add tooltip and doc for background subtracion modes

xsocs/gui/process/FitWidget.py

@@ -189,6 +189,11 @@ class FitWidget(Qt.QWidget):
         layout.addRow('File:', self.__fileEdit)
 
         self.__bgComboBox = Qt.QComboBox()
+        self.__bgComboBox.setToolTip(
+            "Select background subtraction mode:<br><br>"
+            "<b>-</b>: No background<br>"
+            "<b>Constant</b>: Shift data so that min is 0<br>"
+            "<b>Linear</b>: Linear background from first to last data")
         self.__bgComboBox.addItem('-', BackgroundTypes.NONE)
         self.__bgComboBox.addItem('Constant', BackgroundTypes.CONSTANT)
         self.__bgComboBox.addItem('Linear', BackgroundTypes.LINEAR)

xsocs/process/fit/peak_fit.py

@@ -50,6 +50,12 @@ disp_times = False
 
 
 class BackgroundTypes(object):
+    """Enum of background subtraction types:
+
+    - NONE: No background
+    - CONSTANT: Remove constant (= min of the data) background
+    - LINEAR: Remove linear background using line from first to last data
+    """
     ALLOWED = range(3)
     NONE, CONSTANT, LINEAR = ALLOWED