System:

• OSX 10.11
• ROS Kinetic
• QT 5.7.1 (homebrew)
• Ogre 1.9.0 (homebrew osrf/simulation tap)
• RVIZ 1.12.4

After launching Rviz, the render window seems to only draw for the lower-left 1/4 of it's total space:

I've traced this problem back to be related to Qt5's "support" for retina displays (where the rendering units are scaled).

Realizing that this problem was recently addressed by the Ogre development team, I tried the same fix locally (since I am using Ogre 1.9):

In ogre_helpers/render_system.cpp

  params["macAPI"] = "cocoa";
  params["macAPICocoaUseNSView"] = "true";
  // Adding this param for retina display scaling
  params["contentScalingFactor"] = "2.0";

Obviously, this fix requires a number of checks (for presence of Qt5 + Ogre 1.9 and check for retina display) before a merge request can be considered but I wanted to report here in case others are hitting the same issue.