self.mapView.style;
 }
 
+#pragma mark - Tests
+
+// This test does not strictly need to be in this test file/target. Including here for convenience.
+- (void)testOpenGLLayerDoesNotLeakWhenCreatedAndDestroyedWithoutAddingToStyle {
+    MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+    __weak id weakLayer = layer;
+    layer = nil;
+
+    XCTAssertNil(weakLayer);
+}
+
+- (void)testAddingRemovingOpenGLLayerWithoutRendering {
+    XCTAssertNotNil(self.style);
+
+    void(^addRemoveGLLayer)(void) = ^{
+        __weak id weakLayer = nil;
+
+        @autoreleasepool {
+            MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+            [self.style insertLayer:layer atIndex:0];
+            weakLayer = layer;
+
+            // Nil the layer prior to remove to ensure it's being retained
+            layer = nil;
+            [self.style removeLayer:weakLayer];
+        }
+
+        XCTAssertNil(weakLayer);
+    };
+
+    addRemoveGLLayer();
+    addRemoveGLLayer();
+    addRemoveGLLayer();
+}
+
+- (void)testReusingOpenGLLayerIdentifier {
+    __weak MGLOpenGLStyleLayer *weakLayer2;
+
+    @autoreleasepool {
+        MGLOpenGLStyleLayer *layer1 = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+        [self.style insertLayer:layer1 atIndex:0];
+        [self waitForMapViewToBeRendered];
+        [self.style removeLayer:layer1];
+
+        MGLOpenGLStyleLayer *layer2 = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+        weakLayer2 = layer2;
+
+        XCTAssertNotNil(layer2);
+        XCTAssert(layer1 != layer2);
+
+        [self.style insertLayer:layer2 atIndex:0];
+        [self waitForMapViewToBeRendered];
+        [self.style removeLayer:layer2];
+
+        XCTAssertNil([layer1 style]);
+        XCTAssertNil([layer2 style]);
+    }
+
+    // At this point, layer2 (and layer1) should still be around,
+    // since the render process needs to keep a reference to them.
+    XCTAssertNotNil(weakLayer2);
+
+    // Let render loop run enough to release the layers
+    [self waitForMapViewToBeRendered];
+    XCTAssertNil(weakLayer2);
+}
+
 - (void)testAddingRemovingOpenGLLayer {
     XCTAssertNotNil(self.style);
 
     void(^addRemoveGLLayer)(void) = ^{
-        MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
-        [self.style insertLayer:layer atIndex:0];
-        layer = nil;
 
-        [[NSRunLoop currentRunLoop] runUntilDate:[NSDate date]];
+        __weak id retrievedLayer = nil;
+        
+        @autoreleasepool {
+            MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+            [self.style insertLayer:layer atIndex:0];
+            layer = nil;
+            
+            [self waitForMapViewToBeRendered];
 
-        id retrievedLayer = [self.style layerWithIdentifier:@"gl-layer"];
-        XCTAssertNotNil(retrievedLayer);
-        [self.style removeLayer:retrievedLayer];
+            retrievedLayer = [self.style layerWithIdentifier:@"gl-layer"];
+            XCTAssertNotNil(retrievedLayer);
+
+            [self.style removeLayer:retrievedLayer];
+            [self waitForMapViewToBeRendered];
+        }
+
+        XCTAssertNil(retrievedLayer);
     };
 
     addRemoveGLLayer();
@@ -71,33 +166,97 @@
 }
 
 - (void)testReusingOpenGLLayer {
-    NSTimeInterval waitInterval = 0.01;
-
     MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
     [self.style insertLayer:layer atIndex:0];
-
-    [[NSRunLoop currentRunLoop] runUntilDate:[[NSDate date] dateByAddingTimeInterval:waitInterval]];
+    [self waitForMapViewToBeRendered];
+    
+    [self.style removeLayer:layer];
+    [self waitForMapViewToBeRendered];
+    
+    [self.style insertLayer:layer atIndex:0];
+    [self waitForMapViewToBeRendered];
 
     [self.style removeLayer:layer];
+    [self waitForMapViewToBeRendered];
+}
 
-    [[NSRunLoop currentRunLoop] runUntilDate:[[NSDate date] dateByAddingTimeInterval:waitInterval]];
+- (void)testOpenGLLayerDoesNotLeakWhenRemovedFromStyle {
+    __weak id weakLayer;
+    @autoreleasepool {
+        MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+        weakLayer = layer;
+        [self.style insertLayer:layer atIndex:0];
+        layer = nil;
 
-    [self.style insertLayer:layer atIndex:0];
+        [self waitForMapViewToBeRendered];
+        [self.style removeLayer:[self.style layerWithIdentifier:@"gl-layer"]];
+    }
 
-    [[NSRunLoop currentRunLoop] runUntilDate:[[NSDate date] dateByAddingTimeInterval:waitInterval]];
+    MGLStyleLayer *layer2 = weakLayer;
 
-    [self.style removeLayer:layer];
+    XCTAssertNotNil(weakLayer);
+    [self waitForMapViewToBeRendered];
 
-    [[NSRunLoop currentRunLoop] runUntilDate:[[NSDate date] dateByAddingTimeInterval:waitInterval]];
+    layer2 = nil;
+    XCTAssertNil(weakLayer);
 }
 
-// This test does not strictly need to be in this test file/target. Including here for convenience.
-- (void)testOpenGLLayerDoesNotLeakWhenCreatedAndDestroyedWithoutAddingToStyle {
-    MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
-    __weak id weakLayer = layer;
-    layer = nil;
-    
+- (void)testOpenGLLayerDoesNotLeakWhenStyleChanged {
+    __weak MGLOpenGLStyleLayer *weakLayer;
+
+    @autoreleasepool {
+        {
+            MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+            weakLayer = layer;
+            [self.style insertLayer:layer atIndex:0];
+            layer = nil;
+        }
+    }
+
+    XCTAssertNotNil(weakLayer);
+
+    [self waitForMapViewToBeRendered];
+
+    MGLStyleLayer *layer2 = [self.mapView.style layerWithIdentifier:@"gl-layer"];
+
+    NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
+    _styleLoadingExpectation = [self expectationWithDescription:@"Map view should finish loading style."];
+    [self.mapView setStyleURL:styleURL];
+    [self waitForExpectations:@[_styleLoadingExpectation] timeout:10];
+
+    // At this point the C++ CustomLayer will have been destroyed, and the rawLayer pointer has been NULLed
+    XCTAssert(weakLayer == layer2);
+    XCTAssertNotNil(weakLayer);
+
+    // Asking the style for the layer should return nil
+    MGLStyleLayer *layer3 = [self.mapView.style layerWithIdentifier:@"gl-layer"];
+    XCTAssertNil(layer3);
+}
+
+
+- (void)testOpenGLLayerDoesNotLeakWhenMapViewDeallocs {
+    __weak id weakLayer;
+ 
+    @autoreleasepool {
+
+        NSURL *styleURL = [[NSBundle bundleForClass:[self class]] URLForResource:@"one-liner" withExtension:@"json"];
+        MGLMapView *mapView2 = [[MGLMapView alloc] initWithFrame:UIScreen.mainScreen.bounds styleURL:styleURL];
+        mapView2.delegate = self;
+
+        XCTAssertNil(mapView2.style);
+
+        _styleLoadingExpectation = [self expectationWithDescription:@"Map view should finish loading style."];
+        [self waitForExpectationsWithTimeout:1 handler:nil];
+
+        MGLOpenGLStyleLayer *layer = [[MGLOpenGLStyleLayer alloc] initWithIdentifier:@"gl-layer"];
+        weakLayer = layer;
+        [mapView2.style insertLayer:layer atIndex:0];
+        layer = nil;
+
+        [self waitForMapViewToBeRendered];
+    }
     XCTAssertNil(weakLayer);
 }
 
 @end
+
diff --git a/src/mbgl/style/layers/custom_layer.cpp b/src/mbgl/style/layers/custom_layer.cpp
index 0e51a70e50..f6749275ee 100644
--- a/src/mbgl/style/layers/custom_layer.cpp
+++ b/src/mbgl/style/layers/custom_layer.cpp
@@ -26,7 +26,6 @@ std::unique_ptr<Layer> CustomLayer::cloneRef(const std::string&) const {
 }
 
 // Visibility
-
 void CustomLayer::setVisibility(VisibilityType value) {
     if (value == getVisibility())
         return;