NSSplitView and autolayout

Question

How should I use auto layout constrains inside NSSplitView subview?

My NSSplitView subview has 3 subview: topPane, tableContainer and bottomPane and I set the constrains like this:

NSDictionary* views = NSDictionaryOfVariableBindings(topPane, tableContainer, bottomPane);

for (NSView* view in [views allValues]) {
    [view setTranslatesAutoresizingMaskIntoConstraints:NO];
}

[myView addConstraints:[NSLayoutConstraint constraintsWithVisualFormat:@"V:|[topPane(34)][tableContainer][bottomPane(24)]|"
                                                               options:0 
                                                               metrics:nil 
                                                                 views:views]];

[mySplitView addSubview:myView];

And got this in console:

Unable to simultaneously satisfy constraints:
(
    "<NSLayoutConstraint:0x7fd6c4b1f770 V:[NSScrollView:0x7fd6c4b234c0]-(0)-[CPane:0x7fd6c4b2fd10]>",
    "<NSLayoutConstraint:0x7fd6c4b30910 V:[CPane:0x7fd6c4b2f870(34)]>",
    "<NSLayoutConstraint:0x7fd6c4b30770 V:|-(0)-[CPane:0x7fd6c4b2f870]   (Names: '|':NSView:0x7fd6c4b22e50 )>",
    "<NSLayoutConstraint:0x7fd6c4b212f0 V:[CPane:0x7fd6c4b2fd10]-(0)-|   (Names: '|':NSView:0x7fd6c4b22e50 )>",
    "<NSLayoutConstraint:0x7fd6c4b2f910 V:[CPane:0x7fd6c4b2f870]-(0)-[NSScrollView:0x7fd6c4b234c0]>",
    "<NSLayoutConstraint:0x7fd6c4b21290 V:[CPane:0x7fd6c4b2fd10(24)]>",
    "<NSAutoresizingMaskLayoutConstraint:0x7fd6c3630430 h=--& v=--& V:[NSView:0x7fd6c4b22e50(0)]>"
)

Will attempt to recover by breaking constraint 
<NSLayoutConstraint:0x7fd6c4b1f770 V:[NSScrollView:0x7fd6c4b234c0]-(0)-[CPane:0x7fd6c4b2fd10]>

I think <NSAutoresizingMaskLayoutConstraint:0x7fd6c3630430 h=--& v=--& V:[NSView:0x7fd6c4b22e50(0)]> causes this, but I can't reset autoresizing mask, because NSSplitView sets it.

What is best way to use auto layout inside split view? And is there any way to handle min/max size of split view subview with auto layout without NSSplitViewDelegate?

Answer 1

I found out that this error appears if I have toolbar in my window and control split view by any of this delegate methods:

splitView:constrainMinCoordinate:ofSubviewAt:   
splitView:constrainMaxCoordinate:ofSubviewAt:
splitView:shouldAdjustSizeOfSubview:

Solution was found in attaching toolbar to window in windowDidLoad.

Answer 2

NSSplitView has been a strange thing since the beginning and it would not surprise me if it'll be gone soon. After trying to get NSSplitView working with AutoLayout for a month now and sinking from one despair attack to another, I finally gave up.

My solution is to not use NSSplitView with AutoLayout at all. So either NSSplitView without Autolayout or Autolayout without NSSplitView: this isn't as complicated as it sounds: just lay out your subviews next to each other and add NSLayoutConstraints as IBOutlets. The constants of these constraints can then be set and changed from the controller in code. With that approach you can set the origin (negative offset to slide it out of the window), the width and the relations to other subviews - plus it's really easy to animate constraints with the view's animator (ever tried to animate a NSSplitView?)

The only thing missing is the mouse drag on the dividers, but this can be implemented with a couple of lines, tracking mouseEvents in your custom "SplitView".

There's an autolayout "splitview" example from Apple (unfortunately only vertical) and I've seen at least one new project on github lately. Though for me, I thought it'd be easier to start over with my custom solution for my app's specific needs, rather than trying to create something very universal (thus making it too complex to handle).

Edit: I now completed my custom splitView that loads its subviews from separate nibs. No constraint issues, no autolayout warnings. Compared to the whole month of trying to get it work with NSSplitView, I have now a working custom splitView based on constraints, easily animatable, created in only one evening. I definitely recommend taking this route!

Answer 3

For anyone who stumbles onto this in the future and is looking for a jump-start into constraint-based NSSplitView replacements, I wrote a small project here that attempts to recreate a portion of NSSplitView's features using Auto Layout:

https://github.com/jwilling/JWSplitView

It's somewhat buggy, but it could be a useful reference to anyone wanting to go this route.