MondrianLayout - Structured layout for AutoLayout

??‍♂️?
We guess we still don't cover the all of use-cases.
Please feel free to ask what you've faced case in Issues!

Describing the layout ergonomically in the code

Structured Layout API (DSL)

view.mondrian.buildSubviews {
  VStackBlock {
  
    titleLabel
    
    HStackBlock {
      cancelButton
      sendButton
    }      
  }
  .padding(24)
}

To keep flexibility of AutoLayout, we have classical style API

Classical Layout API

sendButton.mondrian.layout
  .width(120)
  .top(.toSuperview)
  .trailing(.toSuperview)
  .leading(.to(cancelButton).trailing)
  .activate()
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This image laid out by MondrianLayout

Layout code 

HStackBlock(spacing: 2, alignment: .fill) {
  VStackBlock(spacing: 2, alignment: .fill) {
    UIView.mock(
      backgroundColor: .mondrianRed,
      preferredSize: .init(width: 28, height: 28)
    )

    UIView.mock(
      backgroundColor: .layeringColor,
      preferredSize: .init(width: 28, height: 50)
    )

    UIView.mock(
      backgroundColor: .mondrianYellow,
      preferredSize: .init(width: 28, height: 28)
    )

    UIView.mock(
      backgroundColor: .layeringColor,
      preferredSize: .init(width: 28, height: 28)
    )

    HStackBlock(alignment: .fill) {
      UIView.mock(
        backgroundColor: .layeringColor,
        preferredSize: .init(width: 28, height: 28)
      )
      UIView.mock(
        backgroundColor: .layeringColor,
        preferredSize: .init(width: 28, height: 28)
      )
    }
  }

  VStackBlock(spacing: 2, alignment: .fill) {
    HStackBlock(spacing: 2, alignment: .fill) {
      UIView.mock(
        backgroundColor: .layeringColor,
        preferredSize: .init(width: 28, height: 28)
      )
      VStackBlock(spacing: 2, alignment: .fill) {
        HStackBlock(spacing: 2, alignment: .fill) {
          UIView.mock(
            backgroundColor: .mondrianYellow,
            preferredSize: .init(width: 28, height: 28)
          )
          UIView.mock(
            backgroundColor: .layeringColor,
            preferredSize: .init(width: 28, height: 28)
          )
        }
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
      }
    }

    HStackBlock(spacing: 2, alignment: .fill) {
      VStackBlock(spacing: 2, alignment: .fill) {
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
        UIView.mock(
          backgroundColor: .mondrianBlue,
          preferredSize: .init(width: 28, height: 28)
        )
      }

      UIView.mock(
        backgroundColor: .layeringColor,
        preferredSize: .init(width: 28, height: 28)
      )

      VStackBlock(spacing: 2, alignment: .fill) {
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
      }
    }

    HStackBlock(spacing: 2, alignment: .fill) {
      UIView.mock(
        backgroundColor: .mondrianRed,
        preferredSize: .init(width: 28, height: 28)
      )
      VStackBlock(spacing: 2, alignment: .fill) {
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
        UIView.mock(
          backgroundColor: .layeringColor,
          preferredSize: .init(width: 28, height: 28)
        )
      }
    }

  }

}
.overlay(
  UILabel.mockMultiline(text: "Mondrian Layout", textColor: .white)
    .viewBlock
    .padding(4)
    .background(
      UIView.mock(
        backgroundColor: .layeringColor
      )
      .viewBlock
    )
    .relative(bottom: 8, right: 8)
)

Structured layout API and Classical layout API

  • ? Ergonomically Enables us to describe layout by DSL (like SwiftUI's layout).
  • ? Automatic adding subviews according to layout representation.
  • ? Supports integeration with system AutoLayout API.
  • ? Provides classical layout API that describing constraints each view.

Introduction

A DSL based layout builder with AutoLayout

AutoLayout is super powerful to describe the layout and how it changes according to the bounding box.
What if we get a more ergonomic interface to declare the constraints.

Structured layout API
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Unstructured layout API (classic style)

classic@2x

Future direction

  • Optimize the code - still verbose implementation because we're not sure if the API can be stable.
  • Brushing up the DSL - to be stable in describing.
  • Adding more modifiers for fine tuning in layout.
  • Tuning up the stack block's behavior.
  • Adding a way to setting constraints independently besides DSL
    • AutoLayout is definitely powerful to describe the layout. We might need to set the constraints additionally since DSL can't describe every pattern of the layout.

Demo app

You can see many layout examples from the demo application.

https://user-images.githubusercontent.com/1888355/122651186-142e7d00-d172-11eb-8bde-f4432d0a0ac9.mp4

Overview

MondrianLayout enables us to describe layouts of subviews by DSL (powered by resultBuilders)
It's like describing in SwiftUI, but this behavior differs a bit since laying out by AutoLayout system.

