Wayland Display server and fractional scaling

Has anyone tried wayland fractional scaling on Ubuntu 17.10 using a 27 inch 4K monitor?

I have read complaints about fractional scaling making the windows look blurry (this could mean that the scaling is being done up from 100% (1.0) resolution.

The reason I ask is that I want to buy two 27 inch displays, and I want to know if I can benefit from the higher pixel density of the 4k resolution.

4k resolution at 200% DPI will look like a 27 inch 1080p display (for that resolution everything will be scaled too big, this is the reason why Apple uses the 21 inch monitor for the iMac as 4k, and not the 27 inch.

I suppose that the 27 inch 4k display will look good at 150% scaling. If I had one I could experiment by writing an app.

I am sure there are cases where it scales up and some other cases where it scales down.

I cant find documentation regarthing this.


  • Luis

PD: If It does not work I might consider getting the 1440p which should run and render fine at 100% DPI. But now days with all the retina displays everywhere I can see a huge difference, at least with 96 DPI (windows 100%). And the 1440p DPI should be around 114%

It could be possible to tweak that with a different display manager. GDM and Lightdm isn’t really the best for DPI scaling, but SDDM and KDE thought of DPI scaling a while ago. Cinnamon has a DPI scaling for fonts only and it can do 1/10th increments, but that’s for the font elements only.

KDE does support the fractional scaling, but not sure the feature will work on Wayland. I read some posts said that Wayland doesn’t support the factional scaling yet.

I use Gnome and GDM for my Crossover 289K I will post my settings when I get back, but for the most part I have my browsers zoom to 150-160% for easy reading.

I didn’t mess with the scaling too much, instead I changed the font size to be readable on the 4k 28 in display. For some reason Gnome scales windows with text so I decided to keep the same scale, just with font size increased.

I would agree with others that 4k is ideal with displays greater than 30 inches.

I bet you can ask @wendell what the ideal resolution and monitor size is for 4k as he has reviewed multiple panels and would have a good general sense of size

I know what the ideal resolutions per DPI are. I want to avoid font only scaling because that breaks down quicly, imagine running a 4K 13 inch laptop, and just being able to change fond size.

Linux needs propper DPI scaling, gnome 3.26 has the option to set 100% and 200%, but in certain cases like 4K at 27 inch you need more like 150%.

My question is in regards of the code being scaled down from from 200% or up from 100%, since I don’t own a 4K monitor I don’t know which is the case.

That’s because only multiples of full resolution look sharp. Going to different resolution requires rescaling of the window contents, which is exactly what you don’t want

For these toolkits yes, but look at what Apple is doing, it looks sharp on all high DPI variants, scaling does not necesary ruin thinks if on high DPI monitors and with the right scaling algorithm.

Here is the problem with sticking with 100% and 200% and avoid fractional scaling, the 200% equivalent of a 27 inch display is a 5k monitor, and those are like 1.5 each.

So I am down to 1440p, or 4k with fractional scaling. But I have never seen fractional scaling on 4k, 27 inch displays, since it was not available until 17.10 for Wayland.

I am aware that apps that had no possible scaling (GTK2… etc) will always scale up from 100%.


Unless they’ve changed anything apple also uses 2x scaling. Besides, there’s nothing GNOME or Linux can do about the user’s toolkit choices.

Font rendering is difficult and needs lots attention to detail to look ok even without scaling. Any scaling algorithm is either going to mangle text or be computationally expensive. I don’t think there’s an easy way around this.

Note that you can globally change GTK’s font size using the GNOME tweak tool. This is pretty close to scaling the interface because the size of most elements is determined by font size.

That’s what I was trying to get to, but I guess I misread