Vector Measurement Feature

Overview

The vector measurement feature extends the existing measurement system to work with vector networks. It provides the same axis-aligned distance measurements (X/Y independently) but adds support for:

• Vector2 points (treated as zero-size rectangles)
• Curve evaluation (dynamic points on Bézier curves)
• Vector-specific geometry (vertices, segments, regions)

How It Works

The feature activates when you:

1. Hover over a curve segment or vertex in vector edit mode
2. Hold the Alt key while hovering

It uses the same visual system as regular measurements: guide lines, auxiliary lines, and distance labels showing top/right/bottom/left spacing.

Measurement Triggers

• Segment hover: When hovering over a curve segment, measures from selection to the parametric point on the curve
• Vertex hover: When hovering over a vertex (snapped), measures from selection to the exact vertex position

Measurement Types

A	A Type	B	B Type	Description
Vertex	Vector2	Parametric Point	Vector2	Measures axis-aligned distances from a selected vertex to a point on the hovered curve
Vertex	Vector2	Vertex	Vector2	Measures axis-aligned distances from a selected vertex to another vertex (when hovering over a vertex)
Vertices (BBox)	Rectangle	Parametric Point	Vector2	Measures axis-aligned distances from the bounding box of selected vertices to a point on the hovered curve
Region (BBox)	Rectangle	Region (BBox)	Rectangle	Measures axis-aligned distances between two selected regions
Vertex	Vector2	Region (BBox)	Rectangle	Measures axis-aligned distances from a selected vertex to a region's boundary
Vertices (BBox)	Rectangle	Region (BBox)	Rectangle	Measures axis-aligned distances from the bounding box of selected vertices to a region's boundary

A-B De-duplication

The measurement system prevents redundant measurements by detecting when the target (B) is already part of the source selection (A). This ensures that measurements are meaningful and avoids measuring a selection against itself.

De-duplication Rules

Source Selection (A)	Target (B)	Measurement	Reason
Selected Vertex	Same Vertex	❌ Skipped	Cannot measure vertex to itself
Selected Segment	Vertex of that Segment	❌ Skipped	Target is part of the selected segment
Multiple Vertices	Any Selected Vertex	❌ Skipped	Target is already in the selection
Multiple Segments	Vertex of any Selected Segment	❌ Skipped	Target is part of one of the selected segments
Selected Vertex	Different Vertex	✅ Measured	Valid measurement between distinct points
Selected Segment	Vertex of Different Segment	✅ Measured	Valid measurement between distinct elements
Selected Vertex	Parametric Point on Curve	✅ Measured	Valid measurement to dynamic curve point

Implementation Details

• Direct Vertex Check: If the target vertex is directly selected, measurement is skipped
• Segment Vertex Check: If the target vertex is an endpoint of any selected segment, measurement is skipped
• Priority: Mathematical snapping (snapped_vertex_idx) takes precedence over UI hovering (hovered_vertex_index)
• Performance: Early detection prevents unnecessary calculation of source rectangles and measurements

Implementation Notes

• Vector2 points are treated as zero-size rectangles for consistency with the existing measurement system
• Curve evaluation uses cmath.bezier.evaluate to calculate dynamic points on Bézier curves
• Mouse projection uses cmath.bezier.project to find the closest point on the curve to the mouse cursor
• Vertex detection uses the snapped_vertex_idx state to identify when hovering over a vertex
• Same visual output as regular measurements: red guide lines with distance labels
• Same axis-aligned calculation showing top, right, bottom, left distances independently
• Integration with existing Alt key binding and measurement system