Inspect Glyph Metrics Visually in FontForge

Inspecting glyph metrics visually in FontForge allows you to evaluate and adjust character spacing, advance widths, side bearings, and kerning in real time. Rather than relying solely on numerical tables, FontForge provides dedicated graphical environments—primarily the Metrics Window and the Glyph Edit Window—to view how glyph outlines interact with their typographic boundaries.

Opening the Metrics Window

The Metrics Window is the primary environment for visually inspecting and modifying spacing.

  1. In the main Font View window, select one or more glyphs you want to inspect. Hold Shift or Ctrl (or Cmd on macOS) to select multiple characters in sequence.
  2. Navigate to the top menu and select Metrics > Open Metrics Window, or press the shortcut Ctrl + K (Cmd + K on macOS).
  3. The selected glyphs will appear side-by-side on a continuous baseline.

Reading the Visual Metric Lines

Inside the Metrics Window, each glyph is displayed alongside several visual indicators:

  • Baseline: The solid horizontal line representing the alignment base for standard characters.
  • Left Side Bearing (LSB): The vertical dashed line to the left of the glyph. It represents the space between the origin (zero point) and the leftmost edge of the glyph’s outline.
  • Right Side Bearing (RSB): The vertical dashed line to the right of the glyph. It marks the space between the rightmost edge of the glyph's outline and the advance width.
  • Advance Width: The total horizontal distance between the origin and the RSB line. This line marks where the next character in a text sequence will begin.

Adjusting Metrics Visually

You can interact directly with the visual cues in the Metrics Window:

  • Drag Metric Lines: Click and drag the vertical LSB or RSB lines with your mouse to visually expand or contract the spacing around the glyph.
  • Move the Outline: Click directly on the glyph outline and drag it left or right to rebalance the space between the fixed boundaries.
  • Compare Pairings: Click in the text entry field at the top of the window to type custom words, numbers, or punctuation alongside your glyphs to inspect rhythmic consistency and visual weight across different combinations.

Inspecting Metrics in the Glyph Edit Window

You can also inspect individual metrics while drawing or editing an outline:

  1. Double-click any glyph in the Font View to open the standard Glyph Edit Window.
  2. Ensure metric lines are visible by going to View > Show and verifying that Side Bearings and Guidelines are checked.
  3. The zero-coordinate axis indicates your origin/LSB, and a vertical line further right indicates the current Advance Width/RSB. You can drag the Advance Width line directly within this window to adjust width as you draw.