Add GTK GUI with real-time pot control

[ChrisX101010]

Adds a GTK-based GUI addressing #60.

Features:

• Guitar pedal style interface with 4 rotary knobs
• Real-time pot control using --control= interface (ea71138)
• All 9 effects supported (reads from Makefile)
• Smooth mouse drag and scroll wheel for knobs
• Keyboard shortcuts: Tab (select), ←→ (±5), ↑↓ (±1), Space (play), 1-9 (effect), R (reset)
• Works with aplay (~100ms latency) or ffplay fallback

Requirements:

sudo apt install python3-gi python3-gi-cairo gir1.2-gtk-3.0

Usage:

python3 gui.py

Closes #60

[sinderoth]

I'm not sure if this is something wanted in this repo, but it helped me while experimenting with some effects locally, so thanks!

There's a minor issue: if you press play with an effect and then change the effect, the start/stop controls don't sync correctly and stops working as expected.

Also this is surely a personal preference, but I changed the knob dragging from horizontal to vertical: dragging up increases the value, dragging down decreases it. This matches the behavior in GarageBand and feels more natural to me.

[ChrisX101010]

I'm not sure if this is something wanted in this repo, but it helped me while experimenting with some effects locally, so thanks!

There's a minor issue: if you press play with an effect and then change the effect, the start/stop controls don't sync correctly and stops working as expected.

Also this is surely a personal preference, but I changed the knob dragging from horizontal to vertical: dragging up increases the value, dragging down decreases it. This matches the behavior in GarageBand and feels more natural to me.

You are most welcome, sir! I am glad it helped someone at least, it is still a prototype and as you said experiment, the issue for the audio automatically stopping after switching is due to the convert.c file, I had a similar issue with my TUI Linus originally approved I can make, I think it is the same issue here too and I can fix it, but yeah please feel free to commit any changes and the scroll bar regarding tuning is a cooler concept for a GUI imho, so yeah. Feel free to share the code and I will work on fixing these issues for the weekend and let's get it working! 🙂