Positioning Strategies

    Position strategies determine where the content is displayed in the provided IgxOverlayService. By default, the content is positioned in the middle of the screen.

    Angular Positioning Strategies Example

    Strategies Overview

    There are five positioning strategies:

    Global

    Positions the content, based on the directions passed in through positionSettings. These are Left/Center/Right for horizontalDirection and Top/Middle/Bottom for verticalDirection. Defaults are:

    horizontalDirection verticalDirection
    HorizontalAlignment.Center VerticalAlignment.Middle

    Container

    Positions the content as GlobalPositionStrategy. Instead of position related to the screen ContainerPositionStrategy positions the content related to the provided in OverlaySettings outlet. Defaults are:

    horizontalDirection verticalDirection
    HorizontalAlignment.Center VerticalAlignment.Middle

    Connected

    Positions the element based on the start point from overlaySettings and directions passed in through positionSettings. It is possible to either pass a start point (type Point) or an HTMLElement as a positioning base. Defaults are:

    target horizontalDirection verticalDirection horizontalStartPoint verticalStartPoint
    new Point(0, 0) HorizontalAlignment.Right VerticalAlignment.Bottom HorizontalAlignment.Left VerticalAlignment.Bottom

    Auto

    Positions the element the same way as the Connected positioning strategy. It also calculates a different starting point in case the element goes partially out of the viewport. The Auto strategy will initially try to show the element like the Connected strategy does. If the element goes out of the viewport Auto will flip the starting point and the direction, i.e. if the direction is 'bottom', it will switch it to 'top' and so on. After flipped, if the element is still out of the viewport, Auto will use the initial directions and the starting point, to push the element into the viewport. For example - if the element goes out of the right side of the viewport, by 50px, Auto will push it by 50px to the left. Afterwards, if the element is partially out of the viewport, then its height or width were greater than the viewport's, Auto will align the element's left/top edge with the viewport's left/top edge. Defaults are:

    target horizontalDirection verticalDirection horizontalStartPoint verticalStartPoint
    new Point(0, 0) HorizontalAlignment.Right VerticalAlignment.Bottom HorizontalAlignment.Left VerticalAlignment.Bottom

    Elastic

    Positions the element like the Connected positioning strategy and re-sizes the element to fit inside the view port (re-calculating width and/or height) in case the element is partially out of view. minSize can be passed in positionSettings to prevent resizing if it would put the element's dimensions below a certain threshold. Defaults are:

    target horizontalDirection verticalDirection horizontalStartPoint verticalStartPoint minSize
    new Point(0, 0) HorizontalAlignment.Right VerticalAlignment.Bottom HorizontalAlignment.Left VerticalAlignment.Bottom
    Note

    It won't try to resize the element if the strategy is using HorizontalDirection = Center / VerticalDirection = Middle.

    Note

    The overlay element will be resized, but the positioning strategy does not handle overflow. For example, if the element needs to have overflow-y when resized, incorporate the appropriate style to provide that.

    Usage

    Position strategies allow you to display content in the overlay in various combinations. To start using different position strategies, you should first include the necessary dependencies for each strategy used like this:

    import {
        AutoPositionStrategy,
        ConnectedPositioningStrategy,
        ContainerPositionStrategy,
        ElasticPositionStrategy,
        GlobalPositionStrategy
    } from 'igniteui-angular';
    

    Then specify the positioning strategy to be used by the overlay. The position strategy is passed in as a property in the overlaySettings parameter when the overlay.attach() method is called. In the example below we are changing the default GlobalPositionStrategy with ConnectedPositionStrategy:

    // Initialize and use overlay settings
    const overlaySettings: OverlaySettings = {
        // Set the target where content should be shown
        target: this.buttonElement.nativeElement,
        // Pass in the positioning strategy
        positionStrategy: new ConnectedPositioningStrategy()
    };
    const overlayId = overlay.attach(dummyElement, overlaySettings); 
    

    Positioning Settings

    Each positioning strategy has its own positioning settings. These settings determine how the content will be shown. In the example below, we are creating a new PositionSettings object. Using it we force the overlay to show the content starting from the top right point of the provided target - the buttonElement. The direction in which the content is shown is set to top-left. Then we create a new ConnectedPositionStrategy and pass it the positionSettings.

    const positionSettings: PositionSettings = {
        horizontalStartPoint: HorizontalAlignment.Right,
        verticalStartPoint: VerticalAlignment.Top,
        horizontalDirection: HorizontalAlignment.Left,
        verticalDirection: VerticalAlignment.Top
    };
    
    const strategy = new ConnectedPositioningStrategy(positionSettings);
    
    // Initialize and use overlay settings
    const overlaySettings: OverlaySettings = {
        target: buttonElement.nativeElement,
        // Pass in the positioning strategy
        positionStrategy: strategy
    };
    this._overlayId = this.overlayService.attach(MyDynamicCardComponent, overlaySettings);
    

    Changing Strategies

    You can also change the positioning strategy, used by the overlay, by overriding the positionStrategy property of the overlaySettings object that is passed to the overlay:

    const myPositionStrategy = new AutoPositionStrategy();
    overlay.attach(element, { positionStrategy: myPositionStrategy }); 
    

    Changing Settings

    To change the position settings of an already existing strategy, override any of the settings in it. If a strategy was already attached you should detach the previously generated ID:

    // overlaySettings is an existing object of type OverlaySettings
    // overlaySettings.positionStrategy is an existing PositionStrategy with settings of type PositionSettings
    Object.assign(overlaySettings.positionStrategy.settings, {
        horizontalStartPoint: HorizontalAlignment.Left,
        horizontalDirection: HorizontalAlignment.Left
    });
    overlaySettings.target = dummyHTMLElement;
    // the element will now start to the left of the target (dummyHTMLElement)
    // and will align itself to the left
    const overlayId = overlay.attach(overlayId, overlaySettings);
    overlay.show(overlayId);
    

    Offsetting Content

    To offset the content along the corresponding axis by a provided amount:

    // deltaX and deltaY determine by how much the content will be offset compared to its' previous position
    const deltaX: number = 30;
    const deltaY: number = 15;
    overlay.setOffset(this._overlayId, deltaX, deltaY);
    

    API References

    Additional Resources