> I as an app developer want to guarantee that my app looks good on your desktop
When your app doesn't follow how my desktop looks it doesn't look good on my desktop. And unsurprisingly most modern Gtk3 and especially Gtk4 apps do not look good on my desktop.
What you actually mean here is that you want to guarantee that your app looks good on your desktop, not mine.
Yeah, I should have clarified that by "your desktop" I mean "your GNOME desktop" - i.e. "if you run GNOME, it'll look good no matter your preferences". But wrt "your desktop" - even if I wanted to, I couldn't guarantee that my app looks good on your desktop specifically, because I have no clue what your desktop looks like! Which is why I want to target a large common denominator of desktops instead, where I know it can look good.
The counter argument to that is "so let the user theme the app, to suit their own desktop", which would be a decent solution, but:
1. My vision for my app might conflict with your vision for your desktop. Maybe I want this button to be a light blue because it meshes well with some other elements in the app, but you want it to be a darker blue because it fits with your desktop's color scheme. What happens then?
2. This still doesn't guarantee that the app will look good. If you theme my app's home page, but don't theme the rest of the pages, then sure it'll look good at the home page - but as soon as you start using it, the look will fall apart. Or, what if I push an update to my app which adds a new page with a new kind of UI element? Do you really want to be maintaining your desktop theme for every single app you have?
3. This adds a burden on me as the developer to make parts customizable. This is the least convincing argument in this list IMO, since if there was better tooling and infrastructure for theming in GTK this wouldn't be a problem - but there isn't, so it is still a problem.
As a practical example, my app makes use of a WebViewGTK to display some info. I inject some custom CSS into this web view to make it look like Adwaita. This touches on points 2 and 3:
2. The webview has some UI widgets which aren't present in the rest of GTK, like a sticky header bar. You would have to manually maintain a stylesheet for this single element.
3. I now need to write a way to let users theme the custom CSS inside the webview, rather than just the CSS of the GTK widgets themselves. (I have already written this, but it's still a maintenance burden.)
> My vision for my app might conflict with your vision for your desktop. Maybe I want this button to be a light blue because it meshes well with some other elements in the app, but you want it to be a darker blue because it fits with your desktop's color scheme. What happens then?
Probably something similar to how Apple platforms handle colors. Instead of providing a single static light blue, you have a couple options:
1. Use a “system color”, which is pre-tuned for optimal contrast, appearance, and usability and adjusts automatically when e.g. the user switches between light/dark mode or enables an accessibility setting related to color or vision
2. Define a light blue that’s actually multiple variants of the color bundled together, with each being optimal to various environments, with the UI framework choosing the right one depending on the situation
Arguably developers should be doing these things anyway for accessibility reasons. It’s not been good practice to use e.g. bare color hexes for quite some time now.
> My vision for my app might conflict with your vision for your desktop. Maybe I want this button to be a light blue because it meshes well with some other elements in the app, but you want it to be a darker blue because it fits with your desktop's color scheme. What happens then?
The user trying to make your app match their desktop should 'win'. Your responsibility is to ship out an app and make sure it works in the way you want it to work.
If the people need to do more work to make it look good on their desktop (as I likely would running awesoemwm), that shouldn't be prevented, but it also need not be encouraged. It should at the least though be facilitated, certainly to a better extent than it is.
When your app doesn't follow how my desktop looks it doesn't look good on my desktop. And unsurprisingly most modern Gtk3 and especially Gtk4 apps do not look good on my desktop.
What you actually mean here is that you want to guarantee that your app looks good on your desktop, not mine.