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36578167: UIKeyboardAssistantBar tries to layout with a height of zero leading to unsatisfiable constraints #19207

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openradar-mirror opened this issue Jan 17, 2018 · 0 comments
Open

36578167: UIKeyboardAssistantBar tries to layout with a height of zero leading to unsatisfiable constraints #19207

openradar-mirror opened this issue Jan 17, 2018 · 0 comments
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classification:other bug reproducible:always status:open
Milestone
iOS + SDK

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@openradar-mirror
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Description

Summary:
When a hardware keyboard is connected and the keyboard is active, then a view controller is pushed on the navigation controller, the UIKeyboardAssistantBar deep within UIKit can have its height set to zero. However it has subviews specifying constraints that require a certain amount of height. This leads to logging in the console about ‘Unable to simultaneously satisfy constraints’. Also if people have a breakpoint set on UIViewAlertForUnsatisfiableConstraints it will be triggered.

I’ve seen two slightly different situations leading to this but the underlying problem seems to be the same.

The unsatisfiable constraints are within the UIRemoteKeyboardWindow, in the bar with undo/redo etc (the only visible part of the keyboard when a hardware keyboard is connected). Here’s a snippet of the view hierarchy in that window:

<UIKeyboardImpl: 0x14e07b800; frame = (0 0; 1366 471); layer = <CALayer: 0x1c003fb40>>
   | <UIKeyboardAssistantBar: 0x14deabf00; frame = (0 0; 1366 0); tintColor = UIExtendedGrayColorSpace 0 1; animations = { position=<CABasicAnimation: 0x1c46237e0>; bounds.origin=<CABasicAnimation: 0x1c46238a0>; bounds.size=<CABasicAnimation: 0x1c46238c0>; }; layer = <CALayer: 0x1c423dec0>>
   |    | <_UIButtonBarStackView: 0x14deacf80; frame = (0 0; 187 55); clipsToBounds = YES; layer = <CALayer: 0x1c423df40>>
   |    |    | <_UIButtonBarButton: 0x14ddd8520; frame = (19 10; 41 36); layer = <CALayer: 0x1c0435860>>

There are unsatisfiable constraints for each button in the bar. They’re all like this:

NSAutoresizingMaskLayoutConstraint:0x1c0484470 h=--& v=--& UIKeyboardAssistantBar:0x14deabf00.height == 0 (active)

V:|-(0)-[_UIButtonBarStackView]-(0)-|
(superview is UIKeyboardAssistantBar)

V:|-(10)-[_UIButtonBarButton]-(9)-|
(superview is _UIButtonBarStackView)

So the buttons needs 10 points above and 9 below but can’t have that because the height of the containing bar is manually set to zero.

Steps to Reproduce:
0. Run the attached sample project on iPad 10.5" (or any size of iPad). Device and Simulator both work.

  1. Attach a hardware keyboard. (With a freshly launched Simulator I need to toggle the Connect Hardware Keyboard command off then on again to get into this state.)

  2. Tap in the text field. You should see just the bar at the bottom with undo/redo etc, not the whole keyboard because a hardware keyboard is attached.

  3. Tap the button to push a view controller.

Expected Results:
The keyboard assistant bar should smoothly animate down off screen and there should be no unsatisfiable constraints so no logging in the console.

This can probably be achieved if UIKit either never sets the height of the UIKeyboardAssistantBar to zero, or hacks around these sorts of problems by setting up the constraints such that they are not required, typically by changing the priority of one constraint to 999.

Actual Results:
The keyboard assistant bar disappears without animation and this stuff is logged: (stack trace below)

