Add some docs and PoC in the nativescript modules

build.sh

@@ -1,5 +1,6 @@
 #!/bin/sh
 
+echo "Clean dist"
 rm -rf dist
 mkdir dist
 mkdir dist/package
@@ -25,7 +26,6 @@ cp LICENSE.md dist/package/LICENSE.md
 cp README.md dist/package/README.md
 cp package.json dist/package/package.json
 
-# npm pack
 echo "NPM pack"
 cd dist/package
 PACKAGE="$(npm pack)"

ios/TNSWidgets/TNSWidgets/UIImage+TNSBlocks.h

@@ -6,10 +6,18 @@
 //  Copyright © 2016 Telerik A D. All rights reserved.
 //
 
-
-
 @interface UIImage (TNSBlocks)
 
-+ (void) tns_imageNamed: (NSString*) name completion: (void (^) (UIImage*))callback;
+/**
+ * Similar to imageNamed: however it runs on a separate queue so the UI thread is not blocked.
+ * It also draws the UIImage in a small thumb to force decoding potentially avoiding UI hicckups when displayed.
+ */
++ (void) tns_safeDecodeImageNamed: (NSString*) name completion: (void (^) (UIImage*))callback;
+
+/**
+ * Same as imageNamed, however calls to this method are sinchronized to be thread safe in iOS8 along with calls to tns_safeImageNamed and tns_safeDecodeImageNamed:completion:
+ * imageNamed is thread safe in iOS 9 and later so in later versions this methods simply fallbacks to imageNamed:
+ */
++ (UIImage*) tns_safeImageNamed: (NSString*) name;
 
 @end

ios/TNSWidgets/TNSWidgets/UIImage+TNSBlocks.m

@@ -10,28 +10,56 @@
 
 @implementation UIImage (TNSBlocks)
 
+static NSLock* image_lock_handle;
 static dispatch_queue_t image_queue;
+
+void image_lock() {
+    if (image_lock_handle) {
+        [image_lock_handle lock];
+    }
+}
+
+void image_unlock() {
+    if (image_lock_handle) {
+        [image_lock_handle unlock];
+    }
+}
+
 + (void) initialize {
     image_queue = dispatch_queue_create("org.nativescript.TNSWidgets.image", NULL);
+    if ([[NSProcessInfo processInfo] operatingSystemVersion].majorVersion >= 9) {
+        // UIImage imageNamed: is said to be thread safe, in iOS9 and later, in offical Apple reference.
+        image_lock_handle = nil;
+    } else {
+        image_lock_handle = [NSLock new];
+    }
 }
 
 - (void) tns_decompressImage {
-    CGImageRef cgImg = [self CGImage];
+    UIGraphicsBeginImageContext(CGSizeMake(1, 1));
-    // TODO: Do performance tests if actual drawing is necessary
+    [self drawAtPoint:CGPointZero];
-
+    UIGraphicsEndImageContext();
-    // UIGraphicsBeginImageContext(CGSizeMake(1, 1));
-    // [self drawAtPoint:CGPointZero];
-    // UIGraphicsEndImageContext();
 }
 
-+ (void) tns_imageNamed: (NSString*) name completion: (void (^) (UIImage*))callback {
++ (void) tns_safeDecodeImageNamed: (NSString*) name completion: (void (^) (UIImage*))callback {
     dispatch_async(image_queue, ^(void){
+        image_lock();
         UIImage* image = [UIImage imageNamed: name];
-        [image tns_decompressImage];
+        if (image) {
+            [image tns_decompressImage];
+        }
+        image_unlock();
         dispatch_async(dispatch_get_main_queue(), ^(void) {
             callback(image);
         });
     });
 }
 
++ (UIImage*) tns_safeImageNamed: (NSString*) name {
+    image_lock();
+    UIImage* image = [UIImage imageNamed: name];
+    image_unlock();
+    return image;
+}
+
 @end