refactor(ios): modernize kroll core with GCD

iphone/TitaniumKit/TitaniumKit.xcodeproj/project.pbxproj

@@ -22,7 +22,7 @@
 
 /* Begin PBXBuildFile section */
 		4A175276218B64E70094C7B6 /* KrollTimerManager.h in Headers */ = {isa = PBXBuildFile; fileRef = 4A175274218B64E70094C7B6 /* KrollTimerManager.h */; };
-		4A175277218B64E70094C7B6 /* KrollTimerManager.m in Sources */ = {isa = PBXBuildFile; fileRef = 4A175275218B64E70094C7B6 /* KrollTimerManager.m */; };
+		4A175277218B64E70094C7B6 /* KrollTimerManager.m in Sources */ = {isa = PBXBuildFile; fileRef = 4A175275218B64E70094C7B6 /* KrollTimerManager.m */; settings = {COMPILER_FLAGS = "-fobjc-arc"; }; };
 		4A1FF4432523262A00A0F923 /* ErrorView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4A1FF4422523262A00A0F923 /* ErrorView.swift */; };
 		B106A6FD24535CB800B1305E /* JSValue+Addons.h in Headers */ = {isa = PBXBuildFile; fileRef = B106A6FB24535CB800B1305E /* JSValue+Addons.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		B106A6FE24535CB800B1305E /* JSValue+Addons.m in Sources */ = {isa = PBXBuildFile; fileRef = B106A6FC24535CB800B1305E /* JSValue+Addons.m */; };

iphone/TitaniumKit/TitaniumKit/Sources/API/Mimetypes.m

@@ -10,20 +10,24 @@
 
 const NSString *svgMimeType = @"image/svg+xml";
 
-static NSDictionary *mimeTypeFromExtensionDict = nil;
+static NSDictionary *MimeTypesDict(void)
+{
+  static NSDictionary *dict = nil;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    // This dictionary contains info on mimetypes currently missing on iOS platform.
+    dict = [[NSDictionary alloc] initWithObjectsAndKeys:
+                                     @"text/css", @"css",
+                                 @"video/x-m4v", @"m4v",
+                                 nil];
+  });
+  return dict;
+}
 
 @implementation Mimetypes
 
 + (void)initialize
 {
-  // This dictionary contains info on mimetypes surrently missing on IOS platform.
-  // This should be updated on a case by case basis.
-  if (mimeTypeFromExtensionDict == nil) {
-    mimeTypeFromExtensionDict = [[NSDictionary alloc] initWithObjectsAndKeys:
-                                                          @"text/css", @"css",
-                                                      @"video/x-m4v", @"m4v",
-                                                      nil];
-  }
 }
 
 + (NSString *)extensionForMimeType:(NSString *)mimetype
@@ -40,9 +44,9 @@ + (NSString *)extensionForMimeType:(NSString *)mimetype
 
   if (extension == NULL) {
     // Missing info is retrieved from dictionary
-    [Mimetypes initialize];
-    for (NSString *key in mimeTypeFromExtensionDict) {
-      NSString *value = [mimeTypeFromExtensionDict objectForKey:key];
+    NSDictionary *extra = MimeTypesDict();
+    for (NSString *key in extra) {
+      NSString *value = [extra objectForKey:key];
       if ([value isEqualToString:mimetype]) {
         return key;
       }
@@ -67,8 +71,7 @@ + (NSString *)mimeTypeForExtension:(NSString *)ext
 
   if (mimetype == NULL) {
     // Missing info is retrieved from dictionary
-    [Mimetypes initialize];
-    NSString *result = [mimeTypeFromExtensionDict objectForKey:[ext pathExtension]];
+    NSString *result = [MimeTypesDict() objectForKey:[ext pathExtension]];
 
     if (result == nil)
       result = @"application/octet-stream";

iphone/TitaniumKit/TitaniumKit/Sources/API/OperationQueue.m

@@ -8,7 +8,8 @@
 #import "OperationQueue.h"
 #import "TiBase.h"
 
-OperationQueue *sharedQueue = nil;
+// Use dispatch_once to ensure thread-safe, one-time singleton init.
+static OperationQueue *sharedQueue = nil;
 
 @interface OperationQueueOp : NSOperation {
   SEL selector;
@@ -93,9 +94,10 @@ - (void)dealloc
 
