steps to reproduce

run the attached example, and observe the initial and dynamic updates

actual result

using checked="false" initially or calling setChecked(false) during the initial rendering causes the checkbox to be checked
calling setChecked(true/false) dynamically works

calling setChecked twice causes multiple response commands sent to the client, causing unnecessary network traffic

using the html conform values such as checked="checked" or not setting the the property at all (calling setDynamicProperty("checked", null/"checked")) works when initially rendering the component, however dynamic changes always result in an unchecked checkbox

expected result

consistent behavior, either true/false or "checked"/null.
This inconsistency requires additional customization when integrating the input element with ZKBind.

To avoid duplicate setAttr commands a mechanism like smartUpdate should be considered

Workaround

a custom component class to get things working from the server side:

@ComponentAnnotation("checked:@ZKBIND(ACCESS=both, SAVE_EVENT=onCheck)")
public class CheckableInput extends Input {
	private static final long serialVersionUID = 1L;
	
	@Override
	public boolean isChecked() {
		return getDynamicProperty("checked") != null;
	}
	
	@Override
	public void setChecked(boolean checked) {
		setDynamicProperty("checked", checked ? true : null);
	}
}

this results in the DOM attribute checked="true" being rendered.
However this should rather be checked="" or checked="checked"
(refer to https://www.w3.org/TR/html-markup/input.checkbox.html#input.checkbox.attrs.checked)