Add generator argument to set_register_stylesheet

qutebrowser/config/style.py

@@ -46,7 +46,7 @@ def get_stylesheet(template_str):
                            config=objreg.get('config'))
 
 
-def set_register_stylesheet(obj):
+def set_register_stylesheet(obj, *, generator=None):
     """Set the stylesheet for an object based on it's STYLESHEET attribute.
 
     Also, register an update when the config is changed.
@@ -54,19 +54,23 @@ def set_register_stylesheet(obj):
     Args:
         obj: The object to set the stylesheet for and register.
              Must have a STYLESHEET attribute.
+        generator: If set, call the given function to dynamically generate a
+                   stylesheet instead.
     """
-    qss = get_stylesheet(obj.STYLESHEET)
+    stylesheet = generator() if generator is not None else obj.STYLESHEET
+    qss = get_stylesheet(stylesheet)
     log.config.vdebug("stylesheet for {}: {}".format(
         obj.__class__.__name__, qss))
     obj.setStyleSheet(qss)
     objreg.get('config').changed.connect(
-        functools.partial(update_stylesheet, obj))
+        functools.partial(_update_stylesheet, obj, generator=generator))
 
 
-def update_stylesheet(obj):
+def _update_stylesheet(obj, *, generator):
     """Update the stylesheet for obj."""
     if not sip.isdeleted(obj):
-        obj.setStyleSheet(get_stylesheet(obj.STYLESHEET))
+        stylesheet = generator() if generator is not None else obj.STYLESHEET
+        obj.setStyleSheet(get_stylesheet(stylesheet))
 
 
 class ColorDict(collections.UserDict):

tests/unit/config/test_style.py

@@ -59,6 +59,24 @@ class Obj(QObject):
         self.rendered_stylesheet = stylesheet
 
 
+class GeneratedObj(QObject):
+
+    def __init__(self, parent=None):
+        super().__init__(parent)
+        self.rendered_stylesheet = None
+        self._generated = False
+
+    def setStyleSheet(self, stylesheet):
+        self.rendered_stylesheet = stylesheet
+
+    def generate(self):
+        if not self._generated:
+            self._generated = True
+            return 'one'
+        else:
+            return 'two'
+
+
 @pytest.mark.parametrize('delete', [True, False])
 def test_set_register_stylesheet(delete, qtbot, config_stub, caplog):
     config_stub.data = {'fonts': {'foo': 'bar'}, 'colors': {}}
@@ -87,6 +105,15 @@ def test_set_register_stylesheet(delete, qtbot, config_stub, caplog):
     assert obj.rendered_stylesheet == expected
 
 
+def test_set_register_stylesheet_generator(qtbot, config_stub):
+    config_stub.data = {'fonts': {}, 'colors': {}}
+    obj = GeneratedObj()
+    style.set_register_stylesheet(obj, generator=obj.generate)
+    assert obj.rendered_stylesheet == 'one'
+    config_stub.changed.emit('foo', 'bar')
+    assert obj.rendered_stylesheet == 'two'
+
+
 class TestColorDict:
 
     @pytest.mark.parametrize('key, expected', [