Auto-adjust docked position to match available screen space

[ThatsJustCheesy]

Fixes #35

Implemented by polling for the size of the "visible frame" every fraction of a second when in docked mode. I don't know of a way to get notified when it changes, but polling allows us to automatically adjust the docked position, fixing the issue described.

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IssueHunt Summary

Referenced issues

This pull request has been submitted to:

• #35: Maintain fixed distance from dock/menu bar when they move or resize

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[sindresorhus]

How about swizzling NSScreen#visibleFrame? We can then just hook when it's set, emit an event, and then forward the original call.

This is what I've used for swizzling in the past:

func swizzle(type: AnyClass, original originalSelector: Selector, swizzled swizzledSelector: Selector) {
	guard
		let originalMethod = class_getInstanceMethod(type, originalSelector),
		let swizzledMethod = class_getInstanceMethod(type, swizzledSelector)
	else {
		return
	}

	// Check if the original method has been swizzelled
	if class_addMethod(
		type,
		originalSelector,
		method_getImplementation(swizzledMethod),
		method_getTypeEncoding(swizzledMethod)
	) {
		class_replaceMethod(
			type,
			swizzledSelector,
			originalMethod,
			method_getTypeEncoding(originalMethod)
		)
	} else {
		method_exchangeImplementations(
			originalMethod,
			swizzledMethod
		)
	}
}

https://nshipster.com/method-swizzling/

[sindresorhus]

I would also like to see the visibleFrame listening logic moved into a NSScreen extension so it can be reused if we need it for other things in the future and for readability reasons.

[sindresorhus]

@ThatsJustCheesy Bump :)

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@Mortennn Any thoughts on this?

[Mortennn]

When the size of the Dock changes a notification is fired which we can then listen for.

func applicationDidFinishLaunching(_ notification: Notification) {
	DistributedNotificationCenter.default().addObserver(self, selector: #selector(dockChangedSize), name: Notification.Name(rawValue: "com.apple.dock.prefchanged"), object: nil)
}

@objc
private func dockSettingsChanged() {
	print("Dock settings changed")
}

[sindresorhus]

@Mortennn That only fires when the Dock preferences are changes, not when the Dock is auto-shown/hidden, which is what we want.

[ThatsJustCheesy]

Hey, sorry for leaving this undone!

It looks like there's no setVisibleFrame: method we can easily hook onto:

(lldb) p Array(UnsafeBufferPointer(start: class_copyMethodList(NSScreen.self, nil), count: 48)).map { method_getName($0) }
([Selector]) $R2 = 48 values {
  [0] = "isEqual:"
  [1] = "hash"
  [2] = "visibleFrame"
  [3] = "frame"
  [4] = "dealloc"
  [5] = "_displayID"
  [6] = "_UUIDString"
  [7] = "displayLinkWithTarget:selector:"
  [8] = "colorSpace"
  [9] = "backingScaleFactor"
  [10] = "_currentSpace"
  [11] = "imageInRect:"
  [12] = "backingAlignedRect:options:"
  [13] = "convertRectToBacking:"
  [14] = "convertRectFromBacking:"
  [15] = "deviceDescription"
  [16] = "canRepresentDisplayGamut:"
  [17] = "_screenNumber"
  [18] = "_dockOrientation"
  [19] = "_initWithDisplay:sharedInfo:"
  [20] = "_isZeroScreen"
  [21] = "_menuBarHeight"
  [22] = "_layoutFrame"
  [23] = "_dockRect"
  [24] = "depth"
  [25] = "_resolution"
  [26] = "_updateWithDisplay:sharedInfo:"
  [27] = "_snapshot"
  [28] = "maximumExtendedDynamicRangeColorComponentValue"
  [29] = "devicePixelCounts"
  [30] = "_dockHidden"
  [31] = "_safeVisibleFrame"
  [32] = "supportedWindowDepths"
  [33] = "userSpaceScaleFactor"
  [34] = "imageInRect:underWindow:"
  [35] = "_isActiveScreen"
  [36] = "displayLinkWithHandler:"
  [37] = "_bestSettingWithBitsPerPixel:width:height:refreshRate:exactMatch:"
  [38] = "_capture:"
  [39] = "_isCaptured"
  [40] = "_releaseCapture:"
  [41] = "_currentSetting"
  [42] = "_availableSettings"
  [43] = "_bestSettingWithBitsPerPixel:width:height:exactMatch:"
  [44] = "_bestSettingSimilarToSetting:exactMatch:"
  [45] = "_switchToSetting:error:"
  [46] = "addUpdateHandler:"
  [47] = {
    ptr = 0x0000000000000000
  }
}

So I'll move the current logic into an NSScreen extension, if that's okay.

[sindresorhus]

I found a better way. Turns out the NSApplication.didChangeScreenParametersNotification notification is fired when the Dock size and position changes (as long as it's not set to auto-hide). So we can use that instead of polling.

[sindresorhus]

Can you add a short comment that explains this logic (Like in the commit message).

And can you move 22 into a variable with a descriptive name?

[Mortennn]

You can use NSStatusBar.system.thickness to retrieve the status bar height (22).

[ThatsJustCheesy]

Oh, excellent! API discoverability is fun…

And I initially saw NSMenu#menuBarHeight to get the menubar thickness, but our app doesn't own a menubar, so it didn't work. Thanks @Mortennn!

[ThatsJustCheesy]

Actually, looking back, this solution could've worked:

When the size of the Dock changes a notification is fired which we can then listen for.

func applicationDidFinishLaunching(_ notification: Notification) {
	DistributedNotificationCenter.default().addObserver(self, selector: #selector(dockChangedSize), name: Notification.Name(rawValue: "com.apple.dock.prefchanged"), object: nil)
}

@objc
private func dockSettingsChanged() {
	print("Dock settings changed")
}

Since none of our solutions have accounted for auto-show anyhow. But, now that we've found it, it's probably best to rely on the documented notification.

[sindresorhus]

Can you fix the merge conflict?

[sindresorhus]

🙌