Alt-Key not working when moving mouse



I'm just reposting this to the linux part of the forum. I just overlooked this section until now.

I'm on Arch LInux with Gnome 3.18.

In my mouseDown(), ... functions the Alt-key never gets set as a modifier. I tried to find the error and after searching in the linux windowing code I think I found it. After the Alt-key was pressed and a keyboard event was send everything is fine and the flag for the Alt-key is set properly. But as soon as you move the mouse it gets unset.

The difference between the two cases is that after a keyboard event updateKeyModifiersFromSym() in juce_linux_Windowing.cpp is called and after a mouse event the function updateKeyModifiers() is called.

The updateKeyModifiers() triggered the Alt-key when I pressed Meta on my keyboard. It checks for a flag specified by Keys::AltMask that is set in updateModifierMappings(). The keycode for Alt gets determined by XKeysymToKeycode(display, XK_Alt_L), and this seems to be the source of the whole error. On my system that function call returns the same keycode for XK_Alt_L and XK_Meta_L. Based on that error also the value for Keys::AltMask gets set wrong. With my configuration everything worked correct when I set Keys::AltMask manually to 8, but I'm not sure how to make this work in a dynamic way with false output from XKeysymToKeycode().

(I'm also not 100% sure if the bitshifting "if (mapping->modifiermap [i << 1] == altLeftCode)" is correct that way, according to the doku it should be something like modifiermap[i * mapping->max_keypermod])

I hope anyone has an idea how to fix this.


I've managed to reproduce this issue and will start digging into it soon.

Thanks for the report!


did you found something or can I help you somehow?


Any more clues on this one would be appreciated!