FontForge Arrows and Direction Handles Explained

This article explains the function and meaning of path arrows and direction handles within FontForge's glyph editing window. Readers will discover how contour arrows dictate path direction and shape fills, as well as how Bézier direction handles control curve tension, curvature, and point transitions during font design.

Contour Arrows and Path Direction

The small arrows located directly on the outlines of a glyph indicate the path direction, also known as the winding rule or contour orientation. In digital typography, the direction a path travels determines whether the inside of that path is filled with black ink or cut out as a transparent counter (a hole, such as the center of the letter "O" or "B").

• Outer Contours vs. Inner Counters: Depending on the font format (PostScript/OpenType versus TrueType), outline fills rely on opposing path directions to distinguish solid shapes from holes. For instance, PostScript curves typically require outer boundaries to run counter-clockwise and inner cutouts to run clockwise.
• Troubleshooting Inverted Fills: If a glyph renders completely filled in or with missing cutouts, it often means an inner counter has the same direction as the outer contour. In FontForge, you can resolve this by selecting the path and using Element > Correct Direction or Element > Reverse Direction.
• Start Point: The arrow also points away from the initial vertex, marking the contour's origin point, which is important for font hinting and file optimization.

Bézier Direction Handles

Direction handles—often appearing as colored lines extending to small circular, square, or cross-shaped markers—are off-curve control points that govern the geometry of Bézier curves. They do not represent physical ink; instead, they define how the curve enters and leaves an on-curve point.

• Handle Length (Tension): The distance between an on-curve point and its direction handle controls the tension or fullness of the curve. Longer handles pull the curve farther out, creating a flatter, broader arc, while shorter handles pull the curve closer to the point, producing a tighter turn.
• Handle Angle (Trajectory): The angle of the handle establishes the exact tangent of the curve at the point of origin. The curve always exits the on-curve point heading precisely toward the direction handle before bending toward the next target point.

Handle States Based on Point Type

FontForge displays and constrains direction handles differently depending on the classification of the anchor point:

• Curve Points (Round/Smooth): The handles on either side of the point are locked into a straight 180-degree line. Moving one handle rotates the opposite handle automatically, ensuring smooth, continuous curvature across the point without sharp breaks.
• Corner Points (Sharp): The incoming and outgoing handles operate entirely independently of each other. This allows you to create sharp angles, abrupt directional shifts, and defined vertices.
• Tangent Points: Tangent points transition smoothly between a straight line segment and a curved segment. FontForge locks the single curve handle in direct alignment with the adjacent straight line, preventing accidental bumps where curves meet flats.