To describe layout, use buildSubviews as entrypoint.
This method creates a set of NSLayoutConstraint, UILayoutGuide, and modifiers of UIView.
Finally, those apply. You don't need to call addSubview. that goes automatically according to hierarchy from layout descriptions.

class MyView: UIView {

  let nameLabel: UILabel
  let detailLabel: UILabel

  init() {
    super.init(frame: .zero)
    
    // Seting up constraints constraints, layoutGuides and adding subviews
    mondrian.buildSubviews {
      VStackBlock {
        nameLabel
        detailLabel
      }
    }
    
    // Seting up constraints for the view itself.
    mondrian.buildSelfSizing {
      $0.width(200).maxHeight(...)... // can be method cain.
    }
    
  }
}

Examples

Sample code assumes run in UIView. (self is UIView)
You can replace it with UIViewController.view.

Layout subviews inside safe-area

Attaching to top and bottom safe-area.

self.mondrian.buildSubviews {
  LayoutContainer(attachedSafeAreaEdges: .vertical) {
    VStackBlock {
      ...
    }
  }
}

Put a view snapping to edge

self.mondrian.buildSubviews {
  ZStackBlock {
    backgroundView.viewBlock.relative(0)    
  }
}

synonyms:

ZStackBlock(alignment: .attach(.all)) {
  backgroundView
}

ZStackBlock {
  backgroundView.viewBlock.alignSelf(.attach(.all))
}

Add constraints to view itself

self.mondrian.buildSelfSizing {
  $0.width(...)
    .height(...)          
}

Stacking views on Z axis

relative(0) fills to the edges of ZStackBlock.

self.mondrian.buildSubviews {
  ZStackBlock {
    profileImageView.viewBlock.relative(0)
    textOverlayView.viewBlock.relative(0)
  }
}

Centering a label with minimum padding

ZStackBlock {
  myLabel
    .relative(.all, .min(20))
}

ZStackBlock {
  ZStackBlock {
    myLabel
  }
  .padding(20) /// a minimum padding for the label in the container
}

Detail

Vertically and Horizontally Stack layout

VStackBlock

Alignment

center(default) leading trailing fill
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HStackBlock

center(default) top bottom fill
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self.mondrian.buildSubviews {
  VStackBlock(spacing: 4, alignment: alignment) {
    UILabel.mockMultiline(text: "Hello", textColor: .white)
      .viewBlock
      .padding(8)
      .background(UIView.mock(backgroundColor: .mondrianYellow))
    UILabel.mockMultiline(text: "Mondrian", textColor: .white)
      .viewBlock
      .padding(8)
      .background(UIView.mock(backgroundColor: .mondrianRed))
    UILabel.mockMultiline(text: "Layout!", textColor: .white)
      .viewBlock
      .padding(8)
      .background(UIView.mock(backgroundColor: .mondrianBlue))
  }
}

Background modifier

label
  .viewBlock // To enable view describes layout
  .padding(8)
  .background(backgroundView)
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Overlay modifier

label
  .viewBlock // To enable view describes layout
  .padding(8)
  .overlay(overlayView)

Relative modifier

.relative modifier describes that the content attaches to specified edges with padding.
Not specified edges do not have constraints to the edge. so the sizing depends on intrinsic content size.

You might use this modifier to pin to edge as an overlay content.

ZStackBlock {
  VStackBlock {
    ...
  }
  .relative(bottom: 8, right: 8)
}

Padding modifier

.padding modifier is similar with .relative but something different.
Different with that, Not specified edges pin to edge with 0 padding.

ZStackBlock {
  VStackBlock {
    ...
  }
  .padding(.horizontal, 10) // other edges work with 0 padding.
}

ZStackBlock
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Stacking views in Z axis (aligns in center)

ZStackBlock {
  view1
  view2
  view3
}

Expands to specified edges each view

ZStackBlock(alignment: .attach(.all)) {
  view1
  view2
  view3
}

Specifying alignment each view

ZStackBlock {

  view1.viewBlock.alignSelf(.attach(.all))

  view2.viewBlock.alignSelf(.attach([.top, .bottom]))
  
  view3.viewBlock.alignSelf(.attach(.top))
}

Animations

// TODO:
https://github.com/muukii/MondrianLayout/issues/19

Classic Layout API

Structured layout API(DSL) does not cover the all of use-cases.
Sometimes we still need a way to describe constraints for a complicated layout.

MondrianLayout provides it as well other AutoLayout libraries.

Activate constraints independently

view.mondrian.layout
  .width(10)
  .top(.toSuperview)
  .right(.toSuperview)
  .leading(.toSuperview)
  .activate() // activate constraints and returns `ConstraintGroup`

Batch layout**

// returns `ConstraintGroup`
mondrianBatchLayout {

  box1.mondrian.layout
    .top(.toSuperview)
    .left(.toSuperview)
    .right(.to(box2).left)
    .bottom(.toSuperview)

  box2.mondrian.layout
    .top(.toSuperview.top, .exact(10))
    .right(.toSuperview)
    .bottom(.toSuperview)
}

Examples

Attach in horizontally

view.layout.horizontal(.toSuperview, .exact(10))

Attach in vertically

view.layout.vertical(.toSuperview, .exact(10))

Edge attaches to other edge

view.layout.edge(.toSuperview)

view.layout.edge(.to(myLayoutGuide))

Installation

CocoaPods

pod "MondrianLayout"

SwiftPM

dependencies: [
    .package(url: "https://github.com/muukii/MondrianLayout.git", exact: "<VERSION>")
]

LICENSE

MondrianLayout is released under the MIT license.

GitHub

https://github.com/muukii/MondrianLayout