core, frontends (xmlui): new LabelContainer:

LabelContainer is like a PairContainer where first widget can only be LabelWidget or EmptyWidget. This case is the most common, and allow to generate better code when label can be associated to widget (e.g. in HTML).

src/tools/xml_tools.py

@@ -111,7 +111,7 @@ def dataForm2Widgets(form_ui, form, read_only=False):
     if form.instructions:
         form_ui.addText('\n'.join(form.instructions), 'instructions')
 
-    form_ui.changeContainer("pairs")
+    form_ui.changeContainer("label")
 
     for field in form.fieldList:
         widget_type, widget_args, widget_kwargs = _dataFormField2XMLUIData(field, read_only)
@@ -303,7 +303,7 @@ def paramsXML2XMLUI(xml):
         label = category.getAttribute('label')
         if not category_name:
             raise exceptions.DataError(_('INTERNAL ERROR: params categories must have a name'))
-        tabs_cont.addTab(category_name, label=label, container=PairsContainer)
+        tabs_cont.addTab(category_name, label=label, container=LabelContainer)
         for param in category.getElementsByTagName("param"):
             widget_kwargs = {}
 
@@ -596,6 +596,10 @@ class PairsContainer(Container):
     type = "pairs"
 
 
+class LabelContainer(Container):
+    type = "label"
+
+
 class TabsContainer(Container):
     type = "tabs"
 
@@ -1042,6 +1046,8 @@ class XMLUI(object):
             - horizontal: elements are disposed left to right
             - pairs: elements come on two aligned columns
               (usually one for a label, the next for the element)
+            - label: associations of one LabelWidget or EmptyWidget with an other widget
+                similar to pairs but specialized in LabelWidget, and not necessarily arranged in 2 columns
             - tabs: elemens are in categories with tabs (notebook)
         @param dialog_opt: only used if panel_type == C.XMLUI_DIALOG. Dictionnary (string/string) where key can be:
             - C.XMLUI_DATA_TYPE: type of dialog, value can be: