AnchorLayout

This is a layout that enables anchoring of contained widgets relative to the container's dimensions. If the container is resized, all anchored items are automatically rerendered according to their anchor rules.

By default, AnchorLayout will calculate anchor measurements based on the size of the container itself. However, if anchorSize is specifed, the layout will use it as a virtual container for the purposes of calculating anchor measurements based on it instead, allowing the container to be sized independently of the anchoring logic if necessary.

The items added to an AnchorLayout can also supply an anchoring-specific layout property (see AnchorData#setAnchorSpec) which is a string containing two values: the horizontal anchor value and the vertical anchor value (for example, '100% 50%'). This value is what tells the layout how the item should be anchored to the container. The following types of anchor values are supported:

• Percentage:
  Any value between 1 and 100, expressed as a percentage. The first anchor is the percentage width that the item should take up within the container, and the second is the percentage height. Example: '100% 50%' would render an item the complete width of the container and 1/2 its height. If only one anchor value is supplied it is assumed to be the width value and the height will default to auto.
• Offsets:
  Any positive or negative integer value. The first anchor is the offset from the right edge of the container, and the second is the offset from the bottom edge. Example: '-50 -100' would render an item the complete width of the container minus 50 pixels and the complete height minus 100 pixels. If only one anchor value is supplied it is assumed to be the right offset value and the bottom offset will default to 0.

Anchor values can also be mixed as needed. For example, '-50 75%' would render the width offset from the container right edge by 50 pixels and 75% of the container's height.

Consider the following code:

3 content panels are added to the viewport using a AnchorLayout. The 3 panels use different combinations of percent, pixel, and offset values. Here is the output of the code: