Use FontForge Metrics View to Adjust Character Spacing

Adjusting character spacing is a critical step in type design to ensure text is legible, balanced, and aesthetically pleasing. In FontForge, this process is managed primarily through the Metrics View, an interactive workspace where you can inspect and modify glyph side bearings, advance widths, and kerning pairs in real time. This guide walks you through opening the Metrics View, understanding spacing parameters, editing horizontal metrics numerically and visually, and applying kerning adjustments across character pairs.

Opening the Metrics View

  1. Open your font project in FontForge.
  2. In the main Font View window, select the glyphs you want to inspect. You can select multiple glyphs by holding Ctrl or Shift while clicking.
  3. Go to the top menu and select Metrics > Open Metrics Window (or press Ctrl + K).
  4. A new window will appear showing the selected characters rendered consecutively along a baseline. You can also type directly into the text field at the top to add, delete, or rearrange characters for live previewing.

Understanding the Metrics Interface

Each glyph in the Metrics View is enclosed by vertical reference lines:

  • Left Side Bearing (LSB): The distance between the character's origin point (left vertical line) and the leftmost point of the glyph contour.
  • Right Side Bearing (RSB): The distance between the rightmost point of the glyph contour and the right boundary line.
  • Advance Width: The total horizontal space assigned to the glyph (LSB + glyph outline width + RSB).

Beneath each glyph, a table displays these values numerically, allowing for both precise numeric entry and intuitive visual editing.

Adjusting Side Bearings and Widths

You can modify metrics using either the graphical display or the data table:

Graphical Adjustment

  1. Hover your cursor over the vertical boundary lines (the LSB or RSB lines) flanking any glyph. The cursor will change to a horizontal resize icon.
  2. Click and drag the line left or right:
    • Dragging the RSB line changes the advance width without affecting the placement of the glyph outline.
    • Dragging the glyph outline itself changes both the LSB and RSB while keeping the total advance width intact.
    • Dragging the LSB line shifts the origin relative to the glyph contour.

Numerical Adjustment

  1. Locate the editable text boxes directly beneath the character in the bottom panel.
  2. Double-click the values for LBearing, RBearing, or Width.
  3. Type your desired unit value and press Enter. The visual representation updates immediately.

Alternatively, you can select a glyph and use the menu commands:

  • Metrics > Set LBearing...
  • Metrics > Set RBearing...
  • Metrics > Set Width...

Setting Kerning Between Pairs

Kerning controls the specific spacing between two adjacent characters when default side bearings produce visual gaps (such as in pairs like "AV", "To", or "WA").

  1. In the text field of the Metrics View, type the two characters side by side (e.g., AV).
  2. Click the second character to select it.
  3. Move the cursor between the two characters until it turns into a horizontal double-arrow.
  4. Click and drag to shift the second character closer to or farther from the first.
  5. If a kerning pair does not yet exist for these two glyphs, FontForge will create one automatically.
  6. To enter an exact kerning value, click the kerning field located between the two glyph columns in the metrics table below and enter a positive or negative numerical value.

Testing and Refining Spacing

Consistent spacing requires testing characters in realistic contexts:

  • Control Strings: Test uppercase letters against straight and round forms (e.g., HHOHOOAOHO, NNONOOAO).
  • Lowercase Testing: Use n and o as reference frames (e.g., nnonooano, nonanono).
  • Zoom and Scale: Use the View menu within the Metrics window to change display sizes. Spacing that looks acceptable at large display sizes may appear unbalanced at smaller text sizes.