HiDPI on external monitor (Dell u2515h) with Macbook Pro So I have Dell U2515H connected to my Macbook Pro 15" Mid 2014 (integrated graphics) and when I try to run it in 16:9 1280x720 HiDPI (I'm using switchresx) resolution it has no effect. However, when I choose any other 16:10 HiDPI resolution like 1280x800 it works just fine but obviously it cuts the screen. Does anyone know what could be the problem? It is very weird that 16:10 resolutions are OK but 16:9 just don't work, given that native monitor aspect ratio is 16:9.
I encountered the very same problem while setting HiDPI mode for my Macbook Pro with SwitchResX. As the HiDPI resolutions didn't fit, I made my own ones.

Here's how it goes:


Follow the instructions on SwitchResX's website on how to temporarily disable "System Integrity Protection"
On the SwitchResX panel for the DELL screen, go to the "Custom Resolutions" tab and create your desired resolutions under the "Scaled resolution" category.
The pixels x lines you scale to are 2 times the "feeling" you want to get, e.g. 3840 x 2160 for a Full HD (1920 x 1080) feeling.


Disabling the SIP made the 720p resolution you mentioned work for me as well.