Not Displaying Full Screen

[mlara51]

I have a Dell S2721HGF monitor that is being connected through a HyperDrive USB-C hub (HDMI at 4k@60Hz) to my MacBook Air M1. When I create a new Dummy at 16:9, it is not showing the mirror to the edge of the screen like normal. No matter what resolution I choose, it does not extend out to the edge of the screen. Is there a step I'm missing?

[waydabber]

Hi there,

• do you experience the same issue if you directly connect the display?
• is the aspect ratio wrong (image stretched on the display)?
• can you provide a photo and screenshots of relevant System Report sections and Displays?

Thanks.

[mlara51]

• do you experience the same issue if you directly connect the display?
  Yes - I connected USB-C to HDMI to my monitor and it still wasn't displaying to the edge of the screen properly.
• is the aspect ratio wrong (image stretched on the display)?
  No it is correctly doing 16:9. I've tried different resolutions and aspect ratios and none fill the screen.
• can you provide a photo and screenshots of relevant System Report sections and Displays?
  See attached:

[waydabber]

Does the display have a DisplayPort input? If so, it would be better to try USB-C (DisplayPort Alt mode) -> DisplayPort. The black bars might be an issue with how macOS detects the display - it either does not recognize the base resolution properly or in this case it might consider the display a HDMI TV set and applies underscan.

(also it would be better to use 60Hz as refresh rate for the display as BetterDummy is using 60Hz anyway).

You can try mirroring your internal display to the display and see if you experience a similar problem (without BetterDummy) for a try.

[mlara51]

Ah! That was it! Dummy does not like 144Hz. Once I switched it to 60Hz it extended out to the edge of the screen. The connection through the USB-C hub with HDMI works just fine as well. I just didn't even think of the refresh rate setting. Thank you for pointing that out!

Edit: Never mind...spoke too soon. When I switched the refresh rate, it actually dumped Dummy for "Optimize for" and switched it back to the Dell monitor. So that is what forced it fullscreen. Even Dummy at 60Hz still doesn't extend to the edge. For some reason switching to 60Hz forces settings back to the Dell monitor, and then if I switch it to Dummy 16:9 it is no longer extended. I will have to try a direct connect of USB-C to Display Port sometime, but I don't have a cable for that on hand.

It will switch to 60Hz extend out to the edge of the screen like it is supposed to

But then it shows it is back to the Dell monitor and not Dummy

[waydabber]

Hey @mlara51 - I don't know why does it revert to Optimize for DELL. You might have to simply try again changing the Optimize for setting until remains on the Dummy, as Monterey sometimes do things like this.

[debaghtk]

facing a similar issue. I have a viewsonic 27 inches 1440p monitor, I created a new dummy display for 16:9 aspect ratio on BD, set the display on mac to optimize for BD(16:9).

There are quite a few resolutions which do not utilise the full screen real estate. the effective length of the monitor that they use is somewhere between 24.2-24.3 inches.

Edit 1 - I now see that the screen shrinks when I use resolutions from 1312x738 till 1920x1080 but they all utilise the HiDPi resolutions.

Going above 1080p, while uses the full screen real estate, is apparently utilising low resolution setting, even when i choose my option from HiDPi. (I have enabled show low resolutions on the app)

[waydabber]

Hi @wallydrag - is tis on Intel or M1? The app was mainly developed with M1 in mind, on Intel virtual screen mirroring works somewhat different with the various AMD and Intel GPU drivers.

[iamqk]

I am using m1 mini and facing the same issue.
This two actions solve the problem, after which I reset the configuration again
1 reconnect hdmi cable(not a good way)
2 after wake up from a real os sleep

[hoanguye99]

I use a HDMI to HDMI cable and have the same issue. My monitor is a 24 inch 16:9 ratio, and the dummy I created is 16:9. However, it appears that the dummy does not extend to the full monitor display.

Edit: My monitor is 75Hz too, so it might be the problem.

[waydabber]

Most of these problems are due to the fact that M1 seems to detect some HDMI displays as TV, adding an underscan/overscan or choosing an erroneous base resolution when doing mirroring. This is a semi-prevalent issue, I got about a dozen or so reports like this so far. At least this is my theory. Some users had some luck with overriding the EDID info of the display but I am not sure if this can be done on Apple Silicon. If possible, it is advised to use USB-C and DisplayPort.

[waydabber]

I'll move this over to discussions + reference this one in #146 as these two seem to be the same problem.

[waydabber]

fyi, there is a solution to this issue which probably works for most (with some caveats).

#146 (comment)

[maximedupre]

I had the same exact issue, but it seems like the problem has more to do with the monitor than macOS.

I just changed my monitor's "Scaling" setting from → "Original size" to "Fullscreen" and everything worked fine after that.

Not sure if this will apply to everyone though 😊

[mlara51]

That is great to hear! Unfortunately, I can't find the scaling option you are referring to for my monitor. Can you walk me through that a bit more?

[maximedupre]

As you can see my monitor has a "Scaling" option. Not sure why it's disabled right now, but in some cases I can do the modification I described 😁