This should not directly affect more complex apps that don't use the ASBasicImageDownloader.
Also disables the default-on text placeholders, as they churn memory during the measurement pass.
These were intended to be written with pure layers (without using backing stores), so I don't
think it is a reasonable default-on behavior until that is fixed.
This provides internal features on _ASAsyncTransaction and ASDisplayNode to facilitate
implementing public API that allows clients to choose if they would prefer to block
on the completion of unfinished rendering, rather than allow a placeholder state to
become visible.
The internal features are:
-[_ASAsyncTransaction waitUntilComplete]
-[ASDisplayNode recursivelyEnsureDisplay]
Also provided are two such implementations:
-[ASCellNode setNeverShowPlaceholders:], which integrates with both Tables and Collections
-[ASViewController setNeverShowPlaceholders:], which should work with Nav and Tab controllers.
Lastly, on ASDisplayNode, a new property .shouldBypassEnsureDisplay allows individual node types
to exempt themselves from blocking the main thread on their display.
By implementing the feature at the ASCellNode level rather than ASTableView & ASCollectionView,
developers can retain fine-grained control on display characteristics. For example, certain
cell types may be appropriate to display to the user with placeholders, whereas others may not.
Follow-up work will include unit tests, revisiting names, and the header locations of definitions.
Use ASBasicImageDownloader by default -- you can now do...
ASNetworkImageNode *imageNode = [[ASNetworkImageNode alloc] init];
imageNode.URL = [NSURL URLWithString:@"..."];
[self.view addSubview:imageNode.view];
...and it'll do the right thing.
Add a `usleep(1.0 * USEC_PER_SEC)` delay to ASBasicImageDownloader and
slowly scroll through the Kittens sample project. Without this patch,
you'll see that images only start downloading after their purple
placeholders appear onscreen. With it, images can download and render
before you scroll them onscreen, thanks to the working range.
