# Layout Constraints

Layout constraints refer to constraints on the aspect ratio and display priority of components.

>  **NOTE**
>
>  The APIs of this module are supported since API version 7. Updates will be marked with a superscript to indicate their earliest API version.


## Attributes

| Name             | Type  | Description                                      |
| --------------- | ------ | ---------------------------------------- |
| aspectRatio     | number | Aspect ratio of the component.                             |
| displayPriority | number | Display priority for the component in the layout container. When the space of the parent container is insufficient, the component with a lower priority is hidden.<br>**NOTE**<br>This attribute is valid only for the **\<Row>**, **\<Column>**, and **\<Flex>** (single-row) container components.|


## Example

```ts
// xxx.ets
@Entry
@Component
struct AspectRatioExample {
  private children : string[] = ['1', '2', '3', '4', '5', '6']

  build() {
    Column({space: 20}) {
      Text('using container: row').fontSize(14).fontColor(0xCCCCCC).width('100%')
      Row({space: 10}) {
        ForEach(this.children, (item) => {
          Text(item)
            .backgroundColor(0xbbb2cb)
            .fontSize(20)
            .aspectRatio(1.5)
            .height(60)
          Text(item)
            .backgroundColor(0xbbb2cb)
            .fontSize(20)
            .aspectRatio(1.5)
            .width(60)
        }, item=>item)
      }
      .size({width: "100%", height: 100})
      .backgroundColor(0xd2cab3)
      .clip(true)

      Text('using container: grid').fontSize(14).fontColor(0xCCCCCC).width('100%')
      Grid() {
        ForEach(this.children, (item) => {
          GridItem() {
            Text(item)
              .backgroundColor(0xbbb2cb)
              .fontSize(40)
              .aspectRatio(1.5)
          }
        }, item=>item)
      }
      .columnsTemplate('1fr 1fr 1fr')
      .columnsGap(10)
      .rowsGap(10)
      .size({width: "100%", height: 165})
      .backgroundColor(0xd2cab3)
    }.padding(10)
  }
}
```

**Figure 1** Portrait display
![en-us_image_0000001256978379](figures/en-us_image_0000001256978379.gif)

**Figure 2** Landscape display
![en-us_image_0000001212218476](figures/en-us_image_0000001212218476.gif)

```ts
class ContainerInfo {
  label : string = ''
  size : string = ''
}

class ChildInfo {
  text : string = ''
  priority : number = 0
}

@Entry
@Component
struct DisplayPriorityExample {
  private container : ContainerInfo[] = [
    {label: 'Big container', size: '90%'},
    {label: 'Middle container', size: '50%'},
    {label: 'Small container', size: '30%'}
  ]
  private children : ChildInfo[] = [
    {text: '1\n(priority:2)', priority: 2},
    {text: '2\n(priority:1)', priority: 1},
    {text: '3\n(priority:3)', priority: 3},
    {text: '4\n(priority:1)', priority: 1},
    {text: '5\n(priority:2)', priority: 2}
  ]
  @State currentIndex : number = 0

  build() {
    Column({space: 10}) {
      Button(this.container[this.currentIndex].label).backgroundColor(0x317aff)
        .onClick((event: ClickEvent) => {
          this.currentIndex = (this.currentIndex + 1) % this.container.length
        })
      Flex({justifyContent: FlexAlign.SpaceBetween}) {
        ForEach(this.children, (item)=>{
          Text(item.text)
            .width(120)
            .height(60)
            .fontSize(24)
            .textAlign(TextAlign.Center)
            .backgroundColor(0xbbb2cb)
            .displayPriority(item.priority)
        }, item=>item.text)
      }
      .width(this.container[this.currentIndex].size)
      .backgroundColor(0xd2cab3)
    }.width("100%").margin({top:50})
  }
}

```

![en-us_image_0000001212058504](figures/en-us_image_0000001212058504.gif)