Synchronize native scroll state with the UI tree

[dogukani]

Problem

Win32 scroll widgets update their own scrollbar and document position, while framework layout keeps a separate scroll offset. After native wheel or scrollbar input, rendered content and the Core tree can disagree.

Change

• Mirror native vertical scroll changes into the UI tree and synchronize the native scrollbar when the tree changes.
• Let framework layout own the vertical content offset for framework-backed widgets. Preserve the existing native offset path for Controls widgets and horizontal scrolling.

Verification

• Windows smoke build and built-in verification passed.
• notes-jsx built; its initial PNG matched the previous regression capture byte for byte.
• Two page-downs in the Notes list produced 2172 device pixels and 1086 logical pixels at 2x scale, with later notes visible.
• With the matching local Core and examples changes, 12 page-downs in virtual-list displayed rows 69–73 instead of a blank viewport.

Integration retest: the first image-based scroll check did not exercise JSX onScroll. Manual interaction exposed that the compiler delegated this non-bubbling event to body; compiler#1 binds it to the target. The rebuilt Windows app with all four changes appeared fixed in manual retest. Merge this PR with that compiler dependency in mind.

Summary by CodeRabbit

• Bug Fixes
  • Improved Win32 scrolling accuracy by keeping scroll positions consistent between device pixels and layout units.
  • Kept scroll-container documents anchored at the top while preserving scrolling behavior for other content.

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: a321c6b0-82da-40b5-af38-ba758a134cf4

📥 Commits

Reviewing files that changed from the base of the PR and between 67cb15f and 1911c6d.

📒 Files selected for processing (2)

• packages/geastack-windows/targets/win32/main/win32_renderer.cpp
• packages/geastack-windows/targets/win32/main/win32_widgets.cpp

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📝 Walkthrough

Walkthrough

Win32 scroll handling now converts positions between native device pixels and tree layout units. Scroll-container documents with nonnegative node IDs remain vertically positioned at zero when scrollbars or scroll positions are updated.

Changes

Win32 scroll synchronization

Layer / File(s)	Summary
Scroll coordinate conversion packages/geastack-windows/targets/win32/main/win32_renderer.cpp	The renderer converts native scroll positions to layout units before updating the tree. It converts tree scroll positions to device pixels before updating the widget.
Scroll-container document offsets packages/geastack-windows/targets/win32/main/win32_widgets.cpp	For widgets with nonnegative node IDs, document vertical positioning remains at zero when scrollbars or scroll positions are updated. Other widgets retain the negative scroll-top offset.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: dashersw

Merge Risk: ⚪ Minimal · up to 1911c

Framework scroll positions and native scrollbar positions are synchronized in their respective units while preserving Controls offsets. No concrete regression remains that should block merging.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: synchronizing native Win32 scroll state with the UI tree.

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