I know a bit of python and I own a rPi B+ with a PiTFT. I was wondering If it's possible to create a GUI application that will show a dashboard with some buttons and some charts on the TFT display without using lxde or gnome or whatever, just from terminal. Is it possible with tkinter, Qt etc. or with any other framework ?
without using lxde or gnome or whatever
Gnome and LXDE are both "desktop environments" (DE's); I have a more in-depth explanation of what that means here (this is WRT a question about Lubuntu, but it applies equally to any normative GNU/Linux distribution including those used on the pi). You will need to understand that.
You don't need to use a DE, and you can write GUI software that will run with or without one but it will still require Xorg.
You can write software that will run without Xorg on the framebuffer, but that would not be the normal way to do this kind of thing, since it can't then be used any other way and (more importantly) will be ridiculously labour intensive. I'm sure you can write a normal (Xorg windowing system based) GUI in python in minutes with a few dozen lines of code. To replicate that on the framebuffer, set aside a few weeks and multiply the LOC by several orders of magnitude. To complete a genuinely useful, reasonably complex app this way, get yourself a team and (presuming you are all putting in at least a few dozen hours a week) consider a release date for sometime next spring. I.e. don't. No one else does.
What you most likely want to do is just run bare Xorg with one application, yours. There's already a question about that here -> "X11" and "Xorg" (or just plain "X") all refer to the same thing; X11 is just an older name.
You might also want to check out Python OS project - it's a GUI framework running on displays like these, it implements a GUI with attachable applications and provides UI elements.
Pygame will work to create a GUI app that can run on PiTFT (the console) without any X11 running.
There are other frameworks (such as Kivy) that in theory could also work on RPI but most of them have requirements for GL rendering which is not available in hardware for the PiTFT which connects via the GPIO header.
Assuming you already have the PiTFT configured and working via AdaFruit's instructions, add this to the python program to send graphics to the PiTFT framebuffer device:
import os os.environ["SDL_FBDEV"] = "/dev/fb1"
Sticky Finger's Kali Pi is running a finger friendly menu on top of kali linux. It's using Pygame and can be found here: