Fix ScatterPlotItem performance regression (#1569)

* Fix ScatterPlotItem performance regression

* Add hover benchmark to ScatterPlotSpeedTest.py

* Removed a performance regression from GraphicsView

* Removed some tests failing due to the last commit

examples/ScatterPlotSpeedTest.py

@@ -27,7 +27,7 @@ param = ptree.Parameter.create(name=translate('ScatterPlot', 'Parameters'), type
     dict(name='_USE_QRECT', title='_USE_QRECT:    ', type='bool', value=pyqtgraph.graphicsItems.ScatterPlotItem._USE_QRECT),
     dict(name='pxMode', title='pxMode:    ', type='bool', value=True),
     dict(name='useCache', title='useCache:    ', type='bool', value=True),
-    dict(name='mode', title=translate('ScatterPlot', 'Mode:    '), type='list', values={'New Item': 'newItem', 'Reuse Item': 'reuseItem', 'Simulate Pan/Zoom': 'panZoom'}, value='reuseItem'),
+    dict(name='mode', title=translate('ScatterPlot', 'Mode:    '), type='list', values={translate('ScatterPlot', 'New Item'): 'newItem', translate('ScatterPlot', 'Reuse Item'): 'reuseItem', translate('ScatterPlot', 'Simulate Pan/Zoom'): 'panZoom', translate('ScatterPlot', 'Simulate Hover'): 'hover'}, value='reuseItem'),
 ])
 for c in param.children():
     c.setDefault(c.value())
@@ -42,6 +42,7 @@ splitter.show()
 
 data = {}
 item = pg.ScatterPlotItem()
+hoverBrush = pg.mkBrush('y')
 ptr = 0
 lastTime = time()
 fps = None
@@ -88,13 +89,21 @@ def getData():
 
 def update():
     global ptr, lastTime, fps
-    if param['mode'] == 'newItem':
+    mode = param['mode']
+    if mode == 'newItem':
         mkItem()
-    elif param['mode'] == 'reuseItem':
+    elif mode == 'reuseItem':
         item.setData(**getData())
-    elif param['mode'] == 'panZoom':
+    elif mode == 'panZoom':
         item.viewTransformChanged()
         item.update()
+    elif mode == 'hover':
+        pts = item.points()
+        old = pts[(ptr - 1) % len(pts)]
+        new = pts[ptr % len(pts)]
+        item.pointsAt(new.pos())
+        old.resetBrush()  # reset old's brush before setting new's to better simulate hovering
+        new.setBrush(hoverBrush)
 
     ptr += 1
     now = time()

pyqtgraph/graphicsItems/ScatterPlotItem.py

@@ -776,14 +776,21 @@ class ScatterPlotItem(GraphicsObject):
             mask = dataSet['sourceRect']['w'] == 0
             if np.any(mask):
                 invalidate = True
-                dataSet['sourceRect'][mask] = self.fragmentAtlas[
+                coords = self.fragmentAtlas[
                     list(zip(*self._style(['symbol', 'size', 'pen', 'brush'], data=dataSet, idx=mask)))
                 ]
+                dataSet['sourceRect'][mask] = coords
                 if _USE_QRECT:
-                    sr = dataSet['sourceRect'][mask]
-                    sru = np.unique(sr)
-                    list(imap(self._sourceQRect.__setitem__, imap(tuple, sru), imap(QtCore.QRectF, *zip(*sru))))
-                    dataSet['sourceQRect'][mask] = list(imap(self._sourceQRect.__getitem__, imap(tuple, sr)))
+                    rects = []
+                    for c in coords:
+                        try:
+                            rect = self._sourceQRect[c]
+                        except KeyError:
+                            rect = QtCore.QRectF(*c)
+                            self._sourceQRect[c] = rect
+                        rects.append(rect)
+
+                    dataSet['sourceQRect'][mask] = rects
                     dataSet['targetQRectValid'][mask] = False
 
             self._maybeRebuildAtlas()

pyqtgraph/widgets/GraphicsView.py

@@ -123,11 +123,6 @@ class GraphicsView(QtGui.QGraphicsView):
         self.scaleCenter = False  ## should scaling center around view center (True) or mouse click (False)
         self.clickAccepted = False
 
-        # Set a transparent background QPalette!
-        palette = self.palette()
-        palette.setColor(QtGui.QPalette.Window, QtCore.Qt.transparent)
-        self.setPalette(palette)
-
     def setAntialiasing(self, aa):
         """Enable or disable default antialiasing.
         Note that this will only affect items that do not specify their own antialiasing options."""

pyqtgraph/widgets/tests/test_graphics_view.py

@@ -9,10 +9,6 @@ def test_basics_graphics_view():
     background_role = view.backgroundRole()
     assert background_role == QtGui.QPalette.Window
 
-    palette = view.palette()
-
-    assert palette.isBrushSet(QtGui.QPalette.Active, QtGui.QPalette.Window)
-    assert palette.color(QtGui.QPalette.Window) == QtCore.Qt.transparent
     assert view.backgroundBrush().color() == QtGui.QColor(0, 0, 0, 255)
 
     assert view.focusPolicy() == QtCore.Qt.StrongFocus
@@ -37,9 +33,6 @@ def test_basics_graphics_view():
     # --------------------------------------
     view.setBackground("w")
     assert view._background == "w"
-    palette = view.palette()
-    assert palette.isBrushSet(QtGui.QPalette.Active, QtGui.QPalette.Window)
-    assert palette.color(QtGui.QPalette.Window) == QtCore.Qt.transparent
     assert view.backgroundBrush().color() == QtCore.Qt.white
 
     # Set anti aliasing