Bug Report: Auto Layout Fill + min-width fails to distribute remaining space
Summary
In a horizontal Auto Layout frame with two Fill children (layoutGrow: 1), when one child's min-width exceeds the equal share of available space, the layout engine fails to redistribute remaining space. The other child falls back to its content width instead of filling the remaining space, leaving an unallocated gap.
Reproduction Steps
- Create a horizontal Auto Layout frame (no gap, no padding)
- Add two child frames, both set to Fill container (layoutGrow: 1)
- Set child A's min-width to 80px, child B's min-width to 160px
- Add text content inside each child (with 8px padding)
- Resize the parent frame to various widths and observe
Setup (common across all cases)
- Both children: Fill container, layoutGrow: 1
- Child A: min-width: 80
- Child B: min-width: 160
- Parent: Horizontal Auto Layout, gap: 0, stroke: 1px OUTSIDE (included in layout)
- Child A content width: ~122px (text + padding)
Results
Analysis
The bug occurs only when the equal share falls between the two min-width values (80 < equal share < 160):
- w: 300 → equal share = 150. Child B’s min-width of 160 exceeds the equal share (150).
- Expected: Child B → 160px, Child A → remaining 140px (> min-width 80, so valid)
- Actual: Child B → 160px, Child A → 122px (content width fallback), 18px unallocated
When equal share ≥ 160 (w: 320, 360), both children Fill correctly. When equal share < 80 (w: 200), both children respect min-widths and overflow as expected. The issue is isolated to the case where one child's min-width forces it above the equal share.
Expected Behavior
When Child B's min-width pushes it above the equal share, the layout engine should allocate the remaining space (parent width − Child B's min-width) to Child A, as long as that value is ≥ Child A's min-width. This matches CSS Flexbox behavior with flex-grow + min-width.
Impact
This prevents common layout patterns such as:
- Fixed-min-width sidebar + flexible main content area
- Navigation panel + content area where both have min-width constraints
- Any two-column layout where columns have different minimum size requirements
Environment
Figma (August 2025)