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IDProjectCategoryView StatusLast Update
0007082ardourbugspublic2016-10-29 19:09
Reportermilasudril Assigned To 
Status newResolutionopen 
Platformx86-64OSUbuntuOS Version16.04.1
Product Version5.X git (version in description) 
Summary0007082: Ardour appears to have a bug in its copy of a theme engine
DescriptionArdour5.3.5 (built using 5.3-5-g0ff233d och GCC version 5.3.1 20160205)

This bug is either a package related issue, or a bug in Ardour. But here it is:

I tried to customize the window background (here a checkerboard) for my Work-In-Progress plug-in UI. It looks correct in Carla, and jalv.gtk. Ardour, however, draws GtkFrame shadow with the window background color, when GTK_SHADOW_NONE is in use. The expected behaviour is that it should not draw any shadow. See comparison in the attached figure.

I succeeded to get the correct result in Ardour. I got a hint from Ardour startup log, that it cannot find Adwaita. Digging further, I saw that Ardour uses its own (maybe outdated) copy of Clearlooks. Symlinking /opt/ardour/lib/gtkengines/engines to /usr/lib/x86_64-linux-gnu/gtk-2.0/2.10.0/engines (the system theme engine path), solves the problem. Disabling themes by renaming the engines directory also works.
Steps To ReproduceLoad a Gtk UI that executes the following code

    auto switch_box=gtk_aspect_frame_new(caption,0.5f,0.5f,1.0f,TRUE);
    gtk_frame_set_shadow_type(reinterpret_cast<GtkFrame*>(switch_box),GTK_SHADOW_NONE); //I do not want a border here...

On a customized background
Additional InformationSuggested fix: Use a symlink to system theme directory, or package Ardour with a newer version of the chosen theme engine.
TagsNo tags attached.



2016-10-29 15:42


bad.png (49,086 bytes)   
bad.png (49,086 bytes)   


2016-10-29 16:30

administrator   ~0018870

Last edited: 2016-10-29 16:31

Please do not use GTK for plugin GUIs. The toolkit is not suitable for that (and does not provide any pro-audio widgets to begin with).

Plugins should be self-contained and since gtk is not relocatable, that's near impossible to achieve. Furthermore the GTK ABI is not stable and also depends on libraries which have no stable ABI (eventually also gcc4/5 if the code uses C++). Last but not least GTK2/3 cannot co-exist in the same memory space (nor can QT4/5) and with gtk4 on the verge things will only get worse. Also x-platform binaries (portable sessions) are a PITA with any of the "big" toolkits.

This has been mentioned on the LV2-dev list every year now like x-mas and it's down to 12 remaining plugin-suites only. Please don't start new projects with a GTK or QT GUI.

see also and soon only 11 to go

Eventually Ardour will move away from gtk (though probably not gdk) at which point plugins relying on gtk-libs being available may stop working altogether.


2016-10-29 18:37

reporter   ~0018872

Last edited: 2016-10-29 19:09

Just fix this bug. My symlink worked, unless I broke something else.

If LV2 had a GUI API, I would have used that. But there is none. Sorry that I cannot roll my own UI. I need the text features. And the pugl has lacks support for any widgets. Also I think GTK should be considered as the native UI on GNU/Linux.

The ABI compatibility issues comes from wrong mindset. Sure if you live in the closed-source world, you need to worry about these issues. But we are free open source software. Every distribution recompile all packages for each distupgrade. This also includes plugins.

Pulling GTK support leaves a vacuum, until LV2 presents its own UI, rendered by the host. In ten years this may happen. But is it really needed.

Can you explain what you mean by "Pro audio widgets". Knobs and switches are trivial to make in any "toolkit". Also different kinds of meters should be easy, just looking at the right standard for what you are trying to achieve (EBU, Peak, LUFS ...). I can even make them work with plane OpenGL. However, if you ask me to render a text label, or even worse, a text input field, I cannot. It just requires a too high degree of expertise in different writing systems, or maybe we do not need to support Psy's language. Luckily, the experts has done all that with Pango, which is used by GTK. So I would at least have a dependency to Cairo, Pango, Freetype, and Harfbuzz for doing the rendering correctly. Pango also pulls in Glib (1). And that is only rendering. I also need to position cursor in text using the mouse. So, I think I skip that part of the UI.

Then, the user needs to choose samples from his filesystem, I need a file chooser. How can I populate that? What should it look like. If I use GTK, the user knows how it works.

Maybe I have many control ports, that needs to be grouped, so layout is nice to have. With a fully implemented toolkit, I get that too.

I want to develop audio plugins, not UI toolkits. Sorry. The one way forward: Use established toolkits. If we are not happy things should be discussed on the GTK list. Like making --enable-static work well can be a good starting point.

If there are any performance problems with GTK, then there is a real issue. I think the UI is responsive, but there is a lot of event mangling in GTK, so maybe it is not very good in a real-time environment.

(1) As expected, GTK already requires these. The full list required to compile my UI is
 '-lgtk-x11-2.0' '-lgdk-x11-2.0' '-lpangocairo-1.0' '-latk-1.0' '-lcairo' '-lgdk_pixbuf-2.0' '-lgio-2.0' '-lpangoft2-1.0' '-lpango-1.0' '-lgobject-2.0' '-lglib-2.0' '-lfontconfig' '-lfreetype'.

Issue History

Date Modified Username Field Change
2016-10-29 15:42 milasudril New Issue
2016-10-29 15:42 milasudril File Added: bad.png
2016-10-29 16:30 x42 Note Added: 0018870
2016-10-29 16:31 x42 Note Edited: 0018870
2016-10-29 18:37 milasudril Note Added: 0018872
2016-10-29 18:45 milasudril Note Edited: 0018872
2016-10-29 18:47 milasudril Note Edited: 0018872
2016-10-29 18:57 milasudril Note Edited: 0018872
2016-10-29 19:01 milasudril Note Edited: 0018872
2016-10-29 19:07 milasudril Note Edited: 0018872
2016-10-29 19:09 milasudril Note Edited: 0018872