feat: add get_icon_state method to SpringBoardServicesClient

[fulln]

Summary

I would like to add a get_icon_state() method to SpringBoardServicesClient for reading the iOS home screen icon layout.

Motivation

Currently, the library has get_icon_pngdata() for retrieving app icons, but there's no way to read the home screen layout structure. This would be useful for:

• Backing up home screen layouts
• Analyzing app organization
• Development tools that need to inspect device state
• Inventory management (listing installed apps and their positions)

Proposed API

pub async fn get_icon_state(
    &mut self,
    format_version: Option<String>,
) -> Result<plist::Value, IdeviceError>

This method:

• Sends getIconState command to SpringBoard service
• Returns complete home screen layout as plist::Value
• Supports optional formatVersion parameter for compatibility

Testing

Tested successfully on:

• Device: iPhone 16,2 (iPhone 15 Pro)
• iOS: 18.7.3 (Build 22H217)

The method correctly retrieves the icon state with all pages, sections, and app metadata.

Implementation

I have a working implementation ready and will submit a PR. The implementation follows the existing code style and is based on libimobiledevice's approach.

Note on set_icon_state

I also investigated adding set_icon_state() but found it doesn't work on iOS 18+ (device accepts command but silently ignores changes). Therefore, the PR will only include the read-only get_icon_state() method.

---

PR incoming: Will add get_icon_state() only, as it's the functional and useful part.

[fulln]

🎉 BREAKTHROUGH: set_icon_state WORKS on iOS 18+!

The Problem Was NOT iOS 18 Blocking the Feature

After extensive debugging, I discovered the real issue: date precision incompatibility.

Root Cause

Rust's plist crate serializes dates with nanosecond precision:

2026-01-17T03:09:58.332738876Z

iOS only accepts second precision:

2026-01-17T03:09:58Z

When icon state contains dates with nanosecond precision, iOS silently rejects the entire payload without errors. This made it appear as if iOS 18 had blocked the feature.

Solution

Created a truncate_dates_to_seconds() utility that:

1. Recursively walks plist structures
2. Truncates all Date values to second precision
3. Applied in get_icon_state() so returned data is immediately compatible

Verification

✅ Tested on iOS 18.7.3 (iPhone 15 Pro Max)
✅ Icons successfully swap positions
✅ Cross-verified with Python pymobiledevice3
✅ All functionality working as expected

Updated PR #63

I've updated PR #63 to include both get_icon_state() and set_icon_state() with the date precision fix. The implementation now:

• ✅ Reads home screen layout
• ✅ Writes home screen layout
• ✅ Works on iOS 18.7.3
• ✅ Handles date precision automatically
• ✅ Includes comprehensive tests

Key Learnings

1. Silent failures are dangerous - iOS accepted the command but ignored it
2. Date serialization matters - Precision differences can break APIs
3. iOS 18 didn't block the feature - It was a data format issue all along

The feature is fully functional! 🚀

[fulln]

Hey @jkcoxson! 👋

Just wanted to bring this breakthrough to your attention. After discovering the date precision bug, I've confirmed that set_icon_state actually works perfectly on iOS 18.7.3.

The feature wasn't blocked by Apple - it was a data format incompatibility. PR #63 now includes both read and write functionality with the fix applied.

Would appreciate your review when you have time! 🙏