Kazrazuru The items property is now settable. The icon to use for the action on Touch Bar. This satisfies most needs for visual atomicity without any extra code. Learn about the updates.

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However, we also had some difficulties discovering the peculiarities of the Mac compared to developing for iOS. This year, Apple harmonized the platforms further and brought frameworks to the Mac that were previously only on iOS, one example being Multipeer Connectivity. The reason why, is when Apple introduced the iPhone, there was the chance to start from a clean slate and take what had been learned from AppKit: bring over the concepts and pieces that had proven to work well, and improve those that were less fortunate designs.

The UI is constructed out of windows and views, with messages being sent over the responder chain just as on iOS. The similarity is more on the conceptual level than in the implementation. And a lot of the design patterns, such as delegation, will be similar. But the devil is in the details — you really need to read the documentation and learn how these classes should be used. Historically, Mac applications had multiple windows, each with its own role, very similar to view controllers on iOS.

But AppKit has changed, since Mac apps are relying more and more on a single window. It is also part of the responder chain by default. Just remember that if you target your Mac app to OS X As Mike Ash writes , a good pattern to instantiate windows on the Mac is to have one nib file and one window controller per window type. Instead, each window holds a reference to its top-level view in the contentView property.

Instead, events will bubble up through the view tree and then go straight to the window and the window controller. In this instance, if you want a view controller to handle events, you will have to add it to the responder chain manually.

In addition to the difference in the responder chain, AppKit also has a stricter convention as to the method signature of actions. Furthermore, in AppKit, controls usually hold a reference to one target and an action pair, whereas you can associate multiple target-action pairs with a control on iOS using the addTarget:action:forControlEvents: method.

Views The view system works very differently on the Mac, for historic reasons. On iOS, views were backed by Core Animation layers by default from the beginning.

But AppKit predates Core Animation by decades. Therefore, the view system heavily relied on the CPU doing the work. AppKit differentiates between layer-backed and layer-hosting views, and layer backing can be turned on and off on a per-view-tree basis. In contrast to iOS, on the Mac you should treat the backing layers as an implementation detail. This means you should not try to interact with the layers directly, as AppKit owns those layers.

For example, on iOS you could simply say: self. If you want to interact with the layer in such ways, then you have to go one step further. Instead, updateLayer will be called during the view update cycle, and this is where you can modify the layer. The alternative to this would be to simply override the drawRect: method to draw the colored background.

Since OS X This can be a good option if you know that you will not need to animate subviews individually. All subviews that are implicitly layer-backed i. However, subviews that do have wantsLayer set to YES will still have their own backing layer and their drawRect: method will be called, no matter what wantsUpdateLayer returns. This resembles the behavior of non-layer-backed views, but it might be detrimental to animation performance if a drawing step is introduced for each frame of the animation.

This way, you have control over when the layer contents need to be redrawn. A frame change will not automatically trigger a redraw anymore; you are now responsible for triggering it by calling -setNeedsDisplay:. This allows you to specify how the existing layer content will be mapped into the layer as it is resized.

There is a whole different option to work with Core Animation layers — called layer-hosting views. In short, with a layer-hosting view, you can do with the layer and its sublayers whatever you want. The price you pay for this is that you cannot add any subviews to this view anymore. A layer-hosting view is a leaf node in the view tree. To create a layer-hosting view, you first have to assign a layer object to the layer property, and then set the wantsLayer to YES.

In order to receive events for the mouse cursor entering or exiting the view or being moved within the view, you need to create a tracking area. These cells should not be confused with table view cells or collection view cells in UIKit. AppKit originally made the distinction between views and cells in order to save resources — views would delegate all their drawing to a more lightweight cell object that could be reused for all views of the same type.

Check out the Cocoa Drawing Guide for more details. Animations As a consequence of the differences in the view system discussed above, animations also work quite differently on the Mac. If your views are not layer-backed, then naturally, animations will be a CPU-intensive process, as every step of the animation has to be drawn accordingly in the window-backing store.

There are a few different ways you can trigger an animation on a view. First, you can use the animator proxy : view. Check out this article by Jonathan Willings for a description of how you can work around this limitation. All the things mentioned above apply to layer-backed views. NSImage is, in many ways, a more powerful class than UIImage, but this comes at the cost of increased complexity. The most important conceptual difference is that NSImage is backed by one or more image representations.

For example, one NSImage object could hold a thumbnail, a full-size, and a PDF representation for printing of the same content. When you draw the image, an image representation matching the current graphics context and drawing dimensions will be picked based on the color space, dimensions, resolution, and depth.

Furthermore, images on the Mac have the notion of resolution in addition to size. An image representation has three properties that play into that: size, pixelsWide, and pixelsHigh. The size property determines the size of the image representation when being rendered, whereas the pixel width and height values specify the raw image size as derived from the image data itself.

Together, those properties determine the resolution of the image representation. When you change an underlying image representation, you have to call recache on the image for the change to take effect. NSImage provides a very easy way to draw a new image, whereas on iOS you would have to create a bitmap context, then create a CGImage from that, and finally use it to initialize an UIImage instance. A common task is to use a color in your app that your designers have specified for you. The standard system color picker has a drop-down menu, where you can choose the color space you want to use.

The file system has always been exposed to the user on the Mac, so sandboxed apps are able to get access to files outside of their containers if the user signals clear intent to do so. However, whereas this approach enhances the prior possibilities on iOS, it restricts the prior possibilities on the Mac. That makes it easy to oversee or forget.

When we started development of Deckset — an app that transforms simple Markdown into presentation slides — we never thought that we might run into sandboxing issues. After all, we only needed read access to the Markdown file. What we forgot about is that we also needed to display the images that are referenced in the Markdown. In this issue, we have articles covering some of these things in depth: cross-process communication , making an app scriptable , scripting other apps in the sandbox , and creating a plugin infrastructure for your apps.

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