16x9 HIDPI doesn't work on my external monitor

[davidbatbold]

I have a 13.3inch, 16x9, 3k (3200x1800) external monitor, and the HIDPI mode for 16x9 resolutions such as 1920x1080, 1600x900 does not do anything. However, HIDPI 16x10 resolutions do work (1440x900, 1900x1200) but it results in black bars on the sides of the monitor. What should I do to fix this issue?

[jnooree]

What is your macOS version? If it is above Catalina (10.15), you might need to install the HEAD version. Also, if you have downloaded the latest release, you must specify the twice of the resolution of your interest. That is, 3840 * 2160 with the HiDPI box checked, for the first one (1920 * 1080).

[davidbatbold]

I am using Catalina. What is the HEAD version?
Also, I tried adding a 3840 * 2160 and 3200 * 1800 with the HiPDI. box checked after turning off SIP, but the lightning bolt is not next to the resolutions. And it doesn't turn on HiDPI mode when I choose the resolutions

[jnooree]

The HEAD version is the current commit of this repository. Please see README.md file for the installation guide.
By the way, if you do not want to build the app on your own,

1. Add the 3840 * 2160 and 3200 * 1800 resolutions, and
2. use the half of them on the app, 1920 * 1080 and 1600 * 900 resolutions, with the lightning marks. The larger ones are just fake resolutions, so normally you wouldn't have to use them.

[davidbatbold]

I installed the head version and tried it, but it still does not work.

[juansaavedrauy]

I went on a bit of a hunt for this issue, but I think I found a solution at the moment. Bit of a patch, but it is a good solution at the moment. I have a 2560x1440 capable monitor, which I could not make it work with 1280x720 HiDPI.

From the author of SwitchResX, this is caused by an Apple bug wich cannot be resolved.

In some cases, you will see a resolution that is half the size of the native resolution of the screen. Selecting it will not work.
If you look in the Console (/Applications/Console), you'll observe a message like this one:

11/11/14 10:35:56,465 WindowServer[123]: CGXCompleteDisplayConfiguration: Monitor 4304241; Mode -1569958512 not available
11/11/14 10:35:56,465 SwitchResX Control[174]: CGSCompleteDisplayConfigurationWithOption

This is a bug within macOS itself. macOS reports this resolution as available when building the resolution list, but doesn't let you select it. There's nothing to do at this point, and SwitchResX cannot avoid showing this resolution in its list.

But I found a blog post with a trick to work around this issue. Just take 1 pixel out of the resolution.

In my case I've defined a 1280x719 HiDPI resolution that works like a charm.

Hope this helps!

[davidbatbold]

Reducing one pixel worked wonderfully! Thanks @elpaquete

[cuong-dang]

This one pixel trick doesn't work for me. The same console message still appears and nothing happens.

[masontin]

It's worked for me and 1280x721 also worked as well, thank you @elpaquete

[masontin]

@davidbatbold @elpaquete Good News everybody!

I just add 3840x2160 with not any checkbox selected, after reboot, I can select 1280x720 in Display Preferences.
(If not worked, you can try select 3840x2160 first, then switch 1280x720.)

This is my configurations

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>DisplayProductName</key>
	<string>LED</string>
	<key>scale-resolutions</key>
	<array>
		<data>
		AAAPAAAACHA=
		</data>
		<data>
		AAAKAAAABaA=
		</data>
		<data>
		AAAKAAAABZ4=
		</data>
		<data>
		AAAJ/gAABaA=
		</data>
		<data>
		AAAJ/gAABZ4=
		</data>
		<data>
		AAAKAAAABaAAAAAJACAAAA==
		</data>
		<data>
		AAAKAAAABZ4AAAAJACAAAA==
		</data>
		<data>
		AAAJ/gAABaAAAAAJACAAAA==
		</data>
		<data>
		AAAJ/gAABZ4AAAAJACAAAA==
		</data>
	</array>
	<key>target-default-ppmm</key>
	<real>10.01</real>
</dict>
</plist>

My System Report also changed

---

macOS Big Sur 11.5

[uhthomas]

Thank you so much for this. The offset by one trick (1280x719 or 1280x721) worked perfectly.

I found that 2560x1080 HiDPI was more appropriate for my 3440x1440 display though, which did not require the aforementioned trick.

Again, cannot thank everyone involved in this project enough. This is millions of times better than "BetterDummy" or other hacks. Although I imagine they may not be much choice on M1...