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Box Selection

Thibaud edited this page 2026-03-19 22:40:54 +01:00

Table of Contents

• Plan: Box Selection
• Overview
• Current State
• Implementation Plan
• 1. Controller changes
• 2. Mouse handling
• 3. Visual feedback
• 4. Selection behavior
• 5. Intersection check
• Files to modify
• Edge cases

Plan: Box Selection

Overview

Add drag-to-select functionality for selecting multiple shapes within a rectangle.

Current State

• Click selects single shape (in Controller.mousePressed)
• Shift+click adds to selection
• Selection uses SelectionAttributes

Implementation Plan

1. Controller changes

• Add state: boxSelectOrigin (Point), boxSelectActive (boolean)
• Add boxSelectionRectangle (Rectangle) for current drag area

2. Mouse handling

• mousePressed:
  • If click on empty area (no shape), start box selection
  • Store origin point
  • Clear current selection unless Shift is held
• mouseDragged:
  • If boxSelectActive, update rectangle from origin to current point
  • Repaint to show selection box
• mouseReleased:
  • Calculate final box rectangle
  • Find all shapes whose bounds intersect with box
  • Add to selection (or replace if no Shift)
  • Clear box selection state, repaint

3. Visual feedback

• Draw semi-transparent rectangle during drag in ShapesView
• Use XOR mode or overlay for drawing
• Box outline: dashed line, gray color

4. Selection behavior

• Default: box replaces current selection
• Shift+drag: box adds to current selection
• Box entirely within shape = shape selected
• Partial overlap: select shape (standard behavior)

5. Intersection check

• Use shape.getBounds().intersects(boxRect)
• Handle composite shapes (SCollection) - check children

Files to modify

• ui/Controller.java - mouse handling
• ui/ShapesView.java - draw box overlay in paintComponent

Edge cases

• Drag on existing selection: allow move instead of box select
• Very small drag (< 5px): treat as click, select shape under point
• Empty box: clear selection