Short circuit | GTK dev notes

Bharat Kalluri / 2020-09-30

You can find the code over at gitlab Short Circuit repo!

So one of my friends and I teamed up to do an developer tool to improve our workflows. Heavily inspired by Boop on mac. Since unfortunately it is not on linux and nothing like that exists on linux, we thought we will learn GTK dev and do it for ourselves and in turn for the community. This is the first time my friend got introduced to the GTK dev space. Although I have some experience, I do not have enough knowledge to give him any kind of constructive guidance.

  • Got some skeleton up and running, one thing I noticed is that there is no go to article which tells how to set up a proper GTK application. We are using python and the source of knowledge for us was other python projects. Specifically Notorious by GabMus. This is something todo, write an article about basic project setup and a collection of links to the documentation for GTK and how to traverse this world.
  • The more I work on this, I personally feel python GTK libs need to have proper auto complete and type support for gtk libraries. I think they are very well designed, but for a beginner like me who has no knowledge of what a method's arguments are, or which arguments exist for a class. I am blind while developing. Like a lot of people, I use PyCharm for development. PyCharm did suggest to install stubs for PyObject, which I did. But there was little to no improvement in terms of IntelliSense. It looks like there is an active discussion going on to add types, this will be a huge boon if it lands! (Although this was opened two years ago 😢)
  • Added Flatpak support to the application today, which involves setting up meson build system. But fortunately gnome builder has gives a ready made template which sets up Flatpak and meson for you. So, I took all the code and sort of migrated it into the gnome builder python template. Although it did work, it was not an easy task. I think there should be one tutorial which takes you through zero to a meson and flatpak supported GTK app, explaining what each file does and how it is important. This is also something I have todo.
  • Gnome builder is a fantastic tool, but it lacks strong python autocomplete. I am not sure if there is something wrong with my setup, but there is no linting or error detection. Which means if I make a simple stupid mistake (like missing a bracket) the editor does not show something is wrong. This is also a pain because we hit play and wait for a while only to realize there is a missing bracket. I also need to research how to debug python applications using gnome builder. This is a must for me since I want to strongly type my code and a debugger will help me do it much faster. Pycharm does it really well, I hope we get something similar for gnome builder.
  • There are two (untold?) patterns which I find are strongly used (at least in the python GTK dev world). One is the idea that all the widgets are usually singleton. And from everywhere you get the singleton and mutate the widget based on class methods. One more principle is that, the complete GTK application should be a python package. Install the application as a python package and make a bin file which just calls the main file of this package.
  • Once the package idea clicks, it is very easy to run the app just using pycharm. Set your package folder as sources root. It essentially adds the folder in PYTHONPATH which makes it to be considered as a python package. Create a dev python file which calls the main method of your package and you will have all the conveniences of PyCharm debugger set!
  • There should be an FAQ which shares recipes for problems like this in different GTK libraries. Since these are not language specific but GNOME specific.
  • Should we have a App Showcase? I think this makes sense. A new comer would love to see what applications are written in python and dive into the source code if stuck. Interesting idea though.
  • There is a gnome design channel, I tried submitting my icon but did not receive much feedback (maybe mine was a bad time to post). But the idea of having a gnome design is fantastic. I would like to also submit my UI for a design review and take feedback. I will post it when I see the group has got active (right now it seems silent).
  • Setting up the complete build system, resource files, schema files etc is a pain, It is very hard to debug issues I feel. I have spent almost two nights to figure out why the icon of the app is not showing up. It would be absolutely awesome if there is a cookiecutter template which has a dummy icon setup, all the build system configured and flatpak working out of the box. That would mean developers can just start working on their apps instead of setting up build systems.
  • There were some more problems I faced which took longer than I expected/did now work out
  • I was not able to get GTK info-bar working in python. I think it would be awesome if a demo app existed with GTK python sample code. Currently the GTK demo only shows up C code. I should formally put this suggestion forward and see what people have to say.
  • Although meson is fantastic, some guidance/explanation would help beginners greatly. This is in my todo, I will write about this in the series I plan on publishing.
  • There should also be a series/tutorial which explains how to package a GTK app, what GResource means, what a desktop file is/what it should contain etc.. (todo)
  • The icon is blurry, not sure why. I asked for help and am waiting for a reply. Still WIP. If this is a common problem.
  • After a while, The Authenticator dev (Bilal) helped me out on the icon issue. Apparently it only happens in dev. Once the flatpak is installed. The icon shows up normally. But during development, it does not show up. A very weird behavior in my opinion. He asked me to raise the issue over at gnome discourse. I will do that sometime soon.
  • It is on flathub now!

Other notes

  • Never hard code user directory paths in code. Always use GLib for this.
  • To use a widget as a template, make sure the composite checkbox is checked in the UI designer.

What does the ecosystem need?

GTK development desperately needs a good developer experience. There is no autocomplete in python, which is a big problem. The whole build setup is complicated (flatpak is hugely simplifying this though) and the documentation (blogs/articles etc..) are pretty sparse. More readable examples for every widget for every language they have official bindings also would help a lot.

Hand crafted by Bharat Kalluri