 + (OperationQueue *)sharedQueue
 {
-  if (sharedQueue == nil) {
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
     sharedQueue = [[OperationQueue alloc] init];
-  }
+  });
   return sharedQueue;
 }
 

iphone/TitaniumKit/TitaniumKit/Sources/API/TiLayoutQueue.m

@@ -10,61 +10,35 @@
 #import "TiLayoutQueue.h"
 #import "TiViewProxy.h"
 #import <CoreFoundation/CoreFoundation.h>
-#import <pthread.h>
+#import <dispatch/dispatch.h>
+#import <os/lock.h>
 
 #define LAYOUT_TIMER_INTERVAL 0.05
 #define LAYOUT_START_INTERVAL 0.01
 
-NSMutableArray *layoutArray = nil;
-CFRunLoopTimerRef layoutTimer = NULL;
-pthread_mutex_t layoutMutex;
-
-void performLayoutRefresh(CFRunLoopTimerRef timer, void *info)
-{
-  NSArray *localLayoutArray = nil;
-
-  // This prevents deadlock if, while laying out, a relayout is requested
-  // (as in the case of redrawing text in a reproxy)
-  pthread_mutex_lock(&layoutMutex);
-  localLayoutArray = layoutArray;
-  layoutArray = nil;
-
-  if ((layoutTimer != NULL) && ([localLayoutArray count] == 0)) {
-    // Might as well stop the timer for now.
-    CFRunLoopTimerInvalidate(layoutTimer);
-    CFRelease(layoutTimer);
-    layoutTimer = NULL;
-  }
-
-  pthread_mutex_unlock(&layoutMutex);
-
-  for (TiViewProxy *thisProxy in localLayoutArray) {
-    [TiLayoutQueue layoutProxy:thisProxy];
-  }
-
-  RELEASE_TO_NIL(localLayoutArray);
-}
+static NSMutableArray *layoutArray = nil;
+static dispatch_source_t layoutTimer = NULL;
+static os_unfair_lock layoutLock = OS_UNFAIR_LOCK_INIT;
 
 @implementation TiLayoutQueue
 
 + (void)initialize
 {
-  pthread_mutex_init(&layoutMutex, NULL);
+  // nothing to initialize; layoutLock is static-initialized
 }
 
 + (void)resetQueue
 {
-  pthread_mutex_lock(&layoutMutex);
+  os_unfair_lock_lock(&layoutLock);
   [layoutArray release];
   layoutArray = nil;
 
   if (layoutTimer != NULL) {
-    CFRunLoopTimerInvalidate(layoutTimer);
-    CFRelease(layoutTimer);
+    dispatch_source_cancel(layoutTimer);
     layoutTimer = NULL;
   }
 
-  pthread_mutex_unlock(&layoutMutex);
+  os_unfair_lock_unlock(&layoutLock);
 }
 
 + (void)layoutProxy:(TiViewProxy *)thisProxy
@@ -78,12 +52,12 @@ + (void)layoutProxy:(TiViewProxy *)thisProxy
 
 + (void)addViewProxy:(TiViewProxy *)newViewProxy
 {
-  pthread_mutex_lock(&layoutMutex);
+  os_unfair_lock_lock(&layoutLock);
 
   if (layoutArray == nil) {
     layoutArray = [[NSMutableArray alloc] initWithObjects:newViewProxy, nil];
   } else if ([layoutArray containsObject:newViewProxy]) { // Nothing to do here. Already added.
-    pthread_mutex_unlock(&layoutMutex);
+    os_unfair_lock_unlock(&layoutLock);
     return;
   } else if ([layoutArray containsObject:[newViewProxy parent]]) { // For safety reasons, we do add this to the list. But since the parent's already here,
     // We add it to the FIRST so that children draw before parents, giving us good layout values for later!
@@ -94,14 +68,38 @@ + (void)addViewProxy:(TiViewProxy *)newViewProxy
   }
 
