tools, frontends (xmlui): add setter methods for widgets + new widget InternalButton to process UI operations

src/tools/xml_tools.py

@@ -299,6 +299,16 @@ class FieldBackElement(Element):
         self.elem.setAttribute('name', name)
 
 
+class InternalFieldElement(Element):
+    """ Used by InternalButtonWidget to indicate which field are manipulated by internal action """
+    type = 'internal_field'
+
+    def __init__(self, parent, name):
+        assert(isinstance(parent, InternalButtonWidget))
+        super(InternalFieldElement, self).__init__(parent.xmlui, parent)
+        self.elem.setAttribute('name', name)
+
+
 class OptionElement(Element):
     """" Used by ListWidget to specify options """
     type = 'option'
@@ -621,6 +631,37 @@ class ButtonWidget(Widget):
             FieldBackElement(self, field)
 
 
+class InternalButtonWidget(Widget):
+    type = 'internal_button'
+
+    def __init__(self, xmlui, action='copy', value=None, fields=None, name=None, parent=None):
+        """Add an button to process internal UI operations.
+
+        The internal button is not associated to any callback id because it is
+        not using the bridge (no communication with the backend).
+
+        @param action (string): a value from:
+                                - 'copy': process the widgets given in 'fields'
+                                  two by two, by copying the values of one widget
+                                  to the other.
+                                - 'move': same than copy but moves the values
+                                          if the source widget is not a List.
+                                - more operation to be added when necessary...
+        @param value (string): label of the button
+        @param fields (list): a list of widget name (string)
+        @param name: name
+        @param parent: parent container
+        """
+        if fields is None:
+            fields = []
+        super(InternalButtonWidget, self).__init__(xmlui, name, parent)
+        self.elem.setAttribute('action', action)
+        if value:
+            self.elem.setAttribute('value', value)
+        for field in fields:
+            InternalFieldElement(self, field)
+
+
 class ListWidget(InputWidget):
     type = 'list'