clean up

mdi.py

@@ -2,6 +2,7 @@ from PyQt5.QtCore import Qt
 from PyQt5.QtWidgets import QMdiArea, QMdiSubWindow, QAction
 from PyQt5.QtGui import QIcon, QPixmap, QPainter, QColor
 from pyqtgraph import PlotWidget
+from theme import MDI_BKG
 
 
 class MDIArea(QMdiArea):
@@ -31,17 +32,21 @@ class MDIArea(QMdiArea):
     def paintEvent(self, event):
         # draw the watermark in the MDI area
         painter = QPainter()
-        painter.begin(self.viewport())
+        vport = self.viewport()
+        painter.begin(vport)
 
-        painter.fillRect(event.rect(), QColor(150, 150, 150))
+        rect = event.rect()
+        painter.fillRect(rect, MDI_BKG)
 
-        logo = self.logo
         margin = 20
+        logo = self.logo
+        logo_width  = logo.width()
+        logo_height = logo.height()
         painter.drawPixmap(
-            self.width()-logo.width()-margin,
-            self.height()-logo.height()-margin,
-            logo.width(),
-            logo.height(),
+            self.width()  - logo_width  - margin,
+            self.height() - logo_height - margin,
+            logo_width,
+            logo_height,
             logo
         )