Remove bundling Gtk platform plugins

[probonopd]

linuxdeploy-plugin-qt/src/deployers/PlatformPluginsDeployer.cpp

Lines 56 to 62 in 43c69b0

	// according to probono, only the files shall be deployed, not their dependencies
	// either loading succeeds, then the system Gtk shall be used anyway, otherwise loading fails and Qt will fall
	// back to the default UI theme
	// we don't care whether this works (it's an experimental feature), therefore we ignore the return values
	const auto libqgtk2Path = platformThemesPath / "libqgtk2.so";
	const auto libqgtk3Path = platformThemesPath / "libqgtk3.so";
	const auto libqxdgPath = platformThemesPath / "libqxdgdesktopportal.so";

Apparently I had been too optimistic at that time.

Bundling Gtk platform plugins created lots of hassle, including

• Gtk:ERROR when trying to start AppImageCommunity/AppImageUpdate#145
• App Seg fault - Crash AppImageCommunity/AppImageUpdate#149
• Crash at startup on Ubuntu 20.04 AppImageCommunity/AppImageUpdate#150
• blank UI in Linux Mint AppImageCommunity/AppImageUpdate#151
• Remove libqgtk3.so and other platformthemes that may lead to crashes AppImageCommunity/AppImageUpdate#152
• Could not start on fedora 33 AppImageCommunity/AppImageUpdate#161
• App doesn't start AppImageCommunity/AppImageUpdate#166

Please remove the bundling of those.

[vadi2]

What is the side effect of removing them?

[TheAssassin]

"Native look" may be gone. But that is overrated anyway. Maybe we can just bundle some standard style like Fusion and make apps use that as a default (unless they change it themselves).

Some apps deliberately delete these files already.

[probonopd]

"Native look" may be gone

Only on Gtk based desktops like Gnome, not on Qt based ones like KDE Plasma.

[TheAssassin]

Even Xfce seems to use Fusion nowadays, not Gtk+, at least for many AppImages I came across. As said, "native look" is overrated...

I think that Gtk+ platform theme bundling stuff was and still is experimental and has shown to cause more issues than it solves. I'll remove them soon.

[vadi2]

It's definitely a loss to have this gone, native look is not overrated and very much desired. It's one of Qt's biggest weakness on Linux that it does not integrate well with the users visual environment, unless they happen to be on KDE.

[probonopd]

Not really a loss since it was not working and caused a lot of trouble for many people over the years. Just look at the many bug reports linked above. What is worse - the application not working or the application not looking like Gtk applications?

[vadi2]

I haven't seen such reports from my users. Please recommend a method to undo this as an opt-in.

[TheAssassin]

@vadi2 if you send a PR to make this opt-in, I'll happily merge it. The PlatformPluginDeployer already shows how this needs to be done. I think if you, as the author, decide you want to enable such an experimental feature, that's completely acceptable. We just need to communicate it's an experiment, and give responsibility into the AppImage author's hands.