fix(ui-ios): #5200 — scrollViewSetOffset binds y, restores without animation

[proggeramlug]

Fixes #5200.

Problem

scrollViewSetOffset(sv, x, y) ignored y and always used x. The shared dispatch row already declares three args (Widget, F64, F64):

// crates/perry-dispatch/src/ui_table.rs
MethodRow { method: "scrollViewSetOffset", runtime: "perry_ui_scrollview_set_offset",
            args: &[ArgKind::Widget, ArgKind::F64, ArgKind::F64], ret: ReturnKind::Void },

…but the iOS FFI and impl took a single offset and bound it to the first f64 (x):

pub extern "C" fn perry_ui_scrollview_set_offset(scroll_handle: i64, offset: f64) { ... }
pub fn set_offset(scroll_handle: i64, offset: f64) {
    let point = CGPoint::new(0.0, offset);  // offset = x (usually 0) → contentOffset.y = 0
    ...
}

So setContentOffset received (0, x) with x almost always 0, and any caller doing scrollViewSetOffset(sv, 0, savedY) snapped to the top instead of savedY — scroll-position restoration broke on every rebuild.

Fix

Thread both coordinates through the FFI into the impl, and set the offset without animation (this path restores position, so animating is wrong):

pub extern "C" fn perry_ui_scrollview_set_offset(scroll_handle: i64, x: f64, y: f64) {
    widgets::scrollview::set_offset(scroll_handle, x, y);
}
pub fn set_offset(scroll_handle: i64, x: f64, y: f64) {
    let point = CGPoint::new(x, y);
    let _: () = msg_send![&*scroll_view, setContentOffset: point, animated: false];
}

cargo check -p perry-ui-ios is clean (only pre-existing warnings).

Note

The same single-offset signature exists in the other native UI backends (perry-ui-macos, tvos, visionos, android, gtk4, windows) and the JS/wasm runtimes, all fed by the same 3-arg dispatch row — so they share this latent y-ignored bug. This PR is scoped to iOS per the issue; the sibling backends are worth a follow-up.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Scroll view positioning now supports both horizontal and vertical offsets independently.

• Bug Fixes

  • Updated scroll view restoration to use non-animated positioning for more reliable scroll behavior.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: e79709fd-5edc-40c5-a62c-bf530fa5044c

📥 Commits

Reviewing files that changed from the base of the PR and between 8b71256 and d666ea2.

📒 Files selected for processing (2)

• crates/perry-ui-ios/src/ffi/widgets_basic.rs
• crates/perry-ui-ios/src/widgets/scrollview.rs

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📝 Walkthrough

Walkthrough

The iOS scroll view FFI function perry_ui_scrollview_set_offset and its backing implementation set_offset are updated to accept two f64 parameters (x, y) instead of one. The implementation constructs a CGPoint from both coordinates and sets the content offset with animated: false.

Changes

Scroll Offset x/y Fix

Layer / File(s)	Summary
set_offset implementation and FFI wrapper crates/perry-ui-ios/src/widgets/scrollview.rs, crates/perry-ui-ios/src/ffi/widgets_basic.rs	set_offset now takes x and y, builds CGPoint::new(x, y), and passes animated: false to setContentOffset. The FFI wrapper perry_ui_scrollview_set_offset is updated to accept and forward both parameters.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

A rabbit once scrolled but kept landing on top,
The y was ignored — what an unfortunate flop!
Now x and y hop together in sync,
CGPoint gets both with a nod and a wink.
No animation needed, just snap to the right spot! 🐇✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main fix: updating scrollViewSetOffset to properly bind both x and y coordinates and restore scroll position without animation.
Description check	✅ Passed	The description includes a clear summary, detailed problem statement, solution with code examples, and notes on scope. However, it lacks explicit test plan checkboxes completion or confirmation of cargo checks.
Linked Issues check	✅ Passed	The PR fully addresses #5200 by fixing the iOS FFI signature and implementation to accept both x and y coordinates and properly pass them to setContentOffset without animation.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to fixing the iOS implementation of scrollViewSetOffset as described in #5200. No unrelated modifications are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/5200-scrollview-set-offset-y

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