Option for logical scaling of monitors

[AntonVucinic]

Description

The scale option in the monitor configuration variable is most often used to scale the UI by that factor. This is done (I think) by dividing the monitor's resolution by the scale factor and rendering at that resolution before scaling it back to the monitor's actual resolution. This works fine for scaling but it has the side effect of affecting the size of the monitor used for determining it's position relative to other monitors.

Currently this is the only way to change the size of the monitor for that purpose. I think this doesn't make much sense. I think a much saner coordinate system used for monitor positioning would be the real word one using the physical size of the monitors. But an even better solution would be give us an option to scale the monitor only in the positioning coordinate system and to have keyword options as well (similar to what we have for setting the resolution): render-scale, physical-scale, etc.

Why would it be beneficial

This is the situation I found myself in where I think the use for the described feature would be the best solution. My main monitor is 15" and 3840x2160 and my secondary monitor is 24" and 1920x1080. Ideally their UIs would be scaled by 2 and 1 respectively but in order to align the monitors in such a way that the mouse moves smoothly from one to another I have to scale the secondary one by 0.666667. This accomplishes the desired goal of having the mouse move (almost) perfectly across their shared border but it also reduces the scaling on an already low DPI monitor to the point at which letters become hard to distinguish. It is also possible to achieve the same goal by increasing the scaling on the main monitor. A much better solution would be to separate the scaling of the UI with the scaling of the monitor sizes in the positioning coordinate system.

[vaxerski]

Can't be done. Wayland scaling fundamentally works like this, and none of your apps will understand it otherwise.

FWIW, MacOS does the same.

My main monitor is 15" and 3840x2160 and my secondary monitor is 24" and 1920x1080. Ideally their UIs would be scaled by 2 and 1 respectively but in order to align the monitors in such a way that the mouse moves smoothly from one to another I have to scale the secondary one by 0.666667.

What? You don't...? 3840x2160 / 2 = 1920x1080, wdym?

[Epikastema]

Because his monitors are different physical (not resolution) sizes he's asking for the ability to make the mouse stay the same height in the real world when moving between displays without changing the display scale. E.g. a separate scale value that only affects where the mouse appears when crossing display boundaries.

I don't think apps are relevant here because afaik hyprland doesn't support full screen apps spanning multiple displays.

[AntonVucinic]

I'm not sure about full screen apps but you certainly can have a floating window open across multiple monitors. Scaling the monitors so they line up will also make those windows line up so it's not just about smooth mouse movement. This just seems to be a fundamental issue when using monitors with widely different PPIs.

[tekstryder]

fundamental issue when using monitors with widely different PPIs

Even so, wouldn't you use scaling factors which attempt to come close to matching PPI?

In my case, I've two differently sized displays, one in portrait orientation:

Display (PHL 328E1): 3840x2160 @ 1.33x in 32", 60 Hz [External]
Display (DELL U2711): 1440x2560 @ 1.07x in 27", 60 Hz [External]

In hyprland, the scaling options are limited, so the closest PPI match for my case, while still near optimal UI visual sizing is:

monitor = DP-1, 3840x2160, 0x0, 1.333333
monitor = DVI-D-1, 2560x1440, 2881x-425, 1.066667, transform, 3

Under sway, with near-limitless scaling options, I can come even closer to an exact PPI match with:

output DP-1 scale 1.35 pos 0 0
output DVI-D-1 scale 1.05 transform 90 pos 2844 -455

Are you simply lacking an offset value?

My mouse and windows span monitors at as-close-to equivalent vertical alignment as achievable with any two factors.

[AntonVucinic]

I tried using different scaling factors and the following configuration is almost perfect for aligning the monitors:

resolution	diagonal	scale
3840x2160	15"	2
1920x1080	24"	0.666667

While this does align them text becomes very hard to read on the larger (but lower resolution) monitor and it's outright impossible to distinguish some symbols. Going the oposite way and increasing the scaling factor on the small 4k monitor makes the UI way to big for my liking and takes up precious space on a small monitor. This doesn't seem like it would be such a big deal to you since your monitors aren't as different (in terms of PPI and dimensions) as mine.
The real solution, I think, would be to just leave the scaling factor on the 1080p display at 1 and increase it on the 4k monitor until they line up and then go around configuring themes for all the various apps to scale them back down. This just seems like too much work to be worth it.

[tekstryder]

since your monitors aren't as different

I understand the dilemma now. That's quite the PPI disparity to deal with!