Adjust Font Slope and Italic Angle in FontForge

Adjusting the slope of a font in FontForge requires two distinct actions: physically slanting the glyph contours to create an oblique or italic design, and updating the font's internal metadata so operating systems recognize the correct slant angle. This guide covers how to skew glyphs uniformly, configure the standard italic angle in FontForge's settings, and update font metrics to ensure proper rendering across different platforms.

Step 1: Skew the Glyph Contours

To physically slant your letterforms:

  1. Open your font file in FontForge.
  2. Select the glyphs you want to slant. To slant the entire font, go to Edit > Select > Select All.
  3. Navigate to Element > Transformations > Transform...
  4. In the transformation window, change the first dropdown menu to Skew.
  5. Enter your desired slant angle. For a standard rightward-leaning italic, enter a negative degree value (typically between -10° and -15°).
  6. Click OK to apply the transformation.

Step 2: Set the Italic Angle Metadata

Font rendering engines rely on font metrics to properly calculate selection boxes, caret placement, and cursor angles.

  1. Go to Element > Font Info.
  2. Select the General category from the left sidebar.
  3. Locate the Italic Angle field.
  4. Enter the same degree value you used when skewing the glyphs (e.g., -12). A standard upright font has an italic angle of 0, while right-leaning italics use negative numbers.
  5. Click OK.

Step 3: Update Font Style Classifications

To ensure applications correctly recognize the slanted font as an Italic variant:

  1. Still inside Font Info, navigate to OS/2 > Misc.
  2. In the Selection field, check the Italic box (and Oblique if applicable).
  3. Switch to the PS Names category.
  4. Update the Fontname, Family Name, and Name for Humans to reflect the new style (for example, adding "-Italic" or " Italic" to the names).
  5. Ensure the Weight dropdown reflects the appropriate style, or specify it under standard style names.

Step 4: Fix Overlaps and Extremities

Skewing glyphs shifts control points and changes where the extreme horizontal and vertical points lie on curved paths:

  1. With the affected glyphs selected, go to Element > Add Extrema to ensure new path extrema points are placed correctly for optimal screen rendering.
  2. If strokes overlap or artifacts appear, go to Element > Overlap > Remove Overlap.

Step 5: Save and Generate

Save your project by clicking File > Save, then export your finished font via File > Generate Fonts... using your target format (such as OpenType CFF or TrueType).