I have dual 4K display under Ubuntu. The problem with launching the client is that the ‘ThinLinc Client’ popup window where you enter your server, username, key is very small. The window is impossible to resize with the mouse and it makes it extremely hard to see (especially with older eyes).
xwininfo reports the window to be 475x261 pixels. This is on a desktop that reports 7680x2160 pixel.
Is there any way to fix this or xdisplay options to change the geometry of the client popup?
Unfortunately no, I don’t think there’s much you can do in Ubuntu’s GNOME or Unity here. We are of course interested in implementing high DPI support in the ThinLinc Client, but it’s not available yet:
Just to be clear, I don’t need HiDPI support for the desktop or anything like that. It is just that the ThinLinc Client window that initially runs is way too small and has resizing disabled on that dialog box. Is that what is written in FLTK (per the bug you mentioned)?
Yes, the ThinLinc Client is built using FLTK.
On macOS and Windows, there are features that allow for scaling of applications that do not have HiDPI support. The Linux desktops that I know of have no such feature.
My understanding is that most desktops environments only consider such features for applications built using their own toolkits. I.e. there is scaling for GTK apps in GNOME, and for QT apps in KDE.
I understand your point, that you don’t need the full solution. But the issue is the lack of independent application-scaling support in the popular Linux desktops, at least when compared to Windows and macOS. So the reality is that we probably have to implement HiDPI support in order to get this to work well in the Linux ThinLinc Client.