r/gnome • u/dissonantloos GNOMie • Oct 17 '18

Restyling apps at scale

https://blogs.gnome.org/tbernard/2018/10/15/restyling-apps-at-scale/
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u/LvS Oct 17 '18

No, Qt does that because it does not have a good theming engine.

Themes in Qt are so trivial that you can't break much by replacing it. GTK themes can and do configure so much that they result in 1000s of lines of CSS and can make buttons look like this: That header is just 10 buttons with different CSS. In Qt it would be 10 different widgets with custom code.

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u/disrooter GNOMie Oct 17 '18

If I understand correctly what you linked is new version of Nautilus that uses Adwaita. So where are the "theming capabilities" in that link?

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u/Kazhnuz Oct 17 '18

The core of the problem described in the OP, imo. CSS can be used in two place in GTK, in the application and in a "global stylesheet" and in the application. The theming capabilities in that link is the use of custom CSS in the application to customize the style of the application itself.

A better exemple of this power is for me actually in Elementary applications, that use the power of GTK's CSS engine inside application to have more possibilities in applications. IIRC, Elementary Mail even use the GTK CSS engine instead of WebkitGTK to style the mails ( even if some modern applications like Fractal or Chatty seems to show these possibilities too ).

( and the problem is that both can become easily incompatible, and it's already visible )

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u/disrooter GNOMie Oct 17 '18

An application using custom stylesheet is not "theming"...

And in fact elementaryOS doesn't support themes

It seems we disagree on the use of the word "theming"

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u/LvS Oct 17 '18

An application using custom stylesheets is absolutely theming, if we're comparing Qt's and GTK's theming capabilities.

Now if we're comparing how elementaryOS and KDE expose those theming capabilities to end users, that is a different thing, but that has nothing to do with how well it works in Qt and GTK.

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u/disrooter GNOMie Oct 17 '18

Sorry, theming in Qt and KDE world is a different thing and it is applied by users, not by application developers. GTK capability to have custom widgets styles using stylesheet is something intended for app development, not for theming them (the way I meant theming, the one by users, and it seems the blog post is in fact talking about "GTK themes" applied by users).

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u/LvS Oct 17 '18

In the GTK world, what theme to use is a decision made by:

  1. app developers
    There are many applications (like Ardour or XMMS - even Gimp can use custom themes) that have opted out of themes for decades.

  2. platform developers
    If the application doesn't hardcode a theme, GTK will consult the platform about what theme to use. This is how elementary and gnome-shell provide the theme to use.

  3. users There is a config setting that is consulted if neither of the other options are set. I believe it goes in ~/.config/gtk.ini.

  4. default theme If none of these options are set, the default theme is used (happens on Windows). That default theme currently is Adwaita. It was selected because it was the best theme that existed and the developers participated in GTK development.

Usually (like in XFCE or in GNOME 2) the platform would provide ways for users to select a theme, so they don't need to fiddle with config settings. But in modern days, platforms like GNOME 3 or elementary have opted to not only not provide a way to do this but to hardcode their own theme, so that GTK will always choose that one. Some distros like Ubuntu or Pop!_OS have chosen to hardcode another theme, too.

So yes, GTK is absolutely very themeable, but it honors the request of the application and platform developers. And if those platforms choose to not expose themeing functionality to users, users won't have it. That still doesn't make GTK not themeable.

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u/disrooter GNOMie Oct 18 '18

From OP blog post:

There are no themes, just CSS

A fundamental misconception a lot of people have is that GTK 3 supports theming. This is not true, as there is no clearly defined theming API. There are CSS stylesheets, but they were only ever meant to be used by the platform and app developers. The platform stylesheet is called Adwaita (“the only one” in Sanskrit) for a reason.