matplotlib
diff --git a/‎lib/matplotlib/backends/qt_editor/_formlayout.py
Copy file name to clipboardExpand all lines: lib/matplotlib/backends/qt_editor/_formlayout.py
+23-2Lines changed: 23 additions & 2 deletions b/‎lib/matplotlib/backends/qt_editor/_formlayout.py
Copy file name to clipboardExpand all lines: lib/matplotlib/backends/qt_editor/_formlayout.py
+23-2Lines changed: 23 additions & 2 deletions
@@ -209,11 +209,30 @@ def is_edit_valid(edit):
 class FormWidget(QtWidgets.QWidget):
     update_buttons = QtCore.Signal()
 
-    def __init__(self, data, comment="", parent=None):
+    def __init__(self, data, comment="", with_margin=False, parent=None):
+        """
+        Parameters
+        ----------
+        data : list of (label, value) pairs
+            The data to be edited in the form.
+        comment : str, optional
+
+        with_margin : bool, optional, default: False
+            If False, the form elements reach to the border of the widget.
+            This is the desired behavior if the FormWidget is used as a widget
+            alongside with other widgets such as a QComboBox, which also do
+            not have a margin around them.
+            However, a margin can be desired if the FormWidget is the only
+            widget within a container, e.g. a tab in a QTabWidget.
+        parent : QWidget or None
+            The parent widget.
+        """
         QtWidgets.QWidget.__init__(self, parent)
         self.data = copy.deepcopy(data)
         self.widgets = []
         self.formlayout = QtWidgets.QFormLayout(self)
+        if not with_margin:
+            self.formlayout.setContentsMargins(0, 0, 0, 0)
         if comment:
             self.formlayout.addRow(QtWidgets.QLabel(comment))
             self.formlayout.addRow(QtWidgets.QLabel(" "))
@@ -370,13 +389,15 @@ def __init__(self, datalist, comment="", parent=None):
         layout = QtWidgets.QVBoxLayout()
         self.tabwidget = QtWidgets.QTabWidget()
         layout.addWidget(self.tabwidget)
+        layout.setContentsMargins(0, 0, 0, 0)
         self.setLayout(layout)
         self.widgetlist = []
         for data, title, comment in datalist:
             if len(data[0]) == 3:
                 widget = FormComboWidget(data, comment=comment, parent=self)
             else:
-                widget = FormWidget(data, comment=comment, parent=self)
+                widget = FormWidget(data, with_margin=True, comment=comment,
+                                    parent=self)
             index = self.tabwidget.addTab(widget, title)
             self.tabwidget.setTabToolTip(index, comment)
             self.widgetlist.append(widget)