[v3][macOS] Window shakes when resizing from top corners with MacTitleBarHiddenInset

[aaadotpm]

Description

When using MacTitleBarHiddenInset with InvisibleTitleBarHeight, resizing the window from the top-left or top-right corners causes the window content to shake/jitter. Resizing from the bottom corners works smoothly.

To Reproduce

1. Create a new Wails v3 app with the following window options:

window := app.Window.NewWithOptions(application.WebviewWindowOptions{
    Title:  "Test",
    Width:  1200,
    Height: 800,
    Mac: application.MacWindow{
        InvisibleTitleBarHeight: 50,
        Backdrop:                application.MacBackdropTranslucent,
        TitleBar:                application.MacTitleBarHiddenInset,
    },
    URL: "https://example.com",
})

2. Run the app
3. Resize the window by dragging the top-left or top-right corner
4. Observe the window content shaking/jittering during resize

Expected behaviour

Window should resize smoothly from all corners, like it does from the bottom corners.

Actual behaviour

• Top-left corner resize: Content shakes
• Top-right corner resize: Content shakes
• Bottom-left corner resize: Smooth ✓
• Bottom-right corner resize: Smooth ✓

Attempted Fixes

We tried the following without success:

• Setting preservesContentDuringLiveResize = YES on the window
• Enabling layer-backing (wantsLayer = YES) on content view
• Setting proper autoresizing masks on content view and subviews

The issue appears to be in how the window handles the invisible title bar area during resize from the top edges.

Related Issues

• [v2] Mac / Frameless window is shaking on resize #1176 - Similar issue reported for v2 frameless windows (closed as stale)

System Details

OS: macOS 26.2 (Tahoe)
Architecture: arm64 (Apple Silicon)
Wails: v3.0.0-alpha.64
Go: 1.25.5

[aaadotpm]

Update: Confirmed root cause

We tested by removing the Mac: application.MacWindow{} configuration entirely (using the default title bar), and the shaking is completely gone.

This confirms the issue is specifically caused by MacTitleBarHiddenInset / InvisibleTitleBarHeight - the standard title bar resizes smoothly from all corners.

[leaanthony]

Merged fix into latest alpha 👍