I have found how to set a button icon then the button is initialized.
unibutton -> ClientEvents -> UniEvents -> beforeInit
function beforeInit(sender, config)
{
config.icon='files/images/test.svg'
}
but, how to change it ?
With my poor JS knoledge i have tryed as follow:
thebut-> ClientEvents -> UniEvents -> afterCreate
function afterCreate(sender)
{
sender.changeicon = function() {
sender.icon='