There are three ways to run Royal TS on high DPI displays: DPI Unaware, System Aware, and Per Monitor Aware.
To change the behavior, go to View -> Options -> User Interface -> General:
DPI Unaware:
Royal TS will render the user interface for 96 DPI. The user interface will be stretched and blurry on high DPI screens. Use this mode for best compatibility.
System Aware:
Royal TS will render the user interface according to the DPI settings of the primary screen.
Per Monitor Aware (Experimental):
Royal TS will adapt the user interface rendering depending on the screen that displays the user interface.
Checking/unchecking this option doesn't seem to make a difference:
In case the above setting does not have an effect, verify that the Compatibility setting of the RoyalTS.exe file (located in the installation directory, by default in %ProgramFiles%\Royal TS V7):
Make sure that the "DPI Unaware" is also configured.
Systems with multiple displays and mixed DPI settings
On newer Windows 10 versions you may need to click the "Change high DPI settings", check the option "Override high DPI scaling behavior." and set "Scaling performed by" to "System" or "System (Enhanced)":
Known Issues and Limitations with Remote Desktop
While Royal TS is now truly DPI aware, there are still some scenarios where you want to go back and uncheck the option above. Most issues with high DPI aware applications are related to the Remote Desktop Protocol (RDP connections). Microsoft introduced dynamic resolution update and scaling level update in RDP 8.1: http://blogs.msdn.com/b/rds/archive/2013/12/16/resolution-and-scaling-level-updates-in-rdp-8-1.aspx
So on the client side (where Royal TS is running) you need to have RDP 8.1 or later installed. If you are running Windows 8.1, Windows 10 or later, you don't have to worry about that. If you are running Windows 7 (SP1) you need to update RDP on your system. Check out this article .
On the server side (where you connect to using Royal TS) you need to have Windows Server 2012R2 or later. Connecting to older Windows versions will not allow you to scale your remote session and adapt to your DPI settings. So depending on your DPI scaling level (>150% or 200%), your remote session content will be tiny and not very readable.
So, if you connect to Windows Server 2012 or older versions of Windows Server, do not enable high DPI mode and keep "DPI Unaware" configured!
Also notice the Zoom In and Zoom Out button in the Actions tab. Those buttons can be used to manually change the scaling in the remote session when you are running the supported client and connect to the supported server versions mentioned above.
Troubleshooting
We've heard from users that in some scenarios display scaling may get messed up. We weren't able to reproduce the issues on our test systems but it seems that in some scenarios the display scaling will be "stuck" in high DPI setting. For example, someone connects to a remote session with dynamic scaling level and set the remote session to 200%. Now another user connects to the very same session (same server, same user) but with a client which does not support dynamic scaling level. In this case, the scaling may stick and the other user (connecting from a normal DPI machine) needs to log off and log on again to get proper scaling.
Also, if you are running your client system on a multi-screen setup where screens have different DPI settings, do not run Royal TS as DPI aware application. Royal TS V7 is based on Windows Forms and there's unfortunately no support for mixed DPI settings.