Compiling with Qt6

Development
1

I’ve been trying to create a Kate plugin by following the tutorial: hxxps://develop.kde.org/docs/apps/kate/plugin/

It’s using KF5, so I replaced the “5” with “6” where appropriate.

Still, cmake fails with a cryptic error:

CMake Error at /usr/lib64/cmake/Qt6Core/Qt6CoreVersionlessTargets.cmake:42 (message):
  Some (but not all) targets in this export set were already defined.

  Targets Defined: Qt::Core

  Targets not yet defined: Qt::CorePrivate

More details here: hxxps://bugreports.qt.io/browse/QTBUG-118512

I tried installing qt5-qtbase-private-devel (Fedora 40), like suggested elsewhere, but this just gives another error:

qt_generate_foreign_qml_types() is only available in Qt 6.

Does anyone know how to fix this?

Does there exist a standalone example plugin that works with KF6? Maybe I converted the example wrong.

2

You can have a look at any built-in kate addons, they are just like regular plugin.

Don’t develop for Qt5, it is end of life and wouldn’t be compatible with current kate. (Can’t mix qt6 and qt6 code)

3

They are not like standalone plugins because they pull the entire Kate’s cmake build system, and my problem is precisely with cmake.

I mean, I could build a plugin as part of Kate, but I was hoping that I don’t have to build the entire thing.

Also, the original error has nothing to do with Qt5. I started out with Qt6.

So, how do I build a standalone plugin with Qt6?

4

You can’t have a standalone one, you need kateprivate link target which is well private to kate codebase.

If you don’t mind me asking, what would be your plugin use-case ?

5

I want the file to be synchronized with what’s on the screen. So basically, press “save” whenever something changes. Then I can use it instead of OpenSCAD’s builtin editor.

6

kate already notifies when file on-disk changes, and it offers then the option to reload automatically as it changes.

It seems you need the opposite, an continuous autosave. Am I understanding correctly ?
If so this does not need to be in a plugin, there are other usecases for it (qml editing…), and it would be hard or impossible to make it work in a plugin.

7

Continuous autosave, yes. Why would it be impossible? There’s the text change signal, and I have access to arbitrary code in the plugin, so I could even send out the document over the Internet if I wanted.

Also, the solution seems to be a cmake flag:

-DBUILD_WITH_QT6=ON

and the plugin definitely can be built standalone.

8

Why would it be impossible? There’s the text change signal, and I have access to arbitrary code in the plugin, so I could even send out the document over the Internet if I wanted.

I was mistaken.

We the use-case you have, I think it would make sense to offer it upstream and include it in kate.

9

I’m having trouble with Qt compilation. I’ve decided to humble myself and ask some better questions, on account’a I actually think it’ll be doable, and looks like a fun way to write apps/fix bugs.

<REDACTED BECAUSE I WAS BEING AN A**>

10

We expect you to be more constructive than this.

The tools for kde to alleviate most build issues is kde-builder (or kdesrc-build).
It has doc KDE Builder Documentation — KDE Builder documentation

11

@meven You know, thanks for the call-out. Funny enough, I am playing with kde-builder, beginning with the qt6-set. As far as basic “QtQuick” app development, do you recommend any other package I should begin with?

My biggest issues had been with Qt Creator and its designer brethren. So question two, (I use arch, btw) should I install that via pacman or the Qt online installer for the best chances of success? I made a good effort to clear out any lingering old installations.

Hey, thanks again, and sorry for my unruly post there. I get grumpy when outsmarted.

12

You can install Qt from your distro, Arch is sufficiently up-to-date. See: Building KDE software | Developer

13

@meven @Herzenschein Thank you both very much, I took the time, and properly configuring kde-builder has been an absolute game-changer.

My problem before was not being connected properly to the correct dependencies for a given project, I think even including QtCreator itself, hence the previous crashes. Anyone looking to fix such problems should take a pause and go through both articles in the couple-or-so posts above this.