[ENH] Projections: Allow transparent subset

Orange/widgets/visualize/owscatterplotgraph.py

@@ -531,7 +531,7 @@ def get_size_data(self):
 
     COLOR_NOT_SUBSET = (128, 128, 128, 0)
     COLOR_SUBSET = (128, 128, 128, 255)
-    COLOR_DEFAULT = (128, 128, 128, 0)
+    COLOR_DEFAULT = (128, 128, 128, 255)
 
     MAX_VISIBLE_LABELS = 500
 
@@ -1048,15 +1048,19 @@ def _get_same_colors(self, subset):
         """
         color = self.plot_widget.palette().color(OWPalette.Data)
         pen = [_make_pen(color, 1.5)] * self.n_shown  # use a single QPen instance
+
+        # Prepare all brushes; we use the first two or the last
+        brushes = []
+        for c in (self.COLOR_SUBSET, self.COLOR_NOT_SUBSET, self.COLOR_DEFAULT):
+            color = QColor(*c)
+            if color.alpha():
+                color.setAlpha(self.alpha_value)
+            brushes.append(QBrush(color))
+
         if subset is not None:
-            brush = np.where(
-                subset,
-                *(QBrush(QColor(*col))
-                  for col in (self.COLOR_SUBSET, self.COLOR_NOT_SUBSET)))
+            brush = np.where(subset, *brushes[:2])
         else:
-            color = QColor(*self.COLOR_DEFAULT)
-            color.setAlpha(self.alpha_value)
-            brush = [QBrush(color)] * self.n_shown  # use a single QBrush instance
+            brush = brushes[-1:] * self.n_shown  # use a single QBrush instance
         return pen, brush
 
     def _get_continuous_colors(self, c_data, subset):
@@ -1102,7 +1106,7 @@ def create_brush(col):
 
         if subset is not None:
             brush[:, 3] = 0
-            brush[subset, 3] = 255
+            brush[subset, 3] = self.alpha_value
 
         cached_brushes = {}
         brush = np.array([reuse(cached_brushes, create_brush, *col)
@@ -1133,7 +1137,7 @@ def _get_discrete_colors(self, c_data, subset):
         pens = np.array(
             [_make_pen(col.darker(self.DarkerValue), 1.5) for col in colors])
         pen = pens[c_data]
-        if subset is None and self.alpha_value < 255:
+        if self.alpha_value < 255:
             for col in colors:
                 col.setAlpha(self.alpha_value)
         brushes = np.array([QBrush(col) for col in colors])
@@ -1504,7 +1508,7 @@ def _update_colored_legend(self, legend, labels, symbols):
         for color, label, symbol in zip(colors, labels, symbols):
             color = QColor(*color)
             pen = _make_pen(color.darker(self.DarkerValue), 1.5)
-            color.setAlpha(255 if self.subset_is_shown else self.alpha_value)
+            color.setAlpha(self.alpha_value)
             brush = QBrush(color)
             legend.addItem(
                 SymbolItemSample(pen=pen, brush=brush, size=10, symbol=symbol),

Orange/widgets/visualize/tests/test_owscatterplot.py

@@ -567,6 +567,21 @@ def test_subset_data(self):
         self.send_signal(w.Inputs.data_subset, data[::30])
         self.assertEqual(len(w.subset_indices), 5)
 
+    def test_opacity_warning(self):
+        data = Table("iris")
+        w = self.widget
+        self.send_signal(w.Inputs.data, data)
+        w.graph.controls.alpha_value.setSliderPosition(10)
+        self.assertFalse(w.Warning.transparent_subset.is_shown())
+        self.send_signal(w.Inputs.data_subset, data[::30])
+        self.assertTrue(w.Warning.transparent_subset.is_shown())
+        w.graph.controls.alpha_value.setSliderPosition(200)
+        self.assertFalse(w.Warning.transparent_subset.is_shown())
+        w.graph.controls.alpha_value.setSliderPosition(10)
+        self.assertTrue(w.Warning.transparent_subset.is_shown())
+        self.send_signal(w.Inputs.data_subset, None)
+        self.assertFalse(w.Warning.transparent_subset.is_shown())
+
     def test_metas_zero_column(self):
         """
         Prevent crash when metas column is zero.

Orange/widgets/visualize/tests/test_owscatterplotbase.py

@@ -614,9 +614,9 @@ def run_tests():
             self.assertEqual(brushes[0].color().alpha(), 0)
             self.assertEqual(brushes[1].color().alpha(), 0)
             self.assertEqual(brushes[4].color().alpha(), 0)
-            self.assertEqual(brushes[5].color().alpha(), 255)
-            self.assertEqual(brushes[6].color().alpha(), 255)
-            self.assertEqual(brushes[7].color().alpha(), 255)
+            self.assertEqual(brushes[5].color().alpha(), 123)
+            self.assertEqual(brushes[6].color().alpha(), 123)
+            self.assertEqual(brushes[7].color().alpha(), 123)
 
         graph = self.graph
 

Orange/widgets/visualize/utils/widget.py

@@ -250,6 +250,7 @@ def can_draw_density(self):
 
     def colors_changed(self):
         self.graph.update_colors()
+        self._update_opacity_warning()
         self.cb_class_density.setEnabled(self.can_draw_density())
 
     # Labels
@@ -378,6 +379,8 @@ class Warning(OWProjectionWidgetBase.Warning):
             "input data")
         subset_independent = Msg(
             "No subset data instances appear in input data")
+        transparent_subset = Msg(
+            "Increase opacity if subset is difficult to see")
 
     settingsHandler = DomainContextHandler()
     selection = Setting(None, schema_only=True)
@@ -473,7 +476,6 @@ def enable_controls(self):
     @check_sql_input
     def set_subset_data(self, subset):
         self.subset_data = subset
-        self.controls.graph.alpha_value.setEnabled(subset is None)
 
     def handleNewSignals(self):
         self._handle_subset_data()
@@ -482,6 +484,7 @@ def handleNewSignals(self):
             self.setup_plot()
         else:
             self.graph.update_point_props()
+        self._update_opacity_warning()
         self.unconditional_commit()
 
     def _handle_subset_data(self):
@@ -497,6 +500,10 @@ def _handle_subset_data(self):
             elif self.subset_indices - ids:
                 self.Warning.subset_not_subset()
 
+    def _update_opacity_warning(self):
+        self.Warning.transparent_subset(
+            shown=self.subset_indices and self.graph.alpha_value < 128)
+
     def set_input_summary(self, data):
         summary = len(data) if data else self.info.NoInput
         detail = format_summary_details(data) if data else ""