Merge pull request #17299 from anntzer/qtzoomdashes

QuLogic · web-flow · commit 78ecc3358631 · 2020-05-01T18:58:01.000-04:00
Avoid "dash motion" in qt zoom box.
diff --git a/lib/matplotlib/backends/backend_qt5.py b/lib/matplotlib/backends/backend_qt5.py
@@ -478,16 +478,23 @@ def drawRectangle(self, rect):
         # Draw the zoom rectangle to the QPainter.  _draw_rect_callback needs
         # to be called at the end of paintEvent.
         if rect is not None:
+            x0, y0, w, h = [pt / self._dpi_ratio for pt in rect]
+            x1 = x0 + w
+            y1 = y0 + h
             def _draw_rect_callback(painter):
-                scaled_rect = [pt / self._dpi_ratio for pt in rect]
                 pen = QtGui.QPen(QtCore.Qt.black, 1 / self._dpi_ratio)
                 pen.setDashPattern([3, 3])
-                painter.setPen(pen)
-                painter.drawRect(*scaled_rect)
-                pen.setDashOffset(3)
-                pen.setColor(QtCore.Qt.white)
-                painter.setPen(pen)
-                painter.drawRect(*scaled_rect)
+                for color, offset in [
+                        (QtCore.Qt.black, 0), (QtCore.Qt.white, 3)]:
+                    pen.setDashOffset(offset)
+                    pen.setColor(color)
+                    painter.setPen(pen)
+                    # Draw the lines from x0, y0 towards x1, y1 so that the
+                    # dashes don't "jump" when moving the zoom box.
+                    painter.drawLine(x0, y0, x0, y1)
+                    painter.drawLine(x0, y0, x1, y0)
+                    painter.drawLine(x0, y1, x1, y1)
+                    painter.drawLine(x1, y0, x1, y1)
         else:
             def _draw_rect_callback(painter):
                 return
