HiDPI scaling wayland gives blurry UI and preview, X11 is fine

I’ll start by saying I did search for this issue beforehand, didn’t find precisely it, not from any recent year anyway, so if the discussion already exists please point me to it : )

I’m using Fedora Workstation (4K display, 150% global scaling) and have been using Rawtherapee for a year or two and like it alot, I appreciate the quick workflows possible and the UI is intuitive. Anyways, I recently switched my KDE display protocol from X11 to Wayland (for issues other than photo editing) and noticed that Rawtherapee’s photo window, including the overlay ui in the top left corner, is slightly blurry. Like 1X upscaled without rerendering the source so to speak (Wayland just recently evolved in such a way that “XWayland” apps can scale appropriately and look good). This makes it practically hard to use.

For reference Darktable does not seem to display the same issue, it’s photo editor window incl the UI is as sharp as under X11.

Since Fedora (and I suppose every other distro) is evolving away from X11 I was wondering what the state is of Rawtherapee’s Wayland support; whether this is a known issue or whether there’s something I can do to help. (The “pseudo Hi-DPI” mode did not help)

Hi @devries,

I read something about that the other day… … …
Give me a few minutes & I will try to rediscover that link.

Found it:


Have fun!
Claes in Lund, Sweden

Hi Claes. Yes I’ve seen those, the RT-wiki page is potentially a bit dated and does not mention the issue I’m experiencing or anything like it.

The other one is a great article for debugging issues with Wayland in Fedora generally, I was kind of hoping to hear from devs or other users on this issue specifically with Rawtherapee since the former will know whether Wayland is a problem and the rest may very well be seeing the same issue since I can’t really be the only one trying to run Rawtherapee on a 4K display with scaling using Wayland : )

I highly doubt many are using Wayland yet, as it does not have working color management, a critical feature for photo editing.


Fedora is a pretty popular distro and certainly Wayland is getting better and better while more and more rumblings are heard about dropping X11 or bits of X11. I’m okay with color profiles working the same in X11 as Wayland, your requirements might differ but please don’t generalize. We can perhaps all agree X11 isn’t the way forward I think. Consider dropping the X11 backend (#5004) · Issues · GNOME / gtk · GitLab

Yet this is patently not what I was asking about. My environ isn’t super uncommon, the fractional scaling issue is not new and Wayland is getting more common. I would very much like to hear from someone who knows anything about it because it seems a bit unlikely there wouldn’t be anyone else who has tried it. During the last months the last “legacy” apps I like using started scaling well under Wayland so RT is really the only app giving me beef currently and I really like it so I’d like to continue using it.

If color management doesn’t work under Wayland, how can you trust anything you see from a color fidelity viewpoint?

Although I’m not (currently) on Linux I agree with @paperdigits , IMO color management is basically a mandatory requirement for photo editing if you have any interest in color accuracy. Admittedly that’s not always possible everywhere (from all others’ viewpoints) but it’s infinitely better than nothing.

But that’s just my opinion, obviously.


I didn’t make this thread to argue on the benefits of the slowly dying X11 project, or what other photogs think is mandatory in terms of postprocessing. I’m fairly happy with my calibrated display. I also realize most people don’t have a calibrated display, and most consumers of my photos couldn’t care less about “color fidelity”, an engaging photo is just that.

Fractional scaling issues are nothing new as hiDPI displays are becoming more common. Wayland is modern and constantly improving and becoming more common. If anyone has any useful input on this specific topic that would be great.

Have a look here:

Especially moomin’s first reply and this quote from that reply:

For my setup, 100% scaling is not an option as everything looks too small, so I have to use 200%.

But when I do, the preview in RT appears blurry, […]

This issue is still open, last entry Oct 4 2022, and from what I can tell not Wayland specific but RT not having true HiDPI support as of yet.


Thanks! That is useful . It seems the last comments on the matter are that fractional scaling is an issue in Wayland and not in X11(with the “pseudi hiDPI” option at least) for RT and they are hoping to make RT compliant with the GTK way of HiDPI and that that ‘should’ take care of Wayland. I guess I have my answer and can ask in the Github issue if I have further queries.

(And for the record I’m not 100% sure what the color fidelity not working under Wayland is since as I mentioned the .icc profile I made via calibration applies the same in Wayland as in X11(after just a little hassle). Could be that there are finer bits in RT that are referred to, well, maybe I’ll reach your level some day in that case :slight_smile: )

This is not generalization, this is fact. There is no full, working color management in Wayland. You can load an ICC profile, and that’s… 30% of it. We still need to be able to run the calibration software itself and it needs the permissions to access the monitor.

Supposedly RedHat is working on it now along with HDR support on Wayland. It will be very welcome when it comes, but it is not here yet, this is a fact.


