watermark.ammy

TextBox {
  #Watermark(bindingPath: "Xaml", watermarkText: "Insert XAML here")
}

mixin Watermark(bindingPath, watermarkText) for TextBox {
  Style: combine Style {
    TargetType: TextBox
    Triggers: [
      DataTrigger {
        Binding: bind $bindingPath convert (string str) => string.IsNullOrEmpty(str)
        Value: true

        #Setter("Text", $watermarkText)
        #Setter("Opacity", 0.3)
      }

      DataTrigger {
        Binding: bind IsFocused from $this
        Value: true

        #Setter("Opacity", 1)
        #Setter("Text", bind Xaml)
      }

      DataTrigger {
        Binding: bind $bindingPath convert (string str) => !string.IsNullOrEmpty(str)
        Value: true 
        #Setter("Text", bind Xaml)
      }
    ]
  }
}