add concentric fill for laser mode closed shapes

[clugtu]

Summary

• Adds a fill toggle and spacing (mm) input to the laser output settings
• When enabled, fillOut() generates concentric inset paths inside each closed shape by repeatedly offsetting the outer boundary inward
• Works correctly for both solid shapes and ring/annular shapes (fill stays within the material region and does not enter holes)

How it works

• The outer boundary of each shape is offset inward by the spacing distance on each iteration; inner children are stripped before offsetting to prevent Clipper from expanding holes and collapsing the ring after just one pass
• For shapes with inner holes (e.g. a circle imported as a thin ring), filling stops when the inset polygon's area shrinks to the hole area, keeping fill rings within the material

Settings

Setting	Default	Description
fill	off	Enable concentric fill for closed shapes
spacing	1 mm	Distance between fill rings

Test plan

• Enable fill in laser output settings, set spacing to 0.2 mm
• Slice a DXF with solid closed shapes — verify concentric rings appear inside each shape
• Slice a DXF with ring/annular shapes — verify fill rings appear only within the ring material, not inside the hole
• Verify fill is absent when the toggle is off
• Verify GCode export includes the fill paths

🤖 Generated with Claude Code