Scaled Resolutions dialog not usable

[jpstotz]

When select the "Edit..." menu entry the "Scaled Resolutions" dialog opens but is unusable (see screnshot).

Is this a limitation or a bug? I am working on Catalina 10.15.7 via VNC without physical monitor attached.

[usr-sse2]

1. Why do you think that it's unusable?
   X, Y, Width and Height fields are not enabled, because no icon is selected. These fields are for adjusting the position of desktop preview inside a custom icon. + button is enabled and allows to add custom resolutions.
2. WARNING: editing VNC/ARD virtual display WILL MAKE YOUR MAC HANG ON BOOT. If you have already done it and can't boot, use single-user mode or Recovery to remove the generated plist. You can find out which one to remove by sorting them by modification date:
   ls -lt /Library/Displays/Contents/Resources/Overrides/*/DisplayProductID-* from single-user mode or
   ls -lt /Volumes/Macintosh HD/Library/Displays/Contents/Resources/Overrides/*/DisplayProductID-* from Recovery, where Macintosh HD is the volume name.
   Of course, you need to mount the volume read-write to remove the plist.

[jpstotz]

@usr-sse2 Thanks for your response. So if I understand you correctly you say that the problem is mainly my understanding of the a bit strange way how this dialog has to be used?
Even after your description I still don't understand for what purpose the section "Resolution Preview Icon" exists. If I click on an icon the fields x, y Width and Height are getting filled with totally strange values e.g. x/y 52/66 width/height 122/76 - a typical screen has a resolution of larger than 1024x768 so what values are displayed there? Or are this density values?

But in the end if I had managed to use the dialog the result would have been a non-working OS!? Don't you think that a little warning message would be helpful in case the "VNC/ARD virtual display" is selected?

[usr-sse2]

This dialog has two independent parts.
The upper part is the selection of display icon, which is shown in System Preferences. You can either select one of built-in icons, or drag your own monitor image (452x452 PNG with transparency) onto the image view. Here is an example of a DELL laptop icon:

Then you can adjust the position of resolution preview, which is shown in System Preferences, so that it is shown within the area.

The result: DELL icon is shown in System Preferences, and the resolution preview is shown in the display area of the icon.

So, X, Y, Width and Height are completely unrelated to the resolution, they specify the position of resolution preview image within the bounds of the icon.

The lower part is used for adding custom scaled resolutions.

Yes, I'll add a warning and usage hints.

[VaibhavKhalane]

What are Unknown 1,2,3 checkboxes? When to check them? I have 1080p Dell P2419H Monitor.