Add session restore support

[cheerfulScumbag]

Adds opt-in session save/restore support to Mango.

When session_restore=1:

• Mango saves a restorable snapshot on clean shutdown
• Mango loads that snapshot on next startup
• Mango relaunches supported apps from persisted launch_command
• Mango restores tag, monitor, floating/fullscreen state, and floating geometry as windows map

When session_restore=0:

• Mango behaves as before
• no session file is written
• no restore or relaunch path runs

Supported config:
'session_restore=0|1'

Optional override config:
'session_launch=app_id|command'
'session_launch=app_id|title|command'

Current launch-command priority:

1. exact command Mango itself used to spawn the app
2. normalized higher-level launcher command recovered from process metadata
3. raw process argv fallback
4. title-specific session_launch
5. app-only session_launch
6. plain app_id

Normalization currently implemented:

• Flatpak apps normalize to desktop-entry launcher command
• desktop-entry-backed apps normalize to the desktop file Exec= command

Validated:

• disabled path writes no session file
• clean shutdown save
• self-relaunch on next Mango startup
• duplicate foot windows with title-specific mappings
• exact command capture for Mango-owned exec-once launches
• process-based recovery for apps Mango did not spawn directly
• single-monitor restore
• floating geometry restore
• tag restore
• two-monitor restore when outputs already exist before clients map

[cheerfulScumbag]

current implementation works, but I want to improve automatic launch recovery so common apps do not require as much manual session_launch configuration

[cheerfulScumbag]

Updated this draft with a stronger automatic launch-command recovery path.

Since the original draft, Mango now:

• tracks exact commands for apps it launches itself
• recovers commands from client process metadata for apps it did not launch directly
• normalizes Flatpak apps to desktop-entry launcher command
• normalizes desktop-entry-backed apps to the desktop file Exec= command

That reduces the need for manual session_launch rules for common apps.

[cheerfulScumbag]

tested on multiple programs and they all restore with no issues
so when session_restore=1:

• Mango saves a restorable snapshot on clean shutdown
• Mango loads that snapshot on next startup
• Mango relaunches supported apps from persisted launch_command
• Mango restores tag, monitor, floating/fullscreen state, and floating geometry as windows map

Give it a test and let me know what you think

[cheerfulScumbag]

Small follow-up: I have been using this for a while now with no bugs i can find, multi-monitor restore works fine.

I also tightened the branch since the original draft with portable desktop-entry lookup, improved launcher recovery, and a trusted session-file check.

@DreamMaoMao whenever you have time, I’d appreciate any feedback on this.

[DreamMaoMao]

I'm still not sure if I want to add this feature.

[cheerfulScumbag]

Thanks for the reply.

Understood. To help me judge whether this is worth pressing further, can i ask what your hesitation mainly about?

I’m happy to reduce scope further if needed, but if the concern is that session restore itself is out of scope for Mango, that’s also useful for me to know.