Do you need to run the calibration software and have it access the monitor if you already have an icc profile that’s the result of it? I don’t. Even if you created it under X11, what does that matter if it can be applied under Wayland? And the generalization comment was ‘a critical feature of photo editing’. If I can apply my icc profile resulting from a calibration session and things look ok in calibration targets that’s fine with me. That’s a fact.

(Another fun albeit anecdotal fact is that under an X11 session the icc profile becomes un-applied everytime the system suspends. This has always been the personal case. In Wayland the profile sticks.)

HDR is a different topic.

Edit. I might try running displaycal to generate a profile under Wayland tomorrow. I never have.

Well calibration is not a one and done thing, and if you want accurate color you should probably be calibrating every one to four months. Are you booting back into X11 for that? Its going to be really inconvient.

Things “looking OK” doesn’t make a calibrated environment. And X11 is deprecated as you suggest, then it is extremely important to be able to run the calibration process in its entirety on Wayland. Again, being able to load an ICC profile is part of it, but not close to the whole process. If we are getting rid of software that works in X11, then we need a matching feature set in its replacement.

Wayland will be great when all that works, I’m sure, but that time is not now and wayland is not feature complete for a general photographic use case.

This doesn’t happen on my machine running X11.

I don’t understand why so many wayland optimists that I’ve encounter can’t understand the use case and are obstanant about accepting the current state of the software.

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I don’t know what your definition of “a calibrated environment” is, as mentioned several times already the profile applies the same as on X11.
Nor am I quite sure why you would be calibrating every four months.
I can say that I don’t own a dedicated photo editing machine and X11 less useful for a few things vs Wayland as things currently stand. I have no love for a particular display protocol over another, you choose what works best.

Your replies haven’t been relevant to my question however (it wasn’t even about colors); you have just seemed to take the opportunity to vent on Wayland. Well done?

  1. Run some calibration software
  2. Generate an ICC profile
  3. Load the ICC profile.

Wayland does #3, but not 1 & 2.

Your display’s color rendition changes it ages. Calibrating will keep it as accurate as it can be.

I totally agree, and wayland also still lacks features for some use cases, like this one.

You choose to keep replying and so do I, that is how this conversation has continued.

Developer here. There is nothing RawTherapee can do to really improve the status quo.

  • We rely on GTK3 for rendering our GUI. As far as I understand, there is no easy way to get real high DPI rendering for large screen sizes. We have a pseudo-mode that you can use, but that may not solve everything.
  • We cannot do anything in our code to ‘support’ Wayland. Any photo editing software should be able to rely on the OS to accurately display colors. If Wayland can’t, we can’t.

Hi there, dev of Rawtherapee I assume.

  • My query had nothing to do with colors. It was paperdigit’s pet peeve or something and I was foolishly led on that. Wayland has no issue with colors afaik.

  • Pseudo mode is for the UI, but not the overlay UI in the photo preview (it doesn’t change anyway whereas most toolbar buttons do). Pseudo mode is not for the photo preview itself either (nor meant to be as I understood the discussion in the linked gh issue). In addition pseudo mode isn’t required, at least not with KDE and “Let legacy apps render themselves” (I didn’t try RT without and don’t know whether it’s affected) (This week in KDE: Wayland fractional scaling! Oh, and we also fixed multi-screen – Adventures in Linux and KDE ) which fixed Obsidian and Insomnia and others for me. I’m just having scaling issues with RT at the moment and Wayland is deffo more the future than X11 :slight_smile:

  • If the issue with fractional scaling is unsolvable maybe it can be indicated in the linked issue?

  • Darktable relies on GTK3 and doesn’t have this issue

If I do any scaling with KDE Wayland it makes everything go blurry which doesn’t happen with x11, doesn’t matter because I don’t need to do any but thought I’d have a look see.

The future isn’t now while ever there’s colour issues as it’s rather important to a lot of people and programs.

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“Everything” used to be X apps but lately that’s been fixed. Ymmv of course.

There are no color issues with an applied profile and this thread was never about colors.

The issue was solely with Rawtherapee and fractional scaling on hiDPI displays (when you zoom a photo to 100% it becomes 150% size) on display protocols that aren’t turning legacy, an issue other Photo editing apps doesn’t seem to have.

Just as RT is still a great app and my favourite photo editor, it seems this thread isn’t going places. I’ll certainly think twice before asking another question here :slight_smile:

It’s a good place for asking questions and you’ve had yours answered. It’s because you’re using something that’s not ready yet. Which is the same as using development versions of software, you’re going to run into issues that currently don’t have solutions, things you have to wait for. In the case of Wayland with some software the solution might always be that you have to use xorg for that.

Well… You wanted to know when support for Wayland would come to fix the blurry GUI. Different people have tried to tell you that nobody is seriously investigating compatibility with Wayland, simply because it does not make sense for a serious photo editing application to be used in an environment what does not support full-fledged color management.

Edit: so it’s not a matter of if there is a scaling issue, but simply that we don’t care yet to fix it.

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