OpenNest/docs/superpowers/specs/2026-03-18-pattern-tile-layout-design.md

Pattern Tile Layout Window

Summary

A standalone tool window for designing two-part tile patterns and previewing how they fill a plate. The user selects two drawings, arranges them into a unit cell by dragging, and sees the pattern tiled across a configurable plate in real time. The unit cell compacts on release using angle-based push. The tiled result can be applied to the current plate or a new plate.

Window Layout

PatternTileForm is a non-MDI dialog opened from the main menu/toolbar. Horizontal SplitContainer:

• Left panel (Unit Cell Editor): A PlateView with Plate.Size = (0, 0) — no plate outline drawn. Shows only the two parts. The user drags parts freely to position them relative to each other. On mouse up after a drag, gravity compaction fires toward the combined center of gravity using the generalized angle-based Compactor.Push. Part spacing from the preview plate is used as the minimum gap during compaction.

• Right panel (Tile Preview): A read-only PlateView (AllowSelect = false, AllowDrop = false) showing the unit cell pattern tiled across a plate with a visible plate outline. Plate size is user-configurable. Rebuilds on mouse up in the unit cell editor (not during drag).

• Top control strip: Two ComboBox dropdowns ("Drawing A", "Drawing B") populated from the active nest's DrawingCollection. Plate size inputs (length, width). An "Auto-Arrange" button. An "Apply" button.

Drawing Selection & Unit Cell

When both dropdowns have a selection, two parts are created and placed side by side horizontally in the left PlateView, centered in the view.

The user drags parts to arrange them. On mouse up:

1. Gravity compaction fires — each part is pushed toward the combined centroid using angle-based Compactor.Push, stopping when spacing is satisfied.
2. The tile preview on the right rebuilds.

Auto-Arrange

A button that tries rotation combinations (0, 90, 180, 270 for each part — 16 combinations) and picks the pair arrangement with the tightest bounding box. The user can fine-tune from there.

Generalized Compactor.Push

Refactor Compactor.Push to accept an arbitrary angle instead of only cardinal PushDirection. The push ray-casts at the given angle to find the closest obstacle, then slides the part along that vector.

Existing PushDirection.Up/Down/Left/Right callers continue to work by mapping to 0/90/180/270 degrees (or equivalent radians).

This is a prerequisite for the unit cell compaction behavior and benefits the rest of the codebase.

Tiling Algorithm

1. Compute the unit cell bounding box from the two parts' combined bounds (including part spacing).
2. Calculate grid dimensions: cols = floor(plateWidth / cellWidth), rows = floor(plateHeight / cellHeight).
3. For each grid position (col, row), clone the two parts offset by (col * cellWidth, row * cellHeight).
4. Place all cloned parts on the preview plate.

Tiling recalculates only on mouse up in the unit cell editor, or when drawing selection or plate size changes.

Apply to Plate

The "Apply" button opens a dialog with two choices:

• Apply to current plate — places the tiled parts onto the active plate in EditNestForm.
• Apply to new plate — creates a new plate in the nest with the preview plate's size, then places the parts.

The form returns the list of parts and the target choice to the caller (EditNestForm), which handles actual placement.

Components

Component	Project	Purpose
PatternTileForm	OpenNest (WinForms)	The dialog window with split layout, controls, and apply logic
Compactor.Push(angle)	OpenNest.Engine	Generalized angle-based push (refactor of existing cardinal-only push)
Menu/toolbar integration	OpenNest (WinForms)	Entry point from MainForm or EditNestForm toolbar