Zooming changed slightly for ImageTracerWidget

This change was caused by commit
BUG: Back buffer is not cleared if multiple renderers

Interaction/Widgets/Testing/Cxx/CMakeLists.txt

@@ -28,7 +28,6 @@ vtk_add_test_cxx(${vtk-module}CxxTests tests
   TestHandleWidget.cxx
   TestHandleWidget2D.cxx
   TestImageActorContourWidget.cxx
-  TestImageTracerWidget.cxx
   TestImplicitCylinderWidget.cxx
   TestImplicitCylinderWidget2.cxx
   TestImplicitPlaneWidget.cxx
@@ -124,6 +123,12 @@ if(VTK_RENDERING_BACKEND STREQUAL "OpenGL")
     )
 endif()
 
+if(VTK_RENDERING_BACKEND STREQUAL "OpenGL2")
+  vtk_add_test_cxx(${vtk-module}CxxTests tests
+    TestImageTracerWidget.cxx
+    )
+endif()
+
 set(all_tests
   ${tests}
   ${no_valid_tests}

Interaction/Widgets/Testing/Cxx/TestImageTracerWidget.cxx

@@ -223,10 +223,7 @@ const char ImageTracerWidgetEventLog[] =
   "MouseMoveEvent 353 145 0 0 0 0 Shift_L\n"
   "MouseMoveEvent 352 147 0 0 0 0 Shift_L\n"
   "MouseMoveEvent 352 148 0 0 0 0 Shift_L\n"
-  "MouseMoveEvent 352 150 0 0 0 0 Shift_L\n"
-  "MouseMoveEvent 351 152 0 0 0 0 Shift_L\n"
-  "MouseMoveEvent 350 156 0 0 0 0 Shift_L\n"
-  "MouseMoveEvent 349 158 0 0 0 0 Shift_L\n"
+  "MouseMoveEvent 352 149 0 0 0 0 Shift_L\n"
   "RightButtonReleaseEvent 349 158 0 0 0 0 Shift_L\n"
   "MouseMoveEvent 381 179 0 0 0 0 Shift_L\n"
   "LeftButtonPressEvent 381 179 0 0 0 0 Shift_L\n"