2018-01-17 10:02:40.301460+0000 Unsatisfied[1100:161150] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1c0281310 h=--& v=--& UIKeyboardAssistantBar:0x151e1f280.height == 0 (active)>",
"<NSLayoutConstraint:0x1c4094eb0 V:|-(0)-[_UIButtonBarStackView:0x151d277e0] (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c4094f00 V:[_UIButtonBarStackView:0x151d277e0]-(0)-| (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c0280dc0 'UIButtonBar.maximumAlignmentSize' UIView:0x151e0c9d0.height == UILayoutGuide:0x1c01be140'UIViewLayoutMarginsGuide'.height (active)>",
"<NSLayoutConstraint:0x1c008ce40 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be140'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151d277e0 )>",
"<NSLayoutConstraint:0x1c008c710 'UIView-topMargin-guide-constraint' V:|-(10)-[UILayoutGuide:0x1c01be140'UIViewLayoutMarginsGuide'] (active, names: '|':_UIButtonBarStackView:0x151d277e0 )>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c008ce40 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be140'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151d277e0 )>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2018-01-17 10:02:40.315803+0000 Unsatisfied[1100:161150] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1c0281310 h=--& v=--& UIKeyboardAssistantBar:0x151e1f280.height == 0 (active)>",
"<NSLayoutConstraint:0x1c4094dc0 V:|-(0)-[_UIButtonBarStackView:0x151e1f560] (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c4094f50 V:[_UIButtonBarStackView:0x151e1f560]-(0)-| (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c0095e50 'UISV-canvas-connection' UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.top == _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.top (active)>",
"<NSLayoutConstraint:0x1c0095b80 'UISV-canvas-connection' UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.bottom == _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.bottom (active)>",
"<NSLayoutConstraint:0x1c40932e0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>",
"<NSLayoutConstraint:0x1c4093330 'UIView-topMargin-guide-constraint' V:|-(10)-[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'] (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c0095b80 'UISV-canvas-connection' UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.bottom == _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.bottom (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2018-01-17 10:02:40.327275+0000 Unsatisfied[1100:161150] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1c0281310 h=--& v=--& UIKeyboardAssistantBar:0x151e1f280.height == 0 (active)>",
"<NSLayoutConstraint:0x1c4094e10 V:|-(0)-[_UIButtonBarStackView:0x151e05970] (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c4094e60 V:[_UIButtonBarStackView:0x151e05970]-(0)-| (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c02802d0 'UIButtonBar.maximumAlignmentSize' _UIButtonBarButton:0x151e46500.height == UILayoutGuide:0x1c41be4c0'UIViewLayoutMarginsGuide'.height (active)>",
"<NSLayoutConstraint:0x1c4090ae0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c41be4c0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e05970 )>",
"<NSLayoutConstraint:0x1c4090540 'UIView-topMargin-guide-constraint' V:|-(10)-[UILayoutGuide:0x1c41be4c0'UIViewLayoutMarginsGuide'] (active, names: '|':_UIButtonBarStackView:0x151e05970 )>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c4090ae0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c41be4c0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e05970 )>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2018-01-17 10:02:40.336392+0000 Unsatisfied[1100:161150] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1c0281310 h=--& v=--& UIKeyboardAssistantBar:0x151e1f280.height == 0 (active)>",
"<NSLayoutConstraint:0x1c4094dc0 V:|-(0)-[_UIButtonBarStackView:0x151e1f560] (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c4094f50 V:[_UIButtonBarStackView:0x151e1f560]-(0)-| (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c0096cb0 'UISV-alignment' UIImageView:0x151e1f770.centerY == UIView:0x151d54950.centerY (active)>",
"<NSLayoutConstraint:0x1c0095e50 'UISV-canvas-connection' UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.top == _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.top (active)>",
"<NSLayoutConstraint:0x1c0095b30 'UISV-canvas-connection' UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.centerY == UIImageView:0x151e1f770.centerY (active)>",
"<NSLayoutConstraint:0x1c0094dc0 'UISV-spanning-boundary' _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.top <= UIView:0x151d54950.top (active)>",
"<NSLayoutConstraint:0x1c40932e0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>",
"<NSLayoutConstraint:0x1c4093330 'UIView-topMargin-guide-constraint' V:|-(10)-[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'] (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c0094dc0 'UISV-spanning-boundary' _UILayoutSpacer:0x1c01dd880'UISV-alignment-spanner'.top <= UIView:0x151d54950.top (active)>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.
2018-01-17 10:02:40.342616+0000 Unsatisfied[1100:161150] [LayoutConstraints] Unable to simultaneously satisfy constraints.
Probably at least one of the constraints in the following list is one you don't want.
Try this:
(1) look at each constraint and try to figure out which you don't expect;
(2) find the code that added the unwanted constraint or constraints and fix it.
(Note: If you're seeing NSAutoresizingMaskLayoutConstraints that you don't understand, refer to the documentation for the UIView property translatesAutoresizingMaskIntoConstraints)
(
"<NSAutoresizingMaskLayoutConstraint:0x1c0281310 h=--& v=--& UIKeyboardAssistantBar:0x151e1f280.height == 0 (active)>",
"<NSLayoutConstraint:0x1c4094dc0 V:|-(0)-[_UIButtonBarStackView:0x151e1f560] (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c4094f50 V:[_UIButtonBarStackView:0x151e1f560]-(0)-| (active, names: '|':UIKeyboardAssistantBar:0x151e1f280 )>",
"<NSLayoutConstraint:0x1c00947d0 'UIButtonBar.maximumAlignmentSize' _UIButtonBarButton:0x151d5ace0.height == UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'.height (active)>",
"<NSLayoutConstraint:0x1c40932e0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>",
"<NSLayoutConstraint:0x1c4093330 'UIView-topMargin-guide-constraint' V:|-(10)-[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide'] (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>"
)

Will attempt to recover by breaking constraint
<NSLayoutConstraint:0x1c40932e0 'UIView-bottomMargin-guide-constraint' V:[UILayoutGuide:0x1c01be3e0'UIViewLayoutMarginsGuide']-(9)-| (active, names: '|':_UIButtonBarStackView:0x151e1f560 )>

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

This is the stack trace:

Version:
iOS 11.2 Xcode 9.2

Notes:
In our project, this only happens when the view controller being pushed returns YES to canBecomeFirstResponder, which is needs to do for shake to undo support. The problem occurs with a different stack trace but both paths lead into an animation block in -[UIKeyboardAssistantBar setShow:].

Our workaround is to make sure we return NO to this method when the navigation controller tries to make the incoming view controller first responder, then after that change our response to YES and call becomeFirstResponder ourselves (which we have to do anyway in case the VC is not pushed but shown some other way).

Product Version: iOS 11.2 Xcode 9.2
Created: 2018-01-17T10:37:42.420010
Originated: 2018-01-17T10:37:00
Open Radar Link: http://www.openradar.me/36578167
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