   if (layoutTimer == NULL) {
-    layoutTimer = CFRunLoopTimerCreate(NULL,
-        CFAbsoluteTimeGetCurrent() + LAYOUT_START_INTERVAL,
-        LAYOUT_TIMER_INTERVAL,
-        0, 0, performLayoutRefresh, NULL);
-    CFRunLoopAddTimer(CFRunLoopGetMain(), layoutTimer, kCFRunLoopCommonModes);
+    // create GCD timer on main queue to coalesce layout flushes
+    dispatch_queue_t queue = dispatch_get_main_queue();
+    layoutTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, queue);
+    uint64_t startNsec = (uint64_t)(LAYOUT_START_INTERVAL * NSEC_PER_SEC);
+    uint64_t intervalNsec = (uint64_t)(LAYOUT_TIMER_INTERVAL * NSEC_PER_SEC);
+    dispatch_source_set_timer(layoutTimer,
+        dispatch_time(DISPATCH_TIME_NOW, startNsec),
+        intervalNsec,
+        (uint64_t)(0.001 * NSEC_PER_SEC)); // 1ms leeway
+
+    dispatch_source_set_event_handler(layoutTimer, ^{
+      NSArray *localLayoutArray = nil;
+      os_unfair_lock_lock(&layoutLock);
+      localLayoutArray = layoutArray;
+      layoutArray = nil;
+      BOOL shouldStop = (localLayoutArray == nil) || ([localLayoutArray count] == 0);
+      os_unfair_lock_unlock(&layoutLock);
+
+      for (TiViewProxy *thisProxy in localLayoutArray) {
+        [TiLayoutQueue layoutProxy:thisProxy];
+      }
+      RELEASE_TO_NIL(localLayoutArray);
+
+      if (shouldStop) {
+        // no queued work: stop timer to save cycles
+        dispatch_source_cancel(layoutTimer);
+        layoutTimer = NULL;
+      }
+    });
+    dispatch_resume(layoutTimer);
   }
-
-  pthread_mutex_unlock(&layoutMutex);
+  os_unfair_lock_unlock(&layoutLock);
 }
 
 @end

iphone/TitaniumKit/TitaniumKit/Sources/Kroll/KrollCallback.m

@@ -8,9 +8,10 @@
 #import "KrollBridge.h"
 #import "KrollObject.h"
 #import "TiExceptionHandler.h"
+#import <os/lock.h>
 
 static NSMutableArray *callbacks;
-static NSLock *callbackLock;
+static os_unfair_lock callbackLock = OS_UNFAIR_LOCK_INIT;
 
 @interface KrollCallback ()
 @property (nonatomic, assign) KrollContext *context;
@@ -22,19 +23,18 @@ @implementation KrollCallback
 
 + (void)shutdownContext:(KrollContext *)context
 {
-  [callbackLock lock];
+  os_unfair_lock_lock(&callbackLock);
   for (KrollCallback *callback in callbacks) {
     if ([callback context] == context) {
       callback.context = nil;
     }
   }
-  [callbackLock unlock];
+  os_unfair_lock_unlock(&callbackLock);
 }
 
 + (void)initialize
 {
   if (callbacks == nil) {
-    callbackLock = [[NSLock alloc] init];
     callbacks = TiCreateNonRetainingArray();
   }
 }
@@ -56,9 +56,9 @@ - (id)initWithCallback:(JSValueRef)function_ thisObject:(JSObjectRef)thisObject_
 
 - (void)dealloc
 {
-  [callbackLock lock];
+  os_unfair_lock_lock(&callbackLock);
   [callbacks removeObject:self];
-  [callbackLock unlock];
+  os_unfair_lock_unlock(&callbackLock);
 
   [type release];
   if ([KrollBridge krollBridgeExists:bridge]) {

iphone/TitaniumKit/TitaniumKit/Sources/Kroll/KrollTimerManager.h

@@ -28,7 +28,7 @@
 /**
  * The method that will be triggered when a timer fires.
  */
-- (void)timerFired:(nonnull NSTimer *)timer;
+- (void)timerFired:(nullable NSTimer *)timer;
 
 @end
 
@@ -38,9 +38,10 @@
 @interface KrollTimerManager : NSObject
 
 /**
- * Map of timer identifiers and the underlying native NSTimer.
+ * Map of timer identifiers to the underlying native timer objects.
+ * Backed by GCD timers for lower overhead and better accuracy.
  */
-@property (nonatomic, strong, nullable) NSMapTable<NSNumber *, NSTimer *> *timers;
+@property (nonatomic, strong, nullable) NSMapTable<NSNumber *, id> *timers;
 
 /**
  * Initializes the timer manager in the given JS context. Exposes the